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Leader to give up leadership lock on graceful shutdown #1460
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kubernetes-client:master
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himanshug:leader_shutdown
Dec 29, 2020
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80 changes: 80 additions & 0 deletions
80
extended/src/test/java/io/kubernetes/client/extended/leaderelection/LeaderElectorTest.java
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,80 @@ | ||
/* | ||
Copyright 2020 The Kubernetes Authors. | ||
Licensed under the Apache License, Version 2.0 (the "License"); | ||
you may not use this file except in compliance with the License. | ||
You may obtain a copy of the License at | ||
http://www.apache.org/licenses/LICENSE-2.0 | ||
Unless required by applicable law or agreed to in writing, software | ||
distributed under the License is distributed on an "AS IS" BASIS, | ||
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
See the License for the specific language governing permissions and | ||
limitations under the License. | ||
*/ | ||
package io.kubernetes.client.extended.leaderelection; | ||
|
||
import java.time.Duration; | ||
import java.util.concurrent.CountDownLatch; | ||
import java.util.concurrent.TimeUnit; | ||
import org.junit.Test; | ||
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/** Leader Election tests using "simulated" locks created by {@link LockSmith} */ | ||
public class LeaderElectorTest { | ||
/** | ||
* Tests that when a leader candidate is stopped gracefully, second candidate immediately becomes | ||
* leader. | ||
*/ | ||
@Test(timeout = 20000L) | ||
public void testLeaderGracefulShutdown() throws Exception { | ||
LockSmith lockSmith = new LockSmith(); | ||
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CountDownLatch startBeingLeader1 = new CountDownLatch(1); | ||
CountDownLatch stopBeingLeader1 = new CountDownLatch(1); | ||
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LeaderElector leaderElector1 = | ||
makeAndRunLeaderElectorAsync(lockSmith, "candidate1", startBeingLeader1, stopBeingLeader1); | ||
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// wait for candidate1 to become leader | ||
startBeingLeader1.await(); | ||
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CountDownLatch startBeingLeader2 = new CountDownLatch(1); | ||
CountDownLatch stopBeingLeader2 = new CountDownLatch(1); | ||
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LeaderElector leaderElector2 = | ||
makeAndRunLeaderElectorAsync(lockSmith, "candidate2", startBeingLeader2, stopBeingLeader2); | ||
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leaderElector1.close(); | ||
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// ensure stopBeingLeader hook is called | ||
stopBeingLeader1.await(); | ||
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// wait for candidate2 to become leader | ||
startBeingLeader2.await(); | ||
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leaderElector2.close(); | ||
} | ||
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private LeaderElector makeAndRunLeaderElectorAsync( | ||
LockSmith lockSmith, | ||
String lockIdentity, | ||
CountDownLatch startBeingLeader, | ||
CountDownLatch stopBeingLeader) { | ||
LeaderElectionConfig leaderElectionConfig = | ||
new LeaderElectionConfig( | ||
lockSmith.makeLock(lockIdentity), | ||
Duration.ofMillis(TimeUnit.MINUTES.toMillis(1)), | ||
Duration.ofMillis(TimeUnit.SECONDS.toMillis(51)), | ||
Duration.ofMillis(TimeUnit.SECONDS.toMillis(3))); | ||
LeaderElector leaderElector = new LeaderElector(leaderElectionConfig); | ||
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Thread thread = | ||
new Thread( | ||
() -> | ||
leaderElector.run( | ||
() -> startBeingLeader.countDown(), () -> stopBeingLeader.countDown()), | ||
String.format("%s-leader-elector-main", lockIdentity)); | ||
thread.setDaemon(true); | ||
thread.start(); | ||
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return leaderElector; | ||
} | ||
} |
84 changes: 84 additions & 0 deletions
84
extended/src/test/java/io/kubernetes/client/extended/leaderelection/LockSmith.java
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,84 @@ | ||
/* | ||
Copyright 2020 The Kubernetes Authors. | ||
Licensed under the Apache License, Version 2.0 (the "License"); | ||
you may not use this file except in compliance with the License. | ||
You may obtain a copy of the License at | ||
http://www.apache.org/licenses/LICENSE-2.0 | ||
Unless required by applicable law or agreed to in writing, software | ||
distributed under the License is distributed on an "AS IS" BASIS, | ||
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
See the License for the specific language governing permissions and | ||
limitations under the License. | ||
*/ | ||
package io.kubernetes.client.extended.leaderelection; | ||
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import io.kubernetes.client.openapi.ApiException; | ||
import java.net.HttpURLConnection; | ||
import java.util.concurrent.atomic.AtomicReference; | ||
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/** Makes simulated {@link Lock} objects that behave as if they were backed by real API server. */ | ||
public class LockSmith { | ||
private AtomicReference<Resource> lockResourceRef = new AtomicReference<>(); | ||
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public Lock makeLock(String identity) { | ||
return new SimulatedLock(identity); | ||
} | ||
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private class SimulatedLock implements Lock { | ||
private final String identity; | ||
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public SimulatedLock(String identity) { | ||
this.identity = identity; | ||
} | ||
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@Override | ||
public LeaderElectionRecord get() throws ApiException { | ||
if (lockResourceRef.get() == null) { | ||
throw new ApiException("Record Not Found", HttpURLConnection.HTTP_NOT_FOUND, null, null); | ||
} | ||
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return lockResourceRef.get().record; | ||
} | ||
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@Override | ||
public boolean create(LeaderElectionRecord record) { | ||
return lockResourceRef.compareAndSet(null, new Resource(record)); | ||
} | ||
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@Override | ||
public boolean update(LeaderElectionRecord record) { | ||
Resource res = lockResourceRef.get(); | ||
if (res == null) { | ||
return false; | ||
} else { | ||
Resource newResource = new Resource(res.version + 1, record); | ||
return lockResourceRef.compareAndSet(res, newResource); | ||
} | ||
} | ||
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@Override | ||
public String identity() { | ||
return identity; | ||
} | ||
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@Override | ||
public String describe() { | ||
return "simulated/lock"; | ||
} | ||
} | ||
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private static class Resource { | ||
final int version; | ||
final LeaderElectionRecord record; | ||
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public Resource(LeaderElectionRecord record) { | ||
this.version = 0; | ||
this.record = record; | ||
} | ||
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public Resource(int version, LeaderElectionRecord record) { | ||
this.version = version; | ||
this.record = record; | ||
} | ||
} | ||
} |
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I feel like there is value in using WireMock and actually talking HTTP for the locks. How hard is it to switch to testing using WireMock like we do elsewhere?
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Thanks for the review.
Here we are more interested in testing the code of LeaderElector which can be tested as long as a well-behaving
Lock
implementation is provided. Also, truth is that it was just super simple/quick to do and does the job :) ... and followed in spirit the existing unit tests for leader election related code.With WireMock, we would actually also test the implementation of Lock itself i.e. ConfigMapLock class etc. I haven't used WireMock in the past, so not sure about the work required, but will try to look into it.
that said, not sure but, I see there is an e2e build that appears to setup a real k8s cluster, how would you feel about this test running as an e2e integration test against real k8s cluster instead of the WireMock ?
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e2e integration is even better :)