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/*
*
* Copyright 2017 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 provides a service that exposes server's health and it must be
// imported to enable support for client-side health checks.
package health
import (
"context"
"sync"
"google.golang.org/grpc/codes"
healthgrpc "google.golang.org/grpc/health/grpc_health_v1"
healthpb "google.golang.org/grpc/health/grpc_health_v1"
"google.golang.org/grpc/status"
)
// Server implements `service Health`.
type Server struct {
healthgrpc.UnimplementedHealthServer
mu sync.RWMutex
// If shutdown is true, it's expected all serving status is NOT_SERVING, and
// will stay in NOT_SERVING.
shutdown bool
// statusMap stores the serving status of the services this Server monitors.
statusMap map[string]healthpb.HealthCheckResponse_ServingStatus
updates map[string]map[healthgrpc.Health_WatchServer]chan healthpb.HealthCheckResponse_ServingStatus
}
// NewServer returns a new Server.
func NewServer() *Server {
return &Server{
statusMap: map[string]healthpb.HealthCheckResponse_ServingStatus{"": healthpb.HealthCheckResponse_SERVING},
updates: make(map[string]map[healthgrpc.Health_WatchServer]chan healthpb.HealthCheckResponse_ServingStatus),
}
}
// Check implements `service Health`.
func (s *Server) Check(ctx context.Context, in *healthpb.HealthCheckRequest) (*healthpb.HealthCheckResponse, error) {
s.mu.RLock()
defer s.mu.RUnlock()
if servingStatus, ok := s.statusMap[in.Service]; ok {
return &healthpb.HealthCheckResponse{
Status: servingStatus,
}, nil
}
return nil, status.Error(codes.NotFound, "unknown service")
}
// Watch implements `service Health`.
func (s *Server) Watch(in *healthpb.HealthCheckRequest, stream healthgrpc.Health_WatchServer) error {
service := in.Service
// update channel is used for getting service status updates.
update := make(chan healthpb.HealthCheckResponse_ServingStatus, 1)
s.mu.Lock()
// Puts the initial status to the channel.
if servingStatus, ok := s.statusMap[service]; ok {
update <- servingStatus
} else {
update <- healthpb.HealthCheckResponse_SERVICE_UNKNOWN
}
// Registers the update channel to the correct place in the updates map.
if _, ok := s.updates[service]; !ok {
s.updates[service] = make(map[healthgrpc.Health_WatchServer]chan healthpb.HealthCheckResponse_ServingStatus)
}
s.updates[service][stream] = update
defer func() {
s.mu.Lock()
delete(s.updates[service], stream)
s.mu.Unlock()
}()
s.mu.Unlock()
var lastSentStatus healthpb.HealthCheckResponse_ServingStatus = -1
for {
select {
// Status updated. Sends the up-to-date status to the client.
case servingStatus := <-update:
if lastSentStatus == servingStatus {
continue
}
lastSentStatus = servingStatus
err := stream.Send(&healthpb.HealthCheckResponse{Status: servingStatus})
if err != nil {
return status.Error(codes.Canceled, "Stream has ended.")
}
// Context done. Removes the update channel from the updates map.
case <-stream.Context().Done():
return status.Error(codes.Canceled, "Stream has ended.")
}
}
}
// SetServingStatus is called when need to reset the serving status of a service
// or insert a new service entry into the statusMap.
func (s *Server) SetServingStatus(service string, servingStatus healthpb.HealthCheckResponse_ServingStatus) {
s.mu.Lock()
defer s.mu.Unlock()
if s.shutdown {
logger.Infof("health: status changing for %s to %v is ignored because health service is shutdown", service, servingStatus)
return
}
s.setServingStatusLocked(service, servingStatus)
}
func (s *Server) setServingStatusLocked(service string, servingStatus healthpb.HealthCheckResponse_ServingStatus) {
s.statusMap[service] = servingStatus
for _, update := range s.updates[service] {
// Clears previous updates, that are not sent to the client, from the channel.
// This can happen if the client is not reading and the server gets flow control limited.
select {
case <-update:
default:
}
// Puts the most recent update to the channel.
update <- servingStatus
}
}
// Shutdown sets all serving status to NOT_SERVING, and configures the server to
// ignore all future status changes.
//
// This changes serving status for all services. To set status for a particular
// services, call SetServingStatus().
func (s *Server) Shutdown() {
s.mu.Lock()
defer s.mu.Unlock()
s.shutdown = true
for service := range s.statusMap {
s.setServingStatusLocked(service, healthpb.HealthCheckResponse_NOT_SERVING)
}
}
// Resume sets all serving status to SERVING, and configures the server to
// accept all future status changes.
//
// This changes serving status for all services. To set status for a particular
// services, call SetServingStatus().
func (s *Server) Resume() {
s.mu.Lock()
defer s.mu.Unlock()
s.shutdown = false
for service := range s.statusMap {
s.setServingStatusLocked(service, healthpb.HealthCheckResponse_SERVING)
}
}
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