gRPC-go load balancing

The gRPC-go Require

• Go 1.15+
• gRPC 1.36.0

Version

Each version corresponds to the corresponding version of GRPC-go.

For example, tag: v1.36.0 -> grpc-go v1.36.0

Cautions

v1.45.0 & v1.46.0-dev running panic like this:

panic: runtime error: comparing uncomparable type MyAttribute

goroutine 1 [running]:
google.golang.org/grpc/attributes.(*Attributes).Equal(0xc00015e4b0, 0xc00013c140)
        /project/vendor/google.golang.org/grpc/attributes/attributes.go:95 +0x194
google.golang.org/grpc/resolver.addressMapEntryList.find({0xc00013c1b8, 0x1, 0x8000102}, {{0xc00015e4c8, 0x13}, {0xc00015e4c8, 0xd}, 0xc00013c140, 0x0, 0x0, ...})
        /project/vendor/google.golang.org/grpc/resolver/map.go:49 +0xb9
google.golang.org/grpc/resolver.(*AddressMap).Get(0xc00013c188, {{0xc00015e4c8, 0x13}, {0xc00015e4c8, 0xd}, 0xc00013c140, 0x0, 0x0, {0x0, 0x0}})
        /project/vendor/google.golang.org/grpc/resolver/map.go:59 +0x94
mesh-sidecar/grpclient_balancer/balancer.(*baseBalancer).UpdateClientConnState(0xc00013b500, {{{0xc000414380, 0x3, 0x3}, 0x0, 0x0}, {0x0, 0x0}})

Your attribute needs implement Equal function. https://github.com/grpc/grpc-go/blob/v1.46.0-dev/attributes/attributes.go#L91

type MyAttribute struct {
    attr string
}

func (ma MyAttribute) Equal(o interface{}) bool {
    return true
}

How it works

The gRPC client-side load balancing to work need to main components, the naming resolver and the load balancing policy

The infra image source itnext.io

gRPC naming resolver & load balancing working principle

On gRPC Load Balancing

Running the Example Application

The gRPC client and server applications used in the example are based on the proto/echo & load_balancing examples found on the gRPC-go examples with the following modifications:

• The server running with port args
• The client used customized balance

Support Balance Strategy

• round robin balancer.RoundRobinBalanceName
• weighted round robin balancer.WeightedRobinBalanceName
• random weighted round robin balancer.RandomWeightedRobinBalanceName
• minimum connection number balancer.MinConnectBalanceName
• minimum response consume balancer.MinRespTimeBalanceName, keep 10 response consume time, remove maximum and minimum and then take the average value.

Customize Advanced Balancing Strategy

1. Modify naming resolver with your requirements, first set attributes.Attributes for per endpoint address, second when one endpoint attributes.Attributes changed then update subConn state.

2. Implement yourself balancer & picker function, then based on attributes.Attributes picker subConn in Pick(balancer.PickInfo) (balancer.PickResult, error)

License

Apache 2.0 license.