# agentkeepalive
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[npm-url]: https://npmjs.org/package/agentkeepalive
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[download-url]: https://npmjs.org/package/agentkeepalive
The enhancement features `keep alive` `http.Agent`. Support `http` and `https`.
## What's different from original `http.Agent`?
- `keepAlive=true` by default
- Disable Nagle's algorithm: `socket.setNoDelay(true)`
- Add free socket timeout: avoid long time inactivity socket leak in the free-sockets queue.
- Add active socket timeout: avoid long time inactivity socket leak in the active-sockets queue.
- TTL for active socket.
## Node.js version required
Support Node.js >= `8.0.0`
## Install
```bash
$ npm install agentkeepalive --save
```
## new Agent([options])
* `options` {Object} Set of configurable options to set on the agent.
Can have the following fields:
* `keepAlive` {Boolean} Keep sockets around in a pool to be used by
other requests in the future. Default = `true`.
* `keepAliveMsecs` {Number} When using the keepAlive option, specifies the initial delay
for TCP Keep-Alive packets. Ignored when the keepAlive option is false or undefined. Defaults to 1000.
Default = `1000`. Only relevant if `keepAlive` is set to `true`.
* `freeSocketTimeout`: {Number} Sets the free socket to timeout
after `freeSocketTimeout` milliseconds of inactivity on the free socket.
The default [server-side timeout](https://nodejs.org/api/http.html#serverkeepalivetimeout) is 5000 milliseconds, to [avoid ECONNRESET exceptions](https://medium.com/ssense-tech/reduce-networking-errors-in-nodejs-23b4eb9f2d83), we set the default value to `4000` milliseconds.
Only relevant if `keepAlive` is set to `true`.
* `timeout`: {Number} Sets the working socket to timeout
after `timeout` milliseconds of inactivity on the working socket.
Default is `freeSocketTimeout * 2` so long as that value is greater than or equal to 8 seconds, otherwise the default is 8 seconds.
* `maxSockets` {Number} Maximum number of sockets to allow per
host. Default = `Infinity`.
* `maxFreeSockets` {Number} Maximum number of sockets (per host) to leave open
in a free state. Only relevant if `keepAlive` is set to `true`.
Default = `256`.
* `socketActiveTTL` {Number} Sets the socket active time to live, even if it's in use.
If not set, the behaviour keeps the same (the socket will be released only when free)
Default = `null`.
## Usage
```js
const http = require('http');
const Agent = require('agentkeepalive');
const keepaliveAgent = new Agent({
maxSockets: 100,
maxFreeSockets: 10,
timeout: 60000, // active socket keepalive for 60 seconds
freeSocketTimeout: 30000, // free socket keepalive for 30 seconds
});
const options = {
host: 'cnodejs.org',
port: 80,
path: '/',
method: 'GET',
agent: keepaliveAgent,
};
const req = http.request(options, res => {
console.log('STATUS: ' + res.statusCode);
console.log('HEADERS: ' + JSON.stringify(res.headers));
res.setEncoding('utf8');
res.on('data', function (chunk) {
console.log('BODY: ' + chunk);
});
});
req.on('error', e => {
console.log('problem with request: ' + e.message);
});
req.end();
setTimeout(() => {
if (keepaliveAgent.statusChanged) {
console.log('[%s] agent status changed: %j', Date(), keepaliveAgent.getCurrentStatus());
}
}, 2000);
```
### `getter agent.statusChanged`
counters have change or not after last checkpoint.
### `agent.getCurrentStatus()`
`agent.getCurrentStatus()` will return a object to show the status of this agent:
```js
{
createSocketCount: 10,
closeSocketCount: 5,
timeoutSocketCount: 0,
requestCount: 5,
freeSockets: { 'localhost:57479:': 3 },
sockets: { 'localhost:57479:': 5 },
requests: {}
}
```
### Support `https`
```js
const https = require('https');
const HttpsAgent = require('agentkeepalive').HttpsAgent;
const keepaliveAgent = new HttpsAgent();
// https://www.google.com/search?q=nodejs&sugexp=chrome,mod=12&sourceid=chrome&ie=UTF-8
const options = {
host: 'www.google.com',
port: 443,
path: '/search?q=nodejs&sugexp=chrome,mod=12&sourceid=chrome&ie=UTF-8',
method: 'GET',
agent: keepaliveAgent,
};
const req = https.request(options, res => {
console.log('STATUS: ' + res.statusCode);
console.log('HEADERS: ' + JSON.stringify(res.headers));
res.setEncoding('utf8');
res.on('data', chunk => {
console.log('BODY: ' + chunk);
});
});
req.on('error', e => {
console.log('problem with request: ' + e.message);
});
req.end();
setTimeout(() => {
console.log('agent status: %j', keepaliveAgent.getCurrentStatus());
}, 2000);
```
### Support `req.reusedSocket`
This agent implements the `req.reusedSocket` to determine whether a request is send through a reused socket.
When server closes connection at unfortunate time ([keep-alive race](https://code-examples.net/en/q/28a8069)), the http client will throw a `ECONNRESET` error. Under this circumstance, `req.reusedSocket` is useful when we want to retry the request automatically.
```js
const http = require('http');
const Agent = require('agentkeepalive');
const agent = new Agent();
const req = http
.get('http://localhost:3000', { agent }, (res) => {
// ...
})
.on('error', (err) => {
if (req.reusedSocket && err.code === 'ECONNRESET') {
// retry the request or anything else...
}
})
```
This behavior is consistent with Node.js core. But through `agentkeepalive`, you can use this feature in older Node.js version.
## [Benchmark](https://github.com/node-modules/agentkeepalive/tree/master/benchmark)
run the benchmark:
```bash
cd benchmark
sh start.sh
```
Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40GHz
node@v0.8.9
50 maxSockets, 60 concurrent, 1000 requests per concurrent, 5ms delay
Keep alive agent (30 seconds):
```js
Transactions: 60000 hits
Availability: 100.00 %
Elapsed time: 29.70 secs
Data transferred: 14.88 MB
Response time: 0.03 secs
Transaction rate: 2020.20 trans/sec
Throughput: 0.50 MB/sec
Concurrency: 59.84
Successful transactions: 60000
Failed transactions: 0
Longest transaction: 0.15
Shortest transaction: 0.01
```
Normal agent:
```js
Transactions: 60000 hits
Availability: 100.00 %
Elapsed time: 46.53 secs
Data transferred: 14.88 MB
Response time: 0.05 secs
Transaction rate: 1289.49 trans/sec
Throughput: 0.32 MB/sec
Concurrency: 59.81
Successful transactions: 60000
Failed transactions: 0
Longest transaction: 0.45
Shortest transaction: 0.00
```
Socket created:
```bash
[proxy.js:120000] keepalive, 50 created, 60000 requestFinished, 1200 req/socket, 0 requests, 0 sockets, 0 unusedSockets, 50 timeout
{" <10ms":662," <15ms":17825," <20ms":20552," <30ms":17646," <40ms":2315," <50ms":567," <100ms":377," <150ms":56," <200ms":0," >=200ms+":0}
----------------------------------------------------------------
[proxy.js:120000] normal , 53866 created, 84260 requestFinished, 1.56 req/socket, 0 requests, 0 sockets
{" <10ms":75," <15ms":1112," <20ms":10947," <30ms":32130," <40ms":8228," <50ms":3002," <100ms":4274," <150ms":181," <200ms":18," >=200ms+":33}
```
## License
[MIT](LICENSE)
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## Contributors
|[<img src="https://avatars.githubusercontent.com/u/156269?v=4" width="100px;"/><br/><sub><b>fengmk2</b></sub>](https://github.com/fengmk2)<br/>|[<img src="https://avatars.githubusercontent.com/u/985607?v=4" width="100px;"/><br/><sub><b>dead-horse</b></sub>](https://github.com/dead-horse)<br/>|[<img src="https://avatars.githubusercontent.com/u/5557458?v=4" width="100px;"/><br/><sub><b>AndrewLeedham</b></sub>](https://github.com/AndrewLeedham)<br/>|[<img src="https://avatars.githubusercontent.com/u/5243774?v=4" width="100px;"/><br/><sub><b>ngot</b></sub>](https://github.com/ngot)<br/>|[<img src="https://avatars.githubusercontent.com/u/25919630?v=4" width="100px;"/><br/><sub><b>wrynearson</b></sub>](https://github.com/wrynearson)<br/>|[<img src="https://avatars.githubusercontent.com/u/26738844?v=4" width="100px;"/><br/><sub><b>aaronArinder</b></sub>](https://github.com/aaronArinder)<br/>|
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