(cherry picked from commit 1d7ce2a39c)
(cherry picked from commit 3af8757583)
(cherry picked from commit 0b81815209)
(cherry picked from commit 7180a3222a)
(cherry picked from commit 069044f4a6)
(cherry picked from commit dd1438f389)
(cherry picked from commit 4ae6b5d64d)
(cherry picked from commit c572666d78)
(cherry picked from commit de0a4480bc)
(cherry picked from commit 60272ef4f7)
(cherry picked from commit a68fdde4be)
(cherry picked from commit ff448cf3a6)
(cherry picked from commit 208498caaa)
(cherry picked from commit 1abd3efad8)
(cherry picked from commit 818c7f4ca9)
(cherry picked from commit 1e552bbe44)
(cherry picked from commit 88dbd6da1d)
(cherry picked from commit b1c86fb777)
(cherry picked from commit 185b1e25b1)
(cherry picked from commit 0af35605ae)
(cherry picked from commit 350975b63f)
(cherry picked from commit 2788142515)
(cherry picked from commit b418a53717b247e10d2dda26d1d236400d423a94)
(cherry picked from commit 086cde3f10)
(cherry picked from commit 3e4818c779)
(cherry picked from commit f2bf1fe64f)
(cherry picked from commit db4eb288ee)
(cherry picked from commit f8db31821b)
(cherry picked from commit 2b13c06f49)
(cherry picked from commit 3fd0092056)
(cherry picked from commit 6f7662507f)
(cherry picked from commit 8a15e41887)
(cherry picked from commit 3540ab6d4a)
(cherry picked from commit a207d02ff2)
(cherry picked from commit 35309db809)
(cherry picked from commit 6ff35732f0)
(cherry picked from commit e6d922612d)
(cherry picked from commit a8df762405)
# ⚠️ 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:
