RATIS-1912. Fix infinity election when perform membership change. by wojiaodoubao · Pull Request #954 · apache/ratis

wojiaodoubao · 2023-10-27T10:33:10Z

What changes were proposed in this pull request?

This patch resolves a membership change bug. See detail in #943.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/RATIS-1912

How was this patch tested?

unit tests

wojiaodoubao · 2023-10-31T01:30:56Z

Hi @szetszwo, could you kindly help to take a review when you have time, thanks.

szetszwo

@wojiaodoubao , thanks a lot for working not this! Please see the comments inlined and also https://issues.apache.org/jira/secure/attachment/13064049/954_review.patch

szetszwo · 2023-11-01T02:47:31Z

ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderElection.java

          return logAndReturn(phase, Result.PASSED, responses, exceptions);
+        } else if (singleMode) {
+          // if candidate is in single mode, candidate pass vote.
+          return logAndReturn(phase, Result.PASSED, responses, exceptions);


Let's add a Result.SINGLE_MODE_PASSED.

szetszwo · 2023-11-01T02:47:46Z

ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderElection.java

    if (conf.hasMajority(votedPeers, server.getId())) {
      return logAndReturn(phase, Result.PASSED, responses, exceptions);
+    } else if (singleMode) {
+      return logAndReturn(phase, Result.PASSED, responses, exceptions);


Use SINGLE_MODE_PASSED.

szetszwo · 2023-11-01T02:48:50Z

ratis-server/src/main/java/org/apache/ratis/server/impl/RaftConfigurationImpl.java

+   * changing from single mode to HA mode.
+   */
+  boolean changeMajority(Collection<RaftPeer> newMembers) {
+    Preconditions.assertNull(oldConf, "Conf must be stable.");


It expect to pass the name, i.e. Preconditions.assertNull(oldConf, "oldConf")

szetszwo · 2023-11-01T02:58:55Z

ratis-server/src/main/java/org/apache/ratis/server/impl/RaftConfigurationImpl.java

+    }
+    // If newPeersCount reaches majority number of new conf size, the cluster may end with infinity
+    // election. See https://issues.apache.org/jira/browse/RATIS-1912 for more details.
+    return newPeersCount >= newMembers.size() / 2 + newMembers.size() % 2;


It may be easier to understand to return newPeersCount >= oldPeersCount, i.e.

final long oldPeersCount = newMembers.size() - newPeersCount; return newPeersCount >= oldPeersCount;

szetszwo · 2023-11-01T02:59:41Z

ratis-server/src/main/java/org/apache/ratis/server/impl/RaftConfigurationImpl.java

+      return oldConf.size() == 1 && oldConf.contains(selfId) && conf.size() == 2 && conf.contains(
+          selfId);


Make it a single line (ratis uses 120 line width).

szetszwo · 2023-11-01T03:03:22Z

ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java

        pending.setReply(newSuccessReply(request));
        return pending.getFuture();
      }
+      if (arguments.getMode() != SetConfigurationRequest.Mode.SET_UNCONDITIONALLY


Since it is not safe, let's don't allow it even for SET_UNCONDITIONALLY.

szetszwo · 2023-11-01T03:05:04Z

ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerProxy.java

  }

-  private RaftServerImpl getImpl(RaftGroupId groupId) throws IOException {
+  public RaftServerImpl getImpl(RaftGroupId groupId) throws IOException {


The method is not used in this change. Let's keep it private.

szetszwo · 2023-11-01T03:19:18Z

ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerProxy.java

+  @VisibleForTesting
+  void setRaftConf(RaftGroupId groupId, RaftConfigurationImpl conf) throws IOException {
+    getImpl(groupId).getState().setRaftConf(conf);
+  }


Move it to RaftServerTestUtil, i.e.

//RaftServerTestUtil public static void setRaftConf(RaftServer proxy, RaftGroupId groupId, RaftConfiguration conf) { ((RaftServerImpl)getDivision(proxy, groupId)).getState().setRaftConf(conf); }

szetszwo · 2023-11-01T03:21:07Z

ratis-server/src/test/java/org/apache/ratis/server/impl/RaftReconfigurationBaseTest.java

+          .build();
+      Assert.assertTrue(oldNewConf.isSingleMode(curPeer.getId()));
+      leaderServer.setRaftConf(groupId, oldNewConf);
+      leaderServer.triggerElection(groupId);


Use transferLeadership with null new leader and then remove the new triggerElection method.

try(RaftClient client = cluster.createClient()) { client.admin().transferLeadership(null, leaderServer.getId(), 10_000); }

szetszwo · 2023-11-01T03:25:12Z

ratis-server/src/test/java/org/apache/ratis/server/impl/RaftReconfigurationBaseTest.java

+      leaderServer.setRaftConf(groupId, oldNewConf);
+      leaderServer.triggerElection(groupId);
+
+      RaftTestUtil.waitForLeader(cluster);


Check new leader and new conf:

final RaftServer.Division newLeader = RaftTestUtil.waitForLeader(cluster); Assert.assertEquals(leaderServer.getId(), newLeader.getId()); Assert.assertEquals(oldNewConf, newLeader.getRaftConf());

wojiaodoubao · 2023-11-01T13:10:13Z

Thanks @szetszwo your nice comments ! Upload v0.7 to trigger workflow. Some unit tests will fail after v0.7. Waiting the workflow to tell me which are they.

szetszwo

+1 the change looks good.

szetszwo · 2023-11-01T17:44:35Z

@wojiaodoubao , there are quite a few tests need to be updated due the new restriction on setConf. Could you take a look?

szetszwo

@wojiaodoubao , thanks for fixing the tests. All tests pass except for TestInstallSnapshotNotificationWithGrpc. Could you take a look?

szetszwo · 2023-11-02T18:25:46Z

ratis-server/src/test/java/org/apache/ratis/server/impl/RaftServerTestUtil.java

+  public interface ConsumerWithIOException {
+    void accept(Collection<RaftPeer> peesToSetConf) throws IOException;
+  }


Use CheckedConsumer, i.e.

public static void runWithMinorityPeers(MiniRaftCluster cluster, Collection<RaftPeer> peersInNewConf, CheckedConsumer<Collection<RaftPeer>, IOException> consumer) throws IOException {

wojiaodoubao · 2023-11-03T03:13:20Z

The failed case is TestInstallSnapshotNotificationWithGrpc#testInstallSnapshotDuringBootstrap. It expected 2 times of 'installSnapshot' after 'setConfiguration', but got 3 times. I failed to reproduce the failure on my local environment. Upload v0.9 based on CheckedConsumer. Re-trigger workflow to see whether the failed case occurs repeatedly.

wojiaodoubao · 2023-11-03T07:07:47Z

In TestInstallSnapshotNotificationWithGrpc#testInstallSnapshotDuringBootstrap, the setConfiguration is separated into 2 rpc calls. Add peer s1 first, then peer s2.

The s2 will be notified twice of install snapshot event. I think it doesn't break the semantic of notifyInstallSnapshot. Let me quote from GrpcLogAppender#shouldNotifyToInstallSnapshot.

Every follower should try to install at least one snapshot during bootstrapping, if available.

The GrpcLogAppender keeps notifyInstallSnapshot to the bootstrapping follower again and again. So install snapshot twice does happen. Changing the assert condition to 2 <= numSnapshotRequests.get() should be fine.

szetszwo · 2023-11-03T21:23:03Z

Since it is not safe, let's don't allow it even for SET_UNCONDITIONALLY.

On a second thought, it is good to have a server conf to enable/disable the restriction since it is more efficient to change

form 1-node to 3-node by one command

than

from 1-node to 2-node and 2-node to 3-node by two commands.

For changing from non-HA to HA, it usually is an one time thing and the admin will monitor it. The split brain problem can be ignored.

@wojiaodoubao , what do you think?

szetszwo · 2023-11-05T17:16:10Z

Filed RATIS-1930.

wojiaodoubao · 2023-11-06T02:38:41Z

Thanks a lot for @szetszwo's kindly help.

On a second thought, it is good to have a server conf to enable/disable the restriction since it is more efficient to change

form 1-node to 3-node by one command
than

from 1-node to 2-node and 2-node to 3-node by two commands.

I totally agree.

…ache#954)

### What changes were proposed in this pull request? Bump Ratis version from 2.5.1 to 3.0.1. Address incompatible changes: - RATIS-589. Eliminate buffer copying in SegmentedRaftLogOutputStream.(apache/ratis#964) - RATIS-1677. Do not auto format RaftStorage in RECOVER.(apache/ratis#718) - RATIS-1710. Refactor metrics api and implementation to separated modules. (apache/ratis#749) ### Why are the changes needed? Bump Ratis version from 2.5.1 to 3.0.1. Ratis has released v3.0.0, v3.0.1, which release note refers to [3.0.0](https://ratis.apache.org/post/3.0.0.html), [3.0.1](https://ratis.apache.org/post/3.0.1.html). The 3.0.x version include new features like pluggable metrics and lease read, etc, some improvements and bugfixes including: - 3.0.0: Change list of ratis 3.0.0 In total, there are roughly 100 commits diffing from 2.5.1 including: - Incompatible Changes - RaftStorage Auto-Format - RATIS-1677. Do not auto format RaftStorage in RECOVER. (apache/ratis#718) - RATIS-1694. Fix the compatibility issue of RATIS-1677. (apache/ratis#731) - RATIS-1871. Auto format RaftStorage when there is only one directory configured. (apache/ratis#903) - Pluggable Ratis-Metrics (RATIS-1688) - RATIS-1689. Remove the use of the thirdparty Gauge. (apache/ratis#728) - RATIS-1692. Remove the use of the thirdparty Counter. (apache/ratis#732) - RATIS-1693. Remove the use of the thirdparty Timer. (apache/ratis#734) - RATIS-1703. Move MetricsReporting and JvmMetrics to impl. (apache/ratis#741) - RATIS-1704. Fix SuppressWarnings(“VisibilityModifier”) in RatisMetrics. (apache/ratis#742) - RATIS-1710. Refactor metrics api and implementation to separated modules. (apache/ratis#749) - RATIS-1712. Add a dropwizard 3 implementation of ratis-metrics-api. (apache/ratis#751) - RATIS-1391. Update library dropwizard.metrics version to 4.x (apache/ratis#632) - RATIS-1601. Use the shaded dropwizard metrics and remove the dependency (apache/ratis#671) - Streaming Protocol Change - RATIS-1569. Move the asyncRpcApi.sendForward(..) call to the client side. (apache/ratis#635) - New Features - Leader Lease (RATIS-1864) - RATIS-1865. Add leader lease bound ratio configuration (apache/ratis#897) - RATIS-1866. Maintain leader lease after AppendEntries (apache/ratis#898) - RATIS-1894. Implement ReadOnly based on leader lease (apache/ratis#925) - RATIS-1882. Support read-after-write consistency (apache/ratis#913) - StateMachine API - RATIS-1874. Add notifyLeaderReady function in IStateMachine (apache/ratis#906) - RATIS-1897. Make TransactionContext available in DataApi.write(..). (apache/ratis#930) - New Configuration Properties - RATIS-1862. Add the parameter whether to take Snapshot when stopping to adapt to different services (apache/ratis#896) - RATIS-1930. Add a conf for enable/disable majority-add. (apache/ratis#961) - RATIS-1918. Introduces parameters that separately control the shutdown of RaftServerProxy by JVMPauseMonitor. (apache/ratis#950) - RATIS-1636. Support re-config ratis properties (apache/ratis#800) - RATIS-1860. Add ratis-shell cmd to generate a new raft-meta.conf. (apache/ratis#901) - Improvements & Bug Fixes - Netty - RATIS-1898. Netty should use EpollEventLoopGroup by default (apache/ratis#931) - RATIS-1899. Use EpollEventLoopGroup for Netty Proxies (apache/ratis#932) - RATIS-1921. Shared worker group in WorkerGroupGetter should be closed. (apache/ratis#955) - RATIS-1923. Netty: atomic operations require side-effect-free functions. (apache/ratis#956) - RaftServer - RATIS-1924. Increase the default of raft.server.log.segment.size.max. (apache/ratis#957) - RATIS-1892. Unify the lifetime of the RaftServerProxy thread pool (apache/ratis#923) - RATIS-1889. NoSuchMethodError: RaftServerMetricsImpl.addNumPendingRequestsGauge apache/ratis#922 (apache/ratis#922) - RATIS-761. Handle writeStateMachineData failure in leader. (apache/ratis#927) - RATIS-1902. The snapshot index is set incorrectly in InstallSnapshotReplyProto. (apache/ratis#933) - RATIS-1912. Fix infinity election when perform membership change. (apache/ratis#954) - RATIS-1858. Follower keeps logging first election timeout. (apache/ratis#894) - 3.0.1:This is a bugfix release. See the [changes between 3.0.0 and 3.0.1](apache/ratis@ratis-3.0.0...ratis-3.0.1) releases. ### Does this PR introduce _any_ user-facing change? No. ### How was this patch tested? Cluster manual test. Closes #2480 from SteNicholas/CELEBORN-1400. Authored-by: SteNicholas <programgeek@163.com> Signed-off-by: Shuang <lvshuang.xjs@alibaba-inc.com>

lijinglun added 2 commits October 27, 2023 14:35

v0.1

861cbdf

v0.2

8c00760

wojiaodoubao changed the title ~~Ratis 1912~~ Fix infinity election when perform membership change. Oct 27, 2023

wojiaodoubao mentioned this pull request Oct 27, 2023

Example to show infinity election when perform membership change. #943

Closed

lijinglun added 2 commits October 30, 2023 11:29

v0.3

ac6de8f

v0.4

88aa0af

SzyWilliam changed the title ~~Fix infinity election when perform membership change.~~ RATIS-1912. Fix infinity election when perform membership change. Oct 31, 2023

v0.5 remove unused import

feeac8d

szetszwo reviewed Nov 1, 2023

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lijinglun added 2 commits November 1, 2023 21:04

v0.6

d3b0134

v0.7

61744a7

szetszwo approved these changes Nov 1, 2023

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v0.8 fix unit tests.

1080e99

szetszwo reviewed Nov 2, 2023

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v0.9

449d485

v0.10

f93e9cc

szetszwo merged commit c35f769 into apache:master Nov 3, 2023

symious pushed a commit to symious/ratis that referenced this pull request Mar 29, 2024

RATIS-1912. Fix infinity election when perform membership change. (ap…

03daaf0

…ache#954)

SteNicholas mentioned this pull request Apr 24, 2024

[CELEBORN-1400] Bump Ratis version from 2.5.1 to 3.0.1 apache/celeborn#2480

Closed

		return oldConf.size() == 1 && oldConf.contains(selfId) && conf.size() == 2 && conf.contains(
		selfId);

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wojiaodoubao commented Oct 27, 2023

What changes were proposed in this pull request?

What is the link to the Apache JIRA

How was this patch tested?

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