cc-metric-collector/sinks/README.md
2022-11-04 14:52:09 +01:00

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# CCMetric sinks
This folder contains the SinkManager and sink implementations for the cc-metric-collector.
# Available sinks:
- [`stdout`](./stdoutSink.md): Print all metrics to `stdout`, `stderr` or a file
- [`http`](./httpSink.md): Send metrics to an HTTP server as POST requests
- [`influxdb`](./influxSink.md): Send metrics to an [InfluxDB](https://www.influxdata.com/products/influxdb/) database
- [`influxasync`](./influxAsyncSink.md): Send metrics to an [InfluxDB](https://www.influxdata.com/products/influxdb/) database with non-blocking write API
- [`nats`](./natsSink.md): Publish metrics to the [NATS](https://nats.io/) network overlay system
- [`ganglia`](./gangliaSink.md): Publish metrics in the [Ganglia Monitoring System](http://ganglia.info/) using the `gmetric` CLI tool
- [`libganglia`](./libgangliaSink.md): Publish metrics in the [Ganglia Monitoring System](http://ganglia.info/) directly using `libganglia.so`
- [`prometeus`](./prometheusSink.md): Publish metrics for the [Prometheus Monitoring System](https://prometheus.io/)
# Configuration
The configuration file for the sinks is a list of configurations. The `type` field in each specifies which sink to initialize.
```json
[
"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
```go
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
}
```