[Tickets #14258] Re: File based cache garbage collection broken

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Ticket URL: https://bugs.horde.org/ticket/14258
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  Ticket             | 14258
  Updated By         | arjen+horde at de-korte.org
  Summary            | File based cache garbage collection broken
  Queue              | Horde Framework Packages
  Type               | Bug
  State              | Resolved
  Priority           | 2. Medium
  Milestone          | Horde_Cache 2.5.3
  Patch              |
  Owners             | Jan Schneider
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arjen+horde at de-korte.org (2016-02-16 19:37) wrote:

I'm not sure if this will fully solve the problem. This patch seems to  
fix the problem of adding cache files to horde_cache_gc where they  
don't belong, but looking at the old horde_cache_gc files, it also  
looks there is an issue with locking the horde_cache_gc files somewhere.

As far as I can see, the format of these files is one cache file  
followed by a timestamp per line. Like the following entry from the  
/var/lib/php5/horde/cache/a/0/0/horde_cache_gc file (showing the  
problem that it contains a cache file that shouldn't be there that is  
fixed by this patch):

/var/lib/php5/horde/cache/0/0/0/cache_000bde1edaebadae73f8069438a0bccd  
  1455770298

But looking further down this same file, I also see lines like

/var/lib/p
5/horde/cache/1/c/6/cache_1c664138a4d63a5d7c5b1e76f81002ae      1455977208

(yes, two lines)

/var/lib/php5/horde//var/lib/php5/horde/cache/1/f/d/cache_1fd41d3ae5f1c30fd29cfc831456143345

(no timestamp and really wonky looking directory)

/var/lib/php/var/lib/php5/horde/ <20000+ characters removed>  
a/f/5/cache_af5590ec1fa2401f6cac6b4cf9a5a5d3  1456247333

It looks to me there might also be a problem with file locking. What  
happens if new entries are added to the horde_cache_gc file while in  
the midst of of GC? The above examples look to me as if two processes  
are writing to the same file simultaneously.