sink(ticdc): waiting the asynchronous ddl to synchronize (#12123) #12466
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Summary of ChangesHello @ti-chi-bot, 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 significantly enhances the robustness of DDL (Data Definition Language) replication in TiCDC. It addresses a critical issue where long-running DDL operations, particularly in TiDB environments, could lead to connection timeouts and perceived failures, even if the DDL was successfully applied downstream. The changes introduce a proactive waiting mechanism that queries the downstream TiDB's DDL job status, ensuring that TiCDC accurately reflects the completion of DDLs and maintains data consistency, especially under network instability or during prolonged schema changes. Highlights
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Code Review
This pull request refactors the DDL sink logic to handle long-running DDLs that might cause connection losses. Instead of failing, it now waits for the DDL to complete by polling its status from the downstream TiDB. This is a solid improvement for the sink's robustness. The overall implementation is good, but I've found a critical issue with merge conflict markers in a configuration file, a high-severity SQL injection vulnerability, and a few medium-severity issues related to error handling and code clarity that should be addressed.
| <<<<<<< HEAD | ||
| ======= | ||
| ["CDC:ErrDDLStateNotFound"] | ||
| error = ''' | ||
| DDL state not found %s | ||
| ''' | ||
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| ["CDC:ErrDDLUnsupportType"] | ||
| error = ''' | ||
| unsupport ddl type %s, query %s | ||
| ''' | ||
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| >>>>>>> d9a7e9f313 (sink(ticdc): waiting the asynchronous ddl to synchronize (#12123)) |
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There are merge conflict markers (<<<<<<< HEAD, =======, >>>>>>>) in this file. This will break the TOML parsing and cause the application to fail. Please remove them and keep the intended error definitions.
["CDC:ErrDDLStateNotFound"]
error = '''
DDL state not found %s
'''
["CDC:ErrDDLUnsupportType"]
error = '''
unsupport ddl type %s, query %s
'''
| showJobs := fmt.Sprintf(`SELECT JOB_ID, JOB_TYPE, SCHEMA_STATE, SCHEMA_ID, TABLE_ID, STATE, QUERY FROM information_schema.ddl_jobs | ||
| WHERE CREATE_TIME >= "%s" AND QUERY = "%s";`, createTime, ddl) | ||
| //nolint:rowserrcheck | ||
| jobsRows, err := db.QueryContext(ctx, showJobs) |
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Constructing SQL queries using fmt.Sprintf with external data (like the DDL query string) is vulnerable to SQL injection. Even if the ddl string is expected to be safe, it's a security best practice to always use parameterized queries to prevent potential vulnerabilities.
Please modify this to use query parameters.
showJobs := `SELECT JOB_ID, JOB_TYPE, SCHEMA_STATE, SCHEMA_ID, TABLE_ID, STATE, QUERY FROM information_schema.ddl_jobs
WHERE CREATE_TIME >= ? AND QUERY = ?;`
//nolint:rowserrcheck
jobsRows, err := db.QueryContext(ctx, showJobs, createTime, ddl)|
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| func (m *DDLSink) checkAsyncExecDDLDone(ctx context.Context, tables map[model.TableName]struct{}) bool { | ||
| ctx, cancel := context.WithTimeout(ctx, timeout) | ||
| ctx, cancel := context.WithTimeout(ctx, 5*time.Second) |
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The timeout value 5*time.Second is used as a magic number. It's better to define a constant for it at the top of the file to improve readability and maintainability, for example const checkAsyncExecDDLDoneTimeout = 5 * time.Second.
| log.Warn("Wait the asynchronous ddl to synchronize", zap.String("ddl", ddl.Query), zap.String("ddlCreateTime", ddlCreateTime), | ||
| zap.String("readTimeout", m.cfg.ReadTimeout), zap.Error(err)) |
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The log message "Wait the asynchronous ddl to synchronize" is grammatically awkward. Consider rephrasing it for clarity, for example: "Waiting for asynchronous DDL to be synchronized".
| log.Warn("Wait the asynchronous ddl to synchronize", zap.String("ddl", ddl.Query), zap.String("ddlCreateTime", ddlCreateTime), | |
| zap.String("readTimeout", m.cfg.ReadTimeout), zap.Error(err)) | |
| log.Warn("Waiting for asynchronous DDL to be synchronized", zap.String("ddl", ddl.Query), zap.String("ddlCreateTime", ddlCreateTime), | |
| zap.String("readTimeout", m.cfg.ReadTimeout), zap.Error(err)) |
| state, err := getDDLStateFromTiDB(ctx, m.db, ddl.Query, ddlCreateTime) | ||
| if err != nil { | ||
| log.Error("Error when getting DDL state from TiDB", zap.Error(err)) | ||
| } |
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The error returned from getDDLStateFromTiDB is logged but not handled. The function continues execution with a zero-value state, which leads to a generic ErrDDLStateNotFound being returned. This loses the original error context, making debugging more difficult. The original error should be returned to be handled by the retry mechanism.
state, err := getDDLStateFromTiDB(ctx, m.db, ddl.Query, ddlCreateTime)
if err != nil {
log.Error("Error when getting DDL state from TiDB", zap.Error(err))
return err
}| for row.Next() { | ||
| err = row.Scan(&ddlCreateTime) | ||
| if err != nil { | ||
| log.Warn("getting ddlCreateTime failed", zap.Error(err)) | ||
| } | ||
| } |
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The query is expected to return at most one row. Using a for loop is not idiomatic for this case. An if statement would be more appropriate and clearer.
if row.Next() {
err = row.Scan(&ddlCreateTime)
if err != nil {
log.Warn("getting ddlCreateTime failed", zap.Error(err))
}
}
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2 participants
This is an automated cherry-pick of #12123
What problem does this PR solve?
Issue Number: close #12114 close #12128
What is changed and how it works?
When a DDL operation takes a long time, the connection may be lost, even though the DDL is actually executed. Instead of throwing a failure state, we can query the downstream and wait for the DDL to complete.
Notice:
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