pusher

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 authorize 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 Users
  • Authorizing 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: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 authorization 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

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)

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

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.
params TriggerParams	Any additional parameters.

Return Value	Description
channels TriggerChannelsList	A struct representing channel attributes for the requested TriggerParams.Info
err error	Any errors encountered

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

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.

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

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.
params TriggerParams	As above.

Return Value	Description
channels TriggerChannelsList	A struct representing channel attributes for the requested TriggerParams.Info
err error	Any errors encountered

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

Argument	Description
batch []Event	A list of events to publish

Return Value	Description
batch TriggerBatchChannelsList	A struct representing channel attributes for the requested TriggerParams.Info
err error	Any errors encountered

pusher.Event

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

Note: Info is part of an experimental feature.

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

Send to user

Argument	Description
userId string	The id of the user who should receive the event.
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.SendToUser("user123", "say_hello", data)

Authenticating Users

Pusher Channels provides a mechanism for authenticating users. This can be used to send messages to specific users based on user id and to terminate misbehaving user connections, for example.

For more information see our docs.

func (c *Client) AuthenticateUser

Argument	Description
params []byte	The request body sent by the client
userData map[string]interface{}	The map containing arbitrary user data. It must contain at least an id field with the user's id as a string. See below.

userData := map[string]interface{} { "id": "1234", "twitter": "jamiepatel" }

Return Value	Description
response []byte	The response to send back to the client, carrying an authentication signature
err error	Any errors generated

func pusherUserAuth(res http.ResponseWriter, req *http.Request) {
    params, _ := ioutil.ReadAll(req.Body)
    userData := map[string]interface{} { "id": "1234", "twitter": "jamiepatel" }
    response, err := pusherClient.AuthenticateUser(params, userData)
    if err != nil {
        panic(err)
    }

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

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

Authorizing Channels

Application security is very important so Pusher Channels provides a mechanism for authorizing 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 authorization signature to send back to the client and authorize them.

For more information see our docs.

Private channels

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 authorization signature
err error	Any errors generated

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

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

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

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.AuthorizePrivateChannel(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)
}

Authorizing 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.

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

pusher.MemberData

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

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

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

response, err := pusherClient.AuthorizePresenceChannel(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

Argument	Description
params ChannelsParams	The query options. The field FilterByPrefix will filter the returned channels. To get the number of users subscribed to a presence-channel, specify an the Info field with value "user_count". Pass in nil if you do not wish to specify any query attributes.

Return Value	Description
channels ChannelsList	A struct representing the list of channels. See below.
err error	Any errors encountered

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
}

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

Argument	Description
name string	The name of the channel
params ChannelParams	The query options. The field Info 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 Channel	A struct representing a channel. See below.
err error	Any errors encountered

pusher.ChannelParams

type Channel struct {
    Info *string
}

pusher.Channel

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

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

Argument	Description
name string	The channel name

Return Value	Description
users Users	A struct representing a list of the users subscribed to the presence-channel. See below
err error	Any errors encountered.

pusher.Users

type Users struct {
    List []User
}

pusher.User

type User struct {
    ID string
}

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.

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.

pusher.Webhook

type Webhook struct {
    TimeMs int
    Events []WebhookEvent
}

pusher.WebhookEvent

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

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	✔
Fetching info on trigger	✔
Send to user	✔
Authenticating users	✔
Authorizing private channels	✔
Authorizing 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.