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From "James Taylor (JIRA)" <>
Subject [jira] [Commented] (PHOENIX-4537) RegionServer initiating compaction can trigger schema migration and deadlock the system
Date Mon, 22 Jan 2018 23:47:00 GMT


James Taylor commented on PHOENIX-4537:

The upgrade *should not* happen from a server-side connection. We have code in place for this
already. See QueryUtil.getConnectionOnServer():
    public static Connection getConnectionOnServer(Properties props, Configuration conf)
            throws ClassNotFoundException,
            SQLException {
        return getConnection(props, conf);

Sounds like we need a bit more discussion on this one before committing given the comfort
level, [~elserj]. What about the idea I outlined above of doing PHOENIX-4530 and removing
the clearTsOnDisabledIndexes altogether?

> RegionServer initiating compaction can trigger schema migration and deadlock the system
> ---------------------------------------------------------------------------------------
>                 Key: PHOENIX-4537
>                 URL:
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: Romil Choksi
>            Assignee: Josh Elser
>            Priority: Critical
>             Fix For: 5.0.0, 4.14.0
>         Attachments: PHOENIX-4537.001.patch
> [~sergey.soldatov] has been doing some great digging around a test failure we've been
seeing at $dayjob. The situation goes like this.
> 0. Run some arbitrary load
> 1. Stop HBase
> 2. Enable schema mapping ({{phoenix.schema.isNamespaceMappingEnabled=true}} and {{phoenix.schema.mapSystemTablesToNamespace=true}}
in hbase-site.xml)
> 3. Start HBase
> 4. Circumstantially, have the SYSTEM.CATALOG table need a compaction to run before a
client first connects
> When the RegionServer initiates the compaction, it will end up running {{UngroupedAggregateRegionObserver.clearTsOnDisabledIndexes}}
which opens a Phoenix connection. While the RegionServer won't upgrade system tables, it *will*
try to migrate them into the schema mapped variants (e.g. SYSTEM.CATALOG to SYSTEM:CATALOG).
> However, one of the first steps in the schema migration is to disable the SYSTEM.CATALOG
table. However, the SYSTEM.CATALOG table can't be disabled until the region is CLOSED, and
the region cannot be CLOSED until the compaction is finished. *deadlock*
> The "obvious" fix is to avoid RegionServers from triggering system table migrations,
but Sergey and [~elserj] both think that this will end badly (RegionServers falling over because
they expect the tables to be migrated and they aren't).
> Thoughts? [~ankit.singhal], [~jamestaylor], any others?

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