finagle-netty4: Avoid NoClassDefFoundError if netty-transport-native-…

…epoll is excluded

Problem

Currently Finagle fails at startup when netty-transport-native-epoll is not
available on the classpath.  Even on OS X, or if epoll is explicitly disabled.
(If I have seen correctly it is even disabled by default here:
finagle/finagle-netty4/src/main/resources/com/twitter/toggles/configs/com.twitter.finagle.netty4.json

Lines 3 to 7 in 835b6c3
   "id": "com.twitter.finagle.netty4.UseNativeEpollV2", "description": "Enable
   native epoll transport for netty4. Requires linux-x86_64", "fraction": 0.0
)

Solution

The solution is to move the creation of the different EventLoopGroups into own
methods with an explicit type signature returning just EventLoopGroup.

Result

As a result it should be possible to exclude netty-transport-native-epoll from
the classpath and therefore reduce the size of the bundle.

Side note: I see that I didn't add any tests. Unfortunately my sbt know how is
not existing, so I don't know how to set up separate tests with different
dependencies.

Signed-off-by: Isabel Martin <imartin@twitter.com>

JIRA Issues: CSL-6407

Differential Revision: https://phabricator.twitter.biz/D172924

CHANGES

@@ -27,6 +27,9 @@ Bug Fixes
     ServicePerEndpoint. It can be set via `c.t.f.thrift.RichClientParam` or a `with`-method
     as `Thrift{Mux}.client.withPerEndpointStats`. ``PHAB_ID=D169427``
 
+  * finagle-netty4: Avoid NoClassDefFoundError if netty-transport-native-epoll is not available
+    on the classpath.
+
 18.5.0
 -------
 

finagle-netty4/src/main/scala/com/twitter/finagle/netty4/ListeningServerBuilder.scala

@@ -47,6 +47,16 @@ private class ListeningServerBuilder(
   // netty4 params
   private[this] val param.Allocator(allocator) = params[param.Allocator]
 
+  private[ListeningServerBuilder] def mkEpollEventLoopGroup(): EventLoopGroup =
+    new EpollEventLoopGroup(
+      1 /*nThreads*/,
+      new NamedPoolThreadFactory("finagle/netty4/boss", makeDaemons = true))
+
+  private[ListeningServerBuilder] def mkNioEventLoopGroup(): EventLoopGroup =
+    new NioEventLoopGroup(
+      1 /*nThreads*/,
+      new NamedPoolThreadFactory("finagle/netty4/boss", makeDaemons = true))
+
   /**
    * Listen for connections and apply the `serveTransport` callback on
    * connected [[Transport transports]].
@@ -62,15 +72,9 @@ private class ListeningServerBuilder(
     new ListeningServer with CloseAwaitably {
       private[this] val bossLoop: EventLoopGroup =
         if (nativeEpoll.enabled)
-          new EpollEventLoopGroup(
-            1 /*nThreads*/,
-            new NamedPoolThreadFactory("finagle/netty4/boss", makeDaemons = true)
-          )
+          mkEpollEventLoopGroup()
         else
-          new NioEventLoopGroup(
-            1 /*nThreads*/,
-            new NamedPoolThreadFactory("finagle/netty4/boss", makeDaemons = true)
-          )
+          mkNioEventLoopGroup()
 
       private[this] val bootstrap = new ServerBootstrap()
       if (nativeEpoll.enabled)

finagle-netty4/src/main/scala/com/twitter/finagle/netty4/param/WorkerPool.scala

@@ -19,10 +19,9 @@ import java.util.concurrent.{Executor, Executors}
  * more granularly (e.g. [[com.twitter.util.FuturePool]] is a good tool for this).
  */
 case class WorkerPool(eventLoopGroup: EventLoopGroup) {
-
   def this(executor: Executor, numWorkers: Int) = this(
-    if (nativeEpoll.enabled) new EpollEventLoopGroup(numWorkers, executor)
-    else new NioEventLoopGroup(numWorkers, executor))
+    if (nativeEpoll.enabled) WorkerPool.mkEpollEventLoopGroup(numWorkers, executor)
+    else WorkerPool.mkNioEventLoopGroup(numWorkers, executor))
 
   def mk() : (WorkerPool, Stack.Param[WorkerPool]) =
     (this, WorkerPool.workerPoolParam)
@@ -38,4 +37,11 @@ object WorkerPool {
     new WorkerPool(Executors.newCachedThreadPool(new BlockingTimeTrackingThreadFactory(
       new NamedPoolThreadFactory("finagle/netty4", makeDaemons = true)
     )), numWorkers()))
+
+  private[netty4] def mkEpollEventLoopGroup(numWorkers: Int, executor: Executor): EventLoopGroup =
+    new EpollEventLoopGroup(numWorkers, executor)
+
+  private[netty4] def mkNioEventLoopGroup(numWorkers: Int, executor: Executor): EventLoopGroup =
+    new NioEventLoopGroup(numWorkers, executor)
+
 }