# ⚠️ Breaking
Many deprecated queue config options are removed (actually, they should
have been removed in 1.18/1.19).
If you see the fatal message when starting Gitea: "Please update your
app.ini to remove deprecated config options", please follow the error
messages to remove these options from your app.ini.
Example:
```
2023/05/06 19:39:22 [E] Removed queue option: `[indexer].ISSUE_INDEXER_QUEUE_TYPE`. Use new options in `[queue.issue_indexer]`
2023/05/06 19:39:22 [E] Removed queue option: `[indexer].UPDATE_BUFFER_LEN`. Use new options in `[queue.issue_indexer]`
2023/05/06 19:39:22 [F] Please update your app.ini to remove deprecated config options
```
Many options in `[queue]` are are dropped, including:
`WRAP_IF_NECESSARY`, `MAX_ATTEMPTS`, `TIMEOUT`, `WORKERS`,
`BLOCK_TIMEOUT`, `BOOST_TIMEOUT`, `BOOST_WORKERS`, they can be removed
from app.ini.
# The problem
The old queue package has some legacy problems:
* complexity: I doubt few people could tell how it works.
* maintainability: Too many channels and mutex/cond are mixed together,
too many different structs/interfaces depends each other.
* stability: due to the complexity & maintainability, sometimes there
are strange bugs and difficult to debug, and some code doesn't have test
(indeed some code is difficult to test because a lot of things are mixed
together).
* general applicability: although it is called "queue", its behavior is
not a well-known queue.
* scalability: it doesn't seem easy to make it work with a cluster
without breaking its behaviors.
It came from some very old code to "avoid breaking", however, its
technical debt is too heavy now. It's a good time to introduce a better
"queue" package.
# The new queue package
It keeps using old config and concept as much as possible.
* It only contains two major kinds of concepts:
* The "base queue": channel, levelqueue, redis
* They have the same abstraction, the same interface, and they are
tested by the same testing code.
* The "WokerPoolQueue", it uses the "base queue" to provide "worker
pool" function, calls the "handler" to process the data in the base
queue.
* The new code doesn't do "PushBack"
* Think about a queue with many workers, the "PushBack" can't guarantee
the order for re-queued unhandled items, so in new code it just does
"normal push"
* The new code doesn't do "pause/resume"
* The "pause/resume" was designed to handle some handler's failure: eg:
document indexer (elasticsearch) is down
* If a queue is paused for long time, either the producers blocks or the
new items are dropped.
* The new code doesn't do such "pause/resume" trick, it's not a common
queue's behavior and it doesn't help much.
* If there are unhandled items, the "push" function just blocks for a
few seconds and then re-queue them and retry.
* The new code doesn't do "worker booster"
* Gitea's queue's handlers are light functions, the cost is only the
go-routine, so it doesn't make sense to "boost" them.
* The new code only use "max worker number" to limit the concurrent
workers.
* The new "Push" never blocks forever
* Instead of creating more and more blocking goroutines, return an error
is more friendly to the server and to the end user.
There are more details in code comments: eg: the "Flush" problem, the
strange "code.index" hanging problem, the "immediate" queue problem.
Almost ready for review.
TODO:
* [x] add some necessary comments during review
* [x] add some more tests if necessary
* [x] update documents and config options
* [x] test max worker / active worker
* [x] re-run the CI tasks to see whether any test is flaky
* [x] improve the `handleOldLengthConfiguration` to provide more
friendly messages
* [x] fine tune default config values (eg: length?)
## Code coverage:
Change all license headers to comply with REUSE specification.
Fix #16132
Co-authored-by: flynnnnnnnnnn <flynnnnnnnnnn@github>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>
* Start adding mechanism to return unhandled data
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Create pushback interface
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Add Pausable interface to WorkerPool and Manager
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Implement Pausable and PushBack for the bytefifos
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Implement Pausable and Pushback for ChannelQueues and ChannelUniqueQueues
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Wire in UI for pausing
Signed-off-by: Andrew Thornton <art27@cantab.net>
* add testcases and fix a few issues
Signed-off-by: Andrew Thornton <art27@cantab.net>
* fix build
Signed-off-by: Andrew Thornton <art27@cantab.net>
* prevent "race" in the test
Signed-off-by: Andrew Thornton <art27@cantab.net>
* fix jsoniter mismerge
Signed-off-by: Andrew Thornton <art27@cantab.net>
* fix conflicts
Signed-off-by: Andrew Thornton <art27@cantab.net>
* fix format
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Add warnings for no worker configurations and prevent data-loss with redis/levelqueue
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Use StopTimer
Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
* move shutdownfns, terminatefns and hammerfns out of separate goroutines
Coalesce the shutdownfns etc into a list of functions that get run at shutdown
rather then have them run at goroutines blocked on selects.
This may help reduce the background select/poll load in certain
configurations.
* The LevelDB queues can actually wait on empty instead of polling
Slight refactor to cause leveldb queues to wait on empty instead of polling.
* Shutdown the shadow level queue once it is empty
* Remove bytefifo additional goroutine for readToChan as it can just be run in run
* Remove additional removeWorkers goroutine for workers
* Simplify the AtShutdown and AtTerminate functions and add Channel Flusher
* Add shutdown flusher to CUQ
* move persistable channel shutdown stuff to Shutdown Fn
* Ensure that UPCQ has the correct config
* handle shutdown during the flushing
* reduce risk of race between zeroBoost and addWorkers
* prevent double shutdown
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Upgrade levelqueue to version 0.2.0
This adds functionality for Unique Queues
* Add UniqueQueue interface and functions to create them
* Add UniqueQueue implementations
* Move TestPullRequests over to use UniqueQueue
* Reduce code duplication
* Add bytefifos
* Ensure invalid types are logged
* Fix close race in PersistableChannelQueue Shutdown
* Make WorkerPools and Queues flushable
Adds Flush methods to Queues and the WorkerPool
Further abstracts the WorkerPool
Adds a final step to Flush the queues in the defer from PrintCurrentTest
Fixes an issue with Settings inheritance in queues
Signed-off-by: Andrew Thornton <art27@cantab.net>
* Change to for loop
* Add IsEmpty and begin just making the queues composed WorkerPools
* subsume workerpool into the queues and create a flushable interface
* Add manager command
* Move flushall to queue.Manager and add to testlogger
* As per @guillep2k
* as per @guillep2k
* Just make queues all implement flushable and clean up the wrapped queue flushes
* cope with no timeout
Co-authored-by: Lauris BH <lauris@nix.lv>
