Enable Cloud Storage Prefix for Remote Build Cache

core/src/main/kotlin/androidx/build/gradle/core/BuildCacheKey.kt

@@ -31,3 +31,10 @@ fun BuildCacheKey.blobKey(): String {
     // a single `/`.
     return hashCode.replace(slashes, "/")
 }
+
+fun String.withPrefix(prefix: String?): String {
+    if (prefix.isNullOrBlank()) return this
+
+    val sanitizedPrefix = prefix.trimEnd('/', '\\')
+    return "$sanitizedPrefix/$this"
+}

core/src/main/kotlin/androidx/build/gradle/core/FileSystemStorageService.kt

@@ -26,11 +26,20 @@ import java.nio.file.Files
  */
 class FileSystemStorageService(
     override val bucketName: String,
+    private val prefix: String?,
     override val isPush: Boolean,
     override val isEnabled: Boolean
 ) : StorageService {
 
-    private val location = Files.createTempDirectory("tmp$bucketName").toFile()
+    private val location: File = createTempDirectory()
+
+    private fun createTempDirectory(): File {
+        val baseDir = prefix?.takeIf { it.isNotBlank() }?.let {
+            File(it).apply { if (!exists()) mkdirs() }
+        } ?: File(System.getProperty(JAVA_IO_TMPDIR))
+
+        return Files.createTempDirectory(baseDir.toPath(), "tmp$bucketName").toFile()
+    }
 
     override fun load(cacheKey: String): InputStream? {
         if (!isEnabled) {
@@ -84,6 +93,8 @@ class FileSystemStorageService(
     }
 
     companion object {
+        private const val JAVA_IO_TMPDIR = "java.io.tmpdir"
+
         private fun File.deleteRecursively() {
             val files = listFiles()
             for (file in files) {

core/src/main/kotlin/androidx/build/gradle/core/RemoteGradleBuildCache.kt

@@ -30,6 +30,13 @@ abstract class RemoteGradleBuildCache : AbstractBuildCache() {
      */
     lateinit var bucketName: String
 
+    /**
+     * The prefix to use when storing cache entries in the bucket.
+     * It becomes new root for all cache entries.
+     * If not specified, the cache entries will be stored at the root of the bucket.
+     */
+    lateinit var prefix: String
+
     /**
      * The type of credentials to use to connect to authenticate to your project instance.
      */

core/src/test/kotlin/androidx/build/gradle/core/FileStorageServiceTest.kt

@@ -24,6 +24,23 @@ class FileStorageServiceTest {
     fun testStoreBlob() {
         val storageService = FileSystemStorageService(
             bucketName = BUCKET_NAME,
+            prefix = null,
+            isPush = true,
+            isEnabled = true
+        )
+        storageService.use {
+            val cacheKey = "test-store.txt"
+            val contents = "The quick brown fox jumped over the lazy dog"
+            val result = storageService.store(cacheKey, contents.toByteArray(Charsets.UTF_8))
+            assert(result)
+        }
+    }
+
+    @Test
+    fun testStoreBlob_withPrefix() {
+        val storageService = FileSystemStorageService(
+            bucketName = BUCKET_NAME,
+            prefix = "test-prefix",
             isPush = true,
             isEnabled = true
         )
@@ -39,6 +56,7 @@ class FileStorageServiceTest {
     fun testLoadBlob() {
         val storageService = FileSystemStorageService(
             bucketName = BUCKET_NAME,
+            prefix = null,
             isPush = true,
             isEnabled = true
         )
@@ -57,6 +75,7 @@ class FileStorageServiceTest {
     fun testStoreBlob_noPushSupport() {
         val storageService = FileSystemStorageService(
             bucketName = BUCKET_NAME,
+            prefix = null,
             isPush = false,
             isEnabled = true
         )
@@ -72,6 +91,7 @@ class FileStorageServiceTest {
     fun testStoreBlob_disabled() {
         val storageService = FileSystemStorageService(
             bucketName = BUCKET_NAME,
+            prefix = null,
             isPush = true,
             isEnabled = false
         )

gcpbuildcache/src/main/kotlin/androidx/build/gradle/gcpbuildcache/GcpBuildCacheService.kt

@@ -19,6 +19,7 @@ package androidx.build.gradle.gcpbuildcache
 
 import androidx.build.gradle.core.FileSystemStorageService
 import androidx.build.gradle.core.blobKey
+import androidx.build.gradle.core.withPrefix
 import org.gradle.api.logging.Logging
 import org.gradle.caching.BuildCacheEntryReader
 import org.gradle.caching.BuildCacheEntryWriter
@@ -37,6 +38,7 @@ import java.io.ByteArrayOutputStream
 internal class GcpBuildCacheService(
     private val projectId: String,
     private val bucketName: String,
+    private val prefix: String?,
     gcpCredentials: GcpCredentials,
     messageOnAuthenticationFailure: String,
     isPush: Boolean,
@@ -46,9 +48,21 @@ internal class GcpBuildCacheService(
 
     private val storageService = if (inTestMode) {
         // Use an implementation backed by the File System when in test mode.
-        FileSystemStorageService(bucketName, isPush, isEnabled)
+        FileSystemStorageService(
+            bucketName = bucketName,
+            prefix = prefix,
+            isPush = isPush,
+            isEnabled = isEnabled,
+        )
     } else {
-        GcpStorageService(projectId, bucketName, gcpCredentials, messageOnAuthenticationFailure, isPush, isEnabled)
+        GcpStorageService(
+            projectId = projectId,
+            bucketName = bucketName,
+            gcpCredentials = gcpCredentials,
+            messageOnAuthenticationFailure = messageOnAuthenticationFailure,
+            isPush = isPush,
+            isEnabled = isEnabled
+        )
     }
 
     override fun close() {
@@ -57,7 +71,9 @@ internal class GcpBuildCacheService(
 
     override fun load(key: BuildCacheKey, reader: BuildCacheEntryReader): Boolean {
         logger.info("Loading ${key.blobKey()}")
-        val cacheKey = key.blobKey()
+        val cacheKey = key
+            .blobKey()
+            .apply { if (prefix != null) withPrefix(prefix) }
         val input = storageService.load(cacheKey) ?: return false
         reader.readFrom(input)
         return true
@@ -66,7 +82,9 @@ internal class GcpBuildCacheService(
     override fun store(key: BuildCacheKey, writer: BuildCacheEntryWriter) {
         if (writer.size == 0L) return // do not store empty entries into the cache
         logger.info("Storing ${key.blobKey()}")
-        val cacheKey = key.blobKey()
+        val cacheKey = key
+            .blobKey()
+            .apply { if (prefix != null) withPrefix(prefix) }
         val output = ByteArrayOutputStream()
         output.use {
             writer.writeTo(output)

gcpbuildcache/src/main/kotlin/androidx/build/gradle/gcpbuildcache/GcpBuildCacheServiceFactory.kt

@@ -32,6 +32,7 @@ class GcpBuildCacheServiceFactory : BuildCacheServiceFactory<GcpBuildCache> {
             .type("GCP-backed")
             .config("projectId", buildCache.projectId)
             .config("bucketName", buildCache.bucketName)
+            .config("prefix", buildCache.prefix)
             .config("isPushSupported", "${buildCache.isPush}")
             .config("isEnabled", "${buildCache.isEnabled}")
             .config(
@@ -40,12 +41,13 @@ class GcpBuildCacheServiceFactory : BuildCacheServiceFactory<GcpBuildCache> {
             )
 
         val service = GcpBuildCacheService(
-            buildCache.projectId,
-            buildCache.bucketName,
-            buildCache.credentials,
-            buildCache.messageOnAuthenticationFailure,
-            buildCache.isPush,
-            buildCache.isEnabled
+            projectId = buildCache.projectId,
+            bucketName = buildCache.bucketName,
+            prefix = buildCache.prefix,
+            gcpCredentials = buildCache.credentials,
+            messageOnAuthenticationFailure = buildCache.messageOnAuthenticationFailure,
+            isPush = buildCache.isPush,
+            isEnabled = buildCache.isEnabled
         )
         service.validateConfiguration()
         return service

s3buildcache/src/main/kotlin/androidx/build/gradle/s3buildcache/S3BuildCacheService.kt

@@ -19,6 +19,7 @@ package androidx.build.gradle.s3buildcache
 
 import androidx.build.gradle.core.FileSystemStorageService
 import androidx.build.gradle.core.blobKey
+import androidx.build.gradle.core.withPrefix
 import org.gradle.api.logging.Logging
 import org.gradle.caching.BuildCacheEntryReader
 import org.gradle.caching.BuildCacheEntryWriter
@@ -42,6 +43,7 @@ class S3BuildCacheService(
     credentials: S3Credentials,
     region: String,
     bucketName: String,
+    private val prefix: String?,
     isPush: Boolean,
     isEnabled: Boolean,
     reducedRedundancy: Boolean,
@@ -52,23 +54,39 @@ class S3BuildCacheService(
         clientOptions(credentials(credentials), region)
     }
     private val storageService = if (inTestMode) {
-        FileSystemStorageService(bucketName, isPush, isEnabled)
+        FileSystemStorageService(
+            bucketName = bucketName,
+            prefix = prefix,
+            isPush = isPush,
+            isEnabled = isEnabled,
+        )
     } else {
-        S3StorageService(bucketName, isPush, isEnabled, client, region, reducedRedundancy)
+        S3StorageService(
+            bucketName = bucketName,
+            isPush = isPush,
+            isEnabled = isEnabled,
+            client = client,
+            region = region,
+            reducedRedundancy = reducedRedundancy
+        )
     }
 
     override fun load(key: BuildCacheKey, reader: BuildCacheEntryReader): Boolean {
         logger.info("Loading ${key.blobKey()}")
-        val cacheKey = key.blobKey()
+        val cacheKey = key
+            .blobKey()
+            .apply { if (prefix != null) withPrefix(prefix) }
         val input = storageService.load(cacheKey) ?: return false
         reader.readFrom(input)
         return true
     }
 
     override fun store(key: BuildCacheKey, writer: BuildCacheEntryWriter) {
         if (writer.size == 0L) return // do not store empty entries into the cache
+        val cacheKey = key
+            .blobKey()
+            .apply { if (prefix != null) withPrefix(prefix) }
         logger.info("Storing ${key.blobKey()}")
-        val cacheKey = key.blobKey()
         val output = ByteArrayOutputStream()
         output.use {
             writer.writeTo(output)

s3buildcache/src/main/kotlin/androidx/build/gradle/s3buildcache/S3BuildCacheServiceFactory.kt

@@ -33,6 +33,7 @@ class S3BuildCacheServiceFactory : BuildCacheServiceFactory<S3BuildCache> {
             .type("AWS-S3-backed")
             .config("region", buildCache.region)
             .config("bucketName", buildCache.bucketName)
+            .config("prefix", buildCache.prefix)
             .config("reducedRedundancy", "${buildCache.reducedRedundancy}")
             .config("isPushSupported", "${buildCache.isPush}")
             .config("isEnabled", "${buildCache.isEnabled}")
@@ -41,6 +42,7 @@ class S3BuildCacheServiceFactory : BuildCacheServiceFactory<S3BuildCache> {
         val service = S3BuildCacheService(
             region = buildCache.region,
             bucketName = buildCache.bucketName,
+            prefix = buildCache.prefix,
             isPush = buildCache.isPush,
             isEnabled = buildCache.isEnabled,
             reducedRedundancy = buildCache.reducedRedundancy,