Add fix and tests for FastCGI persistent connections (#1134)

* 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

* adding persistant fastcgi connections switch to directive

* Support for configurable connection pool.

* ensure positive integer pool size config

* abisofts pool fix + nicer logging for the fastcgi_test

* abisoft wants to have dialer comparison in _test instead of next to struct

* Do not put dead connections back into pool

* Fix fastcgi header error

* Do not put dead connections back into pool

* some code style improvements from the discussion in https://github.com/mholt/caddy/pull/1134

* abisofts naming convention

5 files changed, 184 insertions, 8 deletions

diff --git a/caddyhttp/fastcgi/dialer.go b/caddyhttp/fastcgi/dialer.go
index df33fab62..58a8f1563 100644
--- a/caddyhttp/fastcgi/dialer.go
+++ b/caddyhttp/fastcgi/dialer.go
@@ -27,7 +27,6 @@ type persistentDialer struct {
 
 func (p *persistentDialer) Dial() (*FCGIClient, error) {
 	p.Lock()
-
 	// connection is available, return first one.
 	if len(p.pool) > 0 {
 		client := p.pool[0]
diff --git a/caddyhttp/fastcgi/fastcgi.go b/caddyhttp/fastcgi/fastcgi.go
index 5b40b9367..c3e1cab95 100644
--- a/caddyhttp/fastcgi/fastcgi.go
+++ b/caddyhttp/fastcgi/fastcgi.go
@@ -90,8 +90,6 @@ 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)
 			}
 
-			defer fcgiBackend.Close()
-
 			if err != nil && err != io.EOF {
 				return http.StatusBadGateway, err
 			}
@@ -105,6 +103,8 @@ func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error)
 				return http.StatusBadGateway, err
 			}
 
+			defer rule.dialer.Close(fcgiBackend)
+
 			// Log any stderr output from upstream
 			if fcgiBackend.stderr.Len() != 0 {
 				// Remove trailing newline, error logger already does this.
@@ -269,6 +269,7 @@ func (h Handler) buildEnv(r *http.Request, rule Rule, fpath string) (map[string]
 }
 
 // Rule represents a FastCGI handling rule.
+// It is parsed from the fastcgi directive in the Caddyfile, see setup.go.
 type Rule struct {
 	// The base path to match. Required.
 	Path string
diff --git a/caddyhttp/fastcgi/fastcgi_test.go b/caddyhttp/fastcgi/fastcgi_test.go
index 3d23c44c5..46f06c9bc 100644
--- a/caddyhttp/fastcgi/fastcgi_test.go
+++ b/caddyhttp/fastcgi/fastcgi_test.go
@@ -7,6 +7,7 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"strconv"
+	"sync"
 	"testing"
 )
 
@@ -51,6 +52,101 @@ func TestServeHTTP(t *testing.T) {
 	}
 }
 
+// connectionCounter in fact is a listener with an added counter to keep track
+// of the number of accepted connections.
+type connectionCounter struct {
+	net.Listener
+	sync.Mutex
+	counter int
+}
+
+func (l *connectionCounter) Accept() (net.Conn, error) {
+	l.Lock()
+	l.counter++
+	l.Unlock()
+	return l.Listener.Accept()
+}
+
+// TestPersistent ensures that persistent
+// as well as the non-persistent fastCGI servers
+// send the answers corresnponding to the correct request.
+// It also checks the number of tcp connections used.
+func TestPersistent(t *testing.T) {
+	numberOfRequests := 32
+
+	for _, poolsize := range []int{0, 1, 5, numberOfRequests} {
+		l, err := net.Listen("tcp", "127.0.0.1:0")
+		if err != nil {
+			t.Fatalf("Unable to create listener for test: %v", err)
+		}
+
+		listener := &connectionCounter{l, *new(sync.Mutex), 0}
+
+		// this fcgi server replies with the request URL
+		go fcgi.Serve(listener, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			body := "This answers a request to " + r.URL.Path
+			bodyLenStr := strconv.Itoa(len(body))
+
+			w.Header().Set("Content-Length", bodyLenStr)
+			w.Write([]byte(body))
+		}))
+
+		network, address := parseAddress(listener.Addr().String())
+		handler := Handler{
+			Next:  nil,
+			Rules: []Rule{{Path: "/", Address: listener.Addr().String(), dialer: &persistentDialer{size: poolsize, network: network, address: address}}},
+		}
+
+		var semaphore sync.WaitGroup
+		serialMutex := new(sync.Mutex)
+
+		serialCounter := 0
+		parallelCounter := 0
+		// make some serial followed by some
+		// parallel requests to challenge the handler
+		for _, serialize := range []bool{true, false, false, false} {
+			if serialize {
+				serialCounter++
+			} else {
+				parallelCounter++
+			}
+			semaphore.Add(numberOfRequests)
+
+			for i := 0; i < numberOfRequests; i++ {
+				go func(i int, serialize bool) {
+					defer semaphore.Done()
+					if serialize {
+						serialMutex.Lock()
+						defer serialMutex.Unlock()
+					}
+					r, err := http.NewRequest("GET", "/"+strconv.Itoa(i), nil)
+					if err != nil {
+						t.Errorf("Unable to create request: %v", err)
+					}
+					w := httptest.NewRecorder()
+
+					status, err := handler.ServeHTTP(w, r)
+
+					if status != 0 {
+						t.Errorf("Handler(pool: %v) return status %v", poolsize, status)
+					}
+					if err != nil {
+						t.Errorf("Handler(pool: %v) Error: %v", poolsize, err)
+					}
+					want := "This answers a request to /" + strconv.Itoa(i)
+					if got := w.Body.String(); got != want {
+						t.Errorf("Expected response from handler(pool: %v) to be '%s', got: '%s'", poolsize, want, got)
+					}
+				}(i, serialize)
+			} //next request
+			semaphore.Wait()
+		} // next set of requests (serial/parallel)
+
+		listener.Close()
+		t.Logf("The pool: %v test used %v tcp connections to answer %v * %v serial and %v * %v parallel requests.", poolsize, listener.counter, serialCounter, numberOfRequests, parallelCounter, numberOfRequests)
+	} // next handler (persistent/non-persistent)
+}
+
 func TestRuleParseAddress(t *testing.T) {
 	getClientTestTable := []struct {
 		rule            *Rule
diff --git a/caddyhttp/fastcgi/fcgiclient.go b/caddyhttp/fastcgi/fcgiclient.go
index c06caf73d..d3773c9b4 100644
--- a/caddyhttp/fastcgi/fcgiclient.go
+++ b/caddyhttp/fastcgi/fcgiclient.go
@@ -138,7 +138,7 @@ func (rec *record) read(r io.Reader) (buf []byte, err error) {
 		return
 	}
 	if rec.h.Version != 1 {
-		err = errors.New("fcgi: invalid header version")
+		err = errInvalidHeaderVersion
 		return
 	}
 	if rec.h.Type == EndRequest {
@@ -358,7 +358,9 @@ func (w *streamReader) Read(p []byte) (n int, err error) {
 				rec := &record{}
 				var buf []byte
 				buf, err = rec.read(w.c.rwc)
-				if err != nil {
+				if err == errInvalidHeaderVersion {
+					continue
+				} else if err != nil {
 					return
 				}
 				// standard error output
@@ -561,3 +563,5 @@ func (c *FCGIClient) PostFile(p map[string]string, data url.Values, file map[str
 
 // Checks whether chunked is part of the encodings stack
 func chunked(te []string) bool { return len(te) > 0 && te[0] == "chunked" }
+
+var errInvalidHeaderVersion = errors.New("fcgi: invalid header version")
diff --git a/caddyhttp/fastcgi/setup_test.go b/caddyhttp/fastcgi/setup_test.go
index 123b4b9e8..b9fd6b0d0 100644
--- a/caddyhttp/fastcgi/setup_test.go
+++ b/caddyhttp/fastcgi/setup_test.go
@@ -2,6 +2,7 @@ package fastcgi
 
 import (
 	"fmt"
+	"reflect"
 	"testing"
 
 	"github.com/mholt/caddy"
@@ -35,7 +36,34 @@ func TestSetup(t *testing.T) {
 
 }
 
+func (p *persistentDialer) Equals(q *persistentDialer) bool {
+	if p.size != q.size {
+		return false
+	}
+	if p.network != q.network {
+		return false
+	}
+	if p.address != q.address {
+		return false
+	}
+
+	if len(p.pool) != len(q.pool) {
+		return false
+	}
+	for i, client := range p.pool {
+		if client != q.pool[i] {
+			return false
+		}
+	}
+	// ignore mutex state
+	return true
+}
+
 func TestFastcgiParse(t *testing.T) {
+	defaultAddress := "127.0.0.1:9001"
+	network, address := parseAddress(defaultAddress)
+	t.Logf("Address '%v' was parsed to network '%v' and address '%v'", defaultAddress, network, address)
+
 	tests := []struct {
 		inputFastcgiConfig    string
 		shouldErr             bool
@@ -48,19 +76,21 @@ func TestFastcgiParse(t *testing.T) {
 				Address:    "127.0.0.1:9000",
 				Ext:        ".php",
 				SplitPath:  ".php",
+				dialer:     basicDialer{network: "tcp", address: "127.0.0.1:9000"},
 				IndexFiles: []string{"index.php"},
 			}}},
-		{`fastcgi / 127.0.0.1:9001 {
+		{`fastcgi / ` + defaultAddress + ` {
 	              split .html
 	              }`,
 			false, []Rule{{
 				Path:       "/",
-				Address:    "127.0.0.1:9001",
+				Address:    defaultAddress,
 				Ext:        "",
 				SplitPath:  ".html",
+				dialer:     basicDialer{network: network, address: address},
 				IndexFiles: []string{},
 			}}},
-		{`fastcgi / 127.0.0.1:9001 {
+		{`fastcgi / ` + defaultAddress + ` {
 	              split .html
 	              except /admin /user
 	              }`,
@@ -69,9 +99,32 @@ func TestFastcgiParse(t *testing.T) {
 				Address:         "127.0.0.1:9001",
 				Ext:             "",
 				SplitPath:       ".html",
+				dialer:          basicDialer{network: network, address: address},
 				IndexFiles:      []string{},
 				IgnoredSubPaths: []string{"/admin", "/user"},
 			}}},
+		{`fastcgi / ` + defaultAddress + ` {
+	              pool 0
+	              }`,
+			false, []Rule{{
+				Path:       "/",
+				Address:    defaultAddress,
+				Ext:        "",
+				SplitPath:  "",
+				dialer:     &persistentDialer{size: 0, network: network, address: address},
+				IndexFiles: []string{},
+			}}},
+		{`fastcgi / ` + defaultAddress + ` {
+	              pool 5
+	              }`,
+			false, []Rule{{
+				Path:       "/",
+				Address:    defaultAddress,
+				Ext:        "",
+				SplitPath:  "",
+				dialer:     &persistentDialer{size: 5, network: network, address: address},
+				IndexFiles: []string{},
+			}}},
 	}
 	for i, test := range tests {
 		actualFastcgiConfigs, err := fastcgiParse(caddy.NewTestController("http", test.inputFastcgiConfig))
@@ -107,6 +160,29 @@ func TestFastcgiParse(t *testing.T) {
 					i, j, test.expectedFastcgiConfig[j].SplitPath, actualFastcgiConfig.SplitPath)
 			}
 
+			if reflect.TypeOf(actualFastcgiConfig.dialer) != reflect.TypeOf(test.expectedFastcgiConfig[j].dialer) {
+				t.Errorf("Test %d expected %dth FastCGI dialer to be of type %T, but got %T",
+					i, j, test.expectedFastcgiConfig[j].dialer, actualFastcgiConfig.dialer)
+			} else {
+				equal := true
+				switch actual := actualFastcgiConfig.dialer.(type) {
+				case basicDialer:
+					equal = actualFastcgiConfig.dialer == test.expectedFastcgiConfig[j].dialer
+				case *persistentDialer:
+					if expected, ok := test.expectedFastcgiConfig[j].dialer.(*persistentDialer); ok {
+						equal = actual.Equals(expected)
+					} else {
+						equal = false
+					}
+				default:
+					t.Errorf("Unkonw dialer type %T", actualFastcgiConfig.dialer)
+				}
+				if !equal {
+					t.Errorf("Test %d expected %dth FastCGI dialer to be %v, but got %v",
+						i, j, test.expectedFastcgiConfig[j].dialer, actualFastcgiConfig.dialer)
+				}
+			}
+
 			if fmt.Sprint(actualFastcgiConfig.IndexFiles) != fmt.Sprint(test.expectedFastcgiConfig[j].IndexFiles) {
 				t.Errorf("Test %d expected %dth FastCGI IndexFiles to be  %s  , but got %s",
 					i, j, test.expectedFastcgiConfig[j].IndexFiles, actualFastcgiConfig.IndexFiles)