Salesforce’s open sourcing Centrifuge: A library for accelerating JVM restarts

Yesterday, Paymon Teyer, a principal member of Technical Staff at Salesforce, introduced Centrifuge as a library, which is also a framework for scheduling and running startup and warmup tasks. It focuses mainly on accelerating JVM restarts. It also provides an interface for implementing warmup tasks, like, calling an HTTP endpoint, populating caches and handling pre-compilation tasks for generated code.

When the JVM restarts in a production environment, it affects the performance of the server. The JVM has to reload classes, trigger reflection inflation, rerun its JIT compiler on any code paths, reinitialize objects and dependency injections, and populate component caches.

The performance impact of JVM restarts can be minimized by allowing individual components to execute arbitrary warmup logic themselves, after a cold start. To make this possible, Centrifuge was created with the goal of executing warmup tasks. It also manages resource usage and handles failures. Centrifuge allows users to register and configure warmup tasks either descriptively or programmatically. It also schedules tasks, manages and monitors threads, handles exceptions and retries, and provides status reports.

Centrifuge supports the following two categories of warmup tasks:

Blocking tasks

Blocking tasks prevent the application from returning to the available server pool until they complete. These tasks must be executed for the application to function properly. For example, executing source code generators or populating a cache from storage to meet SLA requirements.

Non-blocking tasks

Non- blocking tasks execute asynchronously and don’t interfere with the application’s readiness. These tasks do the work which is needed after an application restarts but is not required immediately for the application to be in a consistent state. Examples include warmup logic that triggers JIT compilation on code paths or eagerly triggering dependency injection and object creation.

How to Use Centrifuge?

1. The first step is to include a Maven dependency for Centrifuge in the POM
2. Then implementing the Warmer interface for each of the warmup tasks. The warmer class should have an accessible default constructor and it should not swallow InterruptedException.
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3. The warmers can be registered either programmatically with code or descriptively with a configuration file. For adding and removing warmers without recompiling, the warmers should be registered descriptively within a configuration file.
4. Then the configuration file needs to be loaded into the Centrifuge.

How is the HTTP Warmer useful?

Centrifuge provides a simple HTTP warmer which is used to call HTTP endpoints to trigger code path. It is also exercised by the resource implementing the endpoint. If an application provides a homepage URL and when called, connects to a database, populates the caches, etc., then the HTTP warmer can warm these code paths.

Read more about Centrifuge on Salesforce’s official website.

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