Push notifications
Push notifications allow JMAP clients to efficiently receive updates almost instantly and stay in sync with data changes on the JMAP server. There are two different mechanisms by which a client can receive push notifications from Stalwart JMAP:
- Event source allows clients to hold transport connections open over HTTP to receive push notifications directly from the server.
- Push subscriptions in which a client registers a push service with the server. Each time there is a state change a notification is posted to the push service which in turn is responsible for routing these to the client.
Push Subscriptions
JMAP clients can activate push subscriptions by registering a push service URL with Stalwart JMAP. The server will then make an HTTP POST request to this URL for each push notification it wishes to send to the JMAP client.
Even though all notifications sent to the push service URL are encrypted over TLS, for enhanced privacy it is recommended to enable web push encryption by providing Elliptic Curve Diffie-Hellman (ECDH) public keys when registering the push service with Stalwart JMAP.
The push subscription service accepts the following parameters under the jmap.push section:
max-total: Total number of push subscriptions that a given user can activate. Defaults to 100.throttle: Time to wait before sending a new request to the push service. Defaults to 1000 milliseconds (1 second).attempts.max:: Maximum number of push attempts before a notification is discarded. Defaults to 3.attempts.interval: Time to wait between push attempts. Defaults to 60000 milliseconds (1 minute).retry.interval: Time to wait between retry attempts. Defaults to 1000 milliseconds (1 second).timeout.request: Time before a connection with a push service URL times out. Defaults to 10000 milliseconds (10 seconds).timeout.verify: Time to wait for the push service to verify a subscription. Defaults to 60000 milliseconds (1 minute).
Example:
[jmap.push]
max-total = 100
throttle = "1ms"
[jmap.push.attempts]
interval = "1m"
max = 3
[jmap.push.retry]
interval = "1s"
[jmap.push.timeout]
request = "10s"
verify = "1s"
Event Source
JMAP clients that support holding transport connections open can connect directly to Stalwart JMAP to receive
push notifications via a text/event-stream resource, as described in event source specification.
This is a long running HTTP request where the server can push data to the client by appending data without ending the response.
The event source endpoint is listed in the JMAP Session resource object (/.well-known/jmap) and is available at
/jmap/eventsource/?types={types}&closeafter={closeafter}&ping={ping}.
In order to avoid overwhelming the client with notifications, throttling can be configured
to group multiple updates and send them to the client in intervals. The throttling interval can be configured under the jmap.event-source.throttle key.
Example:
[jmap.event-source]
throttle = "1s"