scheduler: fix bugs to make scheduler more robust #1941
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Summary of Changes
Hello @hongyunyan, 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 focuses on enhancing the scheduler's robustness by refining its operational logic and incorporating stability checks, particularly for span merging and balancing. It also introduces a new, comprehensive integration test suite to validate these scheduler improvements under various DML scenarios, alongside minor logging and test utility enhancements.
Highlights
- Scheduler Robustness Improvements: Introduced a configurable
maxLagThresholdfor span merging logic and added a stability check in thebalanceSplitsSchedulerto skip balancing operations when the system is not in a stable state (e.g., during active operations or with absent spans). - Logging Enhancement: Improved the clarity of logging for new task group additions in the replication scheduler by explicitly logging the
groupIDas anint64. - Test Utility Enhancement: Modified the
query_dispatcher_countutility script to support a newcomparisonModeparameter, enabling more flexible assertions (e.g., 'less than or equal') in integration tests. - New Integration Test Suite: Added a comprehensive integration test (
ddl_for_split_tables_random_schedule) to thoroughly validate the scheduler's behavior with both split and non-split tables under random DML workloads across multiple TiCDC servers. - Test Failpoint Refactoring: Removed the
StopSplitSchedulerfailpoint from several existing integration tests, streamlining test configurations and reflecting potential improvements in scheduler stability.
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Code Review
This pull request improves the robustness of the scheduler by adding checks to prevent scheduling during unstable states and by replacing magic numbers with constants. It also enhances logging for better observability. A significant part of this PR is the addition of a new integration test for random scheduling scenarios, which improves test coverage. The changes in existing tests to remove failpoints suggest that the scheduler is now more robust and can be tested in a more realistic environment. I've found a potential issue in the updated test utility script that could cause it to fail if it receives a non-integer value.
| if [ "$value" == "$target" ]; then | ||
| exit 0 | ||
| if [ "$comparisonMode" == "le" ]; then | ||
| if [ "$value" -le "$target" ]; then |
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The arithmetic comparison [ "$value" -le "$target" ] will cause the script to fail if $value is not an integer (e.g., if it's null from the jq command). The previous string comparison == was safer in this regard. To make this more robust, you should check if $value is an integer before performing the arithmetic comparison.
| if [ "$value" -le "$target" ]; then | |
| if [[ "$value" =~ ^[0-9]+$ ]] && [ "$value" -le "$target" ]; then |
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: lidezhu The full list of commands accepted by this bot can be found here. The pull request process is described here
Needs approval from an approver in each of these files:
Approvers can indicate their approval by writing |
[LGTM Timeline notifier]Timeline:
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/retest |
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