cc-metric-collector/sinks/README.md

# CCMetric sinks

This folder contains the SinkManager and sink implementations for the cc-metric-collector.

# Configuration

The configuration file for the sinks is a list of configurations. The `type` field in each specifies which sink to initialize.

```json
[
  {
    "type" : "stdout",
    "meta_as_tags" : false
  },
  {
    "type" : "http",
    "host" : "localhost",
    "port" : "4123",
    "database" : "ccmetric",
    "password" : "<jwt token>"
  }
]
```

This example initializes two sinks, the `stdout` sink printing all metrics to the STDOUT and the `http` sink with the given `host`, `port`, `database` and `password`.

If `meta_as_tags` is set, all meta information attached to CCMetric are printed out as tags.

## Type `stdout`

```json
{
  "type" : "stdout",
  "meta_as_tags" : <true|false>
}
```

The `stdout` sink dumps all metrics to the STDOUT.

## Type `http`

```json
{
  "type" : "http",
  "host" : "<hostname>",
  "port" : "<portnumber>",
  "database" : "<database name>",
  "password" : "<jwt token>",
  "meta_as_tags" : <true|false>
}
```
The sink uses POST requests to send metrics to `http://<host>:<port>/<database>` using the JWT token as a JWT in the 'Authorization' header.

## Type `nats`

```json
{
  "type" : "nats",
  "host" : "<hostname>",
  "port" : "<portnumber>",
  "user" : "<username>",
  "password" : "<password>",
  "database" : "<database name>"
  "meta_as_tags" : <true|false>
}
```

This sink publishes the CCMetric in a NATS environment using `host`, `port`, `user` and `password` for connecting. The metrics are published using the topic `database`. 

## Type `influxdb`

```json
{
  "type" : "influxdb",
  "host" : "<hostname>",
  "port" : "<portnumber>",
  "user" : "<username>",
  "password" : "<password or API key>",
  "database" : "<database name>"
  "organization": "<InfluxDB v2 organization>",
  "ssl" : <true|false>,
  "meta_as_tags" : <true|false>
}
```

This sink submits the CCMetrics to an InfluxDB time-series database. It uses `host`, `port` and `ssl` for connecting. For authentification, it uses either `user:password` if `user` is set and only `password` as API key. The `organization` and `database` are used for writing to the correct database.



# Contributing own sinks
A sink contains three functions and is derived from the type `Sink`:
* `Init(config SinkConfig) error`
* `Write(point CCMetric) error`
* `Flush() error`
* `Close()`

The data structures should be set up in `Init()` like opening a file or server connection. The `Write()` function writes/sends the data. For non-blocking sinks, the `Flush()` method tells the sink to drain its internal buffers. The `Close()` function should tear down anything created in `Init()`.

Finally, the sink needs to be registered in the `sinkManager.go`. There is a list of sinks called `AvailableSinks` which is a map (`sink_type_string` -> `pointer to sink interface`). Add a new entry with a descriptive name and the new sink.