gharris1727 commented on code in PR #14068:
URL: https://github.com/apache/kafka/pull/14068#discussion_r1286461778
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docs/connect.html:
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@@ -543,6 +543,67 @@ <h6>ACL requirements</h6>
</tbody>
</table>
+ <h4><a id="connect_plugindiscovery" href="#connect_plugindiscovery">Plugin
Discovery</a></h4>
+
+ <p>Plugin discovery is the name for the strategy which the Connect worker
uses to find plugin classes and make them accessible to configure and run in
Connectors and Tasks. This is controlled by the <a
href="#connectconfigs_plugin.discovery"><code>plugin.discovery</code> worker
configuration</a>, and has a significant impact on worker startup time.
<code>SERVICE_LOAD</code> is the fastest strategy, but care should be taken to
verify that plugins are compatible before setting this configuration to
<code>SERVICE_LOAD</code>.</p>
+
+ <p>Prior to version 3.6, this strategy was not configurable, and behaved
like the <code>ONLY_SCAN</code> mode which is compatible with all plugins. For
version 3.6 and later, this mode defaults to <code>HYBRID_WARN</code> which is
also compatible with all plugins, but logs a warning for all plugins which are
incompatible with the other modes. For unit-test environments that use the
<code>EmbeddedConnectCluster</code> this defaults to the
<code>HYBRID_FAIL</code> strategy, which stops the worker with an error if an
incompatible plugin is detected. Finally, the <code>SERVICE_LOAD</code>
strategy will silently hide incompatible plugins and make them unusable.</p>
+
+ <h5><a id="connect_plugindiscovery_compatibility"
href="#connect_plugindiscovery_compatibility">Verifying Plugin
Compatibility</a></h5>
+
+ <p>To verify if all of your plugins are compatible, first ensure that you
are using version 3.6 or later of the Connect runtime. You can then perform one
of the following checks:</p>
+
+ <ul>
+ <li>Start your worker with the default
<code>HYBRID_WARN</code>strategy, and WARN logs enabled for the
<code>org.apache.kafka.connect</code> package. At least one WARN log message
mentioning the <code>plugin.discovery</code> configuration should be printed.
This log message will explicitly say that all plugins are compatible, or list
the incompatible plugins.</li>
+ <li>Start your worker in a test environment with
<code>HYBRID_FAIL</code>. If all plugins are compatible, startup will succeed.
If at least one plugin is not compatible the worker will fail to start up, and
all incompatible plugins will be listed in the exception.</li>
+ </ul>
+
+ <p>If the verification step succeeds, then your current set of installed
plugins are compatible, and it should be safe to change the
<code>plugin.discovery</code> configuration to <code>SERVICE_LOAD</code>. If
you change the set of already-installed plugins, they may no longer be
compatible, and you should repeat the above verification. If the verification
fails, you must address the incompatible plugins before using the
<code>SERVICE_LOAD</code> strategy.</p>
+
+ <h5><a id="connect_plugindiscovery_migrateartifact"
href="#connect_plugindiscovery_migrateartifact">Operators: Artifact
Migration</a></h5>
+
+ <p>As an operator of Connect, if you discover incompatible plugins, there
are multiple ways to try to resolve the incompatibility. They are listed below
from most to least preferable.</p>
+
+ <ol>
+ <li>Upgrade your incompatible plugins to the latest release version
from your plugin provider.</li>
+ <li>Contact your plugin provider and request that they migrate the
plugin to be compatible, following the <a
href="#connect_plugindiscovery_migratesource">source migration
instructions</a>, and then upgrade to the migrated version.</li>
+ <li>Migrate the plugin artifacts yourself using the included migration
script.</li>
+ </ol>
+
+ <p>The migration script is located in
<code>bin/connect-plugin-path.sh</code> and
<code>bin\windows\connect-plugin-path.bat</code> of your Kafka installation.
The script can migrate incompatible plugin artifacts already installed on your
Connect worker's <code>plugin.path</code> by adding or modifying JAR or
resource files. This is not suitable for environments using code-signing, as
this may change the artifacts such that they will fail signature verification.
View the built-in help with <code>--help</code>.</p>
+
+ <p>To perform a migration, first use the <code>list</code> subcommand to
get an overview of the plugins available to the script. You must tell the
script where to find plugins, which can be done with the repeatable
<code>--worker-config</code>, <code>--plugin-path</code>, and
<code>--plugin-location</code> arguments. The script will only migrate plugins
present in the paths specified, so if you add plugins to your worker's
classpath, then you will need to specify those plugins via one or more
<code>--plugin-location</code> arguments.</p>
+
+ <p>Once you see that all incompatible plugins are included in the listing,
you can proceed to dry-run the migration with <code>sync-manifests
--dry-run</code>. This will perform all parts of the migration, except for
writing the results of the migration to disk. Note that the
<code>sync-manifests</code> command requires all specified paths to be
writable, and may alter the contents of the directories. Make a backup of the
specified paths, or copy them to a writable directory.</p>
+
+ <p>Ensure that you have a backup and the dry-run succeeds before removing
the <code>--dry-run</code> flag and actually running the migration. If the
migration fails without the <code>--dry-run</code> flag, then the partially
migrated artifacts should be discarded. The migration is idempotent, so running
it multiple times and on already-migrated plugins is safe. After the migration
is completed, you should <a
href="#connect_plugindiscovery_compatibility">verify the migration is
complete</a>. These migration and verification steps may be put into a
Continuous Integration process to automatically migrate plugins.</p>
+
+ <h5><a id="connect_plugindiscovery_migratesource"
href="#connect_plugindiscovery_migratesource">Developers: Source
Migration</a></h5>
+
+ <p>To make plugins compatible with <code>SERVICE_LOAD</code>, it is
necessary to add <a
href="https://docs.oracle.com/javase/8/docs/api/java/util/ServiceLoader.html";>ServiceLoader</a>
manifests to your source code, which should then be packaged in the release
artifact. Manifests are resource files in <code>META-INF/services/</code> named
after their superclass type, and contain a list of fully-qualified subclass
names, one on each line. Manifests should be located in the same module as the
classes they refer to, not in the corresponding test resources.</p>
Review Comment:
I mentioned testing with a pre-release artifact at the end of the source
migration section.
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