Polly -.NET resilience & transient-fault-handling library — Neova Tech Solutions
Introduction
Nowadays cloud-based, microservice-based, or Internet-of-Things ( IoT) applications every so often depend on communicating with other systems across an unreliable network, which leads to unavailability or unreachability for these systems due to transient faults such as network problems and timeouts, being offline, under load or maybe non-responsive.
Polly, a .NET resilience and transient-fault-handling library, offers multiple resilience policies which enable software architects to design suitable reactive strategies for handling transient faults, and also proactive strategies for promoting resilience and stability. Through this post, I will walk you through all the policies/strategies/approaches which Polly library offers to handle transient faults.
Reactive transient fault handling approaches
1. Retry
These short-term faults typically correct themselves after a short span of time, and a robust cloud application should be prepared to deal with them by using a strategy like the “Retry pattern”.
Technically Retry allows callers to retry operations in the anticipation that many faults are short-lived and may self-correct; retrying the operation may succeed maybe after a short delay.
Waiting between retries, allows faults to self-correct. For example, Practices such as ‘Exponential backoff’ and ‘jitter’ enhance this by scheduling retries to avoid them becoming sources of further load or spikes.
2. Circuit-Breaker
There can also be circumstances where faults are because of unexpected events that might take much longer to fix themselves. In these situations, it might be useless for an application to continually retry an operation that is unlikely to succeed. As an alternative, the application should be coded to accept that the operation has failed and handle the failure accordingly.
Using Http retries in these situations could lead to creating a Denial of Service (DoS) attack within your own software. Therefore, you need a defence barrier so that excessive requests stop when it is not worth to keep trying. That defence barrier is precisely the “Circuit Breaker”.
Read more to learn how does circuit-breaker work?
Originally published at https://www.neovasolutions.com on May 16, 2020.
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