rpc

Documentation

Overview

Package rpc provides goma specific rpc features on gRPC.

Load balancing RPC client

gRPC doesn't provide good loadbalancing client (for kubernetes, yet). Typical gRPC client could be created as follows:

conn, err := grpc.Dial(address, grpc.WithInsecure())
if err != nil {
	log.Fatalf("did not connect: %v", err)
}
defer conn.Close()
c := pb.NewGreeterClient(conn)

This package provides load balancing client if address has multiple IP addresses:

type GreeterClient struct {
	c *rpc.Client
}

func NewGreeterClient(address string, opts ...grpc.DialOption) GreeterClient {
	return GreeterClient{
		c: rpc.NewClient(address,
			func(cc *grpc.ClientConn) interface{} {
				return pb.NewGreeterClient(cc)
			}, opts...),
	}
}

func (c GreeterClient) SayHello(ctx context.Context, in *pb.Req, opts...grpc.CallOption) (*pb.Resp, error) {
	var resp *pb.Resp
	var err error
	err = c.Call(ctx, c.client.Pick, "",
		func(client interface{}) error {
			resp, err = client.(GreeterClient).SayHello(ctx, in, opts...)
			return err
		},
	)
	return resp, err
}

c := NewGreeterClient(address, grpc.WithInsecure())

rpc call would return codes.Unavailable if no backends available for address.

TODO: use grpc's Balancer? TODO: use statefulset for sharding?

Index

• func Render(w http.ResponseWriter, req *http.Request)
• func RequestID(r *gomapb.RequesterInfo) string
• func TagID(ctx context.Context, r *gomapb.RequesterInfo) (context.Context, string)
• type Client
  • func NewClient(ctx context.Context, target string, newc func(cc *grpc.ClientConn) interface{}, ...) *Client
  • func (c *Client) Call(ctx context.Context, ...) error
  • func (c *Client) Close() error
  • func (c *Client) Shard(ctx context.Context, key interface{}) (*backend, error)
• type Option
  • func DialOption(opt grpc.DialOption) Option
  • func DialOptions(opts ...grpc.DialOption) []Option
• type RetriableError
  • func (e RetriableError) Error() string
• type Retry
  • func (r Retry) Do(ctx context.Context, f func() error) error

Functions

func Render

func Render(w http.ResponseWriter, req *http.Request)

Render renders backend information. It is handled on /debug/backends on default http mux.

func RequestID

func RequestID(r *gomapb.RequesterInfo) string

RequestID returns string identifier of this request.

func TagID

func TagID(ctx context.Context, r *gomapb.RequesterInfo) (context.Context, string)

TagID tags request id in context.

Types

type Client

type Client struct {
	// contains filtered or unexported fields
}

Client represents load-balancing client.

func NewClient

func NewClient(ctx context.Context, target string, newc func(cc *grpc.ClientConn) interface{}, opts ...Option) *Client

NewClient creates new load-balancing client. newc should return grpc client interface for given *grpc.ClientConn. target is <hostname>:<port>. TODO: support grpc new naming?

func (*Client) Call

func (c *Client) Call(ctx context.Context, picker func(context.Context, interface{}) (*backend, error), key interface{}, f func(interface{}) error) error

Call calls new rpc call. picker and key will be used to pick backend. picker will be Client's Pick, or Shard. Pick will use key for backend addr, or empty for least loaded. Shard will use key for sharding. Rand will use key for *RandomState. f is called with grpc client inferface for selected backend.

func (*Client) Close

func (c *Client) Close() error

func (*Client) Shard

func (c *Client) Shard(ctx context.Context, key interface{}) (*backend, error)

Shard picks one backend from client's target to request the key, and returns selected backend.

type Option

type Option func(*Client)

Option configures Client.

func DialOption

func DialOption(opt grpc.DialOption) Option

DialOption returns an Option to configure dial option.

func DialOptions

func DialOptions(opts ...grpc.DialOption) []Option

DialOptions converts grpc.DialOptions to Options.

type RetriableError

type RetriableError struct {
	Err    error
	Max    int
	Delay  time.Duration
	Factor float64
}

RetriableError represents retriable error in Retry.Do.

func (RetriableError) Error

func (e RetriableError) Error() string

type Retry

type Retry struct {
	// MaxRetry represents how many times to retry.
	// If it is not positive, it retries while error is
	// codes.Unavailable or codes.ResourceExhausted.
	MaxRetry  int
	BaseDelay time.Duration
	MaxDelay  time.Duration

	// backoff factor. default is 1.6
	Factor float64
}

Retry handles rpc retry.

func (Retry) Do

func (r Retry) Do(ctx context.Context, f func() error) error

Do calls f with retry, while f returns RetriableError, codes.Unavailable or codes.ResourceExhausted. It returns codes.DeadlineExceeded if ctx is cancelled. It returns last error if f returns error other than codes.Unavailable or codes.ResourceExhausted, or it reaches too many retries. It respects RetriableError.Delay or errdetail RetryInfo if it is specified as error details.