Tag Routing Rules

Tag Routing Rules

Tag routing divides instances of a service into different groups, constraining traffic with specific tags to flow only within designated groups. Different groups serve different traffic scenarios, achieving traffic isolation. This can be the basis for scenarios such as blue-green deployment and canary release. Currently, there are two ways to tag instances: dynamic rule tagging and static rule tagging. Dynamic rule tagging can dynamically enclose a group of machine instances at runtime, while static rule tagging requires instance restart to take effect. Dynamic rules have higher priority compared to static rules, and when both rules exist and conflict, dynamic rules will prevail.

This article discusses tag routing rules, specifically dynamic rule tagging.

Tag routing is a strictly isolated traffic system. For the same application, once tagged, the subset of addresses is isolated. Only requests with the corresponding tag can access this subset of addresses. This subset will no longer receive traffic without tags or with different tags.

For example, if we tag an application and divide it into three address subsets: tag-a, tag-b, and no tag, then the traffic accessing this application will either route to tag-a (when the request context dubbo.tag=tag-a), route to tag-b (dubbo.tag=tag-b), or route to the no tag address subset (dubbo.tag not set). There will be no mixed routing.

The scope of tag routing is the provider application, and the consumer application does not need to configure tag routing rules. All services within a provider application can only have one grouping rule. There will not be a situation where service A uses one routing rule and service B uses another. The following conditional routing example encloses an isolated environment gray in the shop-detail application. The gray environment includes all machine instances marked with env=gray.

configVersion: v3.0
force: true
enabled: true
key: shop-detail
tags:
  - name: gray
    match:
      - key: env
        value:
          exact: gray

TagRule

The main body of the tag routing rule. Defines the target application for which the routing rule is effective, tag classification rules, and behaviors in specific scenarios.

Field	Type	Description	Required
configVersion	string	The version of the tag rule definition, currently available version is `v3.0`	Yes
key	string	The identifier of the target application that this rule is about to control	Yes
enabled	bool	Whether to enable this rule or not, set `enabled:false` to disable this rule.	Yes
tags	Tag[]	The tag definition of this rule.	Yes
force	bool	The behavior when the instance subset is empty after routing. `true` means return no provider exception while `false` means fallback to subset without any tags.	No
runtime	bool	Whether to run the routing rule for every RPC invocation or use routing cache if available.	No

Tag

Tag definition, filtering out a subset of addresses based on match conditions.

Field	Type	Description	Required
name	string	The name of the tag used to match the `dubbo.tag` value in the request context.	Yes
match	MatchCondition	A set of criteria to be met for instances to be classified as members of this tag.	No

MatchCondition

Defines instance filtering conditions based on specific parameters in the Dubbo URL address.

Field	Type	Description	Required
key	string	The name of the key in the Dubbo URL address.	Yes
value	StringMatch (oneof)	The matching condition for the value in the Dubbo URL address.	Yes

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Last modified September 30, 2024: Update & Translate Overview Docs (#3040) (d37ebceaea7)