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# Your native NodeJS monitoring API
CallCatcher is a flyweight typescript API managing request monitoring for NodeJS apps natively.
Requests and responses saved locally, and redistributed to the developer through [NeDB](https://github.com/louischatriot/nedb).
It is then up to the developer to make use of the distributed data.
# Installation
```shell
$ npm install callcatcher --save
```
# Building
To build the project, run the following command
```shell
$ npm run build
```
Please make sure you lint the project before building it
```shell
$ npm run lint
```
or
```shell
$ npm run lint:fix
```
# Documentation
To generate the documentation use the following command :
```shell
$ npm run doc
```
This will generate a new `docs` folder located at the project's root. The entrypoint to the documentation is the `index.html` file.
# Running tests
To run unit test use the following command :
```shell
$ npm run test
```
This will generate a new `coverage` folder located at the project's root. This folder is used by codecov to calculate the coverage of the tests.
# API
- Methods
- [Probing](#probing)
- [Reporting](#reporting)
- Data structures
- [Report](#report)
- [Hit](#hit)
- Events
- Report
- [onHit](#onHit)
- [onError](#onError)
## Methods
### Probing
The first step for monitoring your server is probing. When creating a server using any NodeJS compatible library,
the freshly created [`http.Server`](https://nodejs.org/api/http.html#http_class_http_server) can be probed using the [`probe()`](src/lib/probe.ts) method.
Calling the [`probe()`](src/lib/probe.ts) method on a [`http.Server`](https://nodejs.org/api/http.html#http_class_http_server) instance,
lets the API know that all ingoing and outgoing http messages should be saved and used later on during reporting.
See [probe](src/lib/probe.ts).
#### Probing example
##### Using Express
```javascript
const monitor = require('callcatcher');
const express = require('express');
const app = express();
app.use(express.json());
// let the express app it has to listen for GET requests on the /icecream route
app.get('/icecream', (req,res) => {
res.status(200).json(/* data */);
})
// create a new http.Server using Express (or any other framework, or even none...)
const server = app.listen(8080, () => {
console.log("Listening on port 8080");
});
// Probe the running server
monitor.probe(server);
```
### Reporting
The second step of monitoring you NodeJS app using CallCatcher is reporting. After probing your [`http.Server`](https://nodejs.org/api/http.html#http_class_http_server),
the last step is to get the data back. The is where the [`report()`](src/lib/report.ts) method comes in handy.
The [`report()`](src/lib/report.ts) method creates a Report instance, which is nothing more than a superset of a NeDB database instance.
NeDB methods can be used on the outputted data. For more information on how to use NeDB, please refer to the [official NeDB github page](https://github.com/louischatriot/nedb).
See [report](src/lib/report.ts).
#### Reporting example
##### Using Express
```javascript
const monitor = require('callcatcher');
const server = /* init a new http.Server */;
// Probe the running server
monitor.probe(server);
// Create a new route to get the monitoring data back.
app.get('/stats', (req,res) => {
res.status(200).json(monitor.report(server).getAllData());
})
```
## Data structures
### Report
A [Report](src/models/report.ts) is an extension of a NeDB database containing Hits.
```typescript
export class Report extends Nedb {}
```
### Hit
A [Hit](src/models/hit.ts) is the data structure of a single api call, which contains information on the request and the response.
```typescript
export interface Hit {
response: {
status: {
code: number;
message: string;
}
datetime?: number;
};
request: {
httpVersion: string;
url?: string;
method?: string;
headers: IncomingHttpHeaders;
body: object;
datetime: number;
};
}
```
## Events
### Report
#### onHit
When inserting documents (a.k.a. hits to a report), the `hit` event gets fired, containing the inserted documents :
```typescript
// models/report.ts
// line 40
this.emit('hit', documents);
```
The emitted documents can then be used as such :
```typescript
const server: Server = /* init a new http.Server */;
const rep: Report = await report(server);
// A hit gets added to the report
rep.on('hit', (docs: Hit[]) => {
console.log(docs);
});
```
#### onError
Similarly, as the hit event, the error event gets emitted with and error message when an error occurred when adding one or many hits to the report.
```typescript
const server: Server = /* init a new http.Server */;
const rep: Report = await report(server);
// A hit gets added to the report, but an error occurres ...
rep.on('error', (err: Error) => {
console.err(err);
});
```