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https://issues.apache.org/jira/browse/FLINK-31324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17696756#comment-17696756
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Jiangjie Qin commented on FLINK-31324:
--------------------------------------
I think `SingleThreadFetcherManager` is indeed somewhat public at the moment.
Connector implementations extend this class from time to time. So we probably
need to make it backwards compatible even though it is marked as internal.
It also looks OK if we make it PublicEvolving. If we do so, the only additional
class that we also need to make public is `FutureCompletingBlockingQueue` as
PublicEvolving. So it does not pull in much unnecessary class exposures to the
users.
> Broken SingleThreadFetcherManager constructor API
> -------------------------------------------------
>
> Key: FLINK-31324
> URL: https://issues.apache.org/jira/browse/FLINK-31324
> Project: Flink
> Issue Type: Bug
> Components: Connectors / Parent
> Reporter: Yun Tang
> Assignee: Yun Tang
> Priority: Blocker
> Labels: pull-request-available
> Fix For: 1.17.0
>
>
> FLINK-28853 changed the default constructor of
> {{SingleThreadFetcherManager}}. Though the {{SingleThreadFetcherManager}} is
> annotated as {{Internal}}, it actually acts as some-degree public API, which
> is widely used in many connector projects:
> [flink-cdc-connector|https://github.com/ververica/flink-cdc-connectors/blob/release-2.3.0/flink-connector-mysql-cdc/src/main/java/com/ververica/cdc/connectors/mysql/source/reader/MySqlSourceReader.java#L93],
>
> [flink-connector-mongodb|https://github.com/apache/flink-connector-mongodb/blob/main/flink-connector-mongodb/src/main/java/org/apache/flink/connector/mongodb/source/reader/MongoSourceReader.java#L58]
> and so on.
> Once flink-1.17 is released, all these existing connectors are broken and
> cannot be used in new release version, and will throw exceptions like:
> {code:java}
> java.lang.NoSuchMethodError:
> org.apache.flink.connector.base.source.reader.fetcher.SingleThreadFetcherManager.<init>(Lorg/apache/flink/connector/base/source/reader/synchronization/FutureCompletingBlockingQueue;Ljava/util/function/Supplier;)V
> at
> com.ververica.cdc.connectors.mysql.source.reader.MySqlSourceReader.<init>(MySqlSourceReader.java:91)
> ~[flink-sql-connector-mysql-cdc-2.3.0.jar:2.3.0]
> at
> com.ververica.cdc.connectors.mysql.source.MySqlSource.createReader(MySqlSource.java:159)
> ~[flink-sql-connector-mysql-cdc-2.3.0.jar:2.3.0]
> at
> org.apache.flink.streaming.api.operators.SourceOperator.initReader(SourceOperator.java:312)
> ~[flink-dist-1.17-SNAPSHOT.jar:1.17-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.SourceOperatorStreamTask.init(SourceOperatorStreamTask.java:94)
> ~[flink-dist-1.17-SNAPSHOT.jar:1.17-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.restoreInternal(StreamTask.java:699)
> ~[flink-dist-1.17-SNAPSHOT.jar:1.17-SNAPSHOT]
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.restore(StreamTask.java:675)
> ~[flink-dist-1.17-SNAPSHOT.jar:1.17-SNAPSHOT]
> at
> org.apache.flink.runtime.taskmanager.Task.runWithSystemExitMonitoring(Task.java:952)
> ~[flink-dist-1.17-SNAPSHOT.jar:1.17-SNAPSHOT]
> at
> org.apache.flink.runtime.taskmanager.Task.restoreAndInvoke(Task.java:921)
> ~[flink-dist-1.17-SNAPSHOT.jar:1.17-SNAPSHOT]
> at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:745)
> ~[flink-dist-1.17-SNAPSHOT.jar:1.17-SNAPSHOT]
> at org.apache.flink.runtime.taskmanager.Task.run(Task.java:562)
> ~[flink-dist-1.17-SNAPSHOT.jar:1.17-SNAPSHOT]
> at java.lang.Thread.run(Thread.java:750) ~[?:1.8.0_362]
> {code}
> Thus, I suggest to make the original SingleThreadFetcherManager constructor
> as depreacted instead of removing it.
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