circuit-breaker-monad
所属分类：硬件设计
开发工具：TypeScript
文件大小：0KB
下载次数：0
上传日期：2023-01-06 17:08:28
上 传 者：
sh-1993
说明： 断路器模式作为单子，
(Circuit Breaker pattern as a monad,)
文件列表:
.travis.yml (1110, 2021-03-11)
LICENSE (1077, 2021-03-11)
package-lock.json (64503, 2021-03-11)
package.json (1164, 2021-03-11)
src/ (0, 2021-03-11)
src/breaker.test.ts (4199, 2021-03-11)
src/helpers.ts (601, 2021-03-11)
src/index.ts (3929, 2021-03-11)
src/types.ts (2096, 2021-03-11)
tsconfig.json (789, 2021-03-11)
tslint.json (3834, 2021-03-11)
# Circuit Breaker pattern as a monad
[](https://www.npmjs.com/package/circuit-breaker-monad)
[](https://travis-ci.org/YBogomolov/circuit-breaker-monad)
Part of [fp-ts](https://github.com/gcanti/fp-ts) ecosystem.
TypeScript implementation of Circuit Breaker pattern. Adaptation of [Glue.CircuitBreaker](https://hackage.haskell.org/package/glue-core-0.4.2/docs/Glue-CircuitBreaker.html) module from Haskell.
You can read a bit more abou the pattern and this implementation [in my article](https://medium.com/@yuriybogomolov/circuit-breaker-in-a-functional-world-9c555c8e9527).
## Usage example
First of all, you need to install the package:
```sh
npm install circuit-breaker-monad
```
Then import the main `circuitBreaker` function:
```ts
import { circuitBreaker } from 'circuit-breaker-monad/lib';
```
This function returns a `Reader`, which, given the corresponding `BreakerOptions`, creates an enhanced fetcher – a function which takes any `Lazy
>` instance and returns a tuple of `IORef` and `TaskEither`. The first element of this tuple is current circuit breaker status, implemented via `IORef` (mutable reference in the IO monad), and the second element of the tuple is ready-to-be-called `TaskEither`.
Let's look at the usage example:
```ts
import { fold } from 'fp-ts/lib/Either';
import { IORef } from 'fp-ts/lib/IORef';
import { circuitBreaker, defaultBreakerOptions } from 'circuit-breaker-monad/lib';
import { BreakerClosed } from 'circuit-breaker-monad/lib/types';
const fetcher = circuitBreaker()(defaultBreakerOptions);
const main = async () => {
const request = () => fetch('http://my-domain.com/my-data.json').then((res) => res.json());
const breakerState = new IORef(new BreakerClosed(0)); // initial breaker state
const [result, ref] = fetcher({ request, breakerState });
const response = await result();
fold(
(e: Error) => { },
(myData) => { },
)(response);
// ref :: BreakerClosed { errorCount: 0 }
// result :: TaskEither
// response :: Either
// myData :: TMyJsonData
};
```
The `ref` variable is resulting circuit breaker status, which can be passed to the next call, so you take the full control over what's going on inside the circuit breaker:
```ts
const [ref, result] = fetcher(promise);
const myData1 = await result();
const [, result2] = fetcher(promise, ref);
const myData2 = await result2();
// here `ref` may be 'Open' if the second call to the service has failed
```
### Configuration
Circuit breaker may be configured by passing these parameters to the Reader:
- `maxBreakerFailures` - how many times the underlying service must fail in the given window before the circuit opens;
- `resetTimeoutSecs` - the window of time in which the underlying service must fail for the circuit to open, seconds;
- `breakerDescription` - description that is attached to the failure so as to identify the particular circuit.
Default options are:
```ts
export const defaultBreakerOptions: BreakerOptions = {
maxBreakerFailures: 3,
resetTimeoutSecs: 60,
breakerDescription: 'Circuit breaker is closed',
};
```
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