gitea/modules/indexer/code/wrapped.go
wxiaoguang 6f9c278559
Rewrite queue (#24505)
# ⚠️ 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:

![image](https://user-images.githubusercontent.com/2114189/236620635-55576955-f95d-4810-b12f-879026a3afdf.png)
2023-05-08 19:49:59 +08:00

105 lines
2.2 KiB
Go

// Copyright 2019 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package code
import (
"context"
"fmt"
"sync"
repo_model "code.gitea.io/gitea/models/repo"
"code.gitea.io/gitea/modules/log"
)
var indexer = newWrappedIndexer()
// ErrWrappedIndexerClosed is the error returned if the indexer was closed before it was ready
var ErrWrappedIndexerClosed = fmt.Errorf("Indexer closed before ready")
type wrappedIndexer struct {
internal Indexer
lock sync.RWMutex
cond *sync.Cond
closed bool
}
func newWrappedIndexer() *wrappedIndexer {
w := &wrappedIndexer{}
w.cond = sync.NewCond(w.lock.RLocker())
return w
}
func (w *wrappedIndexer) set(indexer Indexer) {
w.lock.Lock()
defer w.lock.Unlock()
if w.closed {
// Too late!
indexer.Close()
}
w.internal = indexer
w.cond.Broadcast()
}
func (w *wrappedIndexer) get() (Indexer, error) {
w.lock.RLock()
defer w.lock.RUnlock()
if w.internal == nil {
if w.closed {
return nil, ErrWrappedIndexerClosed
}
w.cond.Wait()
if w.closed {
return nil, ErrWrappedIndexerClosed
}
}
return w.internal, nil
}
// Ping checks if elastic is available
func (w *wrappedIndexer) Ping() bool {
indexer, err := w.get()
if err != nil {
log.Warn("Failed to get indexer: %v", err)
return false
}
return indexer.Ping()
}
func (w *wrappedIndexer) Index(ctx context.Context, repo *repo_model.Repository, sha string, changes *repoChanges) error {
indexer, err := w.get()
if err != nil {
return err
}
return indexer.Index(ctx, repo, sha, changes)
}
func (w *wrappedIndexer) Delete(repoID int64) error {
indexer, err := w.get()
if err != nil {
return err
}
return indexer.Delete(repoID)
}
func (w *wrappedIndexer) Search(ctx context.Context, repoIDs []int64, language, keyword string, page, pageSize int, isMatch bool) (int64, []*SearchResult, []*SearchResultLanguages, error) {
indexer, err := w.get()
if err != nil {
return 0, nil, nil, err
}
return indexer.Search(ctx, repoIDs, language, keyword, page, pageSize, isMatch)
}
func (w *wrappedIndexer) Close() {
w.lock.Lock()
defer w.lock.Unlock()
if w.closed {
return
}
w.closed = true
w.cond.Broadcast()
if w.internal != nil {
w.internal.Close()
}
}