Generate 16 byte length cache key for buildpack paths

When generated key starts with zeros %x formatting strips first zeros.
Add padding to format up to 16 bytes to match the key generated by cloud
controller.

builder/builder_test.go

@@ -60,8 +60,7 @@ var _ = Describe("Building", func() {
 	}
 
 	cpBuildpack := func(buildpack string) {
-		hash := fmt.Sprintf("%x", xxhash.Sum64String(buildpack))
-		cp(filepath.Join(buildpackFixtures, buildpack), filepath.Join(buildpacksDir, hash))
+		cp(filepath.Join(buildpackFixtures, buildpack), filepath.Join(buildpacksDir, buildpackHash(buildpack)))
 	}
 
 	BeforeEach(func() {
@@ -401,8 +400,7 @@ var _ = Describe("Building", func() {
 					Skip("warning is unnecessary on Windows")
 				}
 
-				hash := fmt.Sprintf("%x", xxhash.Sum64String("always-detects"))
-				binDetect := filepath.Join(buildpacksDir, hash, "bin", "detect")
+				binDetect := filepath.Join(buildpacksDir, buildpackHash("always-detects"), "bin", "detect")
 				Expect(os.Chmod(binDetect, 0644)).To(Succeed())
 			})
 
@@ -794,10 +792,10 @@ var _ = Describe("Building", func() {
 					})
 
 					It("the supply buildpacks caches supply output as $CACHE_DIR/<xxhash64 of buildpack URL>", func() {
-						supplyCacheDir := fmt.Sprintf("%x", xxhash.Sum64String("always-detects-creates-build-artifacts"))
+						supplyCacheDir := buildpackHash("always-detects-creates-build-artifacts")
 						Expect(files).To(ContainElement("./" + supplyCacheDir + "/supplied"))
 
-						supplyCacheDir = fmt.Sprintf("%x", xxhash.Sum64String("always-detects"))
+						supplyCacheDir = buildpackHash("always-detects")
 						Expect(files).To(ContainElement("./" + supplyCacheDir + "/supplied"))
 
 						content, err := exec.Command("tar", "-xzOf", outputBuildArtifactsCache, "./"+supplyCacheDir+"/supplied").Output()
@@ -835,10 +833,10 @@ var _ = Describe("Building", func() {
 					})
 
 					It("the supply buildpacks caches supply output as $CACHE_DIR/<xxhash64 of buildpack URL>", func() {
-						supplyCacheDir := fmt.Sprintf("%x", xxhash.Sum64String("always-detects-creates-build-artifacts"))
+						supplyCacheDir := buildpackHash("always-detects-creates-build-artifacts")
 						Expect(files).To(ContainElement("./" + supplyCacheDir + "/supplied"))
 
-						supplyCacheDir = fmt.Sprintf("%x", xxhash.Sum64String("always-detects"))
+						supplyCacheDir = buildpackHash("always-detects")
 						Expect(files).To(ContainElement("./" + supplyCacheDir + "/supplied"))
 
 						content, err := exec.Command("tar", "-xzOf", outputBuildArtifactsCache, "./"+supplyCacheDir+"/supplied").Output()
@@ -860,13 +858,13 @@ var _ = Describe("Building", func() {
 				BeforeEach(func() {
 					rand.Seed(time.Now().UnixNano())
 					cachedSupply = fmt.Sprintf("%d", rand.Int())
-					alwaysDetectsHash = fmt.Sprintf("%x", xxhash.Sum64String("always-detects"))
+					alwaysDetectsHash = buildpackHash("always-detects")
 					err := os.MkdirAll(filepath.Join(buildArtifactsCacheDir, alwaysDetectsHash), 0755)
 					Expect(err).To(BeNil())
 					err = ioutil.WriteFile(filepath.Join(buildArtifactsCacheDir, alwaysDetectsHash, "old-supply"), []byte(cachedSupply), 0644)
 					Expect(err).To(BeNil())
 
-					notInBuildpackOrderHash = fmt.Sprintf("%x", xxhash.Sum64String("not-in-buildpack-order"))
+					notInBuildpackOrderHash = buildpackHash("not-in-buildpack-order")
 					err = os.MkdirAll(filepath.Join(buildArtifactsCacheDir, notInBuildpackOrderHash), 0755)
 					Expect(err).To(BeNil())
 
@@ -1423,3 +1421,7 @@ func removeTrailingSpace(dirty []string) []string {
 
 	return clean
 }
+
+func buildpackHash(key string) string {
+	return fmt.Sprintf("%016x", xxhash.Sum64String(key))
+}

builder_config.go

@@ -159,7 +159,7 @@ func (s LifecycleBuilderConfig) BuildpackPath(buildpackName string) string {
 	if err == nil && buildpackURL.IsAbs() {
 		baseDir = s.BuildpacksDownloadDir()
 	}
-	return filepath.Join(baseDir, fmt.Sprintf("%x", xxhash.Sum64String(buildpackName)))
+	return filepath.Join(baseDir, fmt.Sprintf("%016x", xxhash.Sum64String(buildpackName)))
 }
 
 func (s LifecycleBuilderConfig) LegacyBuildpackPath(buildpackName string) string {

builder_config_test.go

@@ -96,24 +96,36 @@ var _ = Describe("LifecycleBuilderConfig", func() {
 		})
 	})
 
-	It("returns the path to a given system buildpack using legacy md5", func() {
-		key := "my-buildpack/key/::"
-		Expect(builderConfig.LegacyBuildpackPath(key)).To(Equal(filepath.Join(pathPrefix(), "tmp", "buildpacks", "8b2f72a0702aed614f8b5d8f7f5b431b")))
-	})
+	Describe("LegacyBuildpackPath", func() {
+		It("returns the path to a given system buildpack using legacy md5", func() {
+			key := "my-buildpack/key/::"
+			Expect(builderConfig.LegacyBuildpackPath(key)).To(Equal(filepath.Join(pathPrefix(), "tmp", "buildpacks", "8b2f72a0702aed614f8b5d8f7f5b431b")))
+		})
 
-	It("returns the path to a given downloaded buildpack using legacy md5", func() {
-		key := "https://github.com/cloudfoundry/ruby-buildpack"
-		Expect(builderConfig.LegacyBuildpackPath(key)).To(Equal(filepath.Join(pathPrefix(), "tmp", "buildpackdownloads", "21de62d118ecb1f46d868d24f00839ef")))
+		It("returns the path to a given downloaded buildpack using legacy md5", func() {
+			key := "https://github.com/cloudfoundry/ruby-buildpack"
+			Expect(builderConfig.LegacyBuildpackPath(key)).To(Equal(filepath.Join(pathPrefix(), "tmp", "buildpackdownloads", "21de62d118ecb1f46d868d24f00839ef")))
+		})
 	})
 
-	It("returns the path to a given system buildpack", func() {
-		key := "my-buildpack/key/::"
-		Expect(builderConfig.BuildpackPath(key)).To(Equal(filepath.Join(pathPrefix(), "tmp", "buildpacks", "dc91f5556d3ae859")))
-	})
+	Describe("BuildpackPath", func() {
+		It("returns the path to a given system buildpack", func() {
+			key := "my-buildpack/key/::"
+			Expect(builderConfig.BuildpackPath(key)).To(Equal(filepath.Join(pathPrefix(), "tmp", "buildpacks", "dc91f5556d3ae859")))
+		})
+
+		It("returns the path to a given downloaded buildpack", func() {
+			key := "https://github.com/cloudfoundry/ruby-buildpack"
+			Expect(builderConfig.BuildpackPath(key)).To(Equal(filepath.Join(pathPrefix(), "tmp", "buildpackdownloads", "0e1df1251578f504")))
+		})
 
-	It("returns the path to a given downloaded buildpack", func() {
-		key := "https://github.com/cloudfoundry/ruby-buildpack"
-		Expect(builderConfig.BuildpackPath(key)).To(Equal(filepath.Join(pathPrefix(), "tmp", "buildpackdownloads", "e1df1251578f504")))
+		Context("when key generates hash that start with zeros", func() {
+			It("returns the path that contains 16 byte key hash", func() {
+				// xxhash starts with zeros
+				key := "a1b4aa82-e5ae-4736-8284-bdfb013a7121_2845c523cf4f4f1045b331982cc557ef761afde4dc9fc8777831563461309455"
+				Expect(builderConfig.BuildpackPath(key)).To(Equal(filepath.Join(pathPrefix(), "tmp", "buildpacks", "00c84a1da9e0c81e")))
+			})
+		})
 	})
 
 	It("returns the path to the staging metadata", func() {

buildpackrunner/runner.go

@@ -487,7 +487,7 @@ func (runner *Runner) pathHasBinDirectory(pathToTest string) bool {
 }
 
 func (runner *Runner) supplyCachePath(buildpack string) string {
-	return filepath.Join(runner.config.BuildArtifactsCacheDir(), fmt.Sprintf("%x", xxhash.Sum64String(buildpack)))
+	return filepath.Join(runner.config.BuildArtifactsCacheDir(), fmt.Sprintf("%016x", xxhash.Sum64String(buildpack)))
 }
 
 func fileExists(file string) (bool, error) {