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https://issues.apache.org/jira/browse/DRILL-5771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16246879#comment-16246879
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ASF GitHub Bot commented on DRILL-5771:
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Github user paul-rogers commented on the issue:
https://github.com/apache/drill/pull/1014
Not sure the description here is entirely correct. Let's separate two
concepts: the plugin (code) and the plugin definition (the stuff in JSON.)
Plugin definitions are stored in ZK and retrieved by the Foreman. There may
be some form of race condition in the Foreman, but that's not my focus here.
The plugin *definition* is read by the Forman and serialized into the
physical plan. Each worker reads the definition from the physical plan. For
this reason, the worker's definition can never be out of date: it is the
definition used when serializing the plan.
Further, Drill allows table functions which provide query-time name/value
pair settings for format plugin properties. The only way these can work is to
be serialized along with the query. So, the actual serialized format plugin
definition, included with the query, includes both the ZK information and the
table function information.
> Fix serDe errors for format plugins
> -----------------------------------
>
> Key: DRILL-5771
> URL: https://issues.apache.org/jira/browse/DRILL-5771
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.11.0
> Reporter: Arina Ielchiieva
> Assignee: Arina Ielchiieva
> Priority: Minor
> Fix For: 1.12.0
>
>
> Create unit tests to check that all storage format plugins can be
> successfully serialized / deserialized.
> Usually this happens when query has several major fragments.
> One way to check serde is to generate physical plan (generated as json) and
> then submit it back to Drill.
> One example of found errors is described in the first comment. Another
> example is described in DRILL-5166.
> *Serde issues:*
> 1. Could not obtain format plugin during deserialization
> Format plugin is created based on format plugin configuration or its name.
> On Drill start up we load information about available plugins (its reloaded
> each time storage plugin is updated, can be done only by admin).
> When query is parsed, we try to get plugin from the available ones, it we can
> not find one we try to [create
> one|https://github.com/apache/drill/blob/3e8b01d5b0d3013e3811913f0fd6028b22c1ac3f/exec/java-exec/src/main/java/org/apache/drill/exec/store/dfs/FileSystemPlugin.java#L136-L144]
> but on other query execution stages we always assume that [plugin exists
> based on
> configuration|https://github.com/apache/drill/blob/3e8b01d5b0d3013e3811913f0fd6028b22c1ac3f/exec/java-exec/src/main/java/org/apache/drill/exec/store/dfs/FileSystemPlugin.java#L156-L162].
> For example, during query parsing we had to create format plugin on one node
> based on format configuration.
> Then we have sent major fragment to the different node where we used this
> format configuration we could not get format plugin based on it and
> deserialization has failed.
> To fix this problem we need to create format plugin during query
> deserialization if it's absent.
>
> 2. Absent hash code and equals.
> Format plugins are stored in hash map where key is format plugin config.
> Since some format plugin configs did not have overridden hash code and
> equals, we could not find format plugin based on its configuration.
> 3. Named format plugin usage
> Named format plugins configs allow to get format plugin by its name for
> configuration shared among all drillbits.
> They are used as alias for pre-configured format plugiins. User with admin
> priliges can modify them at runtime.
> Named format plugins configs are used instead of sending all non-default
> parameters of format plugin config, in this case only name is sent.
> Their usage in distributed system may cause raise conditions.
> For example,
> 1. Query is submitted.
> 2. Parquet format plugin is created with the following configuration
> (autoCorrectCorruptDates=>true).
> 3. Seralized named format plugin config with name as parquet.
> 4. Major fragment is sent to the different node.
> 5. Admin has changed parquet configuration for the alias 'parquet' on all
> nodes to autoCorrectCorruptDates=>false.
> 6. Named format is deserialized on the different node into parquet format
> plugin with configuration (autoCorrectCorruptDates=>false).
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