[WIP] #4039
[WIP] #4039
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Summary of ChangesHello @lidezhu, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request introduces a new workload type, Highlights
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Code Review
This pull request introduces a new fast_slow workload type to simulate CDC lag, which is a valuable addition for testing purposes. The implementation adds the necessary configuration, schema, and worker logic for this new workload.
I've found a few issues that should be addressed:
- There's a critical bug in
fastslow_ddl.gowhere a new DDL worker is added to aWaitGroupbut never signals completion, which will cause the program to hang. - The new code in
tools/workload/schema/fastslow/fastslow.gouses the globalmath/randsource from concurrent goroutines, which will cause lock contention and impact performance. Each worker should have its ownrand.Randinstance. - There's a minor thread-safety issue in a cache initialization function that can be improved by using
sync.Oncefor robustness.
Overall, this is a good feature addition, and with these fixes, it will be a solid contribution.
| wg.Add(1) | ||
| go func(db *DBWrapper) { | ||
| defer wg.Done() | ||
| app.runFastSlowDDLWorker(db, wl) | ||
| }(db) |
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The runFastSlowDDLWorker function contains an infinite loop and never returns. This means the defer wg.Done() in the calling goroutine will never be executed, causing wg.Wait() in the Execute method to block forever. This is a critical bug that will cause the program to hang.
Given that other workers in this tool also seem to run indefinitely, the DDL worker should probably not be part of the WaitGroup. It should run as a background goroutine that is terminated when the program exits.
Please remove the wg.Add(1) and defer wg.Done() for this goroutine.
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| func (w *FastSlowWorkload) BuildInsertSql(tableIndex int, batchSize int) string { | ||
| tableName := w.TableName(tableIndex) | ||
| n := rand.Int63() |
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The math/rand package uses a global random number source that is protected by a mutex. Calling functions from math/rand (like rand.Int63()) from multiple concurrent goroutines will cause lock contention, which can be a performance bottleneck in a workload generator. This can skew benchmark results.
It is recommended to create a new rand.Rand instance for each worker goroutine (e.g., r := rand.New(rand.NewSource(time.Now().UnixNano()))) and use that for generating random numbers (e.g., r.Int63()). This would require passing the rand.Rand instance through the call chain.
| var ( | ||
| cachePadString = make(map[int]string, cacheSize) | ||
| cacheIdx atomic.Int64 | ||
| ) | ||
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| func initPadStringCache() { | ||
| if len(cachePadString) >= cacheSize { | ||
| return | ||
| } | ||
| for i := 0; i < cacheSize; i++ { | ||
| cachePadString[i] = genRandomPadString(padStringLength) | ||
| } | ||
| log.Info("Initialized pad string cache", | ||
| zap.Int("cacheSize", cacheSize), | ||
| zap.Int("stringLength", padStringLength)) | ||
| } |
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The initPadStringCache function is not safe for concurrent execution. Although it's currently called from a single thread, using sync.Once is the idiomatic and safer way to handle one-time initializations of global resources. This will prevent potential race conditions if the calling pattern changes in the future.
You will also need to add import "sync".
| var ( | |
| cachePadString = make(map[int]string, cacheSize) | |
| cacheIdx atomic.Int64 | |
| ) | |
| func initPadStringCache() { | |
| if len(cachePadString) >= cacheSize { | |
| return | |
| } | |
| for i := 0; i < cacheSize; i++ { | |
| cachePadString[i] = genRandomPadString(padStringLength) | |
| } | |
| log.Info("Initialized pad string cache", | |
| zap.Int("cacheSize", cacheSize), | |
| zap.Int("stringLength", padStringLength)) | |
| } | |
| var ( | |
| cachePadString = make(map[int]string, cacheSize) | |
| cacheIdx atomic.Int64 | |
| initCacheOnce sync.Once | |
| ) | |
| func initPadStringCache() { | |
| initCacheOnce.Do(func() { | |
| for i := 0; i < cacheSize; i++ { | |
| cachePadString[i] = genRandomPadString(padStringLength) | |
| } | |
| log.Info("Initialized pad string cache", | |
| zap.Int("cacheSize", cacheSize), | |
| zap.Int("stringLength", padStringLength)) | |
| }) | |
| } |
What problem does this PR solve?
Issue Number: close #xxx
What is changed and how it works?
Check List
Tests
Questions
Will it cause performance regression or break compatibility?
Do you need to update user documentation, design documentation or monitoring documentation?
Release note