[GitHub] [mesos] Lqp1 opened a new pull request #414: Fix fetcher cache reduction

[GitBox <gi...@apache.org>]

Lqp1 opened a new pull request #414:
URL: https://github.com/apache/mesos/pull/414


   When artifact size is smaller than expected, we want to reduce recorded
   cache usage.
   
   To do it, we actually compute the delta as an off_t (signed). If delta is
   negative, we reclaim the extra space as it's not really used.
   
   This attempt was failing because computed delta is negative,
   and passed as Bytes to releaseSpace, which is unsigned. In
   most cases, casting a negative value into an uint will
   just give an unrelated value due to sign bit disappearing.
   
   By passing the positive value to Bytes(), we have a safer cast.
   
   To give more context, what we observe:
   ```
   W1125 08:54:07.888011 10981 fetcher.cpp:643] URI download result for 'xxxxx' is smaller than expected by 253B at: /var/opt/mesos/cache/xxxxxxxx
   F1125 08:54:07.888082 10981 fetcher.cpp:1272] Check failed: bytes <= tally Attempt to release more cache space than in use - requested: 18446744073709551364B, in use: 1910056052B
   ```
   
   If you try
   ```
   #include <stdio.h>
   #include <stdint.h>
   
   int main() {
       off_t negative = -253;
       printf("%lu\n", (uint64_t)(negative));
   }
   ```
   You'll see the same numbers match.


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[GitHub] [mesos] cf-natali commented on pull request #414: Fix fetcher cache reduction

[GitBox <gi...@apache.org>]

cf-natali commented on pull request #414:
URL: https://github.com/apache/mesos/pull/414#issuecomment-980316494


   Thanks!
   
   Probably worth backporting as well.


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[GitHub] [mesos] cf-natali merged pull request #414: Fix fetcher cache reduction

[GitBox <gi...@apache.org>]

cf-natali merged pull request #414:
URL: https://github.com/apache/mesos/pull/414


   


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