Pusher Channels HTTP Go Library

The Golang library for interacting with the Pusher Channels HTTP API.

This package lets you trigger events to your client and query the state of your Pusher channels. When used with a server, you can validate Pusher Channels webhooks and authenticate private- or presence- channels.

Register for free at https://pusher.com/channels and use the application credentials within your app as shown below.

Supported Platforms

• Go - supports Go 1.11 or greater.

Table of Contents

• Installation
• Getting Started
• Configuration
  • Additional options
  • Google App Engine
• Usage
  • Triggering events
  • Authenticating Channels
  • Application state
  • Webhook validation
• Feature Support
• Developing the Library
  • Running the tests
• License

Installation

$ go get github.com/pusher/pusher-http-go/v5

Getting Started

package main

import (
  "github.com/pusher/pusher-http-go/v5"
)

func main(){
    // instantiate a client
    pusherClient := pusher.Client{
        AppID:   "APP_ID",
        Key:     "APP_KEY",
        Secret:  "APP_SECRET",
        Cluster: "APP_CLUSTER",
    }

    data := map[string]string{"message": "hello world"}

    // trigger an event on a channel, along with a data payload
    err := pusherClient.Trigger("my-channel", "my_event", data)

    // All trigger methods return an error object, it's worth at least logging this!
    if err != nil {
        panic(err)
    }
}

Configuration

The easiest way to configure the library is by creating a new Pusher instance:

pusherClient := pusher.Client{
    AppID:   "APP_ID",
    Key:     "APP_KEY",
    Secret:  "APP_SECRET",
    Cluster: "APP_CLUSTER",
}

Additional options

Instantiation From URL

pusherClient := pusher.ClientFromURL("http://<key>:<secret>@api-<cluster>.pusher.com/apps/app_id")

Note: the API URL differs depending on the cluster your app was created in:

http://key:[email protected]/apps/app_id
http://key:[email protected]/apps/app_id

Instantiation From Environment Variable

pusherClient := pusher.ClientFromEnv("PUSHER_URL")

This is particularly relevant if you are using Pusher Channels as a Heroku add-on, which stores credentials in a "PUSHER_URL" environment variable.

HTTPS

To ensure requests occur over HTTPS, set the Secure property of a pusher.Client to true.

pusherClient.Secure = true

This is false by default.

Request Timeouts

If you wish to set a time-limit for each HTTP request, create a http.Client instance with your specified Timeout field and set it as the Pusher Channels instance's Client:

httpClient := &http.Client{Timeout: time.Second * 3}

pusherClient.HTTPClient = httpClient

If you do not specifically set a HTTP client, a default one is created with a timeout of 5 seconds.

Changing Host

Changing the pusher.Client's Host property will make sure requests are sent to your specified host.

pusherClient.Host = "foo.bar.com"

By default, this is "api.pusherapp.com".

Changing the Cluster

Setting the pusher.Client's Cluster property will make sure requests are sent to the cluster where you created your app.

NOTE! If Host is set then Cluster will be ignored.

pusherClient.Cluster = "eu" // in this case requests will be made to api-eu.pusher.com.

End to End Encryption

This library supports end to end encryption of your private channels. This means that only you and your connected clients will be able to read your messages. Pusher cannot decrypt them. You can enable this feature by following these steps:

1. You should first set up Private channels. This involves creating an authentication endpoint on your server.

2. Next, generate a 32 byte master encryption key, base64 encode it and store it securely.

   This is secret and you should never share this with anyone. Not even Pusher.

   To generate a suitable key from a secure random source, you could use:

   openssl rand -base64 32
   

3. Pass the encoded key when constructing your pusher.Client

   pusherClient := pusher.Client{
       AppID:                    "APP_ID",
       Key:                      "APP_KEY",
       Secret:                   "APP_SECRET",
       Cluster:                  "APP_CLUSTER",
       EncryptionMasterKeyBase64 "<output from command above>",
   }
   

4. Channels where you wish to use end to end encryption should be prefixed with private-encrypted-.

5. Subscribe to these channels in your client, and you're done! You can verify it is working by checking out the debug console on the https://dashboard.pusher.com/ and seeing the scrambled ciphertext.

Important note: This will not encrypt messages on channels that are not prefixed by private-encrypted-.

Google App Engine

As of version 1.0.0, this library is compatible with Google App Engine's urlfetch library. Pass in the HTTP client returned by urlfetch.Client to your Pusher Channels initialization struct.

package helloworldapp

import (
    "appengine"
    "appengine/urlfetch"
    "fmt"
    "github.com/pusher/pusher-http-go/v5"
    "net/http"
)

func init() {
    http.HandleFunc("/", handler)
}

func handler(w http.ResponseWriter, r *http.Request) {
    c := appengine.NewContext(r)
    urlfetchClient := urlfetch.Client(c)

    pusherClient := pusher.Client{
        AppID:      "APP_ID",
        Key:        "APP_KEY",
        Secret:     "APP_SECRET",
        HTTPClient: urlfetchClient,
    }

    pusherClient.Trigger("my-channel", "my_event", map[string]string{"message": "hello world"})

    fmt.Fprint(w, "Hello, world!")
}

Usage

Triggering events

It is possible to trigger an event on one or more channels. Channel names can contain only characters which are alphanumeric, _ or - and have to be at most 200 characters long. Event name can be at most 200 characters long too.

Custom Types

pusher.Event

type TriggerParams struct {
    SocketID *string
    Info     *string
}

Note: Info is part of an experimental feature.

Single channel

func (c *Client) Trigger

Example

data := map[string]string{"hello": "world"}
pusherClient.Trigger("greeting_channel", "say_hello", data)

func (c *Client) TriggerWithParams

Allows additional parameters to be included as part of the request body. The complete list of parameters are documented here.

Example

data := map[string]string{"hello": "world"}
socketID := "1234.12"
attributes := "user_count"
params := pusher.TriggerParams{SocketID: &socketID, Info: &attributes}
channels, err := pusherClient.TriggerWithParams("presence-chatroom", "say_hello", data, params)

// channels => &{Channels:map[presence-chatroom:{UserCount:4}]}

Multiple channels

func (c. *Client) TriggerMulti

Example

pusherClient.TriggerMulti([]string{"a_channel", "another_channel"}, "event", data)

func (c. *Client) TriggerMultiWithParams

Example

data := map[string]string{"hello": "world"}
socketID := "1234.12"
attributes := "user_count"
params := pusher.TriggerParams{SocketID: &socketID, Info: &attributes}
channels, err := pusherClient.TriggerMultiWithParams([]string{"presence-chatroom", "presence-notifications"}, "event", data, params)

// channels => &{Channels:map[presence-chatroom:{UserCount:4} presence-notifications:{UserCount:31}]}

Batches

func (c. *Client) TriggerBatch

Custom Types

pusher.Event

type Event struct {
    Channel  string
    Name     string
    Data     interface{}
    SocketID *string
    Info     *string
}

Note: Info is part of an experimental feature.

Example

socketID := "1234.12"
attributes := "user_count"
batch := []pusher.Event{
  { Channel: "a-channel", Name: "event", Data: "hello world" },
  { Channel: "presence-b-channel", Name: "event", Data: "hi my name is bob", SocketID: &socketID, Info: &attributes },
}
response, err := pusherClient.TriggerBatch(batch)

for i, attributes := range response.Batch {
    if attributes.UserCount != nil {
        fmt.Printf("channel: %s, name: %s, user_count: %d\n", batch[i].Channel, batch[i].Name, *attributes.UserCount)
    } else {
        fmt.Printf("channel: %s, name: %s\n", batch[i].Channel, batch[i].Name)
    }
}

// channel: a-channel, name: event
// channel: presence-b-channel, name: event, user_count: 4

Authenticating Channels

Application security is very important so Pusher Channels provides a mechanism for authenticating a user’s access to a channel at the point of subscription.

This can be used both to restrict access to private channels, and in the case of presence channels notify subscribers of who else is also subscribed via presence events.

This library provides a mechanism for generating an authentication signature to send back to the client and authorize them.

For more information see our docs.

Private channels

func (c *Client) AuthenticatePrivateChannel

Example

func pusherAuth(res http.ResponseWriter, req *http.Request) {
    params, _ := ioutil.ReadAll(req.Body)
    response, err := pusherClient.AuthenticatePrivateChannel(params)
    if err != nil {
        panic(err)
    }

    fmt.Fprintf(res, string(response))
}

func main() {
    http.HandleFunc("/pusher/auth", pusherAuth)
    http.ListenAndServe(":5000", nil)
}

Example (JSONP)

func pusherJsonpAuth(res http.ResponseWriter, req *http.Request) {
    var (
        callback, params string
    )

    {
        q := r.URL.Query()
        callback = q.Get("callback")
        if callback == "" {
            panic("callback missing")
        }
        q.Del("callback")
        params = []byte(q.Encode())
    }

    response, err := pusherClient.AuthenticatePrivateChannel(params)
    if err != nil {
        panic(err)
    }

    res.Header().Set("Content-Type", "application/javascript; charset=utf-8")
    fmt.Fprintf(res, "%s(%s);", callback, string(response))
}

func main() {
    http.HandleFunc("/pusher/auth", pusherJsonpAuth)
    http.ListenAndServe(":5000", nil)
}

Authenticating presence channels

Using presence channels is similar to private channels, but in order to identify a user, clients are sent a user_id and, optionally, custom data.

func (c *Client) AuthenticatePresenceChannel

Custom Types

pusher.MemberData

type MemberData struct {
    UserID   string
    UserInfo map[string]string
}

Example

params, _ := ioutil.ReadAll(req.Body)

presenceData := pusher.MemberData{
    UserID: "1",
    UserInfo: map[string]string{
        "twitter": "jamiepatel",
    },
}

response, err := pusherClient.AuthenticatePresenceChannel(params, presenceData)

if err != nil {
    panic(err)
}

fmt.Fprintf(res, response)

Application state

This library allows you to query our API to retrieve information about your application's channels, their individual properties, and, for presence-channels, the users currently subscribed to them.

Get the list of channels in an application

func (c *Client) Channels

Custom Types

pusher.ChannelsParams

type ChannelsParams struct {
    FilterByPrefix *string
    Info           *string
}

pusher.ChannelsList

type ChannelsList struct {
    Channels map[string]ChannelListItem
}

pusher.ChannelsListItem

type ChannelListItem struct {
    UserCount int
}

Example

prefixFilter := "presence-"
attributes := "user_count"
params := pusher.ChannelsParams{FilterByPrefix: &prefixFilter, Info: &attributes}
channels, err := pusherClient.Channels(params)

// channels => &{Channels:map[presence-chatroom:{UserCount:4} presence-notifications:{UserCount:31}]}

Get the state of a single channel

func (c *Client) Channel

Custom Types

pusher.ChannelParams

type Channel struct {
    Info *string
}

pusher.Channel

type Channel struct {
    Name              string
    Occupied          bool
    UserCount         int
    SubscriptionCount int
}

Example

attributes := "user_count,subscription_count"
params := pusher.ChannelParams{Info: &attributes}
channel, err := client.Channel("presence-chatroom", params)

// channel => &{Name:presence-chatroom Occupied:true UserCount:42 SubscriptionCount:42}

Get a list of users in a presence channel

func (c *Client) GetChannelUsers

Custom Types

pusher.Users

type Users struct {
    List []User
}

pusher.User

type User struct {
    ID string
}

Example

users, err := pusherClient.GetChannelUsers("presence-chatroom")

// users => &{List:[{ID:13} {ID:90}]}

Webhook validation

On your dashboard, you can set up webhooks to POST a payload to your server after certain events. Such events include channels being occupied or vacated, members being added or removed in presence-channels, or after client-originated events. For more information see https://pusher.com/docs/webhooks.

This library provides a mechanism for checking that these POST requests are indeed from Pusher, by checking the token and authentication signature in the header of the request.

func (c *Client) Webhook

Custom Types

pusher.Webhook

type Webhook struct {
    TimeMs int
    Events []WebhookEvent
}

pusher.WebhookEvent

type WebhookEvent struct {
    Name     string
    Channel  string
    Event    string
    Data     string
    SocketID string
}

Example

func pusherWebhook(res http.ResponseWriter, req *http.Request) {
    body, _ := ioutil.ReadAll(req.Body)
    webhook, err := pusherClient.Webhook(req.Header, body)
    if err != nil {
        fmt.Println("Webhook is invalid :(")
    } else {
        fmt.Printf("%+v\n", webhook.Events)
    }
}

Feature Support

Helper Functionality

These are helpers that have been implemented to to ensure interactions with the HTTP API only occur if they will not be rejected e.g. channel naming conventions.

Developing the Library

Feel more than free to fork this repo, improve it in any way you'd prefer, and send us a pull request :)

Running the tests

$ go test

License

This code is free to use under the terms of the MIT license.