69 lines
1.6 KiB
Go
69 lines
1.6 KiB
Go
package healthz
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import (
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"context"
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"fmt"
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"net"
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"net/http"
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"sync/atomic"
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"time"
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)
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// Server is a minimal HTTP health check server.
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type Server struct {
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listener net.Listener
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server *http.Server
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shuttingDown atomic.Bool
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}
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// New creates a health check server listening on the given port.
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// Passing port 0 binds to an available ephemeral port.
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func New(port int) (*Server, error) {
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listener, err := net.Listen("tcp", fmt.Sprintf("127.0.0.1:%d", port))
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if err != nil {
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return nil, fmt.Errorf("failed to create listener: %w", err)
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}
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s := &Server{listener: listener}
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s.server = &http.Server{
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Handler: http.HandlerFunc(s.handleHealthz),
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ReadHeaderTimeout: 5 * time.Second,
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}
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return s, nil
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}
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// Addr returns the bound network address (e.g. "127.0.0.1:8080").
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func (s *Server) Addr() string {
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if s.listener == nil {
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return ""
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}
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return s.listener.Addr().String()
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}
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// Start begins serving HTTP requests. It blocks until Stop is called.
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func (s *Server) Start() error {
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return s.server.Serve(s.listener)
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}
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// Stop initiates graceful shutdown. After Stop is called the /healthz
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// endpoint returns 503 while in-flight requests complete.
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func (s *Server) Stop(ctx context.Context) error {
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s.shuttingDown.Store(true)
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// Grace period so that health checks can observe the 503 state
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// before the listener is closed.
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time.Sleep(100 * time.Millisecond)
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return s.server.Shutdown(ctx)
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}
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func (s *Server) handleHealthz(w http.ResponseWriter, r *http.Request) {
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if r.URL.Path != "/healthz" {
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http.NotFound(w, r)
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return
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}
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if s.shuttingDown.Load() {
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w.WriteHeader(http.StatusServiceUnavailable)
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return
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}
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w.WriteHeader(http.StatusOK)
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}
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