| /* |
| * |
| * Copyright 2018 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| |
| package health |
| |
| import ( |
| "context" |
| "fmt" |
| "io" |
| "time" |
| |
| "google.golang.org/grpc" |
| "google.golang.org/grpc/codes" |
| "google.golang.org/grpc/connectivity" |
| healthpb "google.golang.org/grpc/health/grpc_health_v1" |
| "google.golang.org/grpc/internal" |
| "google.golang.org/grpc/internal/backoff" |
| "google.golang.org/grpc/status" |
| ) |
| |
| var ( |
| backoffStrategy = backoff.DefaultExponential |
| backoffFunc = func(ctx context.Context, retries int) bool { |
| d := backoffStrategy.Backoff(retries) |
| timer := time.NewTimer(d) |
| select { |
| case <-timer.C: |
| return true |
| case <-ctx.Done(): |
| timer.Stop() |
| return false |
| } |
| } |
| ) |
| |
| func init() { |
| internal.HealthCheckFunc = clientHealthCheck |
| } |
| |
| const healthCheckMethod = "/grpc.health.v1.Health/Watch" |
| |
| // This function implements the protocol defined at: |
| // https://github.com/grpc/grpc/blob/master/doc/health-checking.md |
| func clientHealthCheck(ctx context.Context, newStream func(string) (interface{}, error), setConnectivityState func(connectivity.State, error), service string) error { |
| tryCnt := 0 |
| |
| retryConnection: |
| for { |
| // Backs off if the connection has failed in some way without receiving a message in the previous retry. |
| if tryCnt > 0 && !backoffFunc(ctx, tryCnt-1) { |
| return nil |
| } |
| tryCnt++ |
| |
| if ctx.Err() != nil { |
| return nil |
| } |
| setConnectivityState(connectivity.Connecting, nil) |
| rawS, err := newStream(healthCheckMethod) |
| if err != nil { |
| continue retryConnection |
| } |
| |
| s, ok := rawS.(grpc.ClientStream) |
| // Ideally, this should never happen. But if it happens, the server is marked as healthy for LBing purposes. |
| if !ok { |
| setConnectivityState(connectivity.Ready, nil) |
| return fmt.Errorf("newStream returned %v (type %T); want grpc.ClientStream", rawS, rawS) |
| } |
| |
| if err = s.SendMsg(&healthpb.HealthCheckRequest{Service: service}); err != nil && err != io.EOF { |
| // Stream should have been closed, so we can safely continue to create a new stream. |
| continue retryConnection |
| } |
| s.CloseSend() |
| |
| resp := new(healthpb.HealthCheckResponse) |
| for { |
| err = s.RecvMsg(resp) |
| |
| // Reports healthy for the LBing purposes if health check is not implemented in the server. |
| if status.Code(err) == codes.Unimplemented { |
| setConnectivityState(connectivity.Ready, nil) |
| return err |
| } |
| |
| // Reports unhealthy if server's Watch method gives an error other than UNIMPLEMENTED. |
| if err != nil { |
| setConnectivityState(connectivity.TransientFailure, fmt.Errorf("connection active but received health check RPC error: %v", err)) |
| continue retryConnection |
| } |
| |
| // As a message has been received, removes the need for backoff for the next retry by resetting the try count. |
| tryCnt = 0 |
| if resp.Status == healthpb.HealthCheckResponse_SERVING { |
| setConnectivityState(connectivity.Ready, nil) |
| } else { |
| setConnectivityState(connectivity.TransientFailure, fmt.Errorf("connection active but health check failed. status=%s", resp.Status)) |
| } |
| } |
| } |
| } |