# Which Problems Are Solved
The current handling of notification follows the same pattern as all
other projections:
Created events are handled sequentially (based on "position") by a
handler. During the process, a lot of information is aggregated (user,
texts, templates, ...).
This leads to back pressure on the projection since the handling of
events might take longer than the time before a new event (to be
handled) is created.
# How the Problems Are Solved
- The current user notification handler creates separate notification
events based on the user / session events.
- These events contain all the present and required information
including the userID.
- These notification events get processed by notification workers, which
gather the necessary information (recipient address, texts, templates)
to send out these notifications.
- If a notification fails, a retry event is created based on the current
notification request including the current state of the user (this
prevents race conditions, where a user is changed in the meantime and
the notification already gets the new state).
- The retry event will be handled after a backoff delay. This delay
increases with every attempt.
- If the configured amount of attempts is reached or the message expired
(based on config), a cancel event is created, letting the workers know,
the notification must no longer be handled.
- In case of successful send, a sent event is created for the
notification aggregate and the existing "sent" events for the user /
session object is stored.
- The following is added to the defaults.yaml to allow configuration of
the notification workers:
```yaml
Notifications:
# The amount of workers processing the notification request events.
# If set to 0, no notification request events will be handled. This can be useful when running in
# multi binary / pod setup and allowing only certain executables to process the events.
Workers: 1 # ZITADEL_NOTIFIACATIONS_WORKERS
# The amount of events a single worker will process in a run.
BulkLimit: 10 # ZITADEL_NOTIFIACATIONS_BULKLIMIT
# Time interval between scheduled notifications for request events
RequeueEvery: 2s # ZITADEL_NOTIFIACATIONS_REQUEUEEVERY
# The amount of workers processing the notification retry events.
# If set to 0, no notification retry events will be handled. This can be useful when running in
# multi binary / pod setup and allowing only certain executables to process the events.
RetryWorkers: 1 # ZITADEL_NOTIFIACATIONS_RETRYWORKERS
# Time interval between scheduled notifications for retry events
RetryRequeueEvery: 2s # ZITADEL_NOTIFIACATIONS_RETRYREQUEUEEVERY
# Only instances are projected, for which at least a projection-relevant event exists within the timeframe
# from HandleActiveInstances duration in the past until the projection's current time
# If set to 0 (default), every instance is always considered active
HandleActiveInstances: 0s # ZITADEL_NOTIFIACATIONS_HANDLEACTIVEINSTANCES
# The maximum duration a transaction remains open
# before it spots left folding additional events
# and updates the table.
TransactionDuration: 1m # ZITADEL_NOTIFIACATIONS_TRANSACTIONDURATION
# Automatically cancel the notification after the amount of failed attempts
MaxAttempts: 3 # ZITADEL_NOTIFIACATIONS_MAXATTEMPTS
# Automatically cancel the notification if it cannot be handled within a specific time
MaxTtl: 5m # ZITADEL_NOTIFIACATIONS_MAXTTL
# Failed attempts are retried after a confogired delay (with exponential backoff).
# Set a minimum and maximum delay and a factor for the backoff
MinRetryDelay: 1s # ZITADEL_NOTIFIACATIONS_MINRETRYDELAY
MaxRetryDelay: 20s # ZITADEL_NOTIFIACATIONS_MAXRETRYDELAY
# Any factor below 1 will be set to 1
RetryDelayFactor: 1.5 # ZITADEL_NOTIFIACATIONS_RETRYDELAYFACTOR
```
# Additional Changes
None
# Additional Context
- closes#8931
# Which Problems Are Solved
Currently ZITADEL supports RP-initiated logout for clients. Back-channel
logout ensures that user sessions are terminated across all connected
applications, even if the user closes their browser or loses
connectivity providing a more secure alternative for certain use cases.
# How the Problems Are Solved
If the feature is activated and the client used for the authentication
has a back_channel_logout_uri configured, a
`session_logout.back_channel` will be registered. Once a user terminates
their session, a (notification) handler will send a SET (form POST) to
the registered uri containing a logout_token (with the user's ID and
session ID).
- A new feature "back_channel_logout" is added on system and instance
level
- A `back_channel_logout_uri` can be managed on OIDC applications
- Added a `session_logout` aggregate to register and inform about sent
`back_channel` notifications
- Added a `SecurityEventToken` channel and `Form`message type in the
notification handlers
- Added `TriggeredAtOrigin` fields to `HumanSignedOut` and
`TerminateSession` events for notification handling
- Exported various functions and types in the `oidc` package to be able
to reuse for token signing in the back_channel notifier.
- To prevent that current existing session termination events will be
handled, a setup step is added to set the `current_states` for the
`projections.notifications_back_channel_logout` to the current position
- [x] requires https://github.com/zitadel/oidc/pull/671
# Additional Changes
- Updated all OTEL dependencies to v1.29.0, since OIDC already updated
some of them to that version.
- Single Session Termination feature is correctly checked (fixed feature
mapping)
# Additional Context
- closes https://github.com/zitadel/zitadel/issues/8467
- TODO:
- Documentation
- UI to be done: https://github.com/zitadel/zitadel/issues/8469
---------
Co-authored-by: Hidde Wieringa <hidde@hiddewieringa.nl>
This implementation increases parallel write capabilities of the eventstore.
Please have a look at the technical advisories: [05](https://zitadel.com/docs/support/advisory/a10005) and [06](https://zitadel.com/docs/support/advisory/a10006).
The implementation of eventstore.push is rewritten and stored events are migrated to a new table `eventstore.events2`.
If you are using cockroach: make sure that the database user of ZITADEL has `VIEWACTIVITY` grant. This is used to query events.
