# nodejs-health-checker-lw
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## contributors
>Made with [contributors-img](https://contrib.rocks).
____
A successor package for [`nodejs-health-checker`](https://github.com/gritzkoo/nodejs-health-checker) to simplify health checks.
The main purpose of this package is to substitute [`nodejs-health-checker`](https://github.com/gritzkoo/nodejs-health-checker) package and standardize the liveness and readiness actions for Nodejs applications running in Kubernetes deployments, without adding complexity and extra package installs.
Read more about migrating from [`nodejs-health-checker`](https://github.com/gritzkoo/nodejs-health-checker) or creating your tests in [MIGRATIONS GUIDELINES](docs/MIGRATIONS.md)
___
## Liveness method
Will return a `JSON` as below:
```json
{
"status": "fully functional",
"version": "v1.0.0"
}
```
## Readiness method
Will return a `JSON` as below:
>The `status` prop will return true once all your integrations works. If one of then fails, this `status` prop will reflect that something went wrong and you need to check the `status` inside `integrations` prop
```json
{
"name": "myapp",
"version": "v1.0.0",
"status": true,
"date": "2022-07-10T00:46:19.186Z",
"duration": 0.068,
"integrations": [
{
"name": "github integration",
"status": true,
"response_time": 0.068,
"url": "https://github.com/status"
}
]
}
```
___
## How to install
```sh
npm i --save nodejs-health-checker-lw
```
OR
```sh
yarn add nodejs-health-checker-lw
```
## How to init
First, you `need` to write your test like below:
>this example is using http check for API integrations. Remember that you can write using your own methods and patterns. You need only to return an instance of `nodejs-health-checker Check`.
```ts
// file src/integrations/github.ts
import { Check } from 'nodejs-health-checker-lw'
import { fetch } from 'node-fetch'
export async function TestGithubIntegration() Promise {
return new Promise((resolve, _) => {
let result = new Check({ url: 'https://github.com/status' })
// call a url to test connectivity and HTTP status
fetch(result.url, { timeout: 10000 })
.then(response => {
if (response.status !== 200) {
result.error = {
status: response.status,
body: response.body
}
}
})
.catch(error => result.error = error)
.finally(() => resolve(result))
})
}
```
Then in your main declarations, you `MUST` create a `const` with `HealthChecker` from `nodejs-health-checker-lw` and fill a few props to create a re-usable pointer to be called after as below.
> Read more about the `version` [in this topic](README.md#version-in-your-healthchecker)
```ts
// file src/healthchecker.ts
import { HealthChecker} from 'nodejs-health-checker-lw'
import { TestGithubIntegration } from 'src/integrations/github' // as the example above. This list can grow as mush as you need
export const check = new HealthChecker({
name: 'myapp', // set your application name
version: 'v1.0.0', // set the version of your application
// integrations are the list of tests that needs to be executed.
integrations: [
{
// set the name of the integration that will be tested
name: 'github integration',
// pass the functions that tests this integration
handle: MyIntegrationTest
}
]
})
```
## How to use it
Once you create a constant with an instance of HealthChecker, you can now call the methods, liveness, and readiness, in your application, in CLI or API mode
### CLI interface
```js
import check from 'src/healthchecker' // as the example above
const cliArgs = process.argv.slice(2)
switch (cliArgs[0]) {
case 'liveness':
console.log(check.liveness())
break
case 'readiness':
check.readiness().then(response => {
if (!response.status) {
// do something like trigger an alarm or log to other obervability stacks
console.warning(JSON.stringify({message: "health check fails", results: response}))
} else {
// or just log OK to track
console.info(JSON.stringify(response));
}
})
break
default:
console.error(`invalid option: ${cliArgs[0]}... accepty only liveness or readiness`)
}
```
In `Kubernetes` deployment
``` yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: your-nodejs-app
spec:
selector:
matchLabels:
app: your-nodejs-app
template:
metadata:
labels:
app: your-nodejs-app
spec:
containers:
- name: your-nodejs-app
image: your-nodejs-app:tag
resources:
limits:
memory: "128Mi"
cpu: "500m"
ports:
- containerPort: 80
livenessProbe:
exec:
command:
- "/bin/node"
- "your-script.js"
args:
- "liveness"
readinessProbe:
exec:
command:
- "/bin/node"
- "your-script.js"
args:
- "readiness"
```
___
## HTTP interface
In `Javascript`
```ts
import express from 'express'
import check from 'src/healthchecker' // as the example above
const PORT = process.env.PORT||80;
const server = express()
server.get('/health-check/liveness', (_, res) => {
res.json(check.liveness())
})
server.get('/health-check/readiness', async (_, res) => {
const result = await check.readiness()
if (!response.status) {
// do something like trigger an alarm or log to other obervability stacks
console.warning(JSON.stringify({message: "health check fails", results: response}))
} else {
// or just log OK to track
console.info(JSON.stringify(response));
}
res.json(result)
})
server.listen(PORT, () => {
console.log(`[SERVER] Running at http://localhost:${PORT}`);
});
```
In `Kubernetes deployment`
```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: your-nodejs-app
spec:
selector:
matchLabels:
app: your-nodejs-app
template:
metadata:
labels:
app: your-nodejs-app
spec:
containers:
- name: your-nodejs-app
image: your-nodejs-app:tag
resources:
limits:
memory: "128Mi"
cpu: "500m"
ports:
- containerPort: 80
livenessProbe:
httpGet:
path: /health-check/liveness
port: http
readinessProbe:
httpGet:
path: /health-check/readiness
port: http
```
It's important to share that you `MUST` return always an `OK` status in Kubernetes liveness and readiness because if one of your integration fails, this can teardown all of your pods and make your application unavailable. Use other observability stacks like `Zabbix` or `Grafana alarms` to track your application logs and then take actions based on observability! `(I learned it by the hard way =/ )`
___
## More pieces of information
___
### Version in your `HealthChecker`
I highly recommend you fill this prop using a dynamic file content loading like:
- reading the `package.json` file and using the `version` value to fill the `HealthChecker.version` placeholder like below:
```ts
import fs from 'fs'
import path from 'path'
import { HealthChecker } from 'nodejs-health-checker-lw'
import { TestGithubIntegration } from 'src/integrations/github'
const versionFilePath = path('package.json')
const file = {
content: null
error: undefined
}
try {
let tmpRawData = await fs.readFileSync(versionFilePath, {encoding: 'utf8'})
file.content = JSON.parse(tmpRawData)
} catch (error) {
file.error = error
}
export const check = new HealthChecker({
name: 'myapp',
version: file.error || file.content.version
integrations: [/*and the list of your integrations here*/]
})
```
- creating a file like `version.txt` using a command like the below in the pipeline before a `docker build/push` steps:
```sh
git show -s --format="%ai %H %s %aN" HEAD > version.txt
```
then use it in your code like:
```ts
import fs from 'fs'
import path from 'path'
import { HealthChecker } from 'nodejs-health-checker-lw'
import { TestGithubIntegration } from 'src/integrations/github'
const versionFilePath = path('version.txt')
const file = {
content: null
error: undefined
}
try {
file.content = await fs.readFileSync(versionFilePath, {encoding: 'utf8'})
} catch (error) {
file.error = error
}
export const check = new HealthChecker({
name: 'myapp',
version: file.error || file.content
integrations: [/*and the list of your integrations here*/]
})
```