KTOR-7667: Enable Gradle configuration cache (#4741)

* Fix compatibility with configuration cache
* Add a workaround for KT-72933
* Add a workaround for KT-76147

Author: osipxd

build-logic/src/main/kotlin/ktorbuild.kmp.gradle.kts

@@ -58,13 +58,16 @@ if (targets.hasJsOrWasmJs) {
 @Suppress("UnstableApiUsage")
 if (targets.hasNative) {
     tasks.maybeNamed("linkDebugTestLinuxX64") {
-        onlyIf("run only on Linux") { ktorBuild.os.get().isLinux }
+        val os = ktorBuild.os.get()
+        onlyIf("run only on Linux") { os.isLinux }
     }
     tasks.maybeNamed("linkDebugTestLinuxArm64") {
-        onlyIf("run only on Linux") { ktorBuild.os.get().isLinux }
+        val os = ktorBuild.os.get()
+        onlyIf("run only on Linux") { os.isLinux }
     }
     tasks.maybeNamed("linkDebugTestMingwX64") {
-        onlyIf("run only on Windows") { ktorBuild.os.get().isWindows }
+        val os = ktorBuild.os.get()
+        onlyIf("run only on Windows") { os.isWindows }
     }
 }
 

build-logic/src/main/kotlin/ktorbuild.publish.gradle.kts

@@ -57,7 +57,8 @@ configureSigning()
 
 plugins.withId("ktorbuild.kmp") {
     tasks.withType<AbstractPublishToMaven>().configureEach {
-        onlyIf { isAvailableForPublication(ktorBuild.os.get()) }
+        val os = ktorBuild.os.get()
+        onlyIf { isAvailableForPublication(os) }
     }
 
     registerTargetsPublishTasks(ktorBuild.targets)

build-logic/src/main/kotlin/ktorbuild/CInterop.kt

@@ -8,9 +8,11 @@ import ktorbuild.targets.KtorTargets
 import org.gradle.kotlin.dsl.assign
 import org.gradle.kotlin.dsl.getValue
 import org.gradle.kotlin.dsl.provideDelegate
+import org.gradle.kotlin.dsl.withType
 import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
 import org.jetbrains.kotlin.gradle.plugin.mpp.DefaultCInteropSettings
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinNativeTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinNativeCompile
 
 /**
  * Creates a CInterop configuration for all Native targets using the given [sourceSet]
@@ -62,4 +64,9 @@ fun KotlinMultiplatformExtension.createCInterop(
                 configure(targetName)
             }
         }
+
+    // Disable configuration cache for compile[target]MainKotlinMetadata tasks
+    project.tasks.withType<KotlinNativeCompile>()
+        .named { it.endsWith("MainKotlinMetadata") }
+        .configureEach { notCompatibleWithConfigurationCache("Workaround for KT-76147") }
 }

build-settings-logic/src/main/kotlin/ConfigurationCacheWorkarounds.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2014-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+import sun.misc.Unsafe
+import java.lang.reflect.Field
+
+@Suppress("UNCHECKED_CAST")
+internal object ConfigurationCacheWorkarounds {
+    private val ignoreBeanFieldsField = Class.forName("org.gradle.internal.serialize.beans.services.Workarounds")
+        .getDeclaredField("ignoredBeanFields")
+        .apply { isAccessible = true }
+
+    private val unsafe = runCatching {
+        Unsafe::class.java.getDeclaredField("theUnsafe")
+            .apply { isAccessible = true }
+            .get(null) as Unsafe
+    }.getOrNull()
+
+    private var ignoreBeanFields = ignoreBeanFieldsField.get(null) as Array<Pair<String, String>>
+        set(value) {
+            val isSet = runCatching { unsafe?.setFinalStatic(ignoreBeanFieldsField, value) }.getOrNull() != null
+            if (isSet) {
+                field = value
+            } else {
+                // If we can't set a new array to the field, fallback to replacing array's content with new values
+                for (i in 0..minOf(field.lastIndex, value.lastIndex)) field[i] = value[i]
+            }
+        }
+
+    /** Registers fields that should be excluded from configuration cache. */
+    fun addIgnoredBeanFields(vararg fields: Pair<String, String>) {
+        ignoreBeanFields = fields as Array<Pair<String, String>> + ignoreBeanFields
+    }
+}
+
+@Suppress("DEPRECATION")
+private fun Unsafe.setFinalStatic(field: Field, value: Any) {
+    val fieldBase = staticFieldBase(field)
+    val fieldOffset = staticFieldOffset(field)
+
+    putObject(fieldBase, fieldOffset, value)
+}

build-settings-logic/src/main/kotlin/ktorbuild.configuration-cache.settings.gradle.kts

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2014-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+import org.gradle.kotlin.dsl.support.serviceOf
+
+val features = serviceOf<BuildFeatures>()
+
+if (features.configurationCache.requested.get()) {
+    // KT-72933: Storing these fields leads to OOM
+    ConfigurationCacheWorkarounds.addIgnoredBeanFields(
+        "transformationParameters" to "org.jetbrains.kotlin.gradle.plugin.mpp.MetadataDependencyTransformationTask",
+        "parameters" to "org.jetbrains.kotlin.gradle.targets.native.internal.CInteropMetadataDependencyTransformationTask",
+    )
+
+    // Mark these tasks as incompatible with configuration cache as we partially exclude their state from CC
+    gradle.beforeProject {
+        tasks.matching { it::class.java.simpleName.contains("MetadataDependencyTransformationTask") }
+            .configureEach { notCompatibleWithConfigurationCache("Workaround for KT-72933") }
+    }
+
+    println("Configuration Cache: Workaround for KT-72933 was applied")
+}

build-settings-logic/src/main/kotlin/ktorbuild.develocity.settings.gradle.kts

@@ -18,6 +18,9 @@ develocity {
     // Should be in sync with settings.gradle.kts
     server = "https://ge.jetbrains.com"
 
+    // Copy the value to the local variable for compatibility with configuration cache
+    val isCIRun = isCIRun
+
     buildScan {
         uploadInBackground = !isCIRun
 

gradle.properties

@@ -43,6 +43,8 @@ doctor.enableTaskMonitoring=false
 org.gradle.daemon=true
 org.gradle.caching=true
 org.gradle.parallel=true
+org.gradle.configuration-cache=true
+org.gradle.configuration-cache.parallel=true
 org.gradle.kotlin.dsl.allWarningsAsErrors=true
 
 # kotlin
@@ -54,6 +56,9 @@ kotlin.mpp.applyDefaultHierarchyTemplate=false
 kotlin.apple.xcodeCompatibility.nowarn=true
 kotlin.suppressGradlePluginWarnings=IncorrectCompileOnlyDependencyWarning
 kotlin.daemon.useFallbackStrategy=false
+# Enable new project model to be prepared for enabling isolated projects
+# TODO: Remove when we enable isolated projects in Gradle
+kotlin.kmp.isolated-projects.support=enable
 
 # dokka
 # workaround for resolving platform dependencies, see https://github.com/Kotlin/dokka/issues/3153

ktor-test-server/src/main/kotlin/test-server.gradle.kts

@@ -4,9 +4,8 @@
 
 import test.server.TestServerService
 
-val testServerService = TestServerService.registerIfAbsent(project)
-
 tasks.withType<AbstractTestTask>().configureEach {
+    val testServerService = TestServerService.registerIfAbsent(project)
     usesService(testServerService)
     // Trigger server start if it is not started yet
     doFirst("start test server") { testServerService.get() }

settings.gradle.kts

@@ -2,6 +2,8 @@
  * Copyright 2014-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
+enableFeaturePreview("STABLE_CONFIGURATION_CACHE")
+
 pluginManagement {
     includeBuild("build-settings-logic")
 }
@@ -10,6 +12,7 @@ plugins {
     id("org.gradle.toolchains.foojay-resolver-convention") version "0.9.0"
     id("conventions-dependency-resolution-management")
     id("ktorbuild.develocity")
+    id("ktorbuild.configuration-cache")
 }
 
 rootProject.name = "ktor"