README.md

CCMetric sinks

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

Available sinks:

• stdout: Print all metrics to stdout, stderr or a file
• http: Send metrics to an HTTP server as POST requests
• influxdb: Send metrics to an InfluxDB database
• influxasync: Send metrics to an InfluxDB database with non-blocking write API
• nats: Publish metrics to the NATS network overlay system
• ganglia: Publish metrics in the Ganglia Monitoring System using the gmetric CLI tool
• libganglia: Publish metrics in the Ganglia Monitoring System directly using libganglia.so
• prometeus: Publish metrics for the Prometheus Monitoring System

Configuration

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

[
  "mystdout" : {
    "type" : "stdout",
    "meta_as_tags" : [
    	"unit"
    ]
  },
  "metricstore" : {
    "type" : "http",
    "host" : "localhost",
    "port" : "4123",
    "database" : "ccmetric",
    "password" : "<jwt token>"
  }
]

Contributing own sinks

A sink contains five functions and is derived from the type sink:

• Init(name string, config json.RawMessage) error
• Write(point CCMetric) error
• Flush() error
• Close()
• New<Typename>(name string, config json.RawMessage) (Sink, error) (calls the Init() function)

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.

Sample sink

package sinks

import (
	"encoding/json"
	"log"
	lp "github.com/ClusterCockpit/cc-metric-collector/internal/ccMetric"
)

type SampleSinkConfig struct {
	defaultSinkConfig  // defines JSON tags for 'name' and 'meta_as_tags'
}

type SampleSink struct {
	sink              // declarate 'name' and 'meta_as_tags'
	config StdoutSinkConfig // entry point to the SampleSinkConfig
}

// Initialize the sink by giving it a name and reading in the config JSON
func (s *SampleSink) Init(name string, config json.RawMessage) error {
	s.name = fmt.Sprintf("SampleSink(%s)", name)   // Always specify a name here
  // Read in the config JSON
	if len(config) > 0 {
		err := json.Unmarshal(config, &s.config)
		if err != nil {
			return err
		}
	}
	return nil
}

// Code to submit a single CCMetric to the sink
func (s *SampleSink) Write(point lp.CCMetric) error {
	log.Print(point)
	return nil
}

// If the sink uses batched sends internally, you can tell to flush its buffers
func (s *SampleSink) Flush() error {
	return nil
}


// Close sink: close network connection, close files, close libraries, ...
func (s *SampleSink) Close() {}


// New function to create a new instance of the sink
func NewSampleSink(name string, config json.RawMessage) (Sink, error) {
	s := new(SampleSink)
	err := s.Init(name, config)
	return s, err
}