implemented 0.db as admin database architecture + updated test file

Cargo.toml

@@ -24,6 +24,7 @@ age = "0.10"
 secrecy = "0.8"
 ed25519-dalek = "2"
 base64 = "0.22"
+jsonrpsee = { version = "0.26.0", features = ["http-client", "ws-client", "server", "macros"] }
 
 [dev-dependencies]
 redis = { version = "0.24", features = ["aio", "tokio-comp"] }

src/admin_meta.rs

@@ -0,0 +1,361 @@
+use std::path::PathBuf;
+use std::sync::{Arc, OnceLock, Mutex, RwLock};
+use std::collections::HashMap;
+
+use crate::error::DBError;
+use crate::options;
+use crate::rpc::Permissions;
+use crate::storage::Storage;
+use crate::storage_sled::SledStorage;
+use crate::storage_trait::StorageBackend;
+
+// Key builders
+fn k_admin_next_id() -> &'static str {
+    "admin:next_id"
+}
+fn k_admin_dbs() -> &'static str {
+    "admin:dbs"
+}
+fn k_meta_db(id: u64) -> String {
+    format!("meta:db:{}", id)
+}
+fn k_meta_db_keys(id: u64) -> String {
+    format!("meta:db:{}:keys", id)
+}
+fn k_meta_db_enc(id: u64) -> String {
+    format!("meta:db:{}:enc", id)
+}
+
+// Global cache of admin DB 0 handles per base_dir to avoid sled/reDB file-lock contention
+// and to correctly isolate different test instances with distinct directories.
+static ADMIN_STORAGES: OnceLock<RwLock<HashMap<String, Arc<dyn StorageBackend>>>> = OnceLock::new();
+
+// Global registry for data DB storages to avoid double-open across process.
+static DATA_STORAGES: OnceLock<RwLock<HashMap<u64, Arc<dyn StorageBackend>>>> = OnceLock::new();
+static DATA_INIT_LOCK: Mutex<()> = Mutex::new(());
+
+fn init_admin_storage(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+) -> Result<Arc<dyn StorageBackend>, DBError> {
+    let db_file = PathBuf::from(base_dir).join("0.db");
+    if let Some(parent_dir) = db_file.parent() {
+        std::fs::create_dir_all(parent_dir).map_err(|e| {
+            DBError(format!("Failed to create directory {}: {}", parent_dir.display(), e))
+        })?;
+    }
+    let storage: Arc<dyn StorageBackend> = match backend {
+        options::BackendType::Redb => Arc::new(Storage::new(&db_file, true, Some(admin_secret))?),
+        options::BackendType::Sled => Arc::new(SledStorage::new(&db_file, true, Some(admin_secret))?),
+    };
+    Ok(storage)
+}
+
+// Get or initialize a cached handle to admin DB 0 per base_dir (thread-safe, no double-open race)
+pub fn open_admin_storage(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+) -> Result<Arc<dyn StorageBackend>, DBError> {
+    let map = ADMIN_STORAGES.get_or_init(|| RwLock::new(HashMap::new()));
+    // Fast path
+    if let Some(st) = map.read().unwrap().get(base_dir) {
+        return Ok(st.clone());
+    }
+    // Slow path with write lock
+    {
+        let mut w = map.write().unwrap();
+        if let Some(st) = w.get(base_dir) {
+            return Ok(st.clone());
+        }
+        let st = init_admin_storage(base_dir, backend, admin_secret)?;
+        w.insert(base_dir.to_string(), st.clone());
+        return Ok(st);
+    }
+}
+
+// Ensure admin structures exist in encrypted DB 0
+pub fn ensure_bootstrap(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+) -> Result<(), DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+
+    // Initialize next id if missing
+    if !admin.exists(k_admin_next_id())? {
+        admin.set(k_admin_next_id().to_string(), "1".to_string())?;
+    }
+    // admin:dbs is a hash; it's fine if it doesn't exist (hlen -> 0)
+    Ok(())
+}
+
+// Get or initialize a shared handle to a data DB (> 0), avoiding double-open across subsystems
+pub fn open_data_storage(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+    id: u64,
+) -> Result<Arc<dyn StorageBackend>, DBError> {
+    if id == 0 {
+        return open_admin_storage(base_dir, backend, admin_secret);
+    }
+
+    // Validate existence in admin metadata
+    if !db_exists(base_dir, backend.clone(), admin_secret, id)? {
+        return Err(DBError(format!(
+            "Cannot open database instance {}, as that database instance does not exist.",
+            id
+        )));
+    }
+
+    let map = DATA_STORAGES.get_or_init(|| RwLock::new(HashMap::new()));
+    // Fast path
+    if let Some(st) = map.read().unwrap().get(&id) {
+        return Ok(st.clone());
+    }
+
+    // Slow path with init lock
+    let _guard = DATA_INIT_LOCK.lock().unwrap();
+    if let Some(st) = map.read().unwrap().get(&id) {
+        return Ok(st.clone());
+    }
+
+    // Determine per-db encryption
+    let enc = get_enc_key(base_dir, backend.clone(), admin_secret, id)?;
+    let should_encrypt = enc.is_some();
+
+    // Build database file path and ensure parent dir exists
+    let db_file = PathBuf::from(base_dir).join(format!("{}.db", id));
+    if let Some(parent_dir) = db_file.parent() {
+        std::fs::create_dir_all(parent_dir).map_err(|e| {
+            DBError(format!("Failed to create directory {}: {}", parent_dir.display(), e))
+        })?;
+    }
+
+    // Open storage
+    let storage: Arc<dyn StorageBackend> = match backend {
+        options::BackendType::Redb => Arc::new(Storage::new(&db_file, should_encrypt, enc.as_deref())?),
+        options::BackendType::Sled => Arc::new(SledStorage::new(&db_file, should_encrypt, enc.as_deref())?),
+    };
+
+    // Publish to registry
+    map.write().unwrap().insert(id, storage.clone());
+    Ok(storage)
+}
+
+// Allocate the next DB id and persist new pointer
+pub fn allocate_next_id(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+) -> Result<u64, DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    let cur = admin
+        .get(k_admin_next_id())?
+        .unwrap_or_else(|| "1".to_string());
+    let id: u64 = cur.parse().unwrap_or(1);
+    let next = id.checked_add(1).ok_or_else(|| DBError("next_id overflow".into()))?;
+    admin.set(k_admin_next_id().to_string(), next.to_string())?;
+
+    // Register into admin:dbs set/hash
+    let _ = admin.hset(k_admin_dbs(), vec![(id.to_string(), "1".to_string())])?;
+
+    // Default meta for the new db: public true
+    let meta_key = k_meta_db(id);
+    let _ = admin.hset(&meta_key, vec![("public".to_string(), "true".to_string())])?;
+
+    Ok(id)
+}
+
+// Check existence of a db id in admin:dbs
+pub fn db_exists(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+    id: u64,
+) -> Result<bool, DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    Ok(admin.hexists(k_admin_dbs(), &id.to_string())?)
+}
+
+// Get per-db encryption key, if any
+pub fn get_enc_key(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+    id: u64,
+) -> Result<Option<String>, DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    admin.get(&k_meta_db_enc(id))
+}
+
+// Set per-db encryption key (called during create)
+pub fn set_enc_key(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+    id: u64,
+    key: &str,
+) -> Result<(), DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    admin.set(k_meta_db_enc(id), key.to_string())
+}
+
+// Set database public flag
+pub fn set_database_public(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+    id: u64,
+    public: bool,
+) -> Result<(), DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    let mk = k_meta_db(id);
+    let _ = admin.hset(&mk, vec![("public".to_string(), public.to_string())])?;
+    Ok(())
+}
+
+// Internal: load public flag; default to true when meta missing
+fn load_public(
+    admin: &Arc<dyn StorageBackend>,
+    id: u64,
+) -> Result<bool, DBError> {
+    let mk = k_meta_db(id);
+    match admin.hget(&mk, "public")? {
+        Some(v) => Ok(v == "true"),
+        None => Ok(true),
+    }
+}
+
+// Add access key for db (value format: "Read:ts" or "ReadWrite:ts")
+pub fn add_access_key(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+    id: u64,
+    key_plain: &str,
+    perms: Permissions,
+) -> Result<(), DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    let hash = crate::rpc::hash_key(key_plain);
+    let v = match perms {
+        Permissions::Read => format!("Read:{}", now_secs()),
+        Permissions::ReadWrite => format!("ReadWrite:{}", now_secs()),
+    };
+    let _ = admin.hset(&k_meta_db_keys(id), vec![(hash, v)])?;
+    Ok(())
+}
+
+// Delete access key by hash
+pub fn delete_access_key(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+    id: u64,
+    key_hash: &str,
+) -> Result<bool, DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    let n = admin.hdel(&k_meta_db_keys(id), vec![key_hash.to_string()])?;
+    Ok(n > 0)
+}
+
+// List access keys, returning (hash, perms, created_at_secs)
+pub fn list_access_keys(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+    id: u64,
+) -> Result<Vec<(String, Permissions, u64)>, DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    let pairs = admin.hgetall(&k_meta_db_keys(id))?;
+    let mut out = Vec::new();
+    for (hash, val) in pairs {
+        let (perm, ts) = parse_perm_value(&val);
+        out.push((hash, perm, ts));
+    }
+    Ok(out)
+}
+
+// Verify access permission for db id with optional key
+// Returns:
+// - Ok(Some(Permissions)) when access is allowed
+// - Ok(None) when not allowed or db missing (caller can distinguish by calling db_exists)
+pub fn verify_access(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+    id: u64,
+    key_opt: Option<&str>,
+) -> Result<Option<Permissions>, DBError> {
+    // Admin DB 0: require exact admin_secret
+    if id == 0 {
+        if let Some(k) = key_opt {
+            if k == admin_secret {
+                return Ok(Some(Permissions::ReadWrite));
+            }
+        }
+        return Ok(None);
+    }
+
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    if !admin.hexists(k_admin_dbs(), &id.to_string())? {
+        return Ok(None);
+    }
+
+    // Public?
+    if load_public(&admin, id)? {
+        return Ok(Some(Permissions::ReadWrite));
+    }
+
+    // Private: require key and verify
+    if let Some(k) = key_opt {
+        let hash = crate::rpc::hash_key(k);
+        if let Some(v) = admin.hget(&k_meta_db_keys(id), &hash)? {
+            let (perm, _ts) = parse_perm_value(&v);
+            return Ok(Some(perm));
+        }
+    }
+    Ok(None)
+}
+
+// Enumerate all db ids
+pub fn list_dbs(
+    base_dir: &str,
+    backend: options::BackendType,
+    admin_secret: &str,
+) -> Result<Vec<u64>, DBError> {
+    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
+    let ids = admin.hkeys(k_admin_dbs())?;
+    let mut out = Vec::new();
+    for s in ids {
+        if let Ok(v) = s.parse() {
+            out.push(v);
+        }
+    }
+    Ok(out)
+}
+
+// Helper: parse permission value "Read:ts" or "ReadWrite:ts"
+fn parse_perm_value(v: &str) -> (Permissions, u64) {
+    let mut parts = v.split(':');
+    let p = parts.next().unwrap_or("Read");
+    let ts = parts
+        .next()
+        .and_then(|s| s.parse().ok())
+        .unwrap_or(0u64);
+    let perm = match p {
+        "ReadWrite" => Permissions::ReadWrite,
+        _ => Permissions::Read,
+    };
+    (perm, ts)
+}
+
+fn now_secs() -> u64 {
+    use std::time::{SystemTime, UNIX_EPOCH};
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs()
+}

src/cmd.rs

@@ -6,7 +6,7 @@ use futures::future::select_all;
 pub enum Cmd {
     Ping,
     Echo(String),
-    Select(u64), // Changed from u16 to u64
+    Select(u64, Option<String>), // db_index, optional_key
     Get(String),
     Set(String, String),
     SetPx(String, String, u128),
@@ -98,11 +98,18 @@ impl Cmd {
                 Ok((
                     match cmd[0].to_lowercase().as_str() {
                         "select" => {
-                            if cmd.len() != 2 {
+                            if cmd.len() < 2 || cmd.len() > 4 {
                                 return Err(DBError("wrong number of arguments for SELECT".to_string()));
                             }
                             let idx = cmd[1].parse::<u64>().map_err(|_| DBError("ERR DB index is not an integer".to_string()))?;
-                            Cmd::Select(idx)
+                            let key = if cmd.len() == 4 && cmd[2].to_lowercase() == "key" {
+                                Some(cmd[3].clone())
+                            } else if cmd.len() == 2 {
+                                None
+                            } else {
+                                return Err(DBError("ERR syntax error".to_string()));
+                            };
+                            Cmd::Select(idx, key)
                         }
                         "echo" => Cmd::Echo(cmd[1].clone()),
                         "ping" => Cmd::Ping,
@@ -642,7 +649,7 @@ impl Cmd {
         }
 
         match self {
-            Cmd::Select(db) => select_cmd(server, db).await,
+            Cmd::Select(db, key) => select_cmd(server, db, key).await,
             Cmd::Ping => Ok(Protocol::SimpleString("PONG".to_string())),
             Cmd::Echo(s) => Ok(Protocol::BulkString(s)),
             Cmd::Get(k) => get_cmd(server, &k).await,
@@ -736,7 +743,14 @@ impl Cmd {
     
     pub fn to_protocol(self) -> Protocol {
         match self {
-            Cmd::Select(db) => Protocol::Array(vec![Protocol::BulkString("select".to_string()), Protocol::BulkString(db.to_string())]),
+            Cmd::Select(db, key) => {
+                let mut arr = vec![Protocol::BulkString("select".to_string()), Protocol::BulkString(db.to_string())];
+                if let Some(k) = key {
+                    arr.push(Protocol::BulkString("key".to_string()));
+                    arr.push(Protocol::BulkString(k));
+                }
+                Protocol::Array(arr)
+            }
             Cmd::Ping => Protocol::Array(vec![Protocol::BulkString("ping".to_string())]),
             Cmd::Echo(s) => Protocol::Array(vec![Protocol::BulkString("echo".to_string()), Protocol::BulkString(s)]),
             Cmd::Get(k) => Protocol::Array(vec![Protocol::BulkString("get".to_string()), Protocol::BulkString(k)]),
@@ -753,9 +767,65 @@ async fn flushdb_cmd(server: &mut Server) -> Result<Protocol, DBError> {
     }
 }
 
-async fn select_cmd(server: &mut Server, db: u64) -> Result<Protocol, DBError> {
-    // Test if we can access the database (this will create it if needed)
+async fn select_cmd(server: &mut Server, db: u64, key: Option<String>) -> Result<Protocol, DBError> {
+    // Authorization and existence checks via admin DB 0
+    // DB 0: require KEY admin-secret
+    if db == 0 {
+        match key {
+            Some(k) if k == server.option.admin_secret => {
+                server.selected_db = 0;
+                server.current_permissions = Some(crate::rpc::Permissions::ReadWrite);
+                // Will create encrypted 0.db if missing
+                match server.current_storage() {
+                    Ok(_) => return Ok(Protocol::SimpleString("OK".to_string())),
+                    Err(e) => return Ok(Protocol::err(&e.0)),
+                }
+            }
+            _ => {
+                return Ok(Protocol::err("ERR invalid access key"));
+            }
+        }
+    }
+
+    // DB > 0: must exist in admin:dbs
+    let exists = match crate::admin_meta::db_exists(
+        &server.option.dir,
+        server.option.backend.clone(),
+        &server.option.admin_secret,
+        db,
+    ) {
+        Ok(b) => b,
+        Err(e) => return Ok(Protocol::err(&e.0)),
+    };
+
+    if !exists {
+        return Ok(Protocol::err(&format!(
+            "Cannot open database instance {}, as that database instance does not exist.",
+            db
+        )));
+    }
+
+    // Verify permissions (public => RW; private => use key)
+    let perms_opt = match crate::admin_meta::verify_access(
+        &server.option.dir,
+        server.option.backend.clone(),
+        &server.option.admin_secret,
+        db,
+        key.as_deref(),
+    ) {
+        Ok(p) => p,
+        Err(e) => return Ok(Protocol::err(&e.0)),
+    };
+
+    let perms = match perms_opt {
+        Some(p) => p,
+        None => return Ok(Protocol::err("ERR invalid access key")),
+    };
+
+    // Set selected database and permissions, then open storage
     server.selected_db = db;
+    server.current_permissions = Some(perms);
+
     match server.current_storage() {
         Ok(_) => Ok(Protocol::SimpleString("OK".to_string())),
         Err(e) => Ok(Protocol::err(&e.0)),
@@ -1003,6 +1073,9 @@ async fn brpop_cmd(server: &Server, keys: &[String], timeout_secs: f64) -> Resul
 }
 
 async fn lpush_cmd(server: &Server, key: &str, elements: &[String]) -> Result<Protocol, DBError> {
+    if !server.has_write_permission() {
+        return Ok(Protocol::err("ERR write permission denied"));
+    }
     match server.current_storage()?.lpush(key, elements.to_vec()) {
         Ok(len) => {
             // Attempt to deliver to any blocked BLPOP waiters
@@ -1134,6 +1207,9 @@ async fn type_cmd(server: &Server, k: &String) -> Result<Protocol, DBError> {
 }
 
 async fn del_cmd(server: &Server, k: &str) -> Result<Protocol, DBError> {
+    if !server.has_write_permission() {
+        return Ok(Protocol::err("ERR write permission denied"));
+    }
     server.current_storage()?.del(k.to_string())?;
     Ok(Protocol::SimpleString("1".to_string()))
 }
@@ -1159,6 +1235,9 @@ async fn set_px_cmd(
 }
 
 async fn set_cmd(server: &Server, k: &str, v: &str) -> Result<Protocol, DBError> {
+    if !server.has_write_permission() {
+        return Ok(Protocol::err("ERR write permission denied"));
+    }
     server.current_storage()?.set(k.to_string(), v.to_string())?;
     Ok(Protocol::SimpleString("OK".to_string()))
 }
@@ -1273,6 +1352,9 @@ async fn get_cmd(server: &Server, k: &str) -> Result<Protocol, DBError> {
 
 // Hash command implementations
 async fn hset_cmd(server: &Server, key: &str, pairs: &[(String, String)]) -> Result<Protocol, DBError> {
+    if !server.has_write_permission() {
+        return Ok(Protocol::err("ERR write permission denied"));
+    }
     let new_fields = server.current_storage()?.hset(key, pairs.to_vec())?;
     Ok(Protocol::SimpleString(new_fields.to_string()))
 }

src/lib.rs

@@ -4,7 +4,10 @@ pub mod crypto;
 pub mod error;
 pub mod options;
 pub mod protocol;
+pub mod rpc;
+pub mod rpc_server;
 pub mod server;
 pub mod storage;
 pub mod storage_trait;  // Add this
 pub mod storage_sled;   // Add this
+pub mod admin_meta;

src/main.rs

@@ -3,6 +3,7 @@
 use tokio::net::TcpListener;
 
 use herodb::server;
+use herodb::rpc_server;
 
 use clap::Parser;
 
@@ -22,18 +23,29 @@ struct Args {
     #[arg(long)]
     debug: bool,
 
-
-    /// Master encryption key for encrypted databases
+    /// Master encryption key for encrypted databases (deprecated; ignored for data DBs)
     #[arg(long)]
     encryption_key: Option<String>,
 
-    /// Encrypt the database
+    /// Encrypt the database (deprecated; ignored for data DBs)
     #[arg(long)]
     encrypt: bool,
 
+    /// Enable RPC management server
+    #[arg(long)]
+    enable_rpc: bool,
+
+    /// RPC server port (default: 8080)
+    #[arg(long, default_value = "8080")]
+    rpc_port: u16,
+
     /// Use the sled backend
     #[arg(long)]
     sled: bool,
+
+    /// Admin secret used to encrypt DB 0 and authorize admin access (required)
+    #[arg(long)]
+    admin_secret: String,
 }
 
 #[tokio::main]
@@ -48,9 +60,19 @@ async fn main() {
         .await
         .unwrap();
 
+    // deprecation warnings for legacy flags
+    if args.encrypt || args.encryption_key.is_some() {
+        eprintln!("warning: --encrypt and --encryption-key are deprecated and ignored for data DBs. Admin DB 0 is always encrypted with --admin-secret.");
+    }
+    // basic validation for admin secret
+    if args.admin_secret.trim().is_empty() {
+        eprintln!("error: --admin-secret must not be empty");
+        std::process::exit(2);
+    }
+
     // new DB option
     let option = herodb::options::DBOption {
-        dir: args.dir,
+        dir: args.dir.clone(),
         port,
         debug: args.debug,
         encryption_key: args.encryption_key,
@@ -60,14 +82,42 @@ async fn main() {
         } else {
             herodb::options::BackendType::Redb
         },
+        admin_secret: args.admin_secret.clone(),
     };
 
+    let backend = option.backend.clone();
+
+    // Bootstrap admin DB 0 before opening any server storage
+    if let Err(e) = herodb::admin_meta::ensure_bootstrap(&args.dir, backend.clone(), &args.admin_secret) {
+        eprintln!("Failed to bootstrap admin DB 0: {}", e.0);
+        std::process::exit(2);
+    }
+
     // new server
     let server = server::Server::new(option).await;
 
     // Add a small delay to ensure the port is ready
     tokio::time::sleep(std::time::Duration::from_millis(100)).await;
 
+    // Start RPC server if enabled
+    let rpc_handle = if args.enable_rpc {
+        let rpc_addr = format!("127.0.0.1:{}", args.rpc_port).parse().unwrap();
+        let base_dir = args.dir.clone();
+
+        match rpc_server::start_rpc_server(rpc_addr, base_dir, backend, args.admin_secret.clone()).await {
+            Ok(handle) => {
+                println!("RPC management server started on port {}", args.rpc_port);
+                Some(handle)
+            }
+            Err(e) => {
+                eprintln!("Failed to start RPC server: {}", e);
+                None
+            }
+        }
+    } else {
+        None
+    };
+
     // accept new connections
     loop {
         let stream = listener.accept().await;

src/options.rs

@@ -9,7 +9,11 @@ pub struct DBOption {
     pub dir: String,
     pub port: u16,
     pub debug: bool,
+    // Deprecated for data DBs; retained for backward-compat on CLI parsing
     pub encrypt: bool,
+    // Deprecated for data DBs; retained for backward-compat on CLI parsing
     pub encryption_key: Option<String>,
     pub backend: BackendType,
+    // New: required admin secret, used to encrypt DB 0 and authorize admin operations
+    pub admin_secret: String,
 }

src/rpc.rs

@@ -0,0 +1,572 @@
+use std::collections::HashMap;
+use std::sync::Arc;
+use tokio::sync::RwLock;
+use jsonrpsee::{core::RpcResult, proc_macros::rpc};
+use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
+
+use crate::server::Server;
+use crate::options::DBOption;
+use crate::admin_meta;
+
+/// Database backend types
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum BackendType {
+    Redb,
+    Sled,
+    // Future: InMemory, Custom(String)
+}
+
+/// Database configuration
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct DatabaseConfig {
+    pub name: Option<String>,
+    pub storage_path: Option<String>,
+    pub max_size: Option<u64>,
+    pub redis_version: Option<String>,
+}
+
+/// Database information returned by metadata queries
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct DatabaseInfo {
+    pub id: u64,
+    pub name: Option<String>,
+    pub backend: BackendType,
+    pub encrypted: bool,
+    pub redis_version: Option<String>,
+    pub storage_path: Option<String>,
+    pub size_on_disk: Option<u64>,
+    pub key_count: Option<u64>,
+    pub created_at: u64,
+    pub last_access: Option<u64>,
+}
+
+/// Access permissions for database keys
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub enum Permissions {
+    Read,
+    ReadWrite,
+}
+
+/// Access key information
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct AccessKey {
+    pub hash: String,
+    pub permissions: Permissions,
+    pub created_at: u64,
+}
+
+/// Database metadata containing access keys
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct DatabaseMeta {
+    pub public: bool,
+    pub keys: HashMap<String, AccessKey>,
+}
+
+/// Access key information returned by RPC
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct AccessKeyInfo {
+    pub hash: String,
+    pub permissions: Permissions,
+    pub created_at: u64,
+}
+
+/// Hash a plaintext key using SHA-256
+pub fn hash_key(key: &str) -> String {
+    let mut hasher = Sha256::new();
+    hasher.update(key.as_bytes());
+    format!("{:x}", hasher.finalize())
+}
+
+/// RPC trait for HeroDB management
+#[rpc(server, client, namespace = "herodb")]
+pub trait Rpc {
+    /// Create a new database with specified configuration
+    #[method(name = "createDatabase")]
+    async fn create_database(
+        &self,
+        backend: BackendType,
+        config: DatabaseConfig,
+        encryption_key: Option<String>,
+    ) -> RpcResult<u64>;
+
+    /// Set encryption for an existing database (write-only key)
+    #[method(name = "setEncryption")]
+    async fn set_encryption(&self, db_id: u64, encryption_key: String) -> RpcResult<bool>;
+
+    /// List all managed databases
+    #[method(name = "listDatabases")]
+    async fn list_databases(&self) -> RpcResult<Vec<DatabaseInfo>>;
+
+    /// Get detailed information about a specific database
+    #[method(name = "getDatabaseInfo")]
+    async fn get_database_info(&self, db_id: u64) -> RpcResult<DatabaseInfo>;
+
+    /// Delete a database
+    #[method(name = "deleteDatabase")]
+    async fn delete_database(&self, db_id: u64) -> RpcResult<bool>;
+
+    /// Get server statistics
+    #[method(name = "getServerStats")]
+    async fn get_server_stats(&self) -> RpcResult<HashMap<String, serde_json::Value>>;
+
+    /// Add an access key to a database
+    #[method(name = "addAccessKey")]
+    async fn add_access_key(&self, db_id: u64, key: String, permissions: String) -> RpcResult<bool>;
+
+    /// Delete an access key from a database
+    #[method(name = "deleteAccessKey")]
+    async fn delete_access_key(&self, db_id: u64, key_hash: String) -> RpcResult<bool>;
+
+    /// List all access keys for a database
+    #[method(name = "listAccessKeys")]
+    async fn list_access_keys(&self, db_id: u64) -> RpcResult<Vec<AccessKeyInfo>>;
+
+    /// Set database public/private status
+    #[method(name = "setDatabasePublic")]
+    async fn set_database_public(&self, db_id: u64, public: bool) -> RpcResult<bool>;
+}
+
+/// RPC Server implementation
+pub struct RpcServerImpl {
+    /// Base directory for database files
+    base_dir: String,
+    /// Managed database servers
+    servers: Arc<RwLock<HashMap<u64, Arc<Server>>>>,
+    /// Next unencrypted database ID to assign
+    next_unencrypted_id: Arc<RwLock<u64>>,
+    /// Next encrypted database ID to assign
+    next_encrypted_id: Arc<RwLock<u64>>,
+    /// Default backend type
+    backend: crate::options::BackendType,
+    /// Encryption keys for databases
+    encryption_keys: Arc<RwLock<HashMap<u64, Option<String>>>>,
+    /// Admin secret used to encrypt DB 0 and authorize admin access
+    admin_secret: String,
+}
+
+impl RpcServerImpl {
+    /// Create a new RPC server instance
+    pub fn new(base_dir: String, backend: crate::options::BackendType, admin_secret: String) -> Self {
+        Self {
+            base_dir,
+            servers: Arc::new(RwLock::new(HashMap::new())),
+            next_unencrypted_id: Arc::new(RwLock::new(0)),
+            next_encrypted_id: Arc::new(RwLock::new(10)),
+            backend,
+            encryption_keys: Arc::new(RwLock::new(HashMap::new())),
+            admin_secret,
+        }
+    }
+
+    /// Get or create a server instance for the given database ID
+    async fn get_or_create_server(&self, db_id: u64) -> Result<Arc<Server>, jsonrpsee::types::ErrorObjectOwned> {
+        // Check if server already exists
+        {
+            let servers = self.servers.read().await;
+            if let Some(server) = servers.get(&db_id) {
+                return Ok(server.clone());
+            }
+        }
+
+        // Validate existence via admin DB 0 (metadata), not filesystem presence
+        let exists = admin_meta::db_exists(&self.base_dir, self.backend.clone(), &self.admin_secret, db_id)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(-32000, e.0, None::<()>))?;
+        if !exists {
+            return Err(jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                format!("Database {} not found", db_id),
+                None::<()>
+            ));
+        }
+
+        // Create server instance with default options
+        let db_option = DBOption {
+            dir: self.base_dir.clone(),
+            port: 0, // Not used for RPC-managed databases
+            debug: false,
+            encryption_key: None,
+            encrypt: false,
+            backend: self.backend.clone(),
+            admin_secret: self.admin_secret.clone(),
+        };
+
+        let mut server = Server::new(db_option).await;
+
+        // Set the selected database to the db_id
+        server.selected_db = db_id;
+
+        // Lazily open/create physical storage according to admin meta (per-db encryption)
+        let _ = server.current_storage();
+
+        // Store the server
+        let mut servers = self.servers.write().await;
+        servers.insert(db_id, Arc::new(server.clone()));
+
+        Ok(Arc::new(server))
+    }
+
+    /// Discover existing database IDs from admin DB 0
+    async fn discover_databases(&self) -> Vec<u64> {
+        admin_meta::list_dbs(&self.base_dir, self.backend.clone(), &self.admin_secret)
+            .unwrap_or_default()
+    }
+
+    /// Get the next available database ID
+    async fn get_next_db_id(&self, is_encrypted: bool) -> u64 {
+        if is_encrypted {
+            let mut id = self.next_encrypted_id.write().await;
+            let current_id = *id;
+            *id += 1;
+            current_id
+        } else {
+            let mut id = self.next_unencrypted_id.write().await;
+            let current_id = *id;
+            *id += 1;
+            current_id
+        }
+    }
+
+    /// Load database metadata from file (static version)
+    pub async fn load_meta_static(base_dir: &str, db_id: u64) -> Result<DatabaseMeta, jsonrpsee::types::ErrorObjectOwned> {
+        let meta_path = std::path::PathBuf::from(base_dir).join(format!("{}_meta.json", db_id));
+
+        // If meta file doesn't exist, create and persist default
+        if !meta_path.exists() {
+            let default_meta = DatabaseMeta {
+                public: true,
+                keys: HashMap::new(),
+            };
+            // Persist default metadata to disk
+            Self::save_meta_static(base_dir, db_id, &default_meta).await?;
+            return Ok(default_meta);
+        }
+
+        // Read file as UTF-8 JSON
+        let json_str = std::fs::read_to_string(&meta_path)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                format!("Failed to read meta file: {}", e),
+                None::<()>
+            ))?;
+
+        serde_json::from_str(&json_str)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                format!("Failed to parse meta JSON: {}", e),
+                None::<()>
+            ))
+    }
+
+    /// Load database metadata from file
+    async fn load_meta(&self, db_id: u64) -> Result<DatabaseMeta, jsonrpsee::types::ErrorObjectOwned> {
+        let meta_path = std::path::PathBuf::from(&self.base_dir).join(format!("{}_meta.json", db_id));
+
+        // If meta file doesn't exist, create and persist default
+        if !meta_path.exists() {
+            let default_meta = DatabaseMeta {
+                public: true,
+                keys: HashMap::new(),
+            };
+            self.save_meta(db_id, &default_meta).await?;
+            return Ok(default_meta);
+        }
+
+        // Read file as UTF-8 JSON (meta files are always plain JSON)
+        let json_str = std::fs::read_to_string(&meta_path)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                format!("Failed to read meta file: {}", e),
+                None::<()>
+            ))?;
+
+        serde_json::from_str(&json_str)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                format!("Failed to parse meta JSON: {}", e),
+                None::<()>
+            ))
+    }
+
+    /// Save database metadata to file (static version)
+    pub async fn save_meta_static(base_dir: &str, db_id: u64, meta: &DatabaseMeta) -> Result<(), jsonrpsee::types::ErrorObjectOwned> {
+        let meta_path = std::path::PathBuf::from(base_dir).join(format!("{}_meta.json", db_id));
+
+        let json_str = serde_json::to_string_pretty(meta)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                format!("Failed to serialize meta: {}", e),
+                None::<()>
+            ))?;
+
+        std::fs::write(&meta_path, json_str)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                format!("Failed to write meta file: {}", e),
+                None::<()>
+            ))?;
+
+        Ok(())
+    }
+
+    /// Save database metadata to file
+    async fn save_meta(&self, db_id: u64, meta: &DatabaseMeta) -> Result<(), jsonrpsee::types::ErrorObjectOwned> {
+        let meta_path = std::path::PathBuf::from(&self.base_dir).join(format!("{}_meta.json", db_id));
+
+        let json_str = serde_json::to_string_pretty(meta)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                format!("Failed to serialize meta: {}", e),
+                None::<()>
+            ))?;
+
+        // Meta files are always stored as plain JSON (even when data DB is encrypted)
+        std::fs::write(&meta_path, json_str)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                format!("Failed to write meta file: {}", e),
+                None::<()>
+            ))?;
+
+        Ok(())
+    }
+
+    /// Build database file path for given server/db_id
+    fn db_file_path(&self, server: &Server, db_id: u64) -> std::path::PathBuf {
+        std::path::PathBuf::from(&server.option.dir).join(format!("{}.db", db_id))
+    }
+
+    /// Recursively compute size on disk for the database path
+    fn compute_size_on_disk(&self, path: &std::path::Path) -> Option<u64> {
+        fn dir_size(p: &std::path::Path) -> u64 {
+            if p.is_file() {
+                std::fs::metadata(p).map(|m| m.len()).unwrap_or(0)
+            } else if p.is_dir() {
+                let mut total = 0u64;
+                if let Ok(read) = std::fs::read_dir(p) {
+                    for entry in read.flatten() {
+                        total += dir_size(&entry.path());
+                    }
+                }
+                total
+            } else {
+                0
+            }
+        }
+        Some(dir_size(path))
+    }
+
+    /// Extract created and last access times (secs) from a path, with fallbacks
+    fn get_file_times_secs(path: &std::path::Path) -> (u64, Option<u64>) {
+        let now = std::time::SystemTime::now();
+        let created = std::fs::metadata(path)
+            .and_then(|m| m.created().or_else(|_| m.modified()))
+            .unwrap_or(now)
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_secs();
+
+        let last_access = std::fs::metadata(path)
+            .and_then(|m| m.accessed())
+            .ok()
+            .and_then(|t| t.duration_since(std::time::UNIX_EPOCH).ok().map(|d| d.as_secs()));
+
+        (created, last_access)
+    }
+
+    /// Compose a DatabaseInfo by probing storage, metadata and filesystem
+    async fn build_database_info(&self, db_id: u64, server: &Server) -> DatabaseInfo {
+        // Probe storage to determine encryption state
+        let storage = server.current_storage().ok();
+        let encrypted = storage.as_ref().map(|s| s.is_encrypted()).unwrap_or(server.option.encrypt);
+
+        // Load meta to get access key count
+        let meta = Self::load_meta_static(&self.base_dir, db_id).await.unwrap_or(DatabaseMeta {
+            public: true,
+            keys: HashMap::new(),
+        });
+        let key_count = Some(meta.keys.len() as u64);
+
+        // Compute size on disk and timestamps
+        let db_path = self.db_file_path(server, db_id);
+        let size_on_disk = self.compute_size_on_disk(&db_path);
+
+        let meta_path = std::path::PathBuf::from(&self.base_dir).join(format!("{}_meta.json", db_id));
+        let (created_at, last_access) = if meta_path.exists() {
+            Self::get_file_times_secs(&meta_path)
+        } else {
+            Self::get_file_times_secs(&db_path)
+        };
+
+        let backend = match server.option.backend {
+            crate::options::BackendType::Redb => BackendType::Redb,
+            crate::options::BackendType::Sled => BackendType::Sled,
+        };
+
+        DatabaseInfo {
+            id: db_id,
+            name: None,
+            backend,
+            encrypted,
+            redis_version: Some("7.0".to_string()),
+            storage_path: Some(server.option.dir.clone()),
+            size_on_disk,
+            key_count,
+            created_at,
+            last_access,
+        }
+    }
+}
+
+#[jsonrpsee::core::async_trait]
+impl RpcServer for RpcServerImpl {
+    async fn create_database(
+        &self,
+        backend: BackendType,
+        _config: DatabaseConfig,
+        encryption_key: Option<String>,
+    ) -> RpcResult<u64> {
+        // Allocate new ID via admin DB 0
+        let db_id = admin_meta::allocate_next_id(&self.base_dir, self.backend.clone(), &self.admin_secret)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(-32000, e.0, None::<()>))?;
+
+        // Persist per-db encryption key in admin DB 0 if provided
+        if let Some(ref key) = encryption_key {
+            admin_meta::set_enc_key(&self.base_dir, self.backend.clone(), &self.admin_secret, db_id, key)
+                .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(-32000, e.0, None::<()>))?;
+        }
+
+        // Ensure base dir exists
+        if let Err(e) = std::fs::create_dir_all(&self.base_dir) {
+            return Err(jsonrpsee::types::ErrorObjectOwned::owned(-32000, format!("Failed to ensure base dir: {}", e), None::<()>));
+        }
+
+        // Create server instance using base_dir and admin secret
+        let option = DBOption {
+            dir: self.base_dir.clone(),
+            port: 0, // Not used for RPC-managed databases
+            debug: false,
+            encryption_key: None,  // per-db key is stored in admin DB 0
+            encrypt: false,        // encryption decided per-db at open time
+            backend: match backend {
+                BackendType::Redb => crate::options::BackendType::Redb,
+                BackendType::Sled => crate::options::BackendType::Sled,
+            },
+            admin_secret: self.admin_secret.clone(),
+        };
+
+        let mut server = Server::new(option).await;
+        server.selected_db = db_id;
+
+        // Initialize storage to create physical <id>.db with proper encryption from admin meta
+        let _ = server.current_storage();
+
+        // Store the server in cache
+        let mut servers = self.servers.write().await;
+        servers.insert(db_id, Arc::new(server));
+
+        Ok(db_id)
+    }
+
+    async fn set_encryption(&self, db_id: u64, _encryption_key: String) -> RpcResult<bool> {
+        // For now, return false as encryption can only be set during creation
+        let _servers = self.servers.read().await;
+        // TODO: Implement encryption setting for existing databases
+        Ok(false)
+    }
+
+    async fn list_databases(&self) -> RpcResult<Vec<DatabaseInfo>> {
+        let db_ids = self.discover_databases().await;
+        let mut result = Vec::new();
+
+        for db_id in db_ids {
+            if let Ok(server) = self.get_or_create_server(db_id).await {
+                // Build accurate info from storage/meta/fs
+                let info = self.build_database_info(db_id, &server).await;
+                result.push(info);
+            }
+        }
+
+        Ok(result)
+    }
+
+    async fn get_database_info(&self, db_id: u64) -> RpcResult<DatabaseInfo> {
+        let server = self.get_or_create_server(db_id).await?;
+        // Build accurate info from storage/meta/fs
+        let info = self.build_database_info(db_id, &server).await;
+        Ok(info)
+    }
+
+    async fn delete_database(&self, db_id: u64) -> RpcResult<bool> {
+        let mut servers = self.servers.write().await;
+
+        if let Some(_server) = servers.remove(&db_id) {
+            // Clean up database files
+            let db_path = std::path::PathBuf::from(&self.base_dir).join(format!("{}.db", db_id));
+            if db_path.exists() {
+                if db_path.is_dir() {
+                    std::fs::remove_dir_all(&db_path).ok();
+                } else {
+                    std::fs::remove_file(&db_path).ok();
+                }
+            }
+            Ok(true)
+        } else {
+            Ok(false)
+        }
+    }
+
+    async fn get_server_stats(&self) -> RpcResult<HashMap<String, serde_json::Value>> {
+        let db_ids = self.discover_databases().await;
+        let mut stats = HashMap::new();
+
+        stats.insert("total_databases".to_string(), serde_json::json!(db_ids.len()));
+        stats.insert("uptime".to_string(), serde_json::json!(
+            std::time::SystemTime::now()
+                .duration_since(std::time::UNIX_EPOCH)
+                .unwrap()
+                .as_secs()
+        ));
+
+        Ok(stats)
+    }
+
+    async fn add_access_key(&self, db_id: u64, key: String, permissions: String) -> RpcResult<bool> {
+        let perms = match permissions.to_lowercase().as_str() {
+            "read" => Permissions::Read,
+            "readwrite" => Permissions::ReadWrite,
+            _ => return Err(jsonrpsee::types::ErrorObjectOwned::owned(
+                -32000,
+                "Invalid permissions: use 'read' or 'readwrite'",
+                None::<()>
+            )),
+        };
+
+        admin_meta::add_access_key(&self.base_dir, self.backend.clone(), &self.admin_secret, db_id, &key, perms)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(-32000, e.0, None::<()>))?;
+        Ok(true)
+    }
+
+    async fn delete_access_key(&self, db_id: u64, key_hash: String) -> RpcResult<bool> {
+        let ok = admin_meta::delete_access_key(&self.base_dir, self.backend.clone(), &self.admin_secret, db_id, &key_hash)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(-32000, e.0, None::<()>))?;
+        Ok(ok)
+    }
+
+    async fn list_access_keys(&self, db_id: u64) -> RpcResult<Vec<AccessKeyInfo>> {
+        let pairs = admin_meta::list_access_keys(&self.base_dir, self.backend.clone(), &self.admin_secret, db_id)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(-32000, e.0, None::<()>))?;
+        let keys: Vec<AccessKeyInfo> = pairs.into_iter().map(|(hash, perm, ts)| AccessKeyInfo {
+            hash,
+            permissions: perm,
+            created_at: ts,
+        }).collect();
+        Ok(keys)
+    }
+
+    async fn set_database_public(&self, db_id: u64, public: bool) -> RpcResult<bool> {
+        admin_meta::set_database_public(&self.base_dir, self.backend.clone(), &self.admin_secret, db_id, public)
+            .map_err(|e| jsonrpsee::types::ErrorObjectOwned::owned(-32000, e.0, None::<()>))?;
+        Ok(true)
+    }
+}

src/rpc_server.rs

@@ -0,0 +1,49 @@
+use std::net::SocketAddr;
+use jsonrpsee::server::{ServerBuilder, ServerHandle};
+use jsonrpsee::RpcModule;
+
+use crate::rpc::{RpcServer, RpcServerImpl};
+
+/// Start the RPC server on the specified address
+pub async fn start_rpc_server(addr: SocketAddr, base_dir: String, backend: crate::options::BackendType, admin_secret: String) -> Result<ServerHandle, Box<dyn std::error::Error + Send + Sync>> {
+    // Create the RPC server implementation
+    let rpc_impl = RpcServerImpl::new(base_dir, backend, admin_secret);
+
+    // Create the RPC module
+    let mut module = RpcModule::new(());
+    module.merge(RpcServer::into_rpc(rpc_impl))?;
+
+    // Build the server with both HTTP and WebSocket support
+    let server = ServerBuilder::default()
+        .build(addr)
+        .await?;
+
+    // Start the server
+    let handle = server.start(module);
+
+    println!("RPC server started on {}", addr);
+
+    Ok(handle)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::time::Duration;
+
+    #[tokio::test]
+    async fn test_rpc_server_startup() {
+        let addr = "127.0.0.1:0".parse().unwrap(); // Use port 0 for auto-assignment
+        let base_dir = "/tmp/test_rpc".to_string();
+        let backend = crate::options::BackendType::Redb; // Default for test
+
+        let handle = start_rpc_server(addr, base_dir, backend, "test-admin".to_string()).await.unwrap();
+
+        // Give the server a moment to start
+        tokio::time::sleep(Duration::from_millis(100)).await;
+
+        // Stop the server
+        handle.stop().unwrap();
+        handle.stopped().await;
+    }
+}

src/server.rs

@@ -11,9 +11,8 @@ use crate::cmd::Cmd;
 use crate::error::DBError;
 use crate::options;
 use crate::protocol::Protocol;
-use crate::storage::Storage;
-use crate::storage_sled::SledStorage;
 use crate::storage_trait::StorageBackend;
+use crate::admin_meta;
 
 #[derive(Clone)]
 pub struct Server {
@@ -22,6 +21,7 @@ pub struct Server {
     pub client_name: Option<String>,
     pub selected_db: u64, // Changed from usize to u64
     pub queued_cmd: Option<Vec<(Cmd, Protocol)>>,
+    pub current_permissions: Option<crate::rpc::Permissions>,
 
     // BLPOP waiter registry: per (db_index, key) FIFO of waiters
     pub list_waiters: Arc<Mutex<HashMap<u64, HashMap<String, Vec<Waiter>>>>>,
@@ -48,6 +48,7 @@ impl Server {
             client_name: None,
             selected_db: 0,
             queued_cmd: None,
+            current_permissions: None,
 
             list_waiters: Arc::new(Mutex::new(HashMap::new())),
             waiter_seq: Arc::new(AtomicU64::new(1)),
@@ -61,44 +62,37 @@ impl Server {
             return Ok(storage.clone());
         }
 
-        
-        // Create new database file
-        let db_file_path = std::path::PathBuf::from(self.option.dir.clone())
-            .join(format!("{}.db", self.selected_db));
-        
-        // Ensure the directory exists before creating the database file
-        if let Some(parent_dir) = db_file_path.parent() {
-            std::fs::create_dir_all(parent_dir).map_err(|e| {
-                DBError(format!("Failed to create directory {}: {}", parent_dir.display(), e))
-            })?;
-        }
-        
-        println!("Creating new db file: {}", db_file_path.display());
-        
-        let storage: Arc<dyn StorageBackend> = match self.option.backend {
-            options::BackendType::Redb => {
-                Arc::new(Storage::new(
-                    db_file_path,
-                    self.should_encrypt_db(self.selected_db),
-                    self.option.encryption_key.as_deref()
-                )?)
-            }
-            options::BackendType::Sled => {
-                Arc::new(SledStorage::new(
-                    db_file_path,
-                    self.should_encrypt_db(self.selected_db),
-                    self.option.encryption_key.as_deref()
-                )?)
-            }
+        // Use process-wide shared handles to avoid sled/reDB double-open lock contention.
+        let storage = if self.selected_db == 0 {
+            // Admin DB 0: always via singleton
+            admin_meta::open_admin_storage(
+                &self.option.dir,
+                self.option.backend.clone(),
+                &self.option.admin_secret,
+            )?
+        } else {
+            // Data DBs: via global registry keyed by id
+            admin_meta::open_data_storage(
+                &self.option.dir,
+                self.option.backend.clone(),
+                &self.option.admin_secret,
+                self.selected_db,
+            )?
         };
 
         cache.insert(self.selected_db, storage.clone());
         Ok(storage)
     }
     
-    fn should_encrypt_db(&self, db_index: u64) -> bool {
-        // DB 0-9 are non-encrypted, DB 10+ are encrypted
-        self.option.encrypt && db_index >= 10
+
+    /// Check if current permissions allow read operations
+    pub fn has_read_permission(&self) -> bool {
+        matches!(self.current_permissions, Some(crate::rpc::Permissions::Read) | Some(crate::rpc::Permissions::ReadWrite))
+    }
+
+    /// Check if current permissions allow write operations
+    pub fn has_write_permission(&self) -> bool {
+        matches!(self.current_permissions, Some(crate::rpc::Permissions::ReadWrite))
     }
 
     // ----- BLPOP waiter helpers -----

tests/debug_hset.rs

@@ -28,6 +28,7 @@ async fn debug_hset_simple() {
         encrypt: false,
         encryption_key: None,
         backend: herodb::options::BackendType::Redb,
+        admin_secret: "test-admin".to_string(),
     };
     
     let mut server = Server::new(option).await;
@@ -48,6 +49,12 @@ async fn debug_hset_simple() {
     sleep(Duration::from_millis(200)).await;
     
     let mut stream = TcpStream::connect(format!("127.0.0.1:{}", port)).await.unwrap();
+    // Acquire ReadWrite permissions on this connection
+    let resp = send_command(
+        &mut stream,
+        "*4\r\n$6\r\nSELECT\r\n$1\r\n0\r\n$3\r\nKEY\r\n$10\r\ntest-admin\r\n",
+    ).await;
+    assert!(resp.contains("OK"), "Failed SELECT handshake: {}", resp);
     
     // Test simple HSET
     println!("Testing HSET...");

tests/debug_hset_simple.rs

@@ -19,6 +19,7 @@ async fn debug_hset_return_value() {
         encrypt: false,
         encryption_key: None,
         backend: herodb::options::BackendType::Redb,
+        admin_secret: "test-admin".to_string(),
     };
     
     let mut server = Server::new(option).await;
@@ -41,11 +42,18 @@ async fn debug_hset_return_value() {
     // Connect and test HSET
     let mut stream = TcpStream::connect("127.0.0.1:16390").await.unwrap();
 
+    // Acquire ReadWrite permissions for this new connection
+    let handshake = "*4\r\n$6\r\nSELECT\r\n$1\r\n0\r\n$3\r\nKEY\r\n$10\r\ntest-admin\r\n";
+    stream.write_all(handshake.as_bytes()).await.unwrap();
+    let mut buffer = [0; 1024];
+    let n = stream.read(&mut buffer).await.unwrap();
+    let resp = String::from_utf8_lossy(&buffer[..n]);
+    assert!(resp.contains("OK"), "Failed SELECT handshake: {}", resp);
+    
     // Send HSET command
     let cmd = "*4\r\n$4\r\nHSET\r\n$4\r\nhash\r\n$6\r\nfield1\r\n$6\r\nvalue1\r\n";
     stream.write_all(cmd.as_bytes()).await.unwrap();
     
-    let mut buffer = [0; 1024];
     let n = stream.read(&mut buffer).await.unwrap();
     let response = String::from_utf8_lossy(&buffer[..n]);
     

tests/redis_integration_tests.rs

@@ -12,7 +12,15 @@ fn get_redis_connection(port: u16) -> Connection {
         match client.get_connection() {
             Ok(mut conn) => {
                 if redis::cmd("PING").query::<String>(&mut conn).is_ok() {
-                    return conn;
+                    // Acquire ReadWrite permissions on this connection
+                    let sel: RedisResult<String> = redis::cmd("SELECT")
+                        .arg(0)
+                        .arg("KEY")
+                        .arg("test-admin")
+                        .query(&mut conn);
+                    if sel.is_ok() {
+                        return conn;
+                    }
                 }
             }
             Err(e) => {
@@ -78,6 +86,8 @@ fn setup_server() -> (ServerProcessGuard, u16) {
             "--port",
             &port.to_string(),
             "--debug",
+            "--admin-secret",
+            "test-admin",
         ])
         .spawn()
         .expect("Failed to start server process");

tests/redis_tests.rs

@@ -23,18 +23,29 @@ async fn start_test_server(test_name: &str) -> (Server, u16) {
         encrypt: false,
         encryption_key: None,
         backend: herodb::options::BackendType::Redb,
+        admin_secret: "test-admin".to_string(),
     };
     
     let server = Server::new(option).await;
     (server, port)
 }
 
-// Helper function to connect to the test server
+ // Helper function to connect to the test server
 async fn connect_to_server(port: u16) -> TcpStream {
     let mut attempts = 0;
     loop {
         match TcpStream::connect(format!("127.0.0.1:{}", port)).await {
-            Ok(stream) => return stream,
+            Ok(mut stream) => {
+                // Obtain ReadWrite permissions for this connection by selecting DB 0 with admin key
+                let resp = send_command(
+                    &mut stream,
+                    "*4\r\n$6\r\nSELECT\r\n$1\r\n0\r\n$3\r\nKEY\r\n$10\r\ntest-admin\r\n",
+                ).await;
+                if !resp.contains("OK") {
+                    panic!("Failed to acquire write permissions via SELECT 0 KEY test-admin: {}", resp);
+                }
+                return stream;
+            }
             Err(_) if attempts < 10 => {
                 attempts += 1;
                 sleep(Duration::from_millis(100)).await;

tests/rpc_tests.rs

@@ -0,0 +1,62 @@
+use std::net::SocketAddr;
+use jsonrpsee::http_client::HttpClientBuilder;
+use jsonrpsee::core::client::ClientT;
+use serde_json::json;
+
+use herodb::rpc::{RpcClient, BackendType, DatabaseConfig};
+
+#[tokio::test]
+async fn test_rpc_server_basic() {
+    // This test would require starting the RPC server in a separate thread
+    // For now, we'll just test that the types compile correctly
+
+    // Test serialization of types
+    let backend = BackendType::Redb;
+    let config = DatabaseConfig {
+        name: Some("test_db".to_string()),
+        storage_path: Some("/tmp/test".to_string()),
+        max_size: Some(1024 * 1024),
+        redis_version: Some("7.0".to_string()),
+    };
+
+    let backend_json = serde_json::to_string(&backend).unwrap();
+    let config_json = serde_json::to_string(&config).unwrap();
+
+    assert_eq!(backend_json, "\"Redb\"");
+    assert!(config_json.contains("test_db"));
+}
+
+#[tokio::test]
+async fn test_database_config_serialization() {
+    let config = DatabaseConfig {
+        name: Some("my_db".to_string()),
+        storage_path: None,
+        max_size: Some(1000000),
+        redis_version: Some("7.0".to_string()),
+    };
+
+    let json = serde_json::to_value(&config).unwrap();
+    assert_eq!(json["name"], "my_db");
+    assert_eq!(json["max_size"], 1000000);
+    assert_eq!(json["redis_version"], "7.0");
+}
+
+#[tokio::test]
+async fn test_backend_type_serialization() {
+    // Test that both Redb and Sled backends serialize correctly
+    let redb_backend = BackendType::Redb;
+    let sled_backend = BackendType::Sled;
+
+    let redb_json = serde_json::to_string(&redb_backend).unwrap();
+    let sled_json = serde_json::to_string(&sled_backend).unwrap();
+
+    assert_eq!(redb_json, "\"Redb\"");
+    assert_eq!(sled_json, "\"Sled\"");
+
+    // Test deserialization
+    let redb_deserialized: BackendType = serde_json::from_str(&redb_json).unwrap();
+    let sled_deserialized: BackendType = serde_json::from_str(&sled_json).unwrap();
+
+    assert!(matches!(redb_deserialized, BackendType::Redb));
+    assert!(matches!(sled_deserialized, BackendType::Sled));
+}

tests/simple_integration_test.rs

@@ -25,6 +25,7 @@ async fn start_test_server(test_name: &str) -> (Server, u16) {
         encrypt: false,
         encryption_key: None,
         backend: herodb::options::BackendType::Redb,
+        admin_secret: "test-admin".to_string(),
     };
     
     let server = Server::new(option).await;
@@ -34,9 +35,16 @@ async fn start_test_server(test_name: &str) -> (Server, u16) {
 // Helper function to send Redis command and get response
 async fn send_redis_command(port: u16, command: &str) -> String {
     let mut stream = TcpStream::connect(format!("127.0.0.1:{}", port)).await.unwrap();
+    
+    // Acquire ReadWrite permissions on this new connection
+    let handshake = "*4\r\n$6\r\nSELECT\r\n$1\r\n0\r\n$3\r\nKEY\r\n$10\r\ntest-admin\r\n";
+    stream.write_all(handshake.as_bytes()).await.unwrap();
+    let mut buffer = [0; 1024];
+    let _ = stream.read(&mut buffer).await.unwrap(); // Read and ignore the OK for handshake
+    
+    // Now send the intended command
     stream.write_all(command.as_bytes()).await.unwrap();
     
-    let mut buffer = [0; 1024];
     let n = stream.read(&mut buffer).await.unwrap();
     String::from_utf8_lossy(&buffer[..n]).to_string()
 }
@@ -184,12 +192,19 @@ async fn test_transaction_operations() {
     
     sleep(Duration::from_millis(100)).await;
     
-    // Use a single connection for the transaction
+     // Use a single connection for the transaction
     let mut stream = TcpStream::connect(format!("127.0.0.1:{}", port)).await.unwrap();
     
+    // Acquire write permissions for this connection
+    let handshake = "*4\r\n$6\r\nSELECT\r\n$1\r\n0\r\n$3\r\nKEY\r\n$10\r\ntest-admin\r\n";
+    stream.write_all(handshake.as_bytes()).await.unwrap();
+    let mut buffer = [0; 1024];
+    let n = stream.read(&mut buffer).await.unwrap();
+    let resp = String::from_utf8_lossy(&buffer[..n]);
+    assert!(resp.contains("OK"));
+    
     // Test MULTI
     stream.write_all("*1\r\n$5\r\nMULTI\r\n".as_bytes()).await.unwrap();
-    let mut buffer = [0; 1024];
     let n = stream.read(&mut buffer).await.unwrap();
     let response = String::from_utf8_lossy(&buffer[..n]);
     assert!(response.contains("OK"));

tests/simple_redis_test.rs

@@ -23,6 +23,7 @@ async fn start_test_server(test_name: &str) -> (Server, u16) {
         encrypt: false,
         encryption_key: None,
         backend: herodb::options::BackendType::Redb,
+        admin_secret: "test-admin".to_string(),
     };
     
     let server = Server::new(option).await;
@@ -38,12 +39,22 @@ async fn send_command(stream: &mut TcpStream, command: &str) -> String {
     String::from_utf8_lossy(&buffer[..n]).to_string()
 }
 
-// Helper function to connect to the test server
+ // Helper function to connect to the test server
 async fn connect_to_server(port: u16) -> TcpStream {
     let mut attempts = 0;
     loop {
         match TcpStream::connect(format!("127.0.0.1:{}", port)).await {
-            Ok(stream) => return stream,
+            Ok(mut stream) => {
+                // Acquire ReadWrite permissions for this connection
+                let resp = send_command(
+                    &mut stream,
+                    "*4\r\n$6\r\nSELECT\r\n$1\r\n0\r\n$3\r\nKEY\r\n$10\r\ntest-admin\r\n",
+                ).await;
+                if !resp.contains("OK") {
+                    panic!("Failed to acquire write permissions via SELECT 0 KEY test-admin: {}", resp);
+                }
+                return stream;
+            }
             Err(_) if attempts < 10 => {
                 attempts += 1;
                 sleep(Duration::from_millis(100)).await;
@@ -98,13 +109,20 @@ async fn test_hset_clean_db() {
     
     let mut stream = connect_to_server(port).await;
 
-    // Test HSET - should return 1 for new field
-    let response = send_command(&mut stream, "*4\r\n$4\r\nHSET\r\n$4\r\nhash\r\n$6\r\nfield1\r\n$6\r\nvalue1\r\n").await;
+    // Ensure clean DB state (admin DB 0 may be shared due to global singleton)
+    let flush = send_command(&mut stream, "*1\r\n$7\r\nFLUSHDB\r\n").await;
+    assert!(flush.contains("OK"), "Failed to FLUSHDB: {}", flush);
+
+    // Test HSET - should return 1 for new field (use a unique key name to avoid collisions)
+    let key = "hash_clean";
+    let hset_cmd = format!("*4\r\n$4\r\nHSET\r\n${}\r\n{}\r\n$6\r\nfield1\r\n$6\r\nvalue1\r\n", key.len(), key);
+    let response = send_command(&mut stream, &hset_cmd).await;
     println!("HSET response: {}", response);
     assert!(response.contains("1"), "Expected HSET to return 1, got: {}", response);
     
     // Test HGET
-    let response = send_command(&mut stream, "*3\r\n$4\r\nHGET\r\n$4\r\nhash\r\n$6\r\nfield1\r\n").await;
+    let hget_cmd = format!("*3\r\n$4\r\nHGET\r\n${}\r\n{}\r\n$6\r\nfield1\r\n", key.len(), key);
+    let response = send_command(&mut stream, &hget_cmd).await;
     println!("HGET response: {}", response);
     assert!(response.contains("value1"));
 }

tests/usage_suite.rs

@@ -23,6 +23,7 @@ async fn start_test_server(test_name: &str) -> (Server, u16) {
         encrypt: false,
         encryption_key: None,
         backend: herodb::options::BackendType::Redb,
+        admin_secret: "test-admin".to_string(),
     };
 
     let server = Server::new(option).await;
@@ -61,7 +62,17 @@ async fn connect(port: u16) -> TcpStream {
     let mut attempts = 0;
     loop {
         match TcpStream::connect(format!("127.0.0.1:{}", port)).await {
-            Ok(s) => return s,
+            Ok(mut s) => {
+                // Acquire ReadWrite permissions for this connection using admin DB 0
+                let resp = send_cmd(&mut s, &["SELECT", "0", "KEY", "test-admin"]).await;
+                assert_contains(&resp, "OK", "SELECT 0 KEY test-admin handshake");
+
+                // Ensure clean slate per test on DB 0
+                let fl = send_cmd(&mut s, &["FLUSHDB"]).await;
+                assert_contains(&fl, "OK", "FLUSHDB after handshake");
+
+                return s;
+            }
             Err(_) if attempts < 30 => {
                 attempts += 1;
                 sleep(Duration::from_millis(100)).await;
@@ -246,9 +257,9 @@ async fn test_01_connection_and_info() {
     let getname = send_cmd(&mut s, &["CLIENT", "GETNAME"]).await;
     assert_contains(&getname, "myapp", "CLIENT GETNAME");
 
-    // SELECT db
-    let sel = send_cmd(&mut s, &["SELECT", "0"]).await;
-    assert_contains(&sel, "OK", "SELECT 0");
+    // SELECT db (requires key on DB 0)
+    let sel = send_cmd(&mut s, &["SELECT", "0", "KEY", "test-admin"]).await;
+    assert_contains(&sel, "OK", "SELECT 0 with key");
 
     // QUIT should close connection after sending OK
     let quit = send_cmd(&mut s, &["QUIT"]).await;