speed up TSA tests

The HTTP client used by the TSA uses http.DefaultTransport, which has an
IdleConnTimeout of 90s. Some of these tests rely on this timeout being
hit, meaning that there's a minimum time of 90s for these tests. This
resulted in the tsa suite being the slowest to complete, typically
taking ~5m.

This commit compiles the tsa binary with an overridden IdleConnTimeout
of 5s in tests. This does not affect the behaviour of Concourse, as the
default behaviour is left unchanged.

Signed-off-by: Aidan Oldershaw <aoldershaw@pivotal.io>

atc/worker/gclient/factory.go

@@ -1,6 +1,7 @@
 package gclient
 
 import (
+	"fmt"
 	"net/http"
 	"time"
 
@@ -12,6 +13,10 @@ import (
 	"github.com/tedsuo/rata"
 )
 
+// Allows tests to override http.DefaultTransport's IdleConnTimeout. Only
+// applies to BasicGardenClientWithRequestTimeout.
+var idleConnTimeoutOverride string
+
 type gardenClientFactory struct {
 	db                         transport.TransportDB
 	logger                     lager.Logger
@@ -73,8 +78,18 @@ func (gcf *gardenClientFactory) NewClient() Client {
 
 // Do not try any client method that requires hijack functionality (streaming logs)!
 func BasicGardenClientWithRequestTimeout(logger lager.Logger, requestTimeout time.Duration, address string) Client {
+	httpTransport := http.DefaultTransport.(*http.Transport).Clone()
+	if idleConnTimeoutOverride != "" {
+		timeout, err := time.ParseDuration(idleConnTimeoutOverride)
+		if err != nil {
+			panic(fmt.Sprintf("invalid idleConnTimeoutOverride: %v", err))
+		}
+		httpTransport.IdleConnTimeout = timeout
+	}
+
 	streamClient := &http.Client{
-		Timeout: requestTimeout,
+		Transport: httpTransport,
+		Timeout:   requestTimeout,
 	}
 
 	streamer := &transport.WorkerHijackStreamer{

tsa/cmd/tsa/register_test.go

@@ -433,13 +433,20 @@ var _ = Describe("Register", func() {
 				Expect(res.StatusCode).To(Equal(http.StatusTeapot))
 
 				By("exiting successfully")
-				// https://golang.org/src/net/http/transport.go -> IdleConnTimeout is 90s in the DefaultTransport used by gclient.BasicGardenClientWithRequestTimeout
-				Eventually(registerErr, time.Second*100).Should(Receive(BeNil()))
+				// If this starts failing, it may be because we are no longer
+				// properly setting atc/worker/gclient.idleConnTimeoutOverride
+				// in the test binary. It defaults to 90s, which is incredibly
+				// slow for these tests.
+				Eventually(registerErr, time.Second*10).Should(Receive(BeNil()))
 			})
 
 			Context("with a drain timeout", func() {
 				BeforeEach(func() {
-					opts.ConnectionDrainTimeout = 5 * time.Second
+					// Note: this must not be "too close" to the idleConnTimeoutOverride
+					// value of 5s - otherwise, these timeouts seem to compound
+					// (e.g. if the drain timeout was also 5s, the effective
+					// timeout would be ~10s). Not too sure why this is
+					opts.ConnectionDrainTimeout = 3 * time.Second
 				})
 
 				It("breaks connections after the configured drain timeout", func() {

tsa/cmd/tsa/suite_test.go

@@ -39,7 +39,7 @@ var tsaPath string
 
 var _ = BeforeSuite(func() {
 	var err error
-	tsaPath, err = gexec.Build("github.com/concourse/concourse/tsa/cmd/tsa")
+	tsaPath, err = gexec.Build("github.com/concourse/concourse/tsa/cmd/tsa", "-ldflags", "-X 'github.com/concourse/concourse/atc/worker/gclient.idleConnTimeoutOverride=5s'")
 	Expect(err).NotTo(HaveOccurred())
 })