Correlation Id

How to use

Create correlation id instance
``javascript
const {createCorrelationId} = require(@vizydrop/correlation-id);
const correlationId = createCorrelationId();
`

Integrate with @vizydrop/logger
`javascript
const {createLogger} = require(@vizydrop/logger);

const logger = createLogger({
correlationId: {
enabled: true,
getCorrelationId: () => correlationId.correlator.getId(),
emptyValue: nocorrelation,
},
});
`

Register middleware. Support koa and express
`javascript
// koa
app.use(correlationId.koaMiddleware);
// express
app.use(correlationId.expressMiddleware);
`

Enhance request so each request will contain correlation id http header.
`javascript
const request = require(request);
const correlatedRequest = correlationId.enhanceRequest(request);
correlatedRequest.get(http://anotherservice:10020/data);
`

Enhance http proxy so each proxied request will contain correlation id http header.
`javascript
const httpProxy = require(http-proxy);
const proxy = httpProxy.createProxyServer({target: http://anotherservice:10020/});
correlationId.enhanceHttpProxy(proxy);
`

Run jobs. Jobs usually do not go through express/koa middleware so correlation id should be generated manually.
`javascript
function jobTask() {}

function runJob() {
correlationId.correlator.withId(correlator.generateDefaultId(), () => {
jobTask();
});
}
`

Settings

Custom settings can be passed as an object to createCorrelationId function.
- generateDefaultId - function that should return new correlation id. By default uuid is used.
- namespaceName - namespace for cls hook. Default value is correlation-id-namespace
- httpHeaderParamName - name of http header that contains correlation id value. Default value is x-correlationid

Correlation ID API


- expressMiddleware - express middleware that runs next middlewares in scope of correlation id async hook
- koaMiddleware - koa middleware that runs next middlewares in scope of correlation id async hook
- enhanceHttpRequest - takes request and return new request instance that adds correlation id header by default
- enhanceHttpProxy - register additional listener that adds correlation id header by default
- correlator.getId() - returns current correlation id
- correlator.withId(id, fn) - run function and all subsequent function with specified correlation id
- correlator.bindEmitter() - see https://github.com/jeff-lewis/cls-hooked#namespacebindemitteremitter
- correlator.bind() - see https://github.com/jeff-lewis/cls-hooked#namespacebindemitteremitter
- correlator.generateId() - generates new correlation id

Known issues

- does not work well with bluebird.promisifyAll. Alternative solution is to explicitly promisify using native promise
`javascript
const redis = require(redis);
const util = require(util);

const client = redis.createClient();

client.setAsync = util.promisify(client.set).bind(client);
client.getAsync = util.promisify(client.get).bind(client);
`

- does not work well with mongoose callbacks. Alternative solution is to use promisified functions.
`javascript
const mongoose = require(mongooose);
mongoose.Promise = global.Promise;

EntityModel.find({name: name}).then((value) => {
// do something
});
``