cc-metric-collector/sinks

This folder contains the sinks for the cc-metric-collector.

metricSink.go

The base class/configuration is located in metricSink.go.

Sinks

• stdoutSink.go: Writes all metrics to stdout in InfluxDB line protocol. The sink does not use https://github.com/influxdata/line-protocol to reduce the executed code for debugging
• influxSink.go: Writes all metrics to an InfluxDB database instance using a blocking writer. It uses https://github.com/influxdata/influxdb-client-go . Configuration for the server, port, ssl, password, database name and organisation are in the global configuration file. The 'password' is used for the token and the 'database' for the bucket. It uses the v2 API of Influx.
• natsSink.go: Sends all metrics to an NATS server using the InfluxDB line protocol as encoding. It uses https://github.com/nats-io/nats.go . Configuration for the server, port, user, password and database name are in the global configuration file. The database name is used as subject for the NATS messages.
• httpSink.go: Sends all metrics to an HTTP endpoint http://<host>:<port>/<database> using a POST request. The body of the request will consist of lines in the InfluxDB line protocol. In case password is specified, that password is used as a JWT in the 'Authorization' header.

Installation

Nothing to do, all sinks are pure Go code

Contributing own sinks

A sink contains three functions and is derived from the type Sink (in metricSink.go):

• Init(config SinkConfig) error
• Write(measurement string, tags map[string]string, fields map[string]interface{}, t time.Time) error
• Flush() error
• Close()

The data structures should be set up in Init() like opening a file or server connection. The Write() function takes a measurement, tags, fields and a timestamp and 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 metric-collector.go. There is a list of sinks called Sinks which is a map (sink_type_string -> pointer to sink). Add a new entry with a descriptive name and the new sink. Afterwards, it can be configured in the main configuration file at type:

{
  "sink": {
    "user": "testuser",
    "password": "testpass",
    "host": "127.0.0.1",
    "port": "9090",
    "database": "testdb",
    "organization": "testorg",
    "ssl": false
    "type": "stdout"
  }
}

Sink configuration

stdoutSink

When configuring type = stdout, all metrics are printed to stdout. No further configuration is required or touched, so you can leave your other-sink-config in there and just change the type for debugging purposes

influxSink

The InfluxDB sink uses blocking write operations to write to an InfluxDB database using the v2 API. It uses the following configuration options:

• host: Hostname of the database instance
• port: Portnumber (as string) of the database
• database: Name of the database, called 'bucket' in InfluxDB v2
• organization: The InfluxDB v2 API uses organizations to separate database instances running on the same host
• ssl: Boolean to activate SSL/TLS
• user: Although the v2 API uses API keys instead of username and password, this field can be used if the sink should authentificate with username:password. If you want to use an API key, leave this field empty.
• password: API key for the InfluxDB v2 API or password if user is set

natsSink

• host: Hostname of the NATS server
• port: Portnumber (as string) of the NATS server
• user: Username for authentification in the NATS transport system
• password: Password for authentification in the NATS transport system

httpSink

• host: Hostname of the HTTP server
• port: Portnumber (as string) of the HTTP server
• database: Endpoint to write to. HTTP POST requests are performed on http://<host>:<port>/<database>
• password: JSON Web token used for authentification