Commit Graph

17 Commits

Author SHA1 Message Date
Daniel Waterworth 7c7098c700 FIX: Off-by-one error setting the distributed mutex key to expire
Accounting for fractional seconds, a distributed mutex can be held for
almost a full second longer than its validity.

For example: if we grab the lock at 10.5 seconds passed the epoch with a
validity of 5 seconds, the lock would be released at 16 seconds passed
the epoch. However, in this case assuming that all other processing
takes a negligible amount of time, the key would be expired at 15.5
seconds passed the epoch.

Using expireat, the key is now expired exactly when the lock is released.
2020-02-03 14:54:50 +00:00
Joffrey JAFFEUX 0d3d2c43a0
DEV: s/\$redis/Discourse\.redis (#8431)
This commit also adds a rubocop rule to prevent global variables.
2019-12-03 10:05:53 +01:00
Daniel Waterworth 1fdba2c5b2 FIX: Harden DistributedMutex
Threadsafety

  Since we use the same redis connection in multiple threads, a rogue
  transaction in another thread can trample the connection state
  (watched keys) that we need to acquire and release the lock properly.

  This is fixed by preventing other threads from using the connection
  when we are performing these actions.

Off-by-one error

  A distributed mutex is now consistently determined to be expired if
  the current time is strictly greater than the expire time.

Unwatch before transaction

  Since the redis connection is used by so much of the code, it is
  difficult to ensure that any watched keys have been cleared. In order
  to defend against this rogue connection state, an unwatch has been
  added before locking and unlocking.

Logging

  Hopefully this log message is more clear.
2019-10-02 13:00:41 +00:00
Neil Lalonde 5f87089b67 FIX: remove dependency on present? in distributed_mutex lib 2019-08-07 15:39:51 -04:00
Sam Saffron 67f5ad5ac0 FEATURE: allow post process mutex to be held longer
Previously we would only hold the post process mutex for 1 minute, that is
not enough when processing a post with lots of images. This raises the bar
to 10 minutes.

It also cleans up error reporting around distributed mutexes expiring. We
used to double report.
2019-08-05 11:57:35 +10:00
Daniel Waterworth 20bc4a38a5
FIX: DistributedMutex (#7953) 2019-08-01 09:12:05 +01:00
Sam Saffron 30990006a9 DEV: enable frozen string literal on all files
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.

Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
2019-05-13 09:31:32 +08:00
Gerhard Schlager ff26b4ed9b DEV: Prevent warning about already initialized constant 2019-02-28 21:57:20 +01:00
Guo Xiang Tan 4d31b425e3 DEV: Validity of distributed mutex configurable once per instance.
Follow up to 4f9e5e19c8.
2019-02-20 09:29:45 +08:00
Guo Xiang Tan f2efa0da66
DEV: Allow validity of lock to be customizable for `DistributedMutex`. (#7025)
- Allows a user to override the default lock validity of 60 seconds.
- Also clean up test which was leaking a redis key
2019-02-20 09:23:42 +08:00
Sam e0be5145cf FIX: correct readonly timeout
So it only applies in readonly mode
2018-09-20 15:15:46 +10:00
Sam e0e6dae6a7 minor cleanup to previous commit from code review 2018-09-19 16:07:29 +10:00
Sam 5302709343 FIX: in redis readonly raise an exception from DistributedMutex
If we detect redis is in readonly we can not correctly get a mutex
raise an exception to notify caller

When getting optimized images avoid the distributed mutex unless
for some reason it is the first call and we need to generate a thumb

In redis readonly no thumbnails will be generated
2018-09-19 15:50:58 +10:00
Guo Xiang Tan 5012d46cbd Add rubocop to our build. (#5004) 2017-07-28 10:20:09 +09:00
Sam 9147af1d62 FIX: eliminate race condition creating posts
FIX: correct message bus posting
2014-07-30 14:18:01 +10:00
Sam 63f4a0e050 Tighten API, add spec for recovery, keep mutex semantics 2014-04-14 10:51:46 +10:00
Vikhyat Korrapati 56ee1ac569 Extract scheduler cross-process locking into DistributedMutex. 2014-04-13 00:05:46 +05:30