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Pusher Channels HTTP Go Library

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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 1.5 or greater.

Table of Contents

Installation

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

Getting Started

package main

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

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:secret@api-eu.pusher.com/apps/app_id
http://key:secret@api-ap1.pusher.com/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"
    "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.

Single channel

func (c *Client) Trigger
Argument Description
channel string The name of the channel you wish to trigger on.
event string The name of the event you wish to trigger
data interface{} The payload you wish to send. Must be marshallable into JSON.
data := map[string]string{"hello": "world"}
pusherClient.Trigger("greeting_channel", "say_hello", data)

Multiple channels

func (c. *Client) TriggerMulti
Argument Description
channels []string A slice of channel names you wish to send an event on. The maximum length is 10.
event string As above.
data interface{} As above.
Example
pusherClient.TriggerMulti([]string{"a_channel", "another_channel"}, "event", data)

Excluding event recipients

func (c *Client) TriggerExclusive and func (c *Client) TriggerMultiExclusive follow the patterns above, except a socket_id is given as the last parameter.

These methods allow you to exclude a recipient whose connection has that socket_id from receiving the event. You can read more here.

Examples

On one channel:

pusherClient.TriggerExclusive("a_channel", "event", data, "123.12")

On multiple channels:

pusherClient.TriggerMultiExclusive([]string{"a_channel", "another_channel"}, "event", data, "123.12")

Batches

func (c. *Client) TriggerBatch
Argument Description
batch []Event A list of events to publish
Example
pusherClient.TriggerBatch([]pusher.Event{
  { Channel: "a_channel", Name: "event", Data: "hello world", nil },
  { Channel: "a_channel", Name: "event", Data: "hi my name is bob", nil },
})

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
Argument Description
params []byte The request body sent by the client
Return Value Description
response []byte The response to send back to the client, carrying an authentication signature
err error Any errors generated
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
Argument Description
params []byte The request body sent by the client
member pusher.MemberData A struct representing what to assign to a channel member, consisting of a UserID and any custom UserInfo. See below
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
Argument Description
additionalQueries map[string]string A map with query options. A key with "filter_by_prefix" will filter the returned channels. To get number of users subscribed to a presence-channel, specify an "info" key with value "user_count".

Pass in nil if you do not wish to specify any query attributes.
Return Value Description
channels *pusher.ChannelsList A struct representing the list of channels. See below.
err error Any errors encountered
Custom Types

pusher.ChannelsList

type ChannelsList struct {
    Channels map[string]ChannelListItem
}

pusher.ChannelsListItem

type ChannelListItem struct {
    UserCount int
}
Example
channelsParams := map[string]string{
    "filter_by_prefix": "presence-",
    "info":             "user_count",
}

channels, err := pusherClient.Channels(channelsParams)

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

Get the state of a single channel

func (c *Client) Channel
Argument Description
name string The name of the channel
additionalQueries map[string]string A map with query options. An "info" key can have comma-separated values of "user_count", for presence-channels, and "subscription_count", for all-channels. To use the "subscription_count" value, first check the "Enable subscription counting" checkbox in your App Settings on your Pusher Channels dashboard.

Pass in nil if you do not wish to specify any query attributes.
Return Value Description
channel *pusher.Channel A struct representing a channel. See below.
err error Any errors encountered
Custom Types

pusher.Channel

type Channel struct {
    Name              string
    Occupied          bool
    UserCount         int
    SubscriptionCount int
}
Example
channelParams := map[string]string{
    "info": "user_count,subscription_count",
}

channel, err := pusherClient.Channel("presence-chatroom", channelParams)

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

Get a list of users in a presence channel

func (c *Client) GetChannelUsers
Argument Description
name string The channel name
Return Value Description
users *pusher.Users A struct representing a list of the users subscribed to the presence-channel. See below
err error Any errors encountered.
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
Argument Description
header http.Header The header of the request to verify
body []byte The body of the request
Return Value Description
webhook *pusher.Webhook If the webhook is valid, this method will return a representation of that webhook that includes its timestamp and associated events. If invalid, this value will be nil.
err error If the webhook is invalid, an error value will be passed.
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

Feature Supported
Trigger event on single channel
Trigger event on multiple channels
Trigger events in batches
Excluding recipients from events
Authenticating private channels
Authenticating presence channels
Get the list of channels in an application
Get the state of a single channel
Get a list of users in a presence channel
WebHook validation
Heroku add-on support
Debugging & Logging
Cluster configuration
Timeouts
HTTPS
HTTP Proxy configuration
HTTP KeepAlive

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.

Helper Functionality Supported
Channel name validation
Limit to 10 channels per trigger
Limit event name length to 200 chars

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.

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