WordPress Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 77 bytes) in wp-includes/wp-db.php on line 1832

Question

I noticed recently on my WordPress website I'm getting sometimes 500 Internal Server Error. I checked logs and I have many lines like:

[Mon Oct 03 01:25:24.357439 2016] [fcgid:warn] [pid 12840] [client 83.27.211.107:36968] mod_fcgid: stderr: PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 77 bytes) in /var/www/vhosts/mywebsite/public_html/wp-includes/wp-db.php on line 1832

I tried to increase memory limit:

define( 'WP_MAX_MEMORY_LIMIT' , '512M' );

define( 'WP_MEMORY_LIMIT' , '512M' );

And even more, but it didn't work. No matter what I set it still exceeding memory limit by some bytes. I think there's a problem with some queries to a database, but how to check which?

Content of the includes/wp-db.php:

} else {
    $num_rows = 0;
    if ( $this->use_mysqli && $this->result instanceof mysqli_result ) {
        while ( $row = mysqli_fetch_object( $this->result ) ) {
            $this->last_result[$num_rows] = $row;
            $num_rows++;
        }
    } elseif ( is_resource( $this->result ) ) {
        // server crashing at line below
        while ( $row = mysql_fetch_object( $this->result ) ) {
            $this->last_result[$num_rows] = $row;
            $num_rows++;
        }
    }

    // Log number of rows the query returned
    // and return number of rows selected
    $this->num_rows = $num_rows;
    $return_val     = $num_rows;
}

so ask yourself WHY you need to cache 500+megs of data in ram. If you HAVE to, then your choices are to either raise/remove the memory limit, or rebuild your system so you DON'T need that much stuff in memory at the same time. Otherwise you're basically asking "I poured 10 liters of water into a 1 liter bucket and it overflowed, how can I keep it form overflowing?" — Marc B
– Marc B, Commented Oct 3, 2016 at 21:19
@MarcB, you don't understand. I have a bug on my website. It's simple WordPress site with 5 widgets, menu and posts loop (20 per page). I don't have an idea why this exceeding memory limit at all. — Dawid Loranc
– Dawid Loranc, Commented Oct 3, 2016 at 21:29
well, then do some basic debugging: take a look at what the query is, and run it yourself to see what data it's bringing back. there's nothing "simple" about wordpress. it is a bloated pig of a system, frankly, and even a "simple" page will be a hefty burden on the system. — Marc B
– Marc B, Commented Oct 3, 2016 at 21:31

Dawid Loranc · Accepted Answer · 2016-10-04 17:53:10Z

1

The problem was caused by iThemes Security plugin. I turned off it and errors have gone. I'll investigate this problem more and edit this answer if I'll know what part of this plugin caused exceeding memory limit.

answered Oct 4, 2016 at 17:53

Dawid Loranc

9022 gold badges9 silver badges22 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Platon K. · Accepted Answer · 2016-11-19 10:43:42Z

1

I had the same issue with "wp-db.php on line 1832" and disabling iThemes Security plugin as was mentioned before worked well for me. However, if you still need to protect your site it's not the solution.

What you need to do is to fix directory permissions of key areas such as wp-content, wp-includes etc...

Go to iThemes Security settings -> File Permissions (Configure Settings) and check if all permissions are set properly. Once you fix permissions as they supposed to be, you won't see that error anymore.

answered Nov 19, 2016 at 10:43

Platon K.

112 bronze badges

1 Comment

justyy Over a year ago

It is the "Database Backups" of iThemes Security that causes OOM. Purely disable that function should be fine.

justyy · Accepted Answer · 2017-06-16 15:18:48Z

1

Disable the "Database Backups" in iThemes Security works for me.

answered Jun 16, 2017 at 15:18

justyy

6,1014 gold badges42 silver badges82 bronze badges

Comments

markratledge · Accepted Answer · 2016-10-03 21:45:24Z

0

The constant WP_MEMORY_LIMIT regulates RAM for all PHP processes for WordPress for the front and backends. Use this on shared hosting. The constant WP_MAX_MEMORY_LIMIT regulates RAM for the backend only. You use WP_MAX_MEMORY_LIMIT when you know you have enough RAM and can use it all, such as on a VPS server you administer.

Go back to

define( 'WP_MAX_MEMORY_LIMIT' , '128M' ); define( 'WP_MEMORY_LIMIT' , '64M' );

and remove those queries you are running (above) and see if the site comes back up. If it does, that's the issue; working on those queries is a different issue.

If this is shared hosting, you are killing the server with those queries; if this is your own server, you need to configure MySQL/PHP for caching and high loads.

answered Oct 3, 2016 at 21:45

markratledge

17.6k12 gold badges65 silver badges108 bronze badges

4 Comments

RST Over a year ago

Seems to me he is copy/pasting the core WP file. I would be surprised if that turned out to be the culprit.

Dawid Loranc Over a year ago

I edited my post. I forgot to mention that part of a code I posted is from wp-incudes/wp-db.php. So, I don't know where is a query that caused this bug. Maybe it's from a plugin, that website worked properly a few weeks ago.

Dawid Loranc Over a year ago

@RST, yes, I forgot to mention that. Sorry.

markratledge Over a year ago

Talk to your host; many shared hosts do not provide enough RAM. If this is a brand new site and new problem on a new hosting account, the host is the problem.

Collectives™ on Stack Overflow

WordPress Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 77 bytes) in wp-includes/wp-db.php on line 1832

4 Answers 4

Comments

1 Comment

Comments

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

1 Comment

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related