Clojure High Performance Programming - Second Edition

Applying back pressure

We discussed back pressure briefly in the last chapter. Without back pressure we cannot build a reasonable load-tolerant system with predictable stability and performance. In this section, we will see how to apply back pressure in different scenarios in an application. At a fundamental level, we should have a threshold of a maximum number of concurrent jobs in the system and, based on that threshold, we should reject new requests above a certain arrival rate. The rejected messages may either be retried by the client or ignored if there is no control over the client. When applying back pressure to user-facing services, it may be useful to detect system load and deny auxiliary services first in order to conserve capacity and ...