How to disconnect from MongoDB in a Perl script?

Question

I am trying to write a Perl5 script that checks the status of a MongoDB server every minute and notifies me if it is down. Any suggestion is welcome for this task. Currently, I am using 'MongoDB' module and 'MongoDB::MongoClient' to establish a connection to see if server is available. Here is the basic idea:

while(1)
{
        my $conn = connectMongoDB();

        if($conn){
                sleep 60;
        }   
        else{
                sendMail();
                last;
        }   
}

sub connectMongoDB
{
        my $client;

        eval{ $client =  MongoDB::MongoClient->new( host => "mongodb://:\@$server");};

        return ($client)?1:0;       
}

The main problem is that there is no way to disconnect from the server. Here is what it says on the cpan page:

"There is no way to explicitly disconnect from the database. However, the connection will automatically be closed and cleaned up when no references to the MongoDB::MongoClient object exist, which occurs when $client goes out of scope (or earlier if you undefine it with undef)."

I tried 'undef' and subroutines. None of them terminates the connection. Because of the loop, the number of connections keep increasing. Is there any other method I can try to keep the number of connections under control?

Any other suggestion for tackling this issue is appreciated as long as it doesn't involve crontab.

Thanks.

EDIT:

This is the output when sleep time is set to 2 secs where db version is v2.4.4 and MongoDB module version is 0.701.4. The problem persists after upgrading MongoDB module to 0.702.1.

Fri Aug 16 20:33:06.986 [initandlisten] connection accepted from 127.0.0.1:51031 #3 (1 connection now open)
Fri Aug 16 20:33:08.989 [initandlisten] connection accepted from 127.0.0.1:51033 #4 (2 connections now open)
Fri Aug 16 20:33:10.991 [initandlisten] connection accepted from 127.0.0.1:51034 #5 (3 connections now open)
Fri Aug 16 20:33:12.994 [initandlisten] connection accepted from 127.0.0.1:51035 #6 (4 connections now open)
Fri Aug 16 20:33:14.996 [initandlisten] connection accepted from 127.0.0.1:51036 #7 (5 connections now open)
Fri Aug 16 20:33:16.999 [initandlisten] connection accepted from 127.0.0.1:51038 #8 (6 connections now open)
Fri Aug 16 20:33:19.003 [initandlisten] connection accepted from 127.0.0.1:51039 #9 (7 connections now open)
Fri Aug 16 20:33:21.006 [initandlisten] connection accepted from 127.0.0.1:51040 #10 (8 connections now open)
Fri Aug 16 20:33:23.009 [initandlisten] connection accepted from 127.0.0.1:51042 #11 (9 connections now open)
Fri Aug 16 20:33:25.013 [initandlisten] connection accepted from 127.0.0.1:51043 #12 (10 connections now open)
Fri Aug 16 20:33:27.016 [initandlisten] connection accepted from 127.0.0.1:51044 #13 (11 connections now open)
Fri Aug 16 20:33:29.019 [initandlisten] connection accepted from 127.0.0.1:51045 #14 (12 connections now open)
Fri Aug 16 20:33:31.022 [initandlisten] connection accepted from 127.0.0.1:51047 #15 (13 connections now open)

EDIT 2: SOLVED!!

I believe the problem is related to auto_connect option. Once it is disabled, The code works fine. Below is something that works for now.

sub connectMongoDB
{
        my $client;

        eval{
                $client =  MongoDB::MongoClient->new( host => "mongodb://:\@$server",
                      auto_connect => 0); 
                $client->connect;
        };  
        return (!$@)?1:0;
}

Best

Answer 1

I'm unable to reproduce this problem with MongoDB 2.4.1 and version 0.702.1 of the MongoDB driver from CPAN.

I ran your code with the sleep timeout changed to 10 seconds, connecting to localhost. After running for a couple minutes, running db.serverStatus() in the mongo shell continued to show just one connection. (That's the connection for the shell session.)

Here's the output from mongod showing the connections being opened and closed every ten seconds. (You can see that I fired up the shell after the first two connections cycled.)

Fri Aug 16 21:36:43.589 [conn1] end connection 127.0.0.1:57722 (0 connections now open)
Fri Aug 16 21:36:53.526 [initandlisten] connection accepted from 127.0.0.1:57723 #2 (1 connection now open)
Fri Aug 16 21:36:53.527 [conn2] end connection 127.0.0.1:57723 (0 connections now open)
Fri Aug 16 21:36:58.421 [initandlisten] connection accepted from 127.0.0.1:57724 #3 (1 connection now open)
Fri Aug 16 21:37:03.529 [initandlisten] connection accepted from 127.0.0.1:57725 #4 (2 connections now open)
Fri Aug 16 21:37:03.529 [conn4] end connection 127.0.0.1:57725 (1 connection now open)
Fri Aug 16 21:37:13.531 [initandlisten] connection accepted from 127.0.0.1:57726 #5 (2 connections now open)
Fri Aug 16 21:37:13.532 [conn5] end connection 127.0.0.1:57726 (1 connection now open)
Fri Aug 16 21:37:23.534 [initandlisten] connection accepted from 127.0.0.1:57727 #6 (2 connections now open)
Fri Aug 16 21:37:23.535 [conn6] end connection 127.0.0.1:57727 (1 connection now open)
Fri Aug 16 21:37:33.537 [initandlisten] connection accepted from 127.0.0.1:57728 #7 (2 connections now open)
Fri Aug 16 21:37:33.538 [conn7] end connection 127.0.0.1:57728 (1 connection now open)
Fri Aug 16 21:37:43.540 [initandlisten] connection accepted from 127.0.0.1:57729 #8 (2 connections now open)
Fri Aug 16 21:37:43.540 [conn8] end connection 127.0.0.1:57729 (1 connection now open)
Fri Aug 16 21:37:53.542 [initandlisten] connection accepted from 127.0.0.1:57730 #9 (2 connections now open)
Fri Aug 16 21:37:53.543 [conn9] end connection 127.0.0.1:57730 (1 connection now open)
Fri Aug 16 21:38:03.545 [initandlisten] connection accepted from 127.0.0.1:57731 #10 (2 connections now open)
Fri Aug 16 21:38:03.545 [conn10] end connection 127.0.0.1:57731 (1 connection now open)
Fri Aug 16 21:38:13.547 [initandlisten] connection accepted from 127.0.0.1:57732 #11 (2 connections now open)
Fri Aug 16 21:38:13.548 [conn11] end connection 127.0.0.1:57732 (1 connection now open)
Fri Aug 16 21:38:23.550 [initandlisten] connection accepted from 127.0.0.1:57734 #12 (2 connections now open)
Fri Aug 16 21:38:23.550 [conn12] end connection 127.0.0.1:57734 (1 connection now open)
Fri Aug 16 21:38:33.552 [initandlisten] connection accepted from 127.0.0.1:57735 #13 (2 connections now open)
Fri Aug 16 21:38:33.553 [conn13] end connection 127.0.0.1:57735 (1 connection now open)
Fri Aug 16 21:38:43.555 [initandlisten] connection accepted from 127.0.0.1:57736 #14 (2 connections now open)
Fri Aug 16 21:38:43.555 [conn14] end connection 127.0.0.1:57736 (1 connection now open)
Fri Aug 16 21:38:53.557 [initandlisten] connection accepted from 127.0.0.1:57737 #15 (2 connections now open)
Fri Aug 16 21:38:53.559 [conn15] end connection 127.0.0.1:57737 (1 connection now open)
Fri Aug 16 21:39:03.560 [initandlisten] connection accepted from 127.0.0.1:57738 #16 (2 connections now open)
Fri Aug 16 21:39:03.561 [conn16] end connection 127.0.0.1:57738 (1 connection now open)
Fri Aug 16 21:39:13.563 [initandlisten] connection accepted from 127.0.0.1:57740 #17 (2 connections now open)
Fri Aug 16 21:39:13.564 [conn17] end connection 127.0.0.1:57740 (1 connection now open)
Fri Aug 16 21:39:23.566 [initandlisten] connection accepted from 127.0.0.1:57741 #18 (2 connections now open)
Fri Aug 16 21:39:23.567 [conn18] end connection 127.0.0.1:57741 (1 connection now open)
Fri Aug 16 21:39:33.569 [initandlisten] connection accepted from 127.0.0.1:57747 #19 (2 connections now open)
Fri Aug 16 21:39:33.570 [conn19] end connection 127.0.0.1:57747 (1 connection now open)
Fri Aug 16 21:39:43.572 [initandlisten] connection accepted from 127.0.0.1:57748 #20 (2 connections now open)
Fri Aug 16 21:39:43.573 [conn20] end connection 127.0.0.1:57748 (1 connection now open)
Fri Aug 16 21:39:53.575 [initandlisten] connection accepted from 127.0.0.1:57750 #21 (2 connections now open)
Fri Aug 16 21:39:53.576 [conn21] end connection 127.0.0.1:57750 (1 connection now open)
Fri Aug 16 21:40:03.579 [initandlisten] connection accepted from 127.0.0.1:57751 #22 (2 connections now open)
Fri Aug 16 21:40:03.579 [conn22] end connection 127.0.0.1:57751 (1 connection now open)
Fri Aug 16 21:40:13.580 [initandlisten] connection accepted from 127.0.0.1:57753 #23 (2 connections now open)
Fri Aug 16 21:40:13.581 [conn23] end connection 127.0.0.1:57753 (1 connection now open)
Fri Aug 16 21:40:23.584 [initandlisten] connection accepted from 127.0.0.1:57754 #24 (2 connections now open)
Fri Aug 16 21:40:23.584 [conn24] end connection 127.0.0.1:57754 (1 connection now open)
Fri Aug 16 21:40:33.586 [initandlisten] connection accepted from 127.0.0.1:57755 #25 (2 connections now open)
Fri Aug 16 21:40:33.586 [conn25] end connection 127.0.0.1:57755 (1 connection now open)
Fri Aug 16 21:40:43.588 [initandlisten] connection accepted from 127.0.0.1:57758 #26 (2 connections now open)
Fri Aug 16 21:40:43.588 [conn26] end connection 127.0.0.1:57758 (1 connection now open)
Fri Aug 16 21:40:53.590 [initandlisten] connection accepted from 127.0.0.1:57760 #27 (2 connections now open)
Fri Aug 16 21:40:53.591 [conn27] end connection 127.0.0.1:57760 (1 connection now open)
Fri Aug 16 21:41:03.592 [initandlisten] connection accepted from 127.0.0.1:57761 #28 (2 connections now open)
Fri Aug 16 21:41:03.593 [conn28] end connection 127.0.0.1:57761 (1 connection now open)

Can you let me know what version of MongoDB (the server) and MongoDB (the driver) you're using?

Answer 2

Change the subroutine as the following,

sub connectMongoDB
{
        my $client;

        eval{
                $client =  MongoDB::MongoClient->new( host => "mongodb://:\@$server",
                      auto_connect => 0); 
                $client->connect;
        };  
        return (!$@)?1:0;
}

The problem was the 'auto_reconnect' option all along.