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OpenAtomFoundation / pika

Pika is a Redis-Compatible database developed by Qihoo's infrastructure team.
BSD 3-Clause "New" or "Revised" License
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fix: add metric is_eligible_for_master_election to support reelection decision in codis-sentinel #2766

Closed cheniujh closed 2 months ago

cheniujh commented 3 months ago

这个PR修复了 fix #2436

1 具体地，通过对外提供指标‘is_eligible_for_master_election’（通过info replication/info命令），告知本实例是否有资格在fail over是成为新master的候选者。

2 在codis-sentinel中加入了使用该指标的逻辑：

This PR fixes issue #2436:

  1. Specifically, it introduces the metric 'is_eligible_for_master_election' (accessible via the info replication/info command) to indicate whether this instance is eligible to be a candidate for the new master during a failover.

    • The characteristics of this metric are as follows: If the current instance is performing a full synchronization (as a slave) or if the last full synchronization in its history was incomplete (due to its own failure or the master's failure), 'is_eligible_for_master_election' will be false. Otherwise, it will be true.
  2. This metric's logic has been integrated into codis-sentinel:
    • 2.1 When the master fails and a new master needs to be elected, nodes with 'is_eligible_for_master_election' set to false are not eligible to be candidates for the new master.
    • 2.2 When a new master has been elected for the cluster and the slave switches to the new master, if 'is_eligible_for_master_election' is found to be false, the slaveof command is executed with the force parameter to enforce full synchronization.

Summary by CodeRabbit

coderabbitai[bot] commented 3 months ago

Walkthrough

The recent changes primarily revolve around enhancing the master election process in the Codis and Pika systems. A new field IsEligibleForMasterElection has been introduced to various structs and methods to ensure that only eligible servers participate in the master election. Additionally, new methods and configurations handle unfinished full sync operations, ensuring consistency and reliability during master-slave switchovers.

Changes

File(s) Change Summary
codis/pkg/models/group.go, codis/pkg/topom/topom_group.go, codis/pkg/topom/topom_sentinel.go, codis/pkg/utils/redis/sentinel.go Added IsEligibleForMasterElection field to relevant structs and methods. Updated master election logic to consider this field.
conf/pika.conf, include/pika_conf.h, src/pika_conf.cc, src/pika_admin.cc, src/pika_repl_client_conn.cc Introduced handling of internal-used-unfinished-full-sync configuration parameter. Added methods to manage unfinished full sync operations.
src/pika_db.cc Added logic to remove unfinished full sync count after setting replication state to kTryConnect.

Assessment against linked issues

Objective (Issue #2436) Addressed Explanation
Introduce a new field to track eligibility for master election ✅
Ensure servers with unfinished full sync are not eligible for master election ✅
Provide a mechanism to handle unfinished full sync operations ✅

Poem

In Codis realms where data streams, A new rule now reigns supreme. Masters chosen with utmost care, Only when syncs are all fair. If full sync's not yet complete, Master role they can't compete. 🐇✨

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