chetcd

README

chetcd

Config-helpers for etcd. The aim is to have some common etcd-client use cases wrapper in an elegant API.

Dir watcher

A dir watcher will simply watch a (directory) key recursively. We can attach key observers to receive these changes via native golang channels.

A typical usage would be if we have a directory for all our config values of the application. We want to watch all those config values and react on them to update our live instance.

Quick Start

Source

go get -u github.com/coreos/etcd go get -u github.com/francoishill/chetcd

Usage

package main

import (
    "fmt"
    "github.com/coreos/etcd/client"
    "github.com/francoishill/chetcd"
    "log"
    "time"
)

func main() {
    cfg := client.Config{
        Endpoints:               []string{"http://127.0.0.1:2379"},
        Transport:               client.DefaultTransport,
        HeaderTimeoutPerRequest: time.Second, // set timeout per request to fail fast when the target endpoint is unavailable
    }

    c, err := client.New(cfg)
    if err != nil {
        log.Fatal(err)
    }

    keysAPI := client.NewKeysAPI(c)

    foodirWatcher := chetcd.NewDirWatcher(keysAPI, "/foodir")

    bar1ConfigValue, err := foodirWatcher.GetObservedConfigValue("/bar1")
    if err != nil {
        log.Fatal(err)
    }

    bar2ConfigValue, err := foodirWatcher.GetObservedConfigValue("/bar2")
    if err != nil {
        log.Fatal(err)
    }

    go func() {
        for {
            select {
            case b1 := <-bar1ConfigValue.ChangesChannel():
                fmt.Printf("Bar 1 changed from '%s' to '%s'\n", b1.OldNode.Value, b1.NewNode.Value)
                break
            case b2 := <-bar2ConfigValue.ChangesChannel():
                fmt.Printf("Bar 2 changed from '%s' to '%s'\n", b2.OldNode.Value, b2.NewNode.Value)
                break
            }
        }
    }()

    //The delay to wait when we receive `watcher.Next()` errors. This could be because the etcd server is down.
    delayOnError := 30 * time.Second
    errChan := foodirWatcher.WatchDir(delayOnError)
    for er := range errChan {
        fmt.Printf("DIR WATCH ERROR: %s, watcher: %q\n", er.Error(), foodirWatcher)
    }
}

Documentation

Index

• type ConfigValue
  • func (c *ConfigValue) ChangesChannel() <-chan *ValueChange
  • func (c *ConfigValue) FullKey() string
  • func (c *ConfigValue) ModifiedIndex() uint64
  • func (c *ConfigValue) String() string
  • func (c *ConfigValue) Value() string
• type DirWatcher
  • func NewDirWatcher(keysAPI client.KeysAPI, dir string) *DirWatcher
  • func (d *DirWatcher) GetObservedConfigValue(keyRelativeToDir string) (*ConfigValue, error)
  • func (d *DirWatcher) WatchDir(delayOnError time.Duration) <-chan error
• type ValueChange

Types

type ConfigValue

type ConfigValue struct {
	// contains filtered or unexported fields
}

func (*ConfigValue) ChangesChannel

func (c *ConfigValue) ChangesChannel() <-chan *ValueChange

func (*ConfigValue) FullKey

func (c *ConfigValue) FullKey() string

func (*ConfigValue) ModifiedIndex

func (c *ConfigValue) ModifiedIndex() uint64

func (*ConfigValue) String

func (c *ConfigValue) String() string

func (*ConfigValue) Value

func (c *ConfigValue) Value() string

type DirWatcher

type DirWatcher struct {
	// contains filtered or unexported fields
}

func NewDirWatcher

func NewDirWatcher(keysAPI client.KeysAPI, dir string) *DirWatcher

func (*DirWatcher) GetObservedConfigValue

func (d *DirWatcher) GetObservedConfigValue(keyRelativeToDir string) (*ConfigValue, error)

func (*DirWatcher) WatchDir

func (d *DirWatcher) WatchDir(delayOnError time.Duration) <-chan error

type ValueChange

type ValueChange struct {
	OldNode client.Node
	NewNode client.Node
}