ECONNRESET Write error when querying database two times in a row [Node.js]

Question

I have a node.js file which has methods that read and write from my heroku postgresql database. I am using the 'pg' module in order to access the DB. My problem is that calling my getSleepMode function more than once in a row causes the ECONNRESET error. This function simply sends a query to my DB and retrieves an integer. I understand it might be because node.js functions are non-blocking, and both instances of getSleepMode() are trying to access my DB at the same time. But wouldn't this pose as a problem if more than one client is trying to get data from my DB at the same time? Assuming my heroku postgresql db can handle queries from multiple clients at the same time, shouldn't this still work? I have relevant parts of the code below:

    [database connection variables omitted]

    var pg = require("pg")
    var conString = "pg://" + USER + ":" + PW + "@" + HOST + ":" + PORT + "/" + 
         DATABASE + "?ssl=true";

    var client = new pg.Client(conString);

     /*This function accesses my database and retrieves an integer field 
      called "sleepmode"*/

    function getSleepMode(username) {

       var query = "SELECT sleepmode FROM \"Users\" where username='" + 
                    username + "';";

       connectWrapper(query, function(err,result) {
           if (err) {
                return console.err("Error getting sleep mode", err);
           } 

           client.end();
           console.log("sleepmode " + result.rows[0].sleepmode);
       });
   }


       /*This function is here so I can reuse it for more than just  
        my getSleepMode() function*/

      function connectWrapper(query, handler) {

         client.connect(function(err) {
           if (err) { 
            return console.error('could not connect to postgresq',err);
           }
           client.query(query, handler);
         });
      }

     getSleepMode("username1");  //This ALONE works
     getSleepMode("username2");  //but when this line follows, i get the error

Running this causes this output:

$user: node dbconnect.js
could not connect to postgresq { [Error: write ECONNRESET] code: 'ECONNRESET', err
ECONNRESET', syscall: 'write' }
could not connect to postgresq { [Error: write ECONNRESET] code: 'ECONNRESET', err
ECONNRESET', syscall: 'write' }

Events.js:72
       throw er; // Unhandled 'error' event
         ^
Error: write ECONNRESET
   at errnoException (net.js:904:11)
   at Socket._write (net.js:645:26)
   at doWrite (_stream_writable.js:225:10)
   at writeOrBuffer (_stream_writable.js:215:5)
   at Socket.Writable.write (_stream_writable.js:182:11)
   at Socket.write (net.js:615:40)
   at write (_stream_readable.js:601:24)
   at flow (_stream_readable.js:610:7)
   at _stream_readable.js:578:7
   at process._tickCallback (node.js:419:13)

But when I run it so that getSleepMode() is called only once, there is no error and it works as expected.

$user: node dbconnect.js
sleepmode 1

score 0 · Answer 1 · answered Aug 06 '14 at 00:29

0

You're ending the client twice (client.end();), which could be causing your issue. Specifically it looks like the connection is closed before the other query finishes executing.

answered Aug 06 '14 at 00:29

mscdex

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So then if I had two different clients that performed their own separate queries, then this should work? For example, if on two different devices this node.js app was loaded, then the two different devices could query the database at the same time with no problem? – user3445268 Aug 06 '14 at 01:11
What you should use instead is a connection pool. Fortunately for you, `pg` has connection pooling built in and [seems to be used by default](https://github.com/brianc/node-postgres/wiki/pg#pgdefaultspoolsize). So as far as I can tell, you just need to call `connect()` once and then just keep calling `query()` and never manually call `end()`. – mscdex Aug 06 '14 at 02:14

ECONNRESET Write error when querying database two times in a row [Node.js]

1 Answers1