Circuit Breaker Plugin

Plugin implementing Circuit Breaker design pattern.

Request maker will have 3 states:

• Closed - all requests are passing to the next plugin allowing to create requests
• Open - no requests are passing to next step, every request throws error from last 'real' request
• Half-Open - only limited number of requests are allowed to actually executes, if these requests were successful state changes to Closed, otherwise goes back to Open

Api

Create options

• getKey: function [= () => ''] - allows to divide requests to different instances of Circuit Breaker, by default only one Circuit Breaker instance is created
• isSystemError: function [=() => true] specifies that error should be treated as a system error and therefore will lead to an increasing counter of failed requests in Circuit Breaker, if the error is not a system error then error is treated as normal behavior and therefore will lead to a decreasing counter of failed requests
• failureTimeout: number [=120000] - time interval in which failed requests will considered to get state
• failureThreshold: number [=50] - percentage of failed requests inside failureTimeout interval, if that number is exceeded state changes to Open
• minimumFailureCount: number [=5] - number of minimum request which should be failed to consider stats from current time interval
• openTimeout: number [=60000] - time interval in which all requests will forcedly fail, after that timeout halfOpenThreshold number of requests will be executed as usual
• halfOpenThreshold: number [=5] - percentage of requests allowed to execute while state is Half-Open

External meta

• CIRCUIT_BREAKER.open: boolean - flag indicating that current request was blocked by Circuit Breaker

Internal meta

• CIRCUIT_BREAKER.breaker - Circuit Breaker instance

How to

Base example

import request from '@tinkoff/request-core';
import circuitBreaker from '@tinkoff/request-plugin-circuit-breaker';

const req = request([
    // ...plugins for any request transforms and cache
    // should be set after transforming plugins and cache plugins
    circuitBreaker(),
    // should be set before protocol plugins
    // ...plugins for making actual request
]);

Validators

import request from '@tinkoff/request-core';
import http, { isNetworkFail } from '@tinkoff/request-plugin-protocol-http';
import circuitBreaker from '@tinkoff/request-plugin-circuit-breaker';

const req = request([
    // ...plugins for any request transforms and cache
    // should be set after transforming plugins and cache plugins
    circuitBreaker({
        isSystemError: isNetworkFail,
    }),
    // should be set before protocol plugins
    // ...plugins for making actual request
    http(),
]);