[squid-dev] [RFC] Do we want paranoid_hit_validation?

Alex Rousskov rousskov at measurement-factory.com
Tue Jan 8 15:01:51 UTC 2019

On 1/8/19 1:50 AM, Amos Jeffries wrote:
> On 8/01/19 4:58 pm, Alex Rousskov wrote:
>> This particular validation does not require checksums or other expensive
>> computations. It does not require disk I/O. The code simply traverses
>> the chain of disk slot metadata for the entry and compares the sum of
>> individual slot sizes with the expected total cache entry size. The
>> validation is able to detect many (but not all) cases of cache index
>> corruption.

> Does it have to be a global directive like proposed?

No, it does not. Each validation check only needs access to the index of
the storage where the hit object was found.

> An option of cache_dir would seem better. That would allow admin to work
> tune it to match their different cache types and object-size separation
> (if any).

Yes, this can be implemented as a cache_dir-specific (and, with even
more work, also as a cache_mem-specific) option. Do you think it is a
good idea to add this feature if it is controllable on individual
cache_dirs basis?

Thank you,


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