Restore Graceful Restarting & Socket Activation (#7274)

* Prevent deadlock in indexer initialisation during graceful restart

* Move from gracehttp to our own service to add graceful ssh

* Add timeout for start of indexers and make hammer time configurable

* Fix issue with re-initialization in indexer during tests

* move the code to detect use of closed to graceful

* Handle logs gracefully - add a pid suffix just before restart

* Move to using a cond and a holder for indexers

* use time.Since

* Add some comments and attribution

* update modules.txt

* Use zero to disable timeout

* Move RestartProcess to its own file

* Add cleanup routine

modules/graceful/server_http.go

@@ -0,0 +1,45 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package graceful
+
+import (
+	"crypto/tls"
+	"net/http"
+)
+
+func newHTTPServer(network, address string, handler http.Handler) (*Server, ServeFunction) {
+	server := NewServer(network, address)
+	httpServer := http.Server{
+		ReadTimeout:    DefaultReadTimeOut,
+		WriteTimeout:   DefaultWriteTimeOut,
+		MaxHeaderBytes: DefaultMaxHeaderBytes,
+		Handler:        handler,
+	}
+	server.OnShutdown = func() {
+		httpServer.SetKeepAlivesEnabled(false)
+	}
+	return server, httpServer.Serve
+}
+
+// HTTPListenAndServe listens on the provided network address and then calls Serve
+// to handle requests on incoming connections.
+func HTTPListenAndServe(network, address string, handler http.Handler) error {
+	server, lHandler := newHTTPServer(network, address, handler)
+	return server.ListenAndServe(lHandler)
+}
+
+// HTTPListenAndServeTLS listens on the provided network address and then calls Serve
+// to handle requests on incoming connections.
+func HTTPListenAndServeTLS(network, address, certFile, keyFile string, handler http.Handler) error {
+	server, lHandler := newHTTPServer(network, address, handler)
+	return server.ListenAndServeTLS(certFile, keyFile, lHandler)
+}
+
+// HTTPListenAndServeTLSConfig listens on the provided network address and then calls Serve
+// to handle requests on incoming connections.
+func HTTPListenAndServeTLSConfig(network, address string, tlsConfig *tls.Config, handler http.Handler) error {
+	server, lHandler := newHTTPServer(network, address, handler)
+	return server.ListenAndServeTLSConfig(tlsConfig, lHandler)
+}