997183bee2
Removed the backticks that were making links not render. Fixed a few typoes, too. Integrating feedback from Artem Artem caught some errors that I had made (and that my editor, Atom, had made - grrr). I fixed them. Thanks, Artem. :) Removing duplicate content I caught that duplicate content somehow got added to preface.adoc. I removed one set of it to make that content not be duplicated. * Fix `jdbc.adoc` typos
101 lines
3.1 KiB
Plaintext
101 lines
3.1 KiB
Plaintext
[[zookeeper]]
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== Zookeeper Support
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Version 4.2 added https://zookeeper.apache.org/[Zookeeper] support to the framework in version 4.2, which consists of:
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* <<zk-metadata-store,A metadata store>>
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* <<zk-lock-registry,A lock registry>>
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* <<zk-leadership,Leadership event handling>>
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[[zk-metadata-store]]
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=== Zookeeper Metadata Store
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You ca use the `ZookeeperMetadataStore` where any `MetadataStore` is needed, such as for persistent file list filters.
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See <<metadata-store>> for more information.
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The following example configures a Zookeeper metadata store with XML:
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====
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[source, xml]
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----
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<bean id="client" class="org.springframework.integration.zookeeper.config.CuratorFrameworkFactoryBean">
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<constructor-arg value="${connect.string}" />
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</bean>
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<bean id="meta" class="org.springframework.integration.zookeeper.metadata.ZookeeperMetadataStore">
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<constructor-arg ref="client" />
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</bean>
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----
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====
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The following example shows how to configure a Zookeeper metadata store with Java:
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====
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[source, java]
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----
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@Bean
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public MetadataStore zkStore(CuratorFramework client) {
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return new ZookeeperMetadataStore(client);
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}
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----
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====
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[[zk-lock-registry]]
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=== Zookeeper Lock Registry
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The `ZookeeperLockRegistry` can be used where any `LockRegistry` is needed, such as when using an aggregator in a clustered environment with a shared `MessageStore`.
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A `LockRegistry` is used to "`look up`" a lock based on a key (the aggregator uses `correlationId`).
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By default, locks in the `ZookeeperLockRegistry` are maintained in zookeeper under the following path: `/SpringIntegration-LockRegistry/`.
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You can customize the path by providing an implementation of `ZookeeperLockRegistry.KeyToPathStrategy`, as the following example shows:
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====
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[source, java]
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----
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public interface KeyToPathStrategy {
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String pathFor(String key);
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boolean bounded();
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}
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----
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====
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If the strategy returns `true` from `isBounded`, unused locks do not need to be harvested.
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For unbounded strategies (such as the default), you need to periodically invoke `expireUnusedOlderThan(long age)` to remove old unused locks from memory.
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[[zk-leadership]]
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=== Zookeeper Leadership Event Handling
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The following example uses XML to configure an application for leader election in Zookeeper:
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====
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[source, xml]
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----
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<int-zk:leader-listener client="client" path="/siNamespace" role="cluster" />
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----
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====
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`client` is a reference to a `CuratorFramework` bean.
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A `CuratorFrameworkFactoryBean` is available.
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When a leader is elected, an `OnGrantedEvent` is published for the role `cluster`.
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Any endpoints in that role are started.
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When leadership is revoked, an `OnRevokedEvent` is published for the role `cluster`.
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Any endpoints in that role are stopped.
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See <<endpoint-roles>> for more information.
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You can use Java configuration to create an instance of the leader initiator, as the following example shows:
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====
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[source, java]
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----
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@Bean
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public LeaderInitiatorFactoryBean leaderInitiator(CuratorFramework client) {
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return new LeaderInitiatorFactoryBean()
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.setClient(client)
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.setPath("/siTest/")
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.setRole("cluster");
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}
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----
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====
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