Spring Microservices in Action, Second Edition by John Carnell & Illary Huaylupo Sánchez

Author:John Carnell & Illary Huaylupo Sánchez [Carnell, John & Sánchez, Illary Huaylupo]
Language: eng
Format: epub
Publisher: Manning Publications Co.
Published: 0101-01-01T00:00:00+00:00

Now that we have our fallback method in place, let’s go ahead and call our endpoint again. This time when we select it in Postman and encounter a timeout error (remember we have a one-in-three chance), we shouldn’t get an exception back from the service call. Instead, the dummy license values will return as in figure 7.8.

Figure 7.8 Your service invocation using a Resilience4j fallback

7.7 Implementing the bulkhead pattern

In a microservice-based application, we’ll often need to call multiple microservices to complete a particular task. Without using a bulkhead pattern, the default behavior for these calls is that these are executed using the same threads that are reserved for handling requests for the entire Java container. In high volumes, performance problems with one service out of many can result in all of the threads for the Java container being maxed out and waiting to process work, while new requests for work back up. The Java container will eventually crash.

The bulkhead pattern segregates remote resource calls in their own thread pools so that a single misbehaving service can be contained and not crash the container. Resilience4j provides two different implementations of the bulkhead pattern. You can use these implementations to limit the number of concurrent executions:

Semaphore bulkhead—Uses a semaphore isolation approach, limiting the number of concurrent requests to the service. Once the limit is reached, it starts rejecting requests.

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