Merge pull request #30 from bluegroundltd/feature/thread-priority

feat: Allow specifying thread priority

README.md

@@ -27,7 +27,7 @@ Transactional Outbox is published on `mavenCentral`. In order to use it just add
 
 ```gradle
 
-implementation("io.github.bluegroundltd:transactional-outbox-core:2.0.4")
+implementation("io.github.bluegroundltd:transactional-outbox-core:2.1.0")
 
 ```
 
@@ -55,6 +55,12 @@ class OutboxConfiguration(
     return TransactionalOutboxBuilder
       .make(clock)
       .withHandlers(outboxHandlers)
+      // Ideally you want your thread pool < db connection pool size or similar
+      .withThreadPoolSize(5) 
+      // Override the default Thread priority with caution
+      // If you are facing performance issues, you should
+      // adjust the thread pool size first.
+      // .withThreadPriority(Thread.NORM_PRIORITY)
       .withMonitorLocksProvider(monitorLocksProvider)
       .withCleanupLocksProvider(cleanupLocksProvider)
       .withStore(outboxStore)

core/gradle.properties

@@ -1,6 +1,6 @@
 GROUP=io.github.bluegroundltd
 POM_ARTIFACT_ID=transactional-outbox-core
-VERSION_NAME=2.0.4
+VERSION_NAME=2.1.0
 
 POM_NAME=Transactional Outbox Core
 POM_DESCRIPTION=Easily implement the transactional outbox pattern in your JVM application

core/src/main/kotlin/io/github/bluegroundltd/outbox/TransactionalOutboxBuilder.kt

@@ -36,6 +36,7 @@ class TransactionalOutboxBuilder(
   BuildStep {
   private val handlers: MutableMap<OutboxType, OutboxHandler> = mutableMapOf()
   private var threadPoolSize: Int? = null
+  private var threadPriority: Int? = null
   private var threadPoolTimeOut: Duration = DEFAULT_THREAD_POOL_TIMEOUT
   private var decorators: MutableList<OutboxItemProcessorDecorator> = mutableListOf()
   private lateinit var monitorLocksProvider: OutboxLocksProvider
@@ -132,6 +133,14 @@ class TransactionalOutboxBuilder(
     return this
   }
 
+  /**
+   * Sets the priority for the threads in the thread pool.
+   */
+  override fun withThreadPriority(threadPriority: Int): BuildStep {
+    this.threadPriority = threadPriority
+    return this
+  }
+
   /**
    * Sets the thread pool timeout upon shutdown for the outbox.
    */
@@ -156,7 +165,7 @@ class TransactionalOutboxBuilder(
    * Builds the outbox.
    */
   override fun build(): TransactionalOutbox {
-    val executorServiceFactory = FixedThreadPoolExecutorServiceFactory(threadPoolSize)
+    val executorServiceFactory = FixedThreadPoolExecutorServiceFactory(threadPoolSize, threadPriority)
     val outboxItemFactory = OutboxItemFactory(clock, handlers.toMap(), rerunAfterDuration)
 
     return TransactionalOutboxImpl(
@@ -198,6 +207,7 @@ interface InstantOutboxPublisherStep {
 
 interface BuildStep {
   fun withThreadPoolSize(threadPoolSize: Int): BuildStep
+  fun withThreadPriority(threadPriority: Int): BuildStep
   fun withThreadPoolTimeOut(threadPoolTimeOut: Duration): BuildStep
   fun addProcessorDecorator(decorator: OutboxItemProcessorDecorator): BuildStep
   fun build(): TransactionalOutbox

core/src/main/kotlin/io/github/bluegroundltd/outbox/executor/FixedThreadPoolExecutorServiceFactory.kt

@@ -11,9 +11,11 @@ import java.util.concurrent.Executors
  */
 internal class FixedThreadPoolExecutorServiceFactory(
   threadPoolSize: Int? = null,
+  threadPriority: Int? = null,
   private val threadNameFormat: String = DEFAULT_THREAD_NAME_FORMAT
 ) {
   private val threadPoolSize = threadPoolSize ?: DEFAULT_THREAD_POOL_SIZE
+  private val threadPriority = threadPriority ?: Thread.NORM_PRIORITY
 
   companion object {
     private const val DEFAULT_THREAD_POOL_SIZE = 10
@@ -25,7 +27,7 @@ internal class FixedThreadPoolExecutorServiceFactory(
     logger.debug("Creating fixed thread pool with size: $threadPoolSize and name format \"$threadNameFormat\"")
     return Executors.newFixedThreadPool(
       threadPoolSize,
-      ThreadFactoryBuilder().setNameFormat(threadNameFormat).build()
+      ThreadFactoryBuilder().setNameFormat(threadNameFormat).setPriority(threadPriority).build()
     )
   }
 }

core/src/test/groovy/io/github/bluegroundltd/outbox/integration/TransactionalOutboxImplSpec.groovy

@@ -60,7 +60,7 @@ class TransactionalOutboxImplSpec extends Specification {
     instantOutboxPublisher,
     outboxItemFactory,
     DURATION_ONE_HOUR,
-    new FixedThreadPoolExecutorServiceFactory(1, "").make(),
+    new FixedThreadPoolExecutorServiceFactory(1, null, "").make(),
     [],
     DURATION_ONE_NANO,
     processingHostComposer

core/src/test/groovy/io/github/bluegroundltd/outbox/unit/executor/FixedThreadPoolExecutorServiceFactorySpec.groovy

@@ -27,9 +27,10 @@ class FixedThreadPoolExecutorServiceFactorySpec extends UnitTestSpecification {
   def "Should create a FixedThreadPool ExecutorService with custom configuration"() {
     given:
       def expectedThreadPoolSize = 5
+      def expectedThreadPriority = Thread.MIN_PRIORITY
 
     when:
-      def factory = new FixedThreadPoolExecutorServiceFactory(5, "")
+      def factory = new FixedThreadPoolExecutorServiceFactory(5, Thread.MIN_PRIORITY, "")
 
     then:
       def executorService = factory.make()
@@ -43,5 +44,6 @@ class FixedThreadPoolExecutorServiceFactorySpec extends UnitTestSpecification {
     and:
       threadPoolExecutorService.getCorePoolSize() == expectedThreadPoolSize
       threadPoolExecutorService.getMaximumPoolSize() == expectedThreadPoolSize
+      threadPoolExecutorService.getThreadFactory().newThread({}).getPriority() == expectedThreadPriority
   }
 }