From 508d59ea5e2865a5bfc6d380527b1ab91e0fddd5 Mon Sep 17 00:00:00 2001
From: John St John <johnthesaintjohn@gmail.com>
Date: Mon, 25 Sep 2017 15:22:20 -0700
Subject: Pull in slickmdc

---
 .../driver/core/database/MdcAsyncExecutor.scala    | 46 ++++++++++++++++++++++
 .../driver/core/database/MdcExecutionContext.scala | 28 +++++++++++++
 2 files changed, 74 insertions(+)
 create mode 100644 src/main/scala/xyz/driver/core/database/MdcAsyncExecutor.scala
 create mode 100644 src/main/scala/xyz/driver/core/database/MdcExecutionContext.scala

(limited to 'src/main/scala/xyz/driver/core/database')

diff --git a/src/main/scala/xyz/driver/core/database/MdcAsyncExecutor.scala b/src/main/scala/xyz/driver/core/database/MdcAsyncExecutor.scala
new file mode 100644
index 0000000..ac8456e
--- /dev/null
+++ b/src/main/scala/xyz/driver/core/database/MdcAsyncExecutor.scala
@@ -0,0 +1,46 @@
+package xyz.driver.core.database
+
+import java.util.concurrent._
+import java.util.concurrent.atomic.AtomicInteger
+
+import scala.concurrent._
+import com.typesafe.scalalogging.StrictLogging
+import slick.util.AsyncExecutor
+
+/** Taken from the original Slick AsyncExecutor and simplified
+  * @see https://github.com/slick/slick/blob/3.1/slick/src/main/scala/slick/util/AsyncExecutor.scala
+  */
+object MdcAsyncExecutor extends StrictLogging {
+
+  /** Create an AsyncExecutor with a fixed-size thread pool.
+    *
+    * @param name The name for the thread pool.
+    * @param numThreads The number of threads in the pool.
+    */
+  def apply(name: String, numThreads: Int): AsyncExecutor = {
+    new AsyncExecutor {
+      val tf = new DaemonThreadFactory(name + "-")
+
+      lazy val executionContext = {
+        new MdcExecutionContext(ExecutionContext.fromExecutor(Executors.newFixedThreadPool(numThreads, tf)))
+      }
+
+      def close(): Unit = {}
+    }
+  }
+
+  def default(name: String = "AsyncExecutor.default"): AsyncExecutor = apply(name, 20)
+
+  private class DaemonThreadFactory(namePrefix: String) extends ThreadFactory {
+    private[this] val group =
+      Option(System.getSecurityManager).fold(Thread.currentThread.getThreadGroup)(_.getThreadGroup)
+    private[this] val threadNumber = new AtomicInteger(1)
+
+    def newThread(r: Runnable): Thread = {
+      val t = new Thread(group, r, namePrefix + threadNumber.getAndIncrement, 0)
+      if (!t.isDaemon) t.setDaemon(true)
+      if (t.getPriority != Thread.NORM_PRIORITY) t.setPriority(Thread.NORM_PRIORITY)
+      t
+    }
+  }
+}
diff --git a/src/main/scala/xyz/driver/core/database/MdcExecutionContext.scala b/src/main/scala/xyz/driver/core/database/MdcExecutionContext.scala
new file mode 100644
index 0000000..f08f16c
--- /dev/null
+++ b/src/main/scala/xyz/driver/core/database/MdcExecutionContext.scala
@@ -0,0 +1,28 @@
+package xyz.driver.core.database
+
+import org.slf4j.MDC
+import scala.concurrent.ExecutionContext
+
+/**
+  * Execution context proxy for propagating SLF4J diagnostic context from caller thread to execution thread.
+  */
+class MdcExecutionContext(executionContext: ExecutionContext) extends ExecutionContext {
+  override def execute(runnable: Runnable): Unit = {
+    val callerMdc = MDC.getCopyOfContextMap
+    executionContext.execute(new Runnable {
+      def run(): Unit = {
+        // copy caller thread diagnostic context to execution thread
+        // scalastyle:off
+        if (callerMdc != null) MDC.setContextMap(callerMdc)
+        try {
+          runnable.run()
+        } finally {
+          // the thread might be reused, so we clean up for the next use
+          MDC.clear()
+        }
+      }
+    })
+  }
+
+  override def reportFailure(cause: Throwable): Unit = executionContext.reportFailure(cause)
+}
-- 
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