XMPP Academy #3

Academy #3
16th November 2015
Mickaël Rémond, @mickael

Questions
ejabberd questions
• How does Apple and Google Push support work on ejabberd SaaS and
ejabberd Business Edition ?
• What is the relationship between ejabberd Push support and XEP-0357:
Push Notifications ?
XMPP questions
• What is the impact of Websocket on Web chat performance ?
• What is the XMPP stack for quick prototyping ?
• Why do we seem to find duplicate in Message Archive Management
backend ?

What are Push Notifications and why do they matter ?
• Most smartphones Operating Systems are saving battery life by preventing
apps to run constantly and access network in background:
• On iOS, since iOS 3.
• On Android since Android 6.
• For a chat application, it means that:
• your application is suspended shortly after user put it to background.
• as a result you cannot directly receive messages.
=> You need an OS provider service that will awake your app when there is
message available for you on ejabberd.

Push app+device are identified with token
ejabberd
Push

ejabberd support for Push
• ejabberd SaaS and Business Edition natively support push notifications.
• Prerequisite for ejabberd configuration:
• iOS:
• App ID
• APNS sandbox and production certificates
• Android:
• Application package name
• API Key
• Prerequisite on client-side:
• iOS: Retrieve or update Device Token.
• Android: Retrieve or update Registration ID

ejabberd support for Push
• Client configuration is done with IQ stanza in the XMPP stream, after authentication.
<iq type='set' id='123'>
<push xmlns='p1:push' apn-sandbox='false'>
<keepalive max="30"/>
<session duration="60"/>
<body send="all" groupchat="true" from="jid"/>
<status type="xa">Text Message when in push mode</status>
<offline>false</offline>
<notification>
<type>applepush</type>
<id>DeviceToken</id>
</notification>
<appid>application1</appid>
</push>
</iq>

iOS notification sub elements
<appid>AppID</appid>
<notification>
<type>applepush</type>
<id>DeviceToken</id>
</notification>
…
</push>
</iq>

Android notification sub elements
<appid>ApplicationPackageName</appid>
<notification>
<type>gcm</type>
<id>RegistrationID</id>
</notification>
…
</push>
</iq>

ejabberd push triggers
• Message received while session is detached or user is offline.
• Groupchat messages while user session is running and possibly detached (optional)
• Badges: Automatic support for message counts. Auto reset on login.

Unread badge reset
<badge xmlns='p1:push' unread='10'/>
</iq>

Push setting customisations: Per sender sound
<iq type="set" id="cust1">
<customize xmlns="p1:push:customize">
<item from="adam@example.com" mute="true"/>
<item from="eve@example.com" sound="horn.wav"/>
</customize>
</iq>

Per message customisation
Custom fields in messages:
• This could allow clients to taylor rendering:
<message>
...
<x xmlns="p1:push:custom" key="AAA" value="BBB">
...
</message>

Per message sound customization:
<message type="chat" from="peer@example.com">
<body>Hello!</body>
<customize xmlns="p1:push:customize" sound="2.wav"/>
</message>
Or mute:
<body>System message: ...</body>
<customize xmlns="p1:push:customize" mute="true"/>
</message>

Customise body and nick displayed:
<body>{matchResult: "2:1", Players: [...]}</body>
<customize xmlns="p1:push:customize" nick="SportBot">
<body>Match result update 2:1 for ...</body>
</customize>
</message>

Support for silent pushes
• Silent pushes are intended for the app only.
• They provide metadata for the app and can trigger background processing without displaying an alert
to the user.
• Useful to trigger background synchronisation when data are available.

Push Caveats
• Groupchat notifications are only possible when user is online or session is running on server in
detached mode.
• => We are adding feature to groupchat to dealt with that part.
• Apple Push buffer only contains one message:
• Do not expected to never miss a push: If your phone is turn off, you will only receive the latest
push when turned off.
• If this was a silent push, nothing will be visible to the user.

What is the relationship between ejabberd Push
support and XEP-0357: Push Notifications ?
• They cover different use cases:
• XEP-0357 defines:
• a way for app devices to pass their push credential to service.
• a standard API to trigger push notification from XMPP packets.
• XEP-0357 does not define the triggers:
• When and what the server is supposed to do to send push notifications to users.
• It assumes that it is mostly used by third-party services or component to send pushes.
• Our push approach fills the gap between:
• Server events that should trigger push notification, along with the format of such notifications.
• Actually sending the push to the device manufacturer push service.

What is the impact of Websocket on Web chat
performance ?
• On server, Websocket is a much more efficient protocol that takes less resources.
• However, impact on latency is directly visible on client.

Measurement of time to open session: Bosh vs
Websocket
• On server, Websocket is a much more efficient protocol that takes less resources.
• However, impact on latency is directly visible on client.
• Bosh (localhost, no SSL): 1428ms
• Websocket (localhost, no SSL): 307ms
• Bosh (remote server, SSL): 2198ms
• Websocket (remote server, SSL): 1446ms
• The more roundtrip you have, the more impact:
• Websocket is much better when there is a lot of interactions: Discovery, forms, server
configuration, etc.

What is the XMPP stack for quick prototyping ?
• Versatile and widely used server: ejabberd
• Client stack:
• Android: Smack 4
• iOS: XMPPFramework
• Web: Strophe

Using Strophe for prototyping / learning XMPP and
experimenting
• With a basic client, you can use the JS console to prepare and send XMPP packets:
presence = $pres();
connection.send(presence);
presence = $pres().c("status").t("away");
connection.send(presence);
message = $msg({to: "test@localhost", type: "chat"}).c("body").t("Hello
XMPP Academy !");
connection.send(message);
iq = $iq({to: "localhost", type: "get", id: "disco1"}).c("query", {xmlns:
"http://jabber.org/protocol/disco#info"});
connection.send(iq);

Why do we seem to find duplicate in Message Archive
Management backend ?
• When thinking about XMPP protocol, you need to think in federated context:
• Two XMPP domains can connect have have user chat between both domains.
• Message is stored once per user as archive can be managed independently (delete entry, etc)

Domain 1
Archive Archive
Domain 2User1 User2

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