Connection Error crashing program

[dks-ait]

I am getting the similar issue as #1165 , while using the pg-cursor and pg. I am not using pool as I need only 2 connections. Any idea on how this can be solved. I am using pg@7.0.2 and pg-cursor@1.2.0

The error that I am getting is (after I have explicitly called cursor.end()) :-

Uncaught Error: Connection terminated unexpectedly at endReadableNT (_stream_readable.js:974:12) at _combinedTickCallback (internal/process/next_tick.js:80:11) at process._tickDomainCallback (internal/process/next_tick.js:128:9)

This happens when I catch the error in case of incorrect query being sent.

My code looks something like :-

      if (err) callback(err, null, null)
      state.client = client
      if (state.cursor == null) {
        var cursor = client.query(new Cursor(exp.rdbms.query, exp.rdbms.values))
        state.cursor = cursor
      }
      state.cursor.read(FETCH_SIZE, function (err, rows) {
        if (err) {
          // As I understand .end() is more like abort, while close
          // closes the connection amicably.
          state.cursor.end(function (err) {
            if (err) logger.error('Cursor ending failed :: ', err)
            delete state.cursor
            state.client.end(function (err) {
              if (err) logger.error('Connection ending failed:: ', err)
              delete state.client
            })
          })
          return callback(err)
        }
        if (!rows || rows.length === 0) {
          state.cursor.close(function (err) {
            if (err) logger.error('error closing cursor', err)
          })
          return callback()
        }
        state.rows = rows
        return callback()
      })
    })```

[dks-ait]

ON Debugging, I can further see the whole stack trace :-

    at Connection.con.once (/<mymodule>/node_modules/pg/lib/client.js:179:21)
    at Connection.g (events.js:291:16)
    at emitNone (events.js:86:13)
    at Connection.emit (events.js:185:7)
    at Socket.<anonymous> (/<mymodule>/node_modules/pg/lib/connection.js:123:10)
    at emitNone (events.js:91:20)
    at Socket.emit (events.js:185:7)
    at endReadableNT (_stream_readable.js:974:12)
    at _combinedTickCallback (internal/process/next_tick.js:80:11)
    at process._tickDomainCallback (internal/process/next_tick.js:128:9)

[eduardobcastro]

I'm getting this error also using Knex

2018-06-20T14:12:01.864502914Z ERROR Error: Connection terminated
2018-06-20T14:12:01.864555652Z     at Connection.con.once (/app/node_modules/pg/lib/client.js:170:29)
2018-06-20T14:12:01.864561989Z     at Object.onceWrapper (events.js:255:19)
2018-06-20T14:12:01.864565623Z     at Connection.emit (events.js:160:13)
2018-06-20T14:12:01.864648360Z     at Socket.<anonymous> (/app/node_modules/pg/lib/connection.js:76:10)
2018-06-20T14:12:01.864654860Z     at Socket.emit (events.js:160:13)
2018-06-20T14:12:01.864736064Z     at TCP._handle.close [as _onclose] (net.js:562:12)
2018-06-20T14:12:01.864741161Z From previous event:
2018-06-20T14:12:01.864743890Z     at Client_PG._query (/app/node_modules/knex/lib/dialects/postgres/index.js:287:12)
2018-06-20T14:12:01.864827939Z     at Client_PG.query (/app/node_modules/knex/lib/client.js:206:17)
2018-06-20T14:12:01.864833037Z     at Runner.<anonymous> (/app/node_modules/knex/lib/runner.js:155:36)
2018-06-20T14:12:01.864835873Z From previous event:
2018-06-20T14:12:01.864838420Z     at /app/node_modules/knex/lib/runner.js:61:21
2018-06-20T14:12:01.864949970Z     at runCallback (timers.js:756:18)
2018-06-20T14:12:01.865175034Z     at tryOnImmediate (timers.js:717:5)
2018-06-20T14:12:01.865200577Z     at processImmediate [as _immediateCallback] (timers.js:697:5)
2018-06-20T14:12:01.865270155Z From previous event:
2018-06-20T14:12:01.865358401Z     at Runner.run (/app/node_modules/knex/lib/runner.js:47:31)
2018-06-20T14:12:01.865363267Z     at Builder.Target.then (/app/node_modules/knex/lib/interface.js:39:43)
2018-06-20T14:12:01.865365706Z     at process._tickCallback (internal/process/next_tick.js:160:7)

I'm also having a connection error crashing my program. I'm not entirely sure what state my Client object is in when this occurs, but I've created a test which produces the same error by abusing the Connection object:

'use strict';

const { Client } = require('pg');

async function main() {
  const client = new Client();

  await client.connect();
  try {
    // Simulate the connection dying unexpectedly.
    client.connection.end();
    await client.query(`SELECT 1 AS one`);
  } finally {
    await client.end();
  }
}

main().then(() => {
  process.exit(0);
}).catch(err => {
  process.exit(1);
});

Even though I'm abusing the Connection object, I would expect this program to print nothing and exit (with exit status 0 or 1). Instead, the built-in events library terminates the program because no error handler is available for the Client object:

events.js:167
      throw er; // Unhandled 'error' event
      ^

Error: Connection terminated unexpectedly
    at Connection.con.once (/mytest/node_modules/pg/lib/client.js:200:9)
    at Object.onceWrapper (events.js:273:13)
    at Connection.emit (events.js:182:13)
    at Socket.<anonymous> (/mytest/node_modules/pg/lib/connection.js:76:10)
    at Socket.emit (events.js:182:13)
    at TCP._handle.close (net.js:606:12)
Emitted 'error' event at:
    at connectedErrorHandler (/mytest/node_modules/pg/lib/client.js:148:10)
    at Connection.con.once (/mytest/node_modules/pg/lib/client.js:216:9)
    at Object.onceWrapper (events.js:273:13)
    [... lines matching original stack trace ...]
    at TCP._handle.close (net.js:606:12)

If I modify the test to add an error listener to the Client object, the program fails in the expected manner:

'use strict';

const { Client } = require('pg');

async function main() {
  const client = new Client();

  client.once('error', err => {});

  await client.connect();
  try {
    // Simulate the connection dying unexpectedly.
    client.connection.end();
    await client.query(`SELECT 1 AS one`);
  } finally {
    await client.end();
  }
}

main().then(() => {
  process.exit(0);
}).catch(err => {
  console.log('Error is caught in anticipated location:');
  console.log(err);
  process.exit(1);
});

Can anyone more familiar with the inner workings of the library comment on what normal situations cause the Client object to emit error events?

[charmander]

@novakka4096 The connection dying unexpectedly is one such situation. In general, you should have an 'error' event listener.

[cobolbaby]

Any progress or difficulty？