Warning: apc_store() [function.apc-store]: Potential cache slam averted for key 'vbo_

[highflow]

Hi,

Currently I'm having this error message popping up randomly:

Warning: apc_store() [function.apc-store]: Potential cache slam averted for key 'vbo_vb.optimiser.stats' in [path]/vboptimise/core/class_operator_apc.php on line 50


See screenshot:

What is causing this and what to do to solve it?
We have this, since we are moved to a new webserver.
But other than that, all files and configuration are the same.

Also the thumbnail option for attachments on our forum are suddenly dissapeared, thumbnails are not created anymore :S
Does this have anything to do with this error?
Cause I can't see the option for enabling and disabling thumbnails anymore in the extension configuration (see screenshot above).


Hope you guys can help us out a.s.a.p.
Thanks in advance.

Freddy

 

[Deceptor]

Hey highflow,

After doing some searching about this issue appears to occur when a key is set more than once in the same execution, typically this will only happen with our stats collection. The warning itself is a feature within APC designed to stop flooding, chances are your old APC setup had the feature disabled, which you can do by adding this to your APC configuration and restarting apache:

apc.slam_defense = Off

Although the configuration is deprecated it may work based on the version of APC you have, let me know either way. If it fails to work, disable stats collection and flush the cache - the error should go away and anything on your forum that's corrupted/missing should pop back in

Edit

If that fails, try:

apc.write_lock = 1

Apparently that's a temporary solution to what appears to be a "bug" within APC when php is running under PHP-FPM.

 

[highflow]

Hi Deceptor, thanks for the suggestion.

I still got problems, now I'm also getting this error while running the system test:
Your Opcache Operator extension is functioning, however it is unable to store data. Please check your extension configuration

APC in enabled, this in the info in php.info:

apc
APC Support enabled
Version 3.1.4
MMAP Support Enabled
MMAP File Mask no value
Locking type pthread mutex Locks
Revision $Revision: 301663 $
Build Date Sep 7 2010 16:13:17

Directive Local Value Master Value
apc.cache_by_default On On
apc.canonicalize On On
apc.coredump_unmap Off Off
apc.enable_cli Off Off
apc.enabled On On
apc.file_md5 Off Off
apc.file_update_protection 2 2
apc.filters no value no value
apc.gc_ttl 3600 3600
apc.include_once_override Off Off
apc.lazy_classes Off Off
apc.lazy_functions Off Off
apc.max_file_size 1M 1M
apc.mmap_file_mask no value no value
apc.num_files_hint 1000 1000
apc.preload_path no value no value
apc.report_autofilter Off Off
apc.rfc1867 Off Off
apc.rfc1867_freq 0 0
apc.rfc1867_name APC_UPLOAD_PROGRESS APC_UPLOAD_PROGRESS
apc.rfc1867_prefix upload_ upload_
apc.rfc1867_ttl 3600 3600
apc.shm_segments 1 1
apc.shm_size 32M 32M
apc.slam_defense Off Off
apc.stat On On
apc.stat_ctime Off Off
apc.ttl 0 0
apc.use_request_time On On
apc.user_entries_hint 4096 4096
apc.user_ttl 0 0
apc.write_lock On On


What can we do next?

Freddy

 

[Deceptor]

Hey highflow, are you running PHP in FastCGI? APC shared cache typically won't work under such a setup, XCache suffers in the same way - on such setups (ours is the same) I'd recommend using Memcached instead.