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Consul cluster manager for Vert.x ecosystem

Introduction

Consul - based cluster manager that is plugable into Vert.x ecosystem. Consul is a distributed, highly available, and data center aware solution to connect and configure applications across dynamic, distributed infrastructure.

Motivation

As we all know Vert.x cluster managers are pluggable and so far we have 6 cluster manager implementations:

• Hazelcast - based: https://vertx.io/docs/vertx-hazelcast/java/
• Apache Zookeeper - based: https://vertx.io/docs/vertx-zookeeper/java/
• Apache Ignite - based: https://vertx.io/docs/vertx-ignite/java/
• JGroups - based: https://github.com/vert-x3/vertx-jgroups
• Atomix - based : https://github.com/atomix/atomix-vertx
• Infinispan - based : https://github.com/vert-x3/vertx-infinispan

If you are already using Consul along with Vert.x within your system - it might be a good fit to use Consul directly as main manager for :

• discovery and group membership of Vert.x nodes in a cluster Maintaining cluster wide topic subscriber lists (so we know which nodes are interested in which event bus addresses)
• distributed map support;
• distributed locks;
• distributed counters;

Note : Cluster managers do not handle the event bus inter-node transport, this is done directly by Vert.x with TCP connections.

Implementation details

Current consul cluster manager implementation is fully based on vertx-consul-client and vertx-core.

How to use

Version compatibility matrix

Gradle

compile 'io.reactiverse:consul-cluster-manager:${cluster-manager-version}'

Maven

<dependency>
  <groupId>io.reactiverse</groupId>
  <artifactId>consul-cluster-manager</artifactId>
  <version>${cluster-manager-version}</version>
</dependency>

There's more than one way to create an instance of consul cluster manager.

• Defaut one:

ConsulClusterManager consulClusterManager = new ConsulClusterManager(); // Consul agent should be running then on localhost:8500.

• Excplicilty specifying configuration:

JsonObject options = new JsonObject()
.put("host", "consulAgentHost") // host on which consul agent is running, if not specified default host will be used which is "localhost".
.put("port", consulAgentPort) // port on wich consul agent is runing, if not specified default port will be used which is "8500".
/*
 * There's an option to utilize built-in internal caching.
 * @{Code false} - enable internal caching of event bus subscribers - this will give us better latency but stale reads (stale subsribers) might appear.
 * @{Code true} - disable internal caching of event bus subscribers - this will give us stronger consistency in terms of fetching event bus subscribers,
 * but this will result in having much more round trips to consul kv store where event bus subs are being kept.
 */
.put("preferConsistency", false)
/*
 * Option to provide custom service name which is visible on web ui
 */
.put("serviceName", "my-custom-service")
/*
 * There's also an option to specify explictly host address on which given cluster manager will be operating on.
 * By defult InetAddress.getLocalHost().getHostAddress() will be executed.
 * Linux systems enumerate the loopback network interface the same way as regular LAN network interfaces, but the JDK
 * InetAddress.getLocalHost method does not specify the algorithm used to select the address returned under such circumstances, and will
 * often return the loopback address, which is not valid for network communication.
 */
 .put("nodeHost", "10.0.0.1");
 // consul client options can be additionally specified as needed.
ConsulClusterManager consulClusterManager = new ConsulClusterManager(options);

• Once cluster manager instance is created we can easily create clustered vertx. Voilà!

VertxOptions vertxOptions = new VertxOptions();
vertxOptions.setClusterManager(consulClusterManager);
Vertx.clusteredVertx(vertxOptions, res -> {
    if (res.succeeded()) {
	    // clustered vertx instance has been successfully created!
	    Vertx vertx = res.result();
	} else {
	    // something went wrong :(
	}
}

Restrictions

• Compliant with ONLY Vert.x 3.6.0+ release.
• The limit on a key's value size of any of the consul maps is 512KB.