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README.md

grpc_retry

import "github.com/grpc-ecosystem/go-grpc-middleware/retry"

Overview

grpc_retry provides client-side request retry logic for gRPC.

Client-Side Request Retry Interceptor

It allows for automatic retry, inside the generated gRPC code of requests based on the gRPC status of the reply. It supports unary (1:1), and server stream (1:n) requests.

By default the interceptors are disabled, preventing accidental use of retries. You can easily override the number of retries (setting them to more than 0) with a grpc.ClientOption, e.g.:

myclient.Ping(ctx, goodPing, grpc_retry.WithMax(5))

Other default options are: retry on ResourceExhausted and Unavailable gRPC codes, use a 50ms linear backoff with 10% jitter.

For chained interceptors, the retry interceptor will call every interceptor that follows it whenever when a retry happens.

Please see examples for more advanced use.

Example:

Click to expand code. 
grpc.Dial("myservice.example.com",
    grpc.WithStreamInterceptor(grpc_retry.StreamClientInterceptor()),
    grpc.WithUnaryInterceptor(grpc_retry.UnaryClientInterceptor()),
)

Example:

Click to expand code. 
opts := []grpc_retry.CallOption{
    grpc_retry.WithBackoff(grpc_retry.BackoffLinear(100 * time.Millisecond)),
    grpc_retry.WithCodes(codes.NotFound, codes.Aborted),
}
grpc.Dial("myservice.example.com",
    grpc.WithStreamInterceptor(grpc_retry.StreamClientInterceptor(opts...)),
    grpc.WithUnaryInterceptor(grpc_retry.UnaryClientInterceptor(opts...)),
)

Example:

Click to expand code. 
client := pb_testproto.NewTestServiceClient(cc)
stream, _ := client.PingList(newCtx(1*time.Second), &pb_testproto.PingRequest{}, grpc_retry.WithMax(3))

for {
    pong, err := stream.Recv() // retries happen here
    if err == io.EOF {
        break
    } else if err != nil {
        return
    }
    fmt.Printf("got pong: %v", pong)
}

Imported Packages

Index

Examples

Package files

backoff.go doc.go options.go retry.go

Constants

const (
    AttemptMetadataKey = "x-retry-attempty"
)

Variables

var (
    // DefaultRetriableCodes is a set of well known types gRPC codes that should be retri-able.
    //
    // `ResourceExhausted` means that the user quota, e.g. per-RPC limits, have been reached.
    // `Unavailable` means that system is currently unavailable and the client should retry again.
    DefaultRetriableCodes = []codes.Code{codes.ResourceExhausted, codes.Unavailable}
)

func StreamClientInterceptor

func StreamClientInterceptor(optFuncs ...CallOption) grpc.StreamClientInterceptor

StreamClientInterceptor returns a new retrying stream client interceptor for server side streaming calls.

The default configuration of the interceptor is to not retry at all. This behaviour can be changed through options (e.g. WithMax) on creation of the interceptor or on call (through grpc.CallOptions).

Retry logic is available only for ServerStreams, i.e. 1:n streams, as the internal logic needs to buffer the messages sent by the client. If retry is enabled on any other streams (ClientStreams, BidiStreams), the retry interceptor will fail the call.

func UnaryClientInterceptor

func UnaryClientInterceptor(optFuncs ...CallOption) grpc.UnaryClientInterceptor

UnaryClientInterceptor returns a new retrying unary client interceptor.

The default configuration of the interceptor is to not retry at all. This behaviour can be changed through options (e.g. WithMax) on creation of the interceptor or on call (through grpc.CallOptions).

type BackoffFunc

type BackoffFunc func(attempt uint) time.Duration

BackoffFunc denotes a family of functions that control the backoff duration between call retries.

They are called with an identifier of the attempt, and should return a time the system client should hold off for. If the time returned is longer than the context.Context.Deadline of the request the deadline of the request takes precedence and the wait will be interrupted before proceeding with the next iteration.

func BackoffLinear

func BackoffLinear(waitBetween time.Duration) BackoffFunc

BackoffLinear is very simple: it waits for a fixed period of time between calls.

func BackoffLinearWithJitter

func BackoffLinearWithJitter(waitBetween time.Duration, jitterFraction float64) BackoffFunc

BackoffLinearWithJitter waits a set period of time, allowing for jitter (fractional adjustment).

For example waitBetween=1s and jitter=0.10 can generate waits between 900ms and 1100ms.

type CallOption

type CallOption struct {
    grpc.EmptyCallOption // make sure we implement private after() and before() fields so we don't panic.
    // contains filtered or unexported fields
}

CallOption is a grpc.CallOption that is local to grpc_retry.

func Disable

func Disable() CallOption

Disable disables the retry behaviour on this call, or this interceptor.

Its semantically the same to WithMax

func WithBackoff

func WithBackoff(bf BackoffFunc) CallOption

WithBackoff sets the BackoffFunc used to control time between retries.

func WithCodes

func WithCodes(retryCodes ...codes.Code) CallOption

WithCodes sets which codes should be retried.

Please use with care, as you may be retrying non-idempotend calls.

You cannot automatically retry on Cancelled and Deadline, please use WithPerRetryTimeout for these.

func WithMax

func WithMax(maxRetries uint) CallOption

WithMax sets the maximum number of retries on this call, or this interceptor.

func WithPerRetryTimeout

func WithPerRetryTimeout(timeout time.Duration) CallOption

WithPerRetryTimeout sets the RPC timeout per call (including initial call) on this call, or this interceptor.

The context.Deadline of the call takes precedence and sets the maximum time the whole invocation will take, but WithPerRetryTimeout can be used to limit the RPC time per each call.

For example, with context.Deadline = now + 10s, and WithPerRetryTimeout(3 * time.Seconds), each of the retry calls (including the initial one) will have a deadline of now + 3s.

A value of 0 disables the timeout overrides completely and returns to each retry call using the parent context.Deadline.

Example:

Click to expand code. 
client := pb_testproto.NewTestServiceClient(cc)
pong, _ := client.Ping(
    newCtx(5*time.Second),
    &pb_testproto.PingRequest{},
    grpc_retry.WithMax(3),
    grpc_retry.WithPerRetryTimeout(1*time.Second))

fmt.Printf("got pong: %v", pong)

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