snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

examples/features/customloadbalancer/README.md

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+# Custom Load Balancer
+
+This example shows how to deploy a custom load balancer in a `ClientConn`.
+
+## Try it
+
+```
+go run server/main.go
+```
+
+```
+go run client/main.go
+```
+
+## Explanation
+
+Two echo servers are serving on "localhost:20000" and "localhost:20001". They
+will include their serving address in the response. So the server on
+"localhost:20001" will reply to the RPC with `this is
+examples/customloadbalancing (from localhost:20001)`.
+
+A client is created, to connect to both of these servers (they get both server
+addresses from the name resolver in two separate endpoints). The client is
+configured with the load balancer specified in the service config, which in this
+case is custom_round_robin.
+
+### custom_round_robin
+
+The client is configured to use `custom_round_robin`. `custom_round_robin`
+creates a pick first child for every endpoint it receives. It waits until both
+pick first children become ready, then defers to the first pick first child's
+picker, choosing the connection to localhost:20000, except every chooseSecond
+times, where it defers to second pick first child's picker, choosing the
+connection to localhost:20001 (or vice versa).
+
+`custom_round_robin` is written as a delegating policy wrapping `pick_first`
+load balancers, one for every endpoint received. This is the intended way a user
+written custom lb should be specified, as pick first will contain a lot of
+useful functionality, such as Sticky Transient Failure, Happy Eyeballs, and
+Health Checking.
+
+```
+this is examples/customloadbalancing (from localhost:50050)
+this is examples/customloadbalancing (from localhost:50050)
+this is examples/customloadbalancing (from localhost:50051)
+this is examples/customloadbalancing (from localhost:50050)
+this is examples/customloadbalancing (from localhost:50050)
+this is examples/customloadbalancing (from localhost:50051)
+this is examples/customloadbalancing (from localhost:50050)
+this is examples/customloadbalancing (from localhost:50050)
+this is examples/customloadbalancing (from localhost:50051)
+```