library for generating standard health check endpoints which return useful stats including host stats and reports of downstream dependencies.
to install this library, run npm install @gopuff/healthz
import the HealthZ object and instantiate a new instance
const { HealthZ } = require('@gopuff/healthz')
const hz = new HealthZ()Register dependencies by providing a name of the dependency, the function to perform, and the arguments of that function
Example with a raw function
import * as rpn from 'request-promise-native'
import * as https from 'https'
const agent = new https.Agent({ keepAlive: true })
const rp = rpn.defaults({ agent })
hz.registerDep('lorem', rp, 'https://jsonplaceholder.typicode.com/todos/1')Example with an object function that uses the this context
// Psuedo azure cosmos client object
import { CosmosService } from '../lib/cosmos'
const cosmos = new CosmosService('connection_string', 'collection', 'container')
// Register the dependency with HealthZ
hz.registerDep(
'cosmos-mycontainer',
(query: string) => cosmos.query(query), // need to pass as anonymous or we'll lose this binding
'Select * from c where c.partitionKey = "my_patition_key"'
)Generate the health stats to return to the caller
const health = await hz.getHealth()
res.status(hz.status).json(health)This will return a response object with the status set to 200 if all dependencies are successful and 500 if any are unsuccessful. The object looks like this:
{
"host": {
"memoryUsageMB": 40.86183547973633,
"cpuTime": {
"user": 327468000,
"system": 26531000
},
"platform": "win32",
"version": "v12.18.0",
"uptime": 11230.1285054
},
"dependencies": {
"cosmos": {
"latency": 52,
"success": true
},
"lorem": {
"latency": 3,
"success": true
}
}
}If a dependency is unsuccessful, an error is included in the object like so:
{
"host": {
"memoryUsageMB": 40.86183547973633,
"cpuTime": {
"user": 327468000,
"system": 26531000
},
"platform": "win32",
"version": "v12.18.0",
"uptime": 11230.1285054
},
"dependencies": {
"cosmos": {
"latency": 52,
"success": true
},
"error-endpoint": {
"success": false,
"latency": 78,
"error": {
"name": "StatusCodeError",
"statusCode": 404,
"message": "404 - \"{}\"",
"error": "{}",
"options": {
...
},
"response": {
"statusCode": 404,
"body": "{}",
"headers": {
...
},
"request": {
...
},
"method": "GET",
"headers": {}
}
}
}
}
}In an express app, we can add a route to /healthcheck with the following controller:
It can be useful to chain these if you have multiple services that use the healthz library since the lib will set the status to a 500 if any dependencies are unsuccessful. This way, we can deduce if the service in question is unhealthy or if it is a downstream dependency. This isn't required as any simple request can be used as well which we can do like this:
// Express
import { Router, Request, Response, NextFunction } from 'express'
const router = Router()
// Request client
import * as rpn from 'request-promise-native'
import * as https from 'https'
const agent = new https.Agent({ keepAlive: true })
const rp = rpn.defaults({ agent })
// HealthZ lib
const { HealthZ } = require('@gopuff/healthz')
const hz = new HealthZ()
// Register our service endpoint
hz.registerDep(
'myservice',
rp,
'https://myservice.mydomain.com/healthcheck' // uses the healthz lib
)
// Endpoint
router.get('/', async (req: Request, res: Response, next: NextFunction) => {
try {
const health = await hz.getHealth()
res.status(hz.status).json(health)
} catch (err) {
console.log(err)
next(err)
}
})
export const HealthCheckController: Router = router// Express
import { Router, Request, Response, NextFunction } from 'express'
const router = Router()
// Psuedo Cosmos client
import { CosmosService } from '../lib/cosmos'
const cosmos = new CosmosService('connection_string', 'collection', 'container')
// Instantiate HealthZ and register our Cosmos client
const { HealthZ } = require('@gopuff/healthz')
const hz = new HealthZ()
// Register our Cosmos client
hz.registerDep(
'cosmos',
(query: string) => cosmos.query(query),
'Select * from c where c.partitionKey = "my_partition_key"'
)
// Endpoint
router.get('/', async (req: Request, res: Response, next: NextFunction) => {
try {
const health = await hz.getHealth()
res.status(hz.status).json(health)
} catch (err) {
console.log(err)
next(err)
}
})
export const HealthCheckController: Router = router
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