ably-go

README

Ably Go

Ably is the platform that powers synchronized digital experiences in realtime. Whether attending an event in a virtual venue, receiving realtime financial information, or monitoring live car performance data – consumers simply expect realtime digital experiences as standard. Ably provides a suite of APIs to build, extend, and deliver powerful digital experiences in realtime for more than 250 million devices across 80 countries each month. Organizations like Bloomberg, HubSpot, Verizon, and Hopin depend on Ably’s platform to offload the growing complexity of business-critical realtime data synchronization at global scale. For more information, see the Ably documentation.

This is a Go client library for Ably.

Installation

~ $ go get -u github.com/ably/ably-go/ably

Supported Versions of Go

Whenever a new version of Go is released, Ably adds support for that version. The Go Release Policy supports the last two major versions. This SDK follows the same policy of supporting the last two major versions of Go.

Breaking API Changes in Version 1.2.x

Please see our Upgrade / Migration Guide for notes on changes you need to make to your code to update it to use the new API introduced by version 1.2.x.

Users updating from version 1.1.5 of this library will note that there are significant breaking changes to the API. Our current approach to versioning is not compliant with semantic versioning, which is why these changes are breaking despite presenting only a change in the minor component of the version number.

Using the Realtime API

Creating a client

client, err := ably.NewRealtime(ably.WithKey("xxx:xxx"))
if err != nil {
        panic(err)
}

channel := client.Channels.Get("test")

Subscribing to events

You may monitor events on connections and channels.

client, err = ably.NewRealtime(
ably.WithKey("xxx:xxx"),
ably.WithAutoConnect(false), // Set this option to avoid missing state changes.
)
if err != nil {
        panic(err)
}

// Set up connection events handler.
client.Connection.OnAll(func(change ably.ConnectionStateChange) {
        fmt.Printf("Connection event: %s state=%s reason=%s", change.Event, change.Current, change.Reason)
})

// Then connect.
client.Connect()

channel = client.Channels.Get("test")

channel.OnAll(func(change ably.ChannelStateChange) {
        fmt.Printf("Channel event event: %s channel=%s state=%s reason=%s", channel.Name, change.Event, change.Current, change.Reason)
})

Subscribing to a channel for all messages

unsubscribe, err := channel.SubscribeAll(ctx, func(msg *ably.Message) {
        fmt.Printf("Received message: name=%s data=%v\n", msg.Name, msg.Data)
})
if err != nil {
        panic(err)
}

Subscribing to a channel for EventName1 and EventName2 message names

unsubscribe1, err := channel.Subscribe(ctx, "EventName1", func(msg *ably.Message) {
        fmt.Printf("Received message: name=%s data=%v\n", msg.Name, msg.Data)
})
if err != nil {
        panic(err)
}

unsubscribe2, err := channel.Subscribe(ctx, "EventName2", func(msg *ably.Message) {
        fmt.Printf("Received message: name=%s data=%v\n", msg.Name, msg.Data)
})
if err != nil {
        panic(err)
}

Publishing to a channel

err = channel.Publish(ctx, "EventName1", "EventData1")
if err != nil {
        panic(err)
}

Handling errors

Errors returned by this library may have an underlying *ErrorInfo type.

See Ably documentation for ErrorInfo.

badClient, err := ably.NewRealtime(ably.WithKey("invalid:key"))
if err != nil {
        panic(err)
}

err = badClient.Channels.Get("test").Publish(ctx, "event", "data")
if errInfo := (*ably.ErrorInfo)(nil); errors.As(err, &errInfo) {
        fmt.Printf("Error publishing message: code=%v status=%v cause=%v", errInfo.Code, errInfo.StatusCode, errInfo.Cause)
} else if err != nil {
        panic(err)
}

Announcing presence on a channel

err = channel.Presence.Enter(ctx, "presence data")
if err != nil {
        panic(err)
}

Announcing presence on a channel on behalf of other client

err = channel.Presence.EnterClient(ctx, "clientID", "presence data")
if err != nil {
        panic(err)
}

Updating and leaving presence

// Update also has an UpdateClient variant.
err = channel.Presence.Update(ctx, "new presence data")
if err != nil {
        panic(err)
}

// Leave also has an LeaveClient variant.
err = channel.Presence.Leave(ctx, "last presence data")
if err != nil {
        panic(err)
}

Getting all clients present on a channel

clients, err := channel.Presence.Get(ctx)
if err != nil {
        panic(err)
}

for _, client := range clients {
        fmt.Println("Present client:", client)
}

Subscribing to all presence messages

unsubscribe, err = channel.Presence.SubscribeAll(ctx, func(msg *ably.PresenceMessage) {
        fmt.Printf("Presence event: action=%v data=%v", msg.Action, msg.Data)
})
if err != nil {
        panic(err)
}

Subscribing to 'Enter' presence messages only

unsubscribe, err = channel.Presence.Subscribe(ctx, ably.PresenceActionEnter, func(msg *ably.PresenceMessage) {
        fmt.Printf("Presence event: action=%v data=%v", msg.Action, msg.Data)
})
if err != nil {
        panic(err)
}

Using the REST API

Introduction

All examples assume a client and/or channel has been created as follows:

client, err := ably.NewREST(ably.WithKey("xxx:xxx"))
if err != nil {
        panic(err)
}

channel := client.Channels.Get("test")

Publishing a message to a channel

err = channel.Publish(ctx, "HelloEvent", "Hello!")
if err != nil {
        panic(err)
}

// You can also publish multiple messages in a single request.
err = channel.PublishMultiple(ctx, []*ably.Message{
        {Name: "HelloEvent", Data: "Hello!"},
        {Name: "ByeEvent", Data: "Bye!"},
})
if err != nil {
        panic(err)
}

// A REST client can publish messages on behalf of a realtime client
// by providing the connection key of the realtime client.
err := channel.Publish(ctx, "temperature", "12.7", ably.PublishWithConnectionKey("ConnectionKeyOfPublisherClientHere"))
if err != nil {
        panic(err)
}

Querying the History

pages, err := channel.History().Pages(ctx)
if err != nil {
        panic(err)
}
for pages.Next(ctx) {
        for _, message := range pages.Items() {
                fmt.Println(message)
        }
}
if err := pages.Err(); err != nil {
        panic(err)
}

Presence on a channel

pages, err := channel.Presence.Get().Pages(ctx)
if err != nil {
        panic(err)
}
for pages.Next(ctx) {
        for _, presence := range pages.Items() {
                fmt.Println(presence)
        }
}
if err := pages.Err(); err != nil {
        panic(err)
}

Querying the Presence History

pages, err := channel.Presence.History().Pages(ctx)
if err != nil {
        panic(err)
}
for pages.Next(ctx) {
        for _, presence := range pages.Items() {
                fmt.Println(presence)
        }
}
if err := pages.Err(); err != nil {
        panic(err)
}

Fetching your application's stats

pages, err := client.Stats().Pages(ctx)
if err != nil {
        panic(err)
}
for pages.Next(ctx) {
        for _, stat := range pages.Items() {
                fmt.Println(stat)
        }
}
if err := pages.Err(); err != nil {
        panic(err)
}

Feature support

This library targets the Ably 1.2 client library specification.

Known limitations

As of release 1.2.0, the following are not implemented and will be covered in future 1.2.x releases. If there are features that are currently missing that are a high priority for your use-case then please contact Ably customer support. Pull Requests are also welcomed.

REST API

• Push notifications admin API is not implemented.

• JWT authentication is not implemented.

Realtime API

• There is no channel suspended state; this means that the client will not automatically reattach to channels if a connection becomes suspended and then resumes, and presence members associated with the client will not be automatically re-entered.

• Transient realtime publishing is not supported, so a call to publish() on a realtime channel will trigger attachment of the channel.

• Inband reauthentication is not supported; expiring tokens will trigger a disconnection and resume of a realtime connection.

• Realtime connection failure handling is partially implemented.

• Realtime Ping function is not implemented.

• Message Delta Compression is not implemented.

• Push Notification Target functional is not applicable for the SDK and thus not implemented.

Release process

Starting with release 1.2, this library uses semantic versioning. For each release, the following needs to be done:

1. Create a branch for the release, named like release/1.2.3 (where 1.2.3 is the new version number)
2. Replace all references of the current version number with the new version number and commit the changes
3. Run github_changelog_generator to automate the update of the CHANGELOG. This may require some manual intervention, both in terms of how the command is run and how the change log file is modified. Your mileage may vary:

• The command you will need to run will look something like this: github_changelog_generator -u ably -p ably-go --since-tag v1.2.3 --output delta.md
• Using the command above, --output delta.md writes changes made after --since-tag to a new file
• The contents of that new file (delta.md) then need to be manually inserted at the top of the CHANGELOG.md, changing the "Unreleased" heading and linking with the current version numbers
• Also ensure that the "Full Changelog" link points to the new version tag instead of the HEAD

1. Commit this change: git add CHANGELOG.md && git commit -m "Update change log."
2. Make a PR against main
3. Once the PR is approved, merge it into main
4. Add a tag to the new main head commit and push to origin such as git tag v1.2.3 && git push origin v1.2.3
5. Create the release on Github, from the new tag, including populating the release notes
6. Create the entry on the Ably Changelog (via headwayapp)

Further information

Broaden your knowledge of realtime in Go with these useful materials:

• Building realtime apps with Go and WebSockets: client-side considerations
• Guide to Pub/Sub in Golang

Support and feedback

Please visit https://knowledge.ably.com/ for access to our knowledgebase and to ask for any assistance.

You can also view the community reported Github issues.

Contributing

Because this package uses internal packages, all fork development has to happen under $GOPATH/src/github.com/ably/ably-go to prevent use of internal package not allowed errors.

1. Fork github.com/ably/ably-go
2. go to the ably-go directory: cd $GOPATH/src/github.com/ably/ably-go
3. add your fork as a remote: git remote add fork git@github.com:your-username/ably-go
4. create your feature branch: git checkout -b my-new-feature
5. commit your changes (git commit -am 'Add some feature')
6. ensure you have added suitable tests and the test suite is passing for both JSON and MessagePack protocols (see workflow for the test commands executed in the CI environment).
7. push to the branch: git push fork my-new-feature
8. create a new Pull Request