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docs: update readme #235

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merged 2 commits into from
Sep 21, 2024
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docs: update readme #235

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8521ecc
docs: update readme
big-kahuna-burger Sep 19, 2024
3874b0c
Update README.md
big-kahuna-burger Sep 19, 2024
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30 changes: 13 additions & 17 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ fastify.register(require('@fastify/under-pressure'), {
maxEventLoopUtilization:0.98
})

fastify.get('/', (req, reply) => {
fastify.get('/', (request, reply) => {
if (fastify.isUnderPressure()) {
// skip complex computation
}
Expand All @@ -58,14 +58,14 @@ fastify.register(require('@fastify/under-pressure'), {

You can also configure custom Error instance `@fastify/under-pressure` will throw.
```js
class CustomError extends Error {
constructor () {
super('Custom error message')
Error.captureStackTrace(this, CustomError)
}
class CustomError extends Error {
constructor () {
super('Custom error message')
Error.captureStackTrace(this, CustomError)
}
}

fastify.register(require('@fastify/under-pressure'), {
fastify.register(require('@fastify/under-pressure'), {
maxEventLoopDelay: 1000,
customError: CustomError
})
Expand All @@ -74,8 +74,6 @@ You can also configure custom Error instance `@fastify/under-pressure` will thro
The default value for `maxEventLoopDelay`, `maxHeapUsedBytes`, `maxRssBytes` and `maxEventLoopUtilization` is `0`.
If the value is `0` the check will not be performed.

Since [`eventLoopUtilization`](https://nodejs.org/api/perf_hooks.html#perf_hooks_performance_eventlooputilization_utilization1_utilization2) is only available in Node version 14.0.0 and 12.19.0 the check will be disabled in other versions.

Thanks to the encapsulation model of Fastify, you can selectively use this plugin in some subset of routes or even with different thresholds in different plugins.

#### `memoryUsage`
Expand All @@ -95,14 +93,14 @@ const underPressure = require('@fastify/under-pressure')()
fastify.register(underPressure, {
maxHeapUsedBytes: 100000000,
maxRssBytes: 100000000,
pressureHandler: (req, rep, type, value) => {
pressureHandler: (request, reply, type, value) => {
if (type === underPressure.TYPE_HEAP_USED_BYTES) {
fastify.log.warn(`too many heap bytes used: ${value}`)
} else if (type === underPressure.TYPE_RSS_BYTES) {
fastify.log.warn(`too many rss bytes used: ${value}`)
}

rep.send('out of memory') // if you omit this line, the request will be handled normally
reply.send('out of memory') // if you omit this line, the request will be handled normally
}
})
```
Expand All @@ -112,8 +110,8 @@ It is possible as well to return a Promise that will call `reply.send` (or somet
```js
fastify.register(underPressure, {
maxHeapUsedBytes: 100000000,
pressureHandler: (req, rep, type, value) => {
return getPromise().then(() => reply.send({hello: 'world'}))
pressureHandler: (request, reply, type, value) => {
return getPromise().then(() => reply.send({ hello: 'world' }))
}
})
```
Expand All @@ -134,14 +132,14 @@ fastify.register(underPressure, {
fastify.register(async function (fastify) {
fastify.get('/', {
config: {
pressureHandler: (req, rep, type, value) => {
pressureHandler: (request, reply, type, value) => {
if (type === underPressure.TYPE_HEAP_USED_BYTES) {
fastify.log.warn(`too many heap bytes used: ${value}`)
} else if (type === underPressure.TYPE_RSS_BYTES) {
fastify.log.warn(`too many rss bytes used: ${value}`)
}

rep.send('out of memory') // if you omit this line, the request will be handled normally
reply.send('out of memory') // if you omit this line, the request will be handled normally
}
}
}, () => 'A')
Expand Down Expand Up @@ -245,8 +243,6 @@ const fastify = require('fastify')()
fastify.register(require('@fastify/under-pressure'), {
sampleInterval: <your custom sample interval in ms>
})


```

<a name="additional-information"></a>
Expand Down