Pretty much that

src/commands/postgres/tunnel.ts

@@ -2,6 +2,44 @@ import {Command, Flags} from '@oclif/core'
 import {getDisco} from '../../config.js'
 import {request} from '../../auth-request.js'
 import {createTunnel} from 'tunnel-ssh'
+import {AddressInfo, createServer} from 'node:net'
+
+async function portIsAvailable(port: number): Promise<boolean> {
+  const isAvailable = await new Promise<boolean>((resolve) => {
+    const server = createServer()
+    server.once('error', (err: {code: string}) => {
+      if (err.code === 'EADDRINUSE') {
+        resolve(false) // not available
+      }
+    })
+
+    server.once('listening', () => {
+      // close the server if listening doesn't fail
+      server.close()
+      resolve(true)
+    })
+
+    server.listen(port)
+  })
+
+  return isAvailable
+}
+
+async function localPort(portFlag: number | undefined): Promise<number | undefined> {
+  if (portFlag === undefined) {
+    const portInUse = !(await portIsAvailable(5432))
+    if (portInUse) {
+      // port in use, let OS pick another port
+      return undefined
+    } else {
+      // port available, use default Postgres port
+      return 5432
+    }
+  } else {
+    // port specified as CLI arg
+    return portFlag
+  }
+}
 
 export default class PostgresTunnel extends Command {
   static description = 'create a temporary tunnel to access Postgres through localhost'
@@ -12,11 +50,15 @@ export default class PostgresTunnel extends Command {
     disco: Flags.string({required: false}),
     project: Flags.string({required: true}),
     'env-var': Flags.string({required: false}),
+    port: Flags.integer({required: false}),
   }
 
   public async run(): Promise<void> {
     const {flags} = await this.parse(PostgresTunnel)
     const discoConfig = getDisco(flags.disco || null)
+    if (flags.port !== undefined && !(await portIsAvailable(flags.port))) {
+      this.error(`Port ${flags.port} already in use`)
+    }
 
     const dbInfoUrl = `https://${discoConfig.host}/api/projects/postgres-addon/cgi/endpoints/tunnels`
     const dbInfoResponse = await request({
@@ -47,8 +89,6 @@ export default class PostgresTunnel extends Command {
     })
     const respBody = (await res.json()) as {tunnel: {host: string; password: string; port: number}}
     const tunnelPort = respBody.tunnel.port
-    const connString = `postgresql://${dbInfo.user}:${dbInfo.password}@localhost/${dbInfo.database}`
-
     const sshOptions = {
       host: discoConfig.host,
       port: respBody.tunnel.port,
@@ -62,16 +102,30 @@ export default class PostgresTunnel extends Command {
     }
 
     const tunnelOptions = {
-      autoClose: true,
+      // do not close tunnel when third party app disconnects
+      autoClose: false, 
     }
 
     const serverOptions = {
       host: 'localhost',
-      port: 5432,
+      port: await localPort(flags.port),
     }
 
-    const [_, tunnelClient] = await createTunnel(tunnelOptions, serverOptions, sshOptions, forwardOptions)
+    // check again now that sshd container is ready
+    if (flags.port !== undefined && !(await portIsAvailable(flags.port))) {
+      this.error(`Port ${flags.port} already in use`)
+    }
+
+    const [tunnelServer, tunnelClient] = await createTunnel(tunnelOptions, serverOptions, sshOptions, forwardOptions)
+    tunnelServer.on('connection', (socket) => {
+      socket.on('error', () => {
+        // swallow error
+        // instead of crashing on errors like ECONNRESET
+      })
+    })
     this.log('Tunnel created. Connection string:')
+    const {port} = tunnelServer.address() as AddressInfo
+    const connString = `postgresql://${dbInfo.user}:${dbInfo.password}@localhost:${port}/${dbInfo.database}`
     this.log(connString)
     const extendInterval = setInterval(async () => {
       await request({