etcdvar

Documentation

Overview

Package etcdvar provides a runtimevar implementation with variables backed by etcd. Use OpenVariable to construct a *runtimevar.Variable.

URLs

For runtimevar.OpenVariable, etcdvar registers for the scheme "etcd". The default URL opener will dial an etcd server based on the environment variable "ETCD_SERVER_URL". To customize the URL opener, or for more details on the URL format, see URLOpener. See https://sraphs.github.io/gdk/concepts/urls/ for background information.

As

etcdvar exposes the following types for As:

• Snapshot: *clientv3.GetResponse
• Error: rpctypes.EtcdError

Example (OpenVariableFromURL)

package main

import (
	"context"
	"log"

	"github.com/sraphs/gdk/runtimevar"
)

func main() {
	// PRAGMA: This example is used on github.com/sraphs/gdk; PRAGMA comments adjust how it is shown and can be ignored.
	// PRAGMA: On github.com/sraphs/gdk, add a blank import: _ "github.com/sraphs/gdk/runtimevar/etcdvar"
	// PRAGMA: On github.com/sraphs/gdk, hide lines until the next blank line.
	ctx := context.Background()

	// runtimevar.OpenVariable creates a *runtimevar.Variable from a URL.
	// The default opener connects to an etcd server based on the environment
	// variable ETCD_SERVER_URL.

	v, err := runtimevar.OpenVariable(ctx, "etcd://myvarname?decoder=string")
	if err != nil {
		log.Fatal(err)
	}
	defer v.Close()
}

Index

• Constants
• func OpenVariable(cli *clientv3.Client, name string, decoder *runtimevar.Decoder, opts *Options) (*runtimevar.Variable, error)
• type Options
• type URLOpener
  • func (o *URLOpener) OpenVariableURL(ctx context.Context, u *url.URL) (*runtimevar.Variable, error)

Examples

• Package (OpenVariableFromURL)
• OpenVariable

Constants

const Scheme = "etcd"

Scheme is the URL scheme etcdvar registers its URLOpener under on runtimevar.DefaultMux.

Functions

func OpenVariable

func OpenVariable(cli *clientv3.Client, name string, decoder *runtimevar.Decoder, opts *Options) (*runtimevar.Variable, error)

OpenVariable constructs a *runtimevar.Variable that uses client to watch the variable name on an etcd server. etcd returns raw bytes; provide a decoder to decode the raw bytes into the appropriate type for runtimevar.Snapshot.Value. See the runtimevar package documentation for examples of decoders.

Example

package main

import (
	"log"

	clientv3 "go.etcd.io/etcd/client/v3"

	"github.com/sraphs/gdk/runtimevar"
	"github.com/sraphs/gdk/runtimevar/etcdvar"
)

func main() {
	// PRAGMA: This example is used on github.com/sraphs/gdk; PRAGMA comments adjust how it is shown and can be ignored.

	// Connect to the etcd server.
	client, err := clientv3.NewFromURL("http://your.etcd.server:9999")
	if err != nil {
		log.Fatal(err)
	}

	// Construct a *runtimevar.Variable that watches the variable.
	v, err := etcdvar.OpenVariable(client, "cfg-variable-name", runtimevar.StringDecoder, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer v.Close()
}

Types

type Options

type Options struct {
	// Timeout controls the timeout on RPCs to etcd; timeouts will result in
	// errors being returned from Watch. Defaults to 30 seconds.
	Timeout time.Duration
}

Options sets options.

type URLOpener

type URLOpener struct {
	// The Client to use; required.
	Client *clientv3.Client

	// Decoder specifies the decoder to use if one is not specified in the URL.
	// Defaults to runtimevar.BytesDecoder.
	Decoder *runtimevar.Decoder

	// Options specifies the options to pass to OpenVariable.
	Options Options
}

URLOpener opens etcd URLs like "etcd://mykey?decoder=string".

The host+path is used as the variable name.

The following URL parameters are supported:

• decoder: The decoder to use. Defaults to runtimevar.BytesDecoder. See runtimevar.DecoderByName for supported values.

func (*URLOpener) OpenVariableURL

func (o *URLOpener) OpenVariableURL(ctx context.Context, u *url.URL) (*runtimevar.Variable, error)

OpenVariableURL opens a etcdvar Variable for u.