fix(connection): improve connection management

- resolve the creation of two connections. The dynamic import of the connection modules delayed the initialization of the SQLiteCloudConnection object. Between the initialization of the Database object and the call to sql() method, the connection was not yet initialized
- connection to the database and the commands are put in queue to ensure the connection to be ready (the socket connection is a background operation)
- remove the implicit connection to the database in the sql() methods. We want the user be aware of the status of the connection (eg, due to open transactions)
- enable TCP keep alive to be notified of the most of the cases of errors on the TCP socket

Author: Daniele Briggi

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@sqlitecloud/drivers",
-  "version": "1.0.417",
+  "version": "1.0.421",
   "description": "SQLiteCloud drivers for Typescript/Javascript in edge, web and node clients",
   "main": "./lib/index.js",
   "types": "./lib/index.d.ts",

package.json

@@ -2,21 +2,21 @@
  * connection-tls.ts - connection via tls socket and sqlitecloud protocol
  */
 
-import { type SQLiteCloudConfig, SQLiteCloudError, type ErrorCallback, type ResultsCallback, SQLiteCloudCommand } from './types'
 import { SQLiteCloudConnection } from './connection'
-import { getInitializationCommands } from './utilities'
 import {
+  bufferEndsWith,
+  CMD_COMPRESSED,
+  CMD_ROWSET_CHUNK,
+  decompressBuffer,
   formatCommand,
   hasCommandLength,
   parseCommandLength,
-  popData,
-  decompressBuffer,
   parseRowsetChunks,
-  CMD_COMPRESSED,
-  CMD_ROWSET_CHUNK,
-  bufferEndsWith,
+  popData,
   ROWSET_CHUNKS_END
 } from './protocol'
+import { type ErrorCallback, type ResultsCallback, SQLiteCloudCommand, type SQLiteCloudConfig, SQLiteCloudError } from './types'
+import { getInitializationCommands } from './utilities'
 
 // explicitly importing buffer library to allow cross-platform support by replacing it
 import { Buffer } from 'buffer'
@@ -77,6 +77,10 @@ export class SQLiteCloudTlsConnection extends SQLiteCloudConnection {
         callback?.call(this, error)
       })
     })
+    this.socket.setKeepAlive(true)
+    // disable Nagle algorithm because we want our writes to be sent ASAP
+    // https://brooker.co.za/blog/2024/05/09/nagle.html
+    this.socket.setNoDelay(true)
 
     this.socket.on('data', data => {
       this.processCommandsData(data)
@@ -97,6 +101,11 @@ export class SQLiteCloudTlsConnection extends SQLiteCloudConnection {
       this.processCommandsFinish(new SQLiteCloudError('Connection closed', { errorCode: 'ERR_CONNECTION_CLOSED' }))
     })
 
+    this.socket.on('timeout', () => {
+      this.close()
+      this.processCommandsFinish(new SQLiteCloudError('Connection ened due to timeout', { errorCode: 'ERR_CONNECTION_TIMEOUT' }))
+    })
+
     return this
   }
 
@@ -241,7 +250,7 @@ export class SQLiteCloudTlsConnection extends SQLiteCloudConnection {
   }
 
   /** Disconnect immediately, release connection, no events. */
-  close(): this {
+  public close(): this {
     if (this.socket) {
       this.socket.removeAllListeners()
       this.socket.destroy()

src/drivers/connection-tls.ts

@@ -2,10 +2,10 @@
  * transport-ws.ts - handles low level communication with sqlitecloud server via socket.io websocket
  */
 
-import { SQLiteCloudConfig, SQLiteCloudError, ErrorCallback, ResultsCallback, SQLiteCloudCommand, SQLiteCloudDataTypes } from './types'
-import { SQLiteCloudRowset } from './rowset'
-import { SQLiteCloudConnection } from './connection'
 import { io, Socket } from 'socket.io-client'
+import { SQLiteCloudConnection } from './connection'
+import { SQLiteCloudRowset } from './rowset'
+import { ErrorCallback, ResultsCallback, SQLiteCloudCommand, SQLiteCloudConfig, SQLiteCloudError } from './types'
 
 /**
  * Implementation of TransportConnection that connects to the database indirectly
@@ -19,7 +19,7 @@ export class SQLiteCloudWebsocketConnection extends SQLiteCloudConnection {
 
   /** True if connection is open */
   get connected(): boolean {
-    return !!this.socket
+    return !!(this.socket && this.socket?.connected)
   }
 
   /* Opens a connection with the server and sends the initialization commands. Will throw in case of errors. */
@@ -32,11 +32,25 @@ export class SQLiteCloudWebsocketConnection extends SQLiteCloudConnection {
         const connectionstring = this.config.connectionstring as string
         const gatewayUrl = this.config?.gatewayurl || `${this.config.host === 'localhost' ? 'ws' : 'wss'}://${this.config.host as string}:4000`
         this.socket = io(gatewayUrl, { auth: { token: connectionstring } })
+        
+        this.socket.on('connect', () => {
+          callback?.call(this, null)
+        })
+
+        this.socket.on('disconnect', (reason) => {
+          this.close()
+          callback?.call(this, new SQLiteCloudError('Disconnected', { errorCode: 'ERR_CONNECTION_DISCONNECTED', cause: reason }))
+        })
+
+        this.socket.on('error', (error: Error) => {
+          this.close()
+          callback?.call(this, new SQLiteCloudError('Connection error', { errorCode: 'ERR_CONNECTION_ERROR', cause: error }))
+        })        
       }
-      callback?.call(this, null)
     } catch (error) {
       callback?.call(this, error as Error)
     }
+
     return this
   }
 
@@ -78,11 +92,12 @@ export class SQLiteCloudWebsocketConnection extends SQLiteCloudConnection {
   public close(): this {
     console.assert(this.socket !== null, 'SQLiteCloudWebsocketConnection.close - connection already closed')
     if (this.socket) {
+      this.socket?.removeAllListeners()
       this.socket?.close()
       this.socket = undefined
     }
+
     this.operations.clear()
-    this.socket = undefined
     return this
   }
 }