CLI flags for traffic splitting - Traffic splitting | Serving

Knative CLI traffic splitting flags
- Multiple flags and order precedence
- Custom URLs for revisions

The Knative (kn) CLI supports traffic operations on the traffic block of a service as part of the kn service update command.

Knative CLI traffic splitting flags

The following table displays a summary of traffic splitting flags, value formats, and the operation the flag performs. The Repetition column denotes whether repeating the particular value of flag is allowed in a kn service update command.

Flag Value(s) Operation Repetition

Flag	Value(s)	Operation	Repetition
`--traffic`	`RevisionName=Percent`	Gives `Percent` traffic to `RevisionName`	Yes
`--traffic`	`Tag=Percent`	Gives `Percent` traffic to the revision having `Tag`	Yes
`--traffic`	`@latest=Percent`	Gives `Percent` traffic to the latest ready revision	No
`--tag`	`RevisionName=Tag`	Gives `Tag` to `RevisionName`	Yes
`--tag`	`@latest=Tag`	Gives `Tag` to the latest ready revision	No
`--untag`	`Tag`	Removes `Tag` from revision	Yes

--traffic

RevisionName=Percent

Gives Percent traffic to RevisionName

Yes

--traffic

Tag=Percent

Gives Percent traffic to the revision having Tag

Yes

--traffic

@latest=Percent

Gives Percent traffic to the latest ready revision

--tag

RevisionName=Tag

Gives Tag to RevisionName

Yes

--tag

@latest=Tag

Gives Tag to the latest ready revision

--untag

Tag

Removes Tag from revision

Yes

Multiple flags and order precedence

All traffic-related flags can be specified using a single kn service update command. kn defines the precedence of these flags. The order of the flags specified when using the command is not taken into account.

The precedence of the flags as they are evaluated by kn are:

--untag: All the referenced revisions with this flag are removed from the traffic block.
--tag: Revisions are tagged as specified in the traffic block.
--traffic: The referenced revisions are assigned a portion of the traffic split.

You can add tags to revisions and then split traffic according to the tags you have set.

Custom URLs for revisions

Assigning a --tag flag to a service by using the kn service update command creates a custom URL for the revision that is created when you update the service. The custom URL follows the pattern https://<tag>-<service_name>-<namespace>.<domain>; or http://<tag>-<service_name>-<namespace>.<domain>;.

The --tag and --untag flags use the following syntax:

Require one value.
Denote a unique tag in the traffic block of the service.
Can be specified multiple times in one command.

Example: Assign a tag to a revision

The following example assigns the tag latest to a revision named example-revision:

$ kn service update <service_name> --tag @latest=example-tag

Example: Remove a tag from a revision

You can remove a tag to remove the custom URL, by using the --untag flag.

If a revision has its tags removed, and it is assigned 0% of the traffic, the revision is removed from the traffic block entirely.

The following command removes all tags from the revision named example-revision:

$ kn service update <service_name> --untag example-tag