Geode Sequence Generator

1. Overview
2. Building From Source
3. Usage

This project used as the starting point the tool geode-single-32bit-sequence, developed by Charlie Black some years ago.

Overview

Apache Geode is a data management platform that provides real-time, consistent access to data-intensive applications throughout widely distributed cloud architectures.

Sometimes our applications need to use sequential IDs, generating these IDs in distributed systems is generally cumbersome and error-prone.

This project is a simple Apache Geode client wrapper that allows applications to use distributed counters entirely stored and managed through a running Apache Geode cluster.

In order to achieve uniqueness and make sure no clients receive the same ID, the project uses Geode Functions and the Distributed Lock Service.
Long story short, every time a sequence should be computed, the client automatically executes a Function on the server hosting the primary data for the required sequenceId and acquires the respective lock to make sure no other clients can get the same ID.

The above, of course, will generate contention on the server(s) computing the IDs, so it's always advisable to retrieve the IDs in batches from the clients and work with those until a new ID is required.

Building From Source

All platforms require a Java installation with JDK 1.8 or more recent version. The JAVA_HOME environment variable can be set as below:

Platform	Command
Unix	export JAVA_HOME=/usr/java/jdk1.8.0_121
OSX	export JAVA_HOME=/usr/libexec/java_home -v 1.8
Windows	set JAVA_HOME="C:\Program Files\Java\jdk1.8.0_121"

Clone the current repository in your local environment and, within the directory containing the source code, run gradle build:

$ ./gradlew build

Usage

Deploy

Build the tool and deploy it to a running Apache Geode cluster using the gfsh deploy command.

Client Application

Initialize the geode-sequence-generator by invoking the DistributedSequenceFactory.initialize() method. By default the tool will use a PARTITION_PERSISTENT region to store and compute the sequences, but you can further customize the region type and which specific servers will act as the sequence service layer by using other initalize methods from the DistributedSequenceFactory class.

DistributedSequenceFactory.initialize(clientcache);

Acquire your sequence through the DistributedSequenceFactory.getSequence(sequenceId) method.

DistributedSequence ticketsSequence = DistributedSequenceFactory.getSequence("Tickets");

Use the returned DistributedSequence instance to retrieve/compute your sequences.

// Get Current Value
Long currentValue = ticketsSequence.get();

// Increment And Get Current Value 
Long sequencePlusOne = ticketsSequence.incrementAndGet();

// Get Next Batch of Unique Sequences
List<Long> sequences = ticketsSequence.nextBatch(1000);