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

Amos Jeffries squid3 at treenet.co.nz
Tue Jan 15 03:02:33 UTC 2019

On 9/01/19 4:01 am, Alex Rousskov wrote:
> 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?

I think so yes. Long-term I would like to collate these types of tests
into a separate cache management tool. But short of that happening
having some way for Squid to do it is a good ting.


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