server.go

Documentation: sigs.k8s.io/controller-runtime/pkg/manager

     1  /*
     2  Copyright 2022 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8     http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package manager
    18  
    19  import (
    20  	"context"
    21  	"errors"
    22  	"net"
    23  	"net/http"
    24  	"time"
    25  
    26  	crlog "sigs.k8s.io/controller-runtime/pkg/log"
    27  )
    28  
    29  var (
    30  	_ Runnable               = (*Server)(nil)
    31  	_ LeaderElectionRunnable = (*Server)(nil)
    32  )
    33  
    34  // Server is a general purpose HTTP server Runnable for a manager.
    35  // It is used to serve some internal handlers for health probes and profiling,
    36  // but it can also be used to run custom servers.
    37  type Server struct {
    38  	// Name is an optional string that describes the purpose of the server. It is used in logs to distinguish
    39  	// among multiple servers.
    40  	Name string
    41  
    42  	// Server is the HTTP server to run. It is required.
    43  	Server *http.Server
    44  
    45  	// Listener is an optional listener to use. If not set, the server start a listener using the server.Addr.
    46  	// Using a listener is useful when the port reservation needs to happen in advance of this runnable starting.
    47  	Listener net.Listener
    48  
    49  	// OnlyServeWhenLeader is an optional bool that indicates that the server should only be started when the manager is the leader.
    50  	OnlyServeWhenLeader bool
    51  
    52  	// ShutdownTimeout is an optional duration that indicates how long to wait for the server to shutdown gracefully. If not set,
    53  	// the server will wait indefinitely for all connections to close.
    54  	ShutdownTimeout *time.Duration
    55  }
    56  
    57  // Start starts the server. It will block until the server is stopped or an error occurs.
    58  func (s *Server) Start(ctx context.Context) error {
    59  	log := crlog.FromContext(ctx)
    60  	if s.Name != "" {
    61  		log = log.WithValues("name", s.Name)
    62  	}
    63  	log = log.WithValues("addr", s.addr())
    64  
    65  	serverShutdown := make(chan struct{})
    66  	go func() {
    67  		<-ctx.Done()
    68  		log.Info("shutting down server")
    69  
    70  		shutdownCtx := context.Background()
    71  		if s.ShutdownTimeout != nil {
    72  			var shutdownCancel context.CancelFunc
    73  			shutdownCtx, shutdownCancel = context.WithTimeout(context.Background(), *s.ShutdownTimeout)
    74  			defer shutdownCancel()
    75  		}
    76  
    77  		if err := s.Server.Shutdown(shutdownCtx); err != nil {
    78  			log.Error(err, "error shutting down server")
    79  		}
    80  		close(serverShutdown)
    81  	}()
    82  
    83  	log.Info("starting server")
    84  	if err := s.serve(); err != nil && !errors.Is(err, http.ErrServerClosed) {
    85  		return err
    86  	}
    87  
    88  	<-serverShutdown
    89  	return nil
    90  }
    91  
    92  // NeedLeaderElection returns true if the server should only be started when the manager is the leader.
    93  func (s *Server) NeedLeaderElection() bool {
    94  	return s.OnlyServeWhenLeader
    95  }
    96  
    97  func (s *Server) addr() string {
    98  	if s.Listener != nil {
    99  		return s.Listener.Addr().String()
   100  	}
   101  	return s.Server.Addr
   102  }
   103  
   104  func (s *Server) serve() error {
   105  	if s.Listener != nil {
   106  		return s.Server.Serve(s.Listener)
   107  	}
   108  	return s.Server.ListenAndServe()
   109  }
   110
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