--- layout: docs page_title: Connect - L7 Traffic Management sidebar_title: 'L7 Traffic Management' sidebar_current: docs-connect-l7_traffic_management description: >- Layer 7 traffic management allows operators to divide L7 traffic between different subsets of service instances when using Connect. --- -> **1.6.0+:** This feature is available in Consul versions 1.6.0 and newer. # L7 Traffic Management Layer 7 traffic management allows operators to divide L7 traffic between different [subsets](/docs/agent/config-entries/service-resolver.html#service-subsets) of service instances when using Connect. There are many ways you may wish to carve up a single datacenter's pool of services beyond simply returning all healthy instances for load balancing. Canary testing, A/B tests, blue/green deploys, and soft multi-tenancy (prod/qa/staging sharing compute resources) all require some mechanism of carving out portions of the Consul catalog smaller than the level of a single service and configuring when that subset should receive traffic. -> **Note:** This feature is not compatible with the [built-in proxy](/docs/connect/proxies/built-in.html), [native proxies](/docs/connect/native.html), and some [Envoy proxy escape hatches](/docs/connect/proxies/envoy.html#escape-hatch-overrides). ## Stages Connect proxy upstreams are discovered using a series of stages: routing, splitting, and resolution. These stages represent different ways of managing L7 traffic. ![diagram showing l7 traffic discovery stages: routing to splitting to resolution](/img/l7-traffic-stages.svg) Each stage of this discovery process can be dynamically reconfigured via various [configuration entries](/docs/agent/config_entries.html). When a configuration entry is missing, that stage will fall back on reasonable default behavior. ### Routing A [`service-router`](/docs/agent/config-entries/service-router.html) config entry kind is the first configurable stage. A router config entry allows for a user to intercept traffic using L7 criteria such as path prefixes or http headers, and change behavior such as by sending traffic to a different service or service subset. These config entries may only reference `service-splitter` or `service-resolver` entries. [Examples](/docs/agent/config-entries/service-router.html#sample-config-entries) can be found in the `service-router` documentation. ### Splitting A [`service-splitter`](/docs/agent/config-entries/service-splitter.html) config entry kind is the next stage after routing. A splitter config entry allows for a user to choose to split incoming requests across different subsets of a single service (like during staged canary rollouts), or perhaps across different services (like during a v2 rewrite or other type of codebase migration). These config entries may only reference `service-splitter` or `service-resolver` entries. If one splitter references another splitter the overall effects are flattened into one effective splitter config entry which reflects the multiplicative union. For instance: splitter[A]: A_v1=50%, A_v2=50% splitter[B]: A=50%, B=50% --------------------- splitter[effective_B]: A_v1=25%, A_v2=25%, B=50% [Examples](/docs/agent/config-entries/service-splitter.html#sample-config-entries) can be found in the `service-splitter` documentation. ### Resolution A [`service-resolver`](/docs/agent/config-entries/service-resolver.html) config entry kind is the last stage. A resolver config entry allows for a user to define which instances of a service should satisfy discovery requests for the provided name. Examples of things you can do with resolver config entries: - Control where to send traffic if all instances of `api` in the current datacenter are unhealthy. - Configure service subsets based on `Service.Meta.version` values. - Send all traffic for `web` that does not specify a service subset to the `version1` subset. - Send all traffic for `api` to `new-api`. - Send all traffic for `api` in all datacenters to instances of `api` in `dc2`. - Create a "virtual service" `api-dc2` that sends traffic to instances of `api` in `dc2`. This can be referenced in upstreams or in other config entries. If no resolver config is defined for a service it is assumed 100% of traffic flows to the healthy instances of a service with the same name in the current datacenter/namespace and discovery terminates. This should feel similar in spirit to various uses of Prepared Queries, but is not intended to be a drop-in replacement currently. These config entries may only reference other `service-resolver` entries. [Examples](/docs/agent/config-entries/service-resolver.html#sample-config-entries) can be found in the `service-resolver` documentation. -> **Note:** `service-resolver` config entries kinds function at L4 (unlike `service-router` and `service-splitter` kinds). These can be created for services of any protocol such as `tcp`.