cache: uninformative messages for cache_size

[RomanBelozerov]

Scope

We have two problems with uninformative messages:

• ERROR when response body is larger then cache_size:

[254366.985392] [tdb] ERROR: out of free space
[254366.986204] [tempesta fw] ERROR: Cache: cannot copy chunk of HTTP body
[254366.986980] [tempesta fw] ERROR: Cache: cannot copy HTTP body

or

[254387.215313] [tdb] ERROR: out of free space
[254387.216100] [tdb] ERROR: Cannot burst node=00000000285fa02e and bckt=000000007f491702 for key 0x275decc81f1ae60a
[254387.216822] [tdb] ERROR: Cannot allocate cache entry for key=0x275decc81f1ae60a

In this case, I expect a warning in dmesg. For example: [tempesta fw] Warning: The response body is too large to cache or there is not enough space in the cache. Please increase 'cache_size' or change 'cache_fulfill'

• ERROR when cache_size > tempesta_dbmem

[255215.935105] [tdb] Opened table /opt/tempesta/db/filter0.tdb: size=16777216 rec_size=20 base=00000000147db6e5
[255215.936465] [tdb] ERROR: Cannot allocate 262144 pages at node 0
[255215.937231] [tdb] ERROR: Cannot map file
[255215.938009] [tdb] ERROR: Cannot open db for /opt/tempesta/db/cache.tdb
[255215.938844] [tempesta fw] ERROR: Unable to start module 'cache': -12

I also expect a warning in dmesg. For example: [tempesta fw] Warning: 'cache' size is greater then 'tempesta_dbmem'. Please increase 'tempesta_dbmem'. See https://tempesta-tech.com/knowledge-base/Run-and-stop/#prepare-to-start

Testing

We don't have tests for these cases. Please add tests or create issue in tempesta-test.

[krizhanovsky]

We also should reduce the amount of printing to not flood the kernel log