persistent fastcgi connections (#1087)

* keep fastcgi connection open

* poor mans serialisation to make up for the lack of demuxing

* pointing includes to echse's repo

* Revert "pointing includes to echse's repo"

This reverts commit 281daad8d437ba88fadd65fae5af2da99d449bea.

* switch for persistent fcgi connections on/off added

* fixing ineffectual assignments

* camel case instead of _

* only activate persistent sockets on windows (and some naming conventions/cleanup)

* gitfm import sorting

* Revert "fixing ineffectual assignments"

This reverts commit 79760344e7b1231e59a2867246e7689b05e92e18.

# Conflicts:
#	caddyhttp/staticfiles/fileserver.go

* added another mutex and deleting map entries. thx to mholts QA comments!

* thinking about it, this RW lock was not a good idea here

* thread safety

* I keep learning about mutexs in go

* some cosmetics

caddyhttp/fastcgi/fastcgi.go

@@ -12,10 +12,29 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/mholt/caddy/caddyhttp/httpserver"
 )
 
+// persistent fastcgi connections
+
+type serialClient struct {
+	// for read/write serialisation
+	sync.Mutex
+	backend *FCGIClient
+}
+type concurrentPersistentConnectionsMap struct {
+	// for thread safe acces to the map
+	sync.Mutex
+	clientMap map[string]*serialClient
+}
+
+var persistentConnections = &(concurrentPersistentConnectionsMap{clientMap: make(map[string]*serialClient)})
+
+// UsePersistentFcgiConnections TODO: add an option in Caddyfile and pass it down to here
+var UsePersistentFcgiConnections = true
+
 // Handler is a middleware type that can handle requests as a FastCGI client.
 type Handler struct {
 	Next    httpserver.Handler
@@ -73,10 +92,26 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error)
 
 			// Connect to FastCGI gateway
 			network, address := rule.parseAddress()
-			fcgiBackend, err := Dial(network, address)
+
+			var fcgiBackend *FCGIClient
+			var client *serialClient
+			reuse := false
+			if UsePersistentFcgiConnections {
+				persistentConnections.Lock()
+				client, reuse = persistentConnections.clientMap[network+address]
+				persistentConnections.Unlock()
+			}
+
+			if reuse {
+				client.Lock()
+				defer client.Unlock()
+				fcgiBackend = client.backend
+			} else {
+				fcgiBackend, err = Dial(network, address)
 				if err != nil {
 					return http.StatusBadGateway, err
 				}
+			}
 
 			var resp *http.Response
 			contentLength, _ := strconv.Atoi(r.Header.Get("Content-Length"))
@@ -91,14 +126,18 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error)
 				resp, err = fcgiBackend.Post(env, r.Method, r.Header.Get("Content-Type"), r.Body, contentLength)
 			}
 
-			if resp.Body != nil {
-				defer resp.Body.Close()
-			}
-
 			if err != nil && err != io.EOF {
 				return http.StatusBadGateway, err
 			}
 
+			if UsePersistentFcgiConnections {
+				persistentConnections.Lock()
+				persistentConnections.clientMap[network+address] = &(serialClient{backend: fcgiBackend})
+				persistentConnections.Unlock()
+			} else {
+				defer fcgiBackend.Close()
+			}
+
 			// Write response header
 			writeHeader(w, resp)
 
@@ -112,6 +151,10 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error)
 			if fcgiBackend.stderr.Len() != 0 {
 				// Remove trailing newline, error logger already does this.
 				err = LogError(strings.TrimSuffix(fcgiBackend.stderr.String(), "\n"))
+				persistentConnections.Lock()
+				delete(persistentConnections.clientMap, network+address)
+				persistentConnections.Unlock()
+				fcgiBackend.Close()
 			}
 
 			// Normally we would return the status code if it is an error status (>= 400),

caddyhttp/fastcgi/fcgiclient.go

@@ -385,7 +385,7 @@ func (w *streamReader) Read(p []byte) (n int, err error) {
 // Do made the request and returns a io.Reader that translates the data read
 // from fcgi responder out of fcgi packet before returning it.
 func (c *FCGIClient) Do(p map[string]string, req io.Reader) (r io.Reader, err error) {
-	err = c.writeBeginRequest(uint16(Responder), 0)
+	err = c.writeBeginRequest(uint16(Responder), FCGIKeepConn)
 	if err != nil {
 		return
 	}