go-client

Golang Choria Client

This is a low level client to the Choria network protocol. It is not intended to be used for making mcollective compatible RPC calls - such a library exist as part of the mcorpc package in the go-choria project, it uses this client to facilitate network communications.

It's a high performance client that can make multiple parallel connections to the Choria Network Broker and multiplex data into the calling client. It's been shown to do full ping style round trip to 50 000 nodes in less than 1 second.

Features

• Basic client for sending any arbitrary data over the Choria network
• Constructors for Choria filters from strings like those a CLI would get when parsing user input
• mcollective like broadcast discovery client

Basic Usage

The client can publish and receive messages via the choria.Message structure, here's the most basic ping client:

NOTE: this is only the core code, obvious imports etc are omitted, your IDE will add them automatically

package main

import (
   	"github.com/choria-io/go-client/client"
	"github.com/choria-io/go-choria/choria"
	"github.com/choria-io/go-protocol/protocol"
	log "github.com/sirupsen/logrus"
)

func panicIf(err error) {
    if err != nil {
        panic(err)
    }
}

func main() {
    fw, err := choria.New(choria.UserConfig())
    panicIf(err)

    // discovery needs the word 'ping', we're sending it to the mcollective sub collective
    msg, err := fw.NewMessage(base64.StdEncoding.EncodeToString([]byte("ping")), "discovery", "mcollective", "request", nil)
    panicIf(err)

    // create a basic class filter matching nodes with "choria::broker" class,
    // can also use AgentFilter, IdentityFilter, CompoundFilter, FactFilter,
    // CombinedFilter in any combination
    msg.Filter, err = client.NewFilter(client.ClassFilter("choria::broker")
    panicIf(err)

    msg.SetProtocolVersion(protocol.RequestV1)
    msg.SetReplyTo(choria.ReplyTarget(msg, msg.RequestID))

    // severl options exist like Timeout, Receivers and Log
    cl, err := client.New(fw, client.Timeout(20))
    panicIf(err)

    ctx, cancel = context.WithCancel(context.Backgroun())
    defer cancel()

    // publishes the request in msg and calls handler for each, when Receivers() are more than
    // 1 - 3 is the default - this will be called multiple times concurrently, use a mutex if you
    // must or set Receivers(1) when creating the client
    cl.Request(ctx, msg, handler)
    panicIf(err)
}

func handler(ctx context.Context, m *choria.ConnectorMessage) {
    reply, err := b.fw.NewTransportFromJSON(string(m.Data))
    if err != nil {
        log.Errorf("Could not process a reply: %s", err)
        return
    }

    fmt.Println(reply.SenderID())
}

Broadcast Discovery

The above code is basically a discovery, there's a more fleshed out and simpler way to go about it like this:

import (
   	"github.com/choria-io/go-client/broadcast"
    "github.com/choria-io/go-choria/choria"
	"github.com/choria-io/go-protocol/protocol"
)

func main() {
    fw, err := choria.New(choria.UserConfig())
    panicIf(err)

    b := broadcast.New(fw)

    nodes, err := b.Discover(ctx, broadcast.Filter(protocol.NewFilter()), broadcast.Timeout(10*time.Second), broadcast.Collective("test"))

    fmt.Printf("Discovered %d nodes", len(nodes))
}