node-pg

Postgres: lock release when client.end()

'use strict';
const pg = require('pg');

console.time('time');
var LOCK = `BEGIN; LOCK TABLE processed_files IN ACCESS EXCLUSIVE MODE;`;
var client1 = new pg.Client(`postgres://${process.env.POSTGRES_USER}:${process.env.POSTGRES_PASSWORD}@${process.env.POSTGRES_HOST}:${process.env.POSTGRES_PORT}/${process.env.POSTGRES_DB}`);
var client2 = new pg.Client(`postgres://${process.env.POSTGRES_USER}:${process.env.POSTGRES_PASSWORD}@${process.env.POSTGRES_HOST}:${process.env.POSTGRES_PORT}/${process.env.POSTGRES_DB}`);

client1.connect(function (err) {
  console.timeEnd('time');
  console.log('client1 connected to db\n');
  console.timeEnd('time');
  console.log('client1 try to lock table processed_files\n');
  client1.query(LOCK, function (err, result) {
    if (!!err) {
      console.error(err)
    }
    console.timeEnd('time');
    console.log('client1 LOCKed table processed_files\n');
  });
});

client2.connect(function (err) {
  console.timeEnd('time');
  console.log('client2 connected to db\n');
  setTimeout(function () {
    console.timeEnd('time');
    console.log('client2 try to lock table processed_files\n');
    client2.query(LOCK, function (err, result) {
      if (!!err) {
        console.error(err)
      }
      console.timeEnd('time');
      console.log('client2 LOCKed table processed_files\n');
    });

    setTimeout(function () {
      client1.end();
      console.timeEnd('time');
      console.log('client1 disconnected from the server\n');
    }, 1000);

  }, 1000);
});



/*
 time: 19ms
 client1 connected to db

 time: 20ms
 client1 try to lock table processed_files

 time: 21ms
 client2 connected to db

 time: 23ms
 client1 LOCKed table processed_files

 time: 1023ms
 client2 try to lock table processed_files

 time: 2028ms
 client1 disconnected from the server

 time: 2029ms
 client2 LOCKed table processed_files
 */