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https://issues.apache.org/jira/browse/CASSANDRA-18934?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17783464#comment-17783464
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Maxwell Guo commented on CASSANDRA-18934:
-----------------------------------------
Any background on downgrade, and What is the current specific progress?
[~dcapwell][~jjordan][~claude].
I think we can make a clean commitlog and even a system table data before
downgrade back to 4.1 , but I think we should know we are going to do
that , as I think we can not doing normal reading and writing operations,while
cleaning the log at the same time. Am I right ?
> Downgrade to 4.1 fails due to schema changes
> --------------------------------------------
>
> Key: CASSANDRA-18934
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18934
> Project: Cassandra
> Issue Type: Bug
> Components: Local/Startup and Shutdown
> Reporter: David Capwell
> Assignee: Maxwell Guo
> Priority: Normal
> Fix For: 5.0-beta, 5.0.x, 5.x
>
>
> We are required to support 5.0 downgrading to 4.1 as a migration step, but we
> don’t have tests to show this is working… I wrote a quick test to make sure a
> change we needed in Accord wouldn’t block the downgrade and see that we fail
> right now.
> {code}
> ERROR 20:56:39 Exiting due to error while processing commit log during
> initialization.
> org.apache.cassandra.db.commitlog.CommitLogReadHandler$CommitLogReadException:
> Unexpected error deserializing mutation; saved to
> /var/folders/h1/s_3p1x3s3hl0hltbpck67m0h0000gn/T/mutation4184214444767150092dat.
> This may be caused by replaying a mutation against a table with the same
> name but incompatible schema. Exception follows: java.lang.RuntimeException:
> Unknown column compaction_properties during deserialization
> at
> org.apache.cassandra.db.commitlog.CommitLogReader.readMutation(CommitLogReader.java:464)
> at
> org.apache.cassandra.db.commitlog.CommitLogReader.readSection(CommitLogReader.java:397)
> at
> org.apache.cassandra.db.commitlog.CommitLogReader.readCommitLogSegment(CommitLogReader.java:244)
> at
> org.apache.cassandra.db.commitlog.CommitLogReader.readCommitLogSegment(CommitLogReader.java:147)
> at
> org.apache.cassandra.db.commitlog.CommitLogReplayer.replayFiles(CommitLogReplayer.java:191)
> at
> org.apache.cassandra.db.commitlog.CommitLog.recoverFiles(CommitLog.java:223)
> at
> org.apache.cassandra.db.commitlog.CommitLog.recoverSegmentsOnDisk(CommitLog.java:204)
> {code}
> This was caused by a schema change in CASSANDRA-18061
> {code}
> /*
> * Licensed to the Apache Software Foundation (ASF) under one
> * or more contributor license agreements. See the NOTICE file
> * distributed with this work for additional information
> * regarding copyright ownership. The ASF licenses this file
> * to you 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 org.apache.cassandra.distributed.upgrade;
> import java.io.IOException;
> import java.io.File;
> import java.util.concurrent.atomic.AtomicBoolean;
> import org.junit.Test;
> import org.apache.cassandra.distributed.api.IUpgradeableInstance;
> public class DowngradeTest extends UpgradeTestBase
> {
> @Test
> public void test() throws Throwable
> {
> AtomicBoolean first = new AtomicBoolean(true);
> new TestCase()
> .nodes(1)
> .withConfig(c -> {
> if (first.compareAndSet(true, false))
> c.set("storage_compatibility_mode", "CASSANDRA_4");
> })
> .downgradeTo(v41)
> .setup(cluster -> {})
> // Uncomment if you want to test what happens after reading the commit log,
> which fails right now
> // .runBeforeNodeRestart((cluster, nodeId) -> {
> // IUpgradeableInstance inst = cluster.get(nodeId);
> // File f = new File((String)
> inst.config().get("commitlog_directory"));
> // deleteRecursive(f);
> // })
> .runAfterClusterUpgrade(cluster -> {})
> .run();
> }
> private void deleteRecursive(File f)
> {
> if (f.isDirectory())
> {
> File[] children = f.listFiles();
> if (children != null)
> {
> for (File c : children)
> deleteRecursive(c);
> }
> }
> f.delete();
> }
> }
> {code}
> {code}
> diff --git
> a/test/distributed/org/apache/cassandra/distributed/upgrade/UpgradeTestBase.java
>
> b/test/distributed/org/apache/cassandra/distributed/upgrade/UpgradeTestBase.java
> index 5ee8780204..b4111e3b44 100644
> ---
> a/test/distributed/org/apache/cassandra/distributed/upgrade/UpgradeTestBase.java
> +++
> b/test/distributed/org/apache/cassandra/distributed/upgrade/UpgradeTestBase.java
> @@ -226,6 +226,12 @@ public class UpgradeTestBase extends DistributedTestBase
> return this;
> }
> + public TestCase downgradeTo(Semver to)
> + {
> + upgrade.add(new TestVersions(versions.getLatest(CURRENT),
> Collections.singletonList(versions.getLatest(to))));
> + return this;
> + }
> +
> /**
> * performs all supported upgrade paths that exist in between from
> and to that include the current version.
> * This call is equivalent to calling {@code upgradesTo(from,
> CURRENT).upgradesFrom(CURRENT, to)}.
> {code}
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