Hi all, this is the error we have been seeing in our apache HTTP logs:

[cache_disk:error] [pid 421298:tid 421362] (2)No such file or directory: 
[client [REDACTED_IP]] AH00708: Cannot open data file 
/tmp/apache/[HASH_PATH]/AA.data, referer: https://[REFERER_URL]

When I check the cache, that file already exists and was created about the same 
time the error message was triggered. I believe the problem could be a race 
condition by .header being created before .data can be read from a slightly 
earlier request, but I can’t prove this based on the file creation times which 
are rewritten after this error message is triggered and the cache is rewritten. 
I have been unable to recreate this problem even by triggering a request with 
an extremely large .data file that takes longer than [mod_cache: 
CacheLockMaxAge] to write

I have ruled out the problem being that our cache is full and files can’t be 
written or htcacheclean being the problem by starting with a clean cache that 
begins to get these errors before it reaches its max size. I verified that I am 
getting multiple consecutive requests when I see this error

Some information about our configuration:

  *   cache.conf has CacheLock on

  *   This only happens on our production environment which gets millions of 
daily requests

  *   I do not see any other relevant errors when I turn debug mode on

  *   This is an infrequent error message, but it is reoccurring

  *   We are using an overlay file system in a Docker container

Has anyone encountered this issue before? I have not found an apache HTTP 
setting to lock reading the cache, only writing the cache


Thank you,

Grace



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