Staying in Sync with Cloud 2 Device Messaging

Staying in Sync with Cloud 2 Device Messaging

About Me • • Chris Risner chris@chrisrisner. com http: //chrisrisner. com Twitter: chrisrisner

How do we keep our apps up to date? • Goal: Get the latest data to our app. • Techniques: • Polling: the app checks the server periodically. • Pushing: the app waits for information to get sent to it.

What’s wrong with Polling? • If there isn’t any new data, we’re still checking • We’re using bandwidth and battery resources that we don’t need to. • Maybe we should try Pushing!

What is C 2 DM? • C 2 DM is how we push data to our applications. • Allows us to send a small amount of data to any device with our application installed and registered for C 2 DM. • Great for telling our app there is new data, not necessarily for delivering that data. • Uses the same single connection for every app on the device.

Limitations of C 2 DM • The device must be running 2. 2 or greater. • The device must have the Marketplace installed. • Your app needs additional permissions in the manifest. • Doesn’t include any pre-built UI. • Need to have a whitelisted account (more on this later). • Message payload is limited to 1024 bytes!

What’s great about C 2 DM? • Your app doesn’t have to be running to receive the message and process it. • You can display a notification however you want. • Your application server can be written in anything (Java, C#, PHP, etc)

How efficient is it? • A background service establishes and maintains a single SSL-encrypted persistent TCP/IP connection. • Honors background-data setting. • Auto starts when the network becomes available. • Uses heartbeats to auto-reconnect as necessary. • Tuned for different networks. • In the cloud, Google provides a scaled farm of servers to accept and maintain the persistent connections. • Caches session keys to minimize SSL handshakes. • Each app provides its broadcast receiver to accept messages.

App Engine connected Android Projects Us n e s o t d e e M d es g ssa Hosts the web client and web service that our App talks to and sends Messages to the C 2 DM service Stores our Auth Token And Device Registration IDs Reg iste rs a Me nd R ssa ece ges ive s Google’s Servers that Send messages to devices

Step 1: Get an Account • Fill out the signup form at http: //code. google. com/android/c 2 dm/signup. html • Your account MUST be whitelisted to use C 2 DM. • Need to provide the following: – – – App package name. Estimated total # of messages per day. Estimated peak messages per second. Contact email address (your address). A Role email address (gmail and NOT your email address). • Used in application as well as on your app server.

Step 2: Get your App Ready • Add the permissions, receiver, and service to your manifest. • Create a receiver to handle registration result and message notification.

Step 3: Register your App • Connect to C 2 DM from your app with the whitelisted email address. • Get back a device registration ID (dr. ID). • Send the dr. ID to your app server.

Step 4: Save the dr. ID • Your app server needs to expose some way for the app to say “here’s a gmail address and a dr. ID”. – Saving the connection between dr. ID and address allows users to connect multiple devices to your app server. • The server needs to save this somewhere for later use.

Step 5: Get an Auth Token • Connect to the Google Client. Login service. – Send over: • • • Account type Whitelisted email address. Email address password. Server (ac 2 dm) Source • Parse the auth token out of the 200 response or handle the different errors

Step 6: Send a Message • Submit a post to https: //android. apis. google. com/c 2 dm/send with the following: – Device registration ID. – Collapse key (more on this in a second). – Data. – Auth token – Delay_while_idle: optional but allows you to tell C 2 DM to not deliver until the device is active. • Parse the ID of the sent message or an error out of the response.

Step 6. 1: Possible Errors • • Quota Exceeded Device Quota Exceeded Invalid Registration Not Registered Message Too Big Missing Collapse Key 401 503

A Word about the Collapse Key • Used to prevent sending multiple messages when a device comes online. • Also useful for making sure the user doesn’t get a stale notification. • Max of 4 collapse keys “in process” for device.

Step 7: The C 2 DM Servers • Verifies our Auth Token. • Temporarily queues our message to a durable store. – Holds the message until delivered or expired. – Replaces other messages with the same dr. ID and collapse key.

Step 7. 1: More C 2 DM Server • Server keeps track of how many messages have been sent per app, per device, and per collapse key recently. • Prevents firing the radio for every message. • Protects battery life. • Protects the user from getting too many messages.

Step 8: Delivery to Device • When the message is successfully delivered to the app, an acknowledge response is sent back to the server. • The Manifest file ensures that ONLY our app receives the notification and other apps don’t. • If your on. Message needs to do a lot of processing, consider using a wakelock.

Step X: Unregister the Device • Automatically done when app is uninstalled. • Just requires a call to the C 2 DM server. • Doesn’t notify your app server!

App Engine connected Android Projects Us n e s o t d e e M d es g ssa Hosts the web client and web service that our App talks to and sends Messages to the C 2 DM service Stores our Auth Token And Device Registration IDs Reg iste rs a Me nd R ssa ece ges ive s Google’s Servers that Send messages to devices

Quotas • Quotas are assigned to sender accounts, not Applications. • Default quota is 200, 000 messages / day. • If you need more, there is a form you can fill out to request more.

Important Things to Remember • Delivery and order of delivery isn’t guaranteed. • There is a size limit of each message (1024 bytes) • Auth tokens and dr. IDs can “expire”. Your app needs to handle accepting new ones.

Demo 1: http: //chrisrisner. com/upload/One. Dev. Day 2011 a-Presentation. zip Demo 2: http: //chrisrisner. com/upload/One. Dev. Day 2011 b-Presentation. zip

Questions?