Notice: unserialize(): Error at offset 0 of 2527853 bytes in _dmemcache_get_pieces() (line 329 of modules/memcache/dmemcache.inc).

Thanks for the patch, tagging to be sure this is resolved in the next release.

thank you for the patch, It has resolved the issue on our sites.

Thanks for reporting this. I've attached what should be a more correct patch, letting the PECL extension handle this. Testing would be appreciated.

@jeremy : We faced the same issue . We were getting error " unserialize() [function.unserialize]: Error at offset 1048395 of 6028676 bytes in _dmemcache_get_pieces() "

This patch worked like charm !!

Thanks @jeremy.

But why does this issue gets encountered? Is it due to large cached data in memcache or due to distributed server setups where there are multiple db servers with load balancers. This issue popped up on its own but unable to figure out on why this issue has popped up?

Thanks in advance for clarification.

@searchmax: For my case, environment setup is distributed server setup; but issue occurred when size increased for cached data in memcache.

@searchmax, this can happen when you have multiple memcache servers, and you request an item that was large enough to be split into multiple pieces. This is because Memcached::getMulti doesn't guarantee the order in which the pieces will be returned, unless you set the Memcached::GET_PRESERVE_ORDER flag (which the attached patch fixes). So the answer to your question is "yes, both of those together".

Thanks for everyone who tested. Committed to 7.x-1.x:
http://cgit.drupalcode.org/memcache/commit/?id=3039461

@jeremy: I've applied the patch (https://www.drupal.org/files/issues/2415109.patch) successfully, but now seeing a different issue:

PHP Fatal error: Cannot pass parameter 2 by reference in /sites/all/modules/contrib/memcache/dmemcache.inc on line 375
PHP Stack trace:
PHP 1. {main}() /usr/share/pear/drush/drush.php:0
PHP 2. drush_main() /usr/share/pear/drush/drush.php:16
PHP 3. _drush_bootstrap_and_dispatch() /usr/share/pear/drush/drush.php:61
PHP 4. drush_bootstrap_to_phase() /usr/share/pear/drush/drush.php:81
PHP 5. drush_bootstrap() /usr/share/pear/drush/includes/bootstrap.inc:308
PHP 6. _drush_bootstrap_drupal_full() /usr/share/pear/drush/includes/bootstrap.inc:185
PHP 7. drupal_bootstrap() /usr/share/pear/drush/includes/bootstrap.inc:930
PHP 8. _drupal_bootstrap_full() /site/includes/bootstrap.inc:2278
PHP 9. module_invoke_all() /site/includes/common.inc:5215
PHP 10. call_user_func_array() /site/includes/module.inc:895
PHP 11. context_init() /site/includes/module.inc:895
PHP 12. context_get_plugin() /sites/all/modules/contrib/context/context.module:168
PHP 13. context_conditions() /sites/all/modules/contrib/context/context.module:474
PHP 14. _context_registry() /sites/all/modules/contrib/context/context.module:499
PHP 15. context_cache_set() /sites/all/modules/contrib/context/context.module:521
PHP 16. cache_set() /sites/all/modules/contrib/context/context.module:344
PHP 17. MemCacheDrupal->set() /site/includes/cache.inc:136
PHP 18. MemCacheDrupal->wildcardFlushes() /sites/all/modules/contrib/memcache/memcache.inc:188
PHP 19. MemCacheDrupal->wildcards() /sites/all/modules/contrib/memcache/memcache.inc:330
PHP 20. dmemcache_get_multi() /sites/all/modules/contrib/memcache/memcache.inc:378
Drush command terminated abnormally due to an unrecoverable error. [error]
Error: Cannot pass parameter 2 by reference in /sites/all/modules/contrib/memcache/dmemcache.inc, line 375

Attached is a simple patch to fix the php warning issue committed to 7.x-1.x

Thanks @Josh. The updated patch works on my local. Will continue testing on Dev.

It seems this needs the follow-on patch?

Yes 2415109-memcache-7.x-1.x-fix-php-warning.patch did the job for me, no other file needed.

Thanks -- fix committed:
http://cgit.drupalcode.org/memcache/commit/?id=243c2f4

And committed to 6.x-1.x also:
http://cgit.drupalcode.org/memcache/commit/?id=6355fe8

I'm experimenting still this issue when using PECL Memcache library.
I provide patch for fixing the ordering when using the other php memcache library, seems 8.x version already implements similar approach.

See http://cgit.drupalcode.org/memcache/commit/?id=6355fe8 -- this is handled by the memcache/memcached extension. It works fine in the latest release with the recommended memcache extension. The not-recommended memcached extension requires latest -dev.

Ouch, I stand corrected! While fixing the tests I realized you were absolutely correct. Thanks for the patch, committed!