forgejo-federation/modules/queue/base_redis.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

135 lines
3.3 KiB
Go

// Copyright 2023 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package queue
import (
"context"
"sync"
"time"
"code.gitea.io/gitea/modules/graceful"
"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/nosql"
"github.com/redis/go-redis/v9"
)
type baseRedis struct {
client redis.UniversalClient
isUnique bool
cfg *BaseConfig
mu sync.Mutex // the old implementation is not thread-safe, the queue operation and set operation should be protected together
}
var _ baseQueue = (*baseRedis)(nil)
func newBaseRedisGeneric(cfg *BaseConfig, unique bool) (baseQueue, error) {
client := nosql.GetManager().GetRedisClient(cfg.ConnStr)
var err error
for i := 0; i < 10; i++ {
err = client.Ping(graceful.GetManager().ShutdownContext()).Err()
if err == nil {
break
}
log.Warn("Redis is not ready, waiting for 1 second to retry: %v", err)
time.Sleep(time.Second)
}
if err != nil {
return nil, err
}
return &baseRedis{cfg: cfg, client: client, isUnique: unique}, nil
}
func newBaseRedisSimple(cfg *BaseConfig) (baseQueue, error) {
return newBaseRedisGeneric(cfg, false)
}
func newBaseRedisUnique(cfg *BaseConfig) (baseQueue, error) {
return newBaseRedisGeneric(cfg, true)
}
func (q *baseRedis) PushItem(ctx context.Context, data []byte) error {
return backoffErr(ctx, backoffBegin, backoffUpper, time.After(pushBlockTime), func() (retry bool, err error) {
q.mu.Lock()
defer q.mu.Unlock()
cnt, err := q.client.LLen(ctx, q.cfg.QueueFullName).Result()
if err != nil {
return false, err
}
if int(cnt) >= q.cfg.Length {
return true, nil
}
if q.isUnique {
added, err := q.client.SAdd(ctx, q.cfg.SetFullName, data).Result()
if err != nil {
return false, err
}
if added == 0 {
return false, ErrAlreadyInQueue
}
}
return false, q.client.RPush(ctx, q.cfg.QueueFullName, data).Err()
})
}
func (q *baseRedis) PopItem(ctx context.Context) ([]byte, error) {
return backoffRetErr(ctx, backoffBegin, backoffUpper, infiniteTimerC, func() (retry bool, data []byte, err error) {
q.mu.Lock()
defer q.mu.Unlock()
data, err = q.client.LPop(ctx, q.cfg.QueueFullName).Bytes()
if err == redis.Nil {
return true, nil, nil
}
if err != nil {
return true, nil, nil
}
if q.isUnique {
// the data has been popped, even if there is any error we can't do anything
_ = q.client.SRem(ctx, q.cfg.SetFullName, data).Err()
}
return false, data, err
})
}
func (q *baseRedis) HasItem(ctx context.Context, data []byte) (bool, error) {
q.mu.Lock()
defer q.mu.Unlock()
if !q.isUnique {
return false, nil
}
return q.client.SIsMember(ctx, q.cfg.SetFullName, data).Result()
}
func (q *baseRedis) Len(ctx context.Context) (int, error) {
q.mu.Lock()
defer q.mu.Unlock()
cnt, err := q.client.LLen(ctx, q.cfg.QueueFullName).Result()
return int(cnt), err
}
func (q *baseRedis) Close() error {
q.mu.Lock()
defer q.mu.Unlock()
return q.client.Close()
}
func (q *baseRedis) RemoveAll(ctx context.Context) error {
q.mu.Lock()
defer q.mu.Unlock()
c1 := q.client.Del(ctx, q.cfg.QueueFullName)
c2 := q.client.Del(ctx, q.cfg.SetFullName)
if c1.Err() != nil {
return c1.Err()
}
if c2.Err() != nil {
return c2.Err()
}
return nil // actually, checking errors doesn't make sense here because the state could be out-of-sync
}