# @qrvey/health-checker

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An health check library for validating the availability of core service dependencies like Redis, PostgreSQL, and RabbitMQ.

## Installation

```bash
npm install @qrvey/health-checker
```

Or with yarn:

```bash
yarn add @qrvey/health-checker
```

## Supported Health Check Types

| Service     | Dependency Key |
|-------------|----------------|
| PostgreSQL  | `database`     |
| Redis       | `cache`        |
| RabbitMQ    | `eventBroker`  |

## Usage

```js
const {
  HealthCheckService,
} = require('@qrvey/health-checker');


HealthCheckService.check(['cache', 'database', 'eventBroker']).then((result) => {
  console.log(result);
  /*
  {
    status: 'OK',
    details: {
      cache: 'OK',
      database: 'OK',
      eventBroker: 'OK'
    }
  }
  */
});
```

You can also check specific dependencies only:

```js
HealthCheckService.check(['cache']).then((result) => {
  console.log(result);
  /*
  {
    status: 'OK',
    details: {
      cache: 'OK'
    }
  }
  */
});
```

## Usage with Fastify

You can expose the health check as a simple route in your Fastify app.

### Basic Example: `health.routes.js`

```js
const {
  HealthCheckService,
} = require('@qrvey/health-checker');
const Fastify = require('fastify');

async function healthRoutes(fastify, _options) {
  fastify.get('/health', async (_request, reply) => {
    const dependencies = ['database', 'eventBroker'];
    const result = await HealthCheckService.check(dependencies);
    const httpStatus = result.status === "FAILED" ? 503 : 200;
    return reply.code(httpStatus).send(result);
  });
}

const app = Fastify({ logger: true });
app.register(healthRoutes);
app.listen({ port: 3000 });
```

### Basic Example Output

``` json
GET /health

{
  "status": "OK",
  "details": {
    "database": "OK",
    "eventBroker": "OK"
  }
}
```

### Validating Queue Subscriptions (Optional)

If you want to explicitly validate that your service is subscribed to one or more RabbitMQ queues, you can pass an additional params object to the check method.

```js
fastify.get('/health', async (_request, reply) => {
  const dependencies = ['eventBroker'];
  const params = {
    eventBroker: {
      queues: ['queue_name_1', 'queue_name_2'], // these must match the configured subscriptions
    },
  }

  const result = await HealthCheckService.check(dependencies, params);
  const httpStatus = result.status === "FAILED" ? 503 : 200;
  return reply.code(httpStatus).send(result);
});
```

### Sample output

``` json
GET /health

{
  "status": "OK",
  "details": {
    "eventBroker": "OK"
  }
}
```