util-slf4j-bridge: Add Slf4jBridge trait for handler installation in class construction

Problem

Installation of the SLF4JBridgeHandler should happen as early as possible, ideally during
the construction of the main application.

Solution

Add a mixin which can be composed into extensions of `c.t.app.App` which will attempt
installation of the bridge handler via the `Slf4jBridgeUtility` as part of class
construction. Move TwitterServer to use the mixin in util-slf4j-jul-bridge.

Result

A simple way for extensions of `c.t.app.App` to ensure installation of the SLF4JBridgeHandler
is attempted during the constructor of the `App`.

Differential Revision: https://phabricator.twitter.biz/D827493

Author: cacoco

Diff for: CHANGELOG.rst

@@ -16,6 +16,10 @@ New Features
   eden space, sheap, metaspace, survivor space, and old gen) and open file descriptors count in StatsReceiver.
   ``PHAB_ID=D820472``
 
+* util-slf4j-jul-bridge: Add `Slf4jBridge` trait which can be mixed into extensions of `c.t.app.App` in
+  order to attempt installation of the `SLF4JBridgeHandler` via the `Slf4jBridgeUtility` in the constructor
+  of the `c.t.app.App` instance. ``PHAB_ID=D827493``
+
 Runtime Behavior Changes
 ~~~~~~~~~~~~~~~~~~~~~~~~
 

Diff for: build.sbt

@@ -28,7 +28,6 @@ val scalacheckLib = "org.scalacheck" %% "scalacheck" % "1.15.4" % "test"
 val slf4jApi = "org.slf4j" % "slf4j-api" % slf4jVersion
 val snakeyaml = "org.yaml" % "snakeyaml" % "1.24"
 
-
 def travisTestJavaOptions: Seq[String] = {
   // We have some custom configuration for the Travis environment
   // https://docs.travis-ci.com/user/environment-variables/#default-environment-variables
@@ -214,10 +213,9 @@ val sharedSettings =
 val sharedScala3EnabledSettings =
   baseSettings ++
     defaultScala3EnabledSettings ++
-    Seq(libraryDependencies ++= scala3Dependencies) ++ 
+    Seq(libraryDependencies ++= scala3Dependencies) ++
     Seq(excludeDependencies ++= Seq("org.scala-lang.modules" % "scala-collection-compat_3"))
 
-
 lazy val noPublishSettings = Seq(
   publish / skip := true
 )
@@ -245,7 +243,7 @@ def scalatestScalacheckVersionedDep(scalaVersion: String) = {
     )
   }
 }
- 
+
 lazy val util = Project(
   id = "util",
   base = file(".")
@@ -529,7 +527,7 @@ lazy val utilJvm = Project(
     name := "util-jvm",
     libraryDependencies ++= Seq(
       "org.mockito" % "mockito-core" % mockitoVersion % "test",
-   ) ++ scalatestMockitoVersionedDep(scalaVersion.value)
+    ) ++ scalatestMockitoVersionedDep(scalaVersion.value)
   ).dependsOn(utilApp, utilCore, utilStats)
 
 lazy val utilLint = Project(
@@ -617,7 +615,7 @@ lazy val utilSlf4jJulBridge = Project(
   ).settings(
     name := "util-slf4j-jul-bridge",
     libraryDependencies ++= Seq(slf4jApi, "org.slf4j" % "jul-to-slf4j" % slf4jVersion)
-  ).dependsOn(utilCore, utilSlf4jApi)
+  ).dependsOn(utilCore, utilApp, utilSlf4jApi)
 
 lazy val utilSecurity = Project(
   id = "util-security",
@@ -655,18 +653,19 @@ lazy val utilStats = Project(
       scalacheckLib,
       "com.fasterxml.jackson.core" % "jackson-core" % jacksonVersion,
       "com.fasterxml.jackson.core" % "jackson-databind" % jacksonVersion,
-      ("com.fasterxml.jackson.module" %% "jackson-module-scala" % jacksonVersion exclude ("com.google.guava", "guava")).cross(CrossVersion.for3Use2_13),
+      ("com.fasterxml.jackson.module" %% "jackson-module-scala" % jacksonVersion exclude ("com.google.guava", "guava"))
+        .cross(CrossVersion.for3Use2_13),
       "org.mockito" % "mockito-core" % mockitoVersion % "test"
     ) ++ scalatestMockitoVersionedDep(scalaVersion.value)
-    ++ scalatestScalacheckVersionedDep(scalaVersion.value)
-    ++ {
-      CrossVersion.partialVersion(scalaVersion.value) match {
-        case Some((2, major)) if major <= 12 =>
-          Seq()
-        case _ =>
-          Seq("org.scala-lang.modules" %% "scala-parallel-collections" % "1.0.3" % "test")
+      ++ scalatestScalacheckVersionedDep(scalaVersion.value)
+      ++ {
+        CrossVersion.partialVersion(scalaVersion.value) match {
+          case Some((2, major)) if major <= 12 =>
+            Seq()
+          case _ =>
+            Seq("org.scala-lang.modules" %% "scala-parallel-collections" % "1.0.3" % "test")
+        }
       }
-    }
   ).dependsOn(utilApp, utilCore, utilLint)
 
 lazy val utilTest = Project(

Diff for: util-slf4j-jul-bridge/src/main/scala/com/twitter/util/logging/BUILD

@@ -10,6 +10,7 @@ scala_library(
     dependencies = [
         "3rdparty/jvm/org/slf4j:jul-to-slf4j",
         "3rdparty/jvm/org/slf4j:slf4j-api",
+        "util/util-app/src/main/scala",
         "util/util-core/src/main/scala/com/twitter/concurrent",
         "util/util-slf4j-api/src/main/scala/com/twitter/util/logging",
     ],

Diff for: util-slf4j-jul-bridge/src/main/scala/com/twitter/util/logging/Slf4jBridge.scala

@@ -0,0 +1,21 @@
+package com.twitter.util.logging
+
+import com.twitter.app.App
+
+/**
+ * Installing the `SLF4JBridgeHandler` should be done as early as possible in order to capture any
+ * log statements emitted to JUL. Generally it is best to install the handler in the constructor of
+ * the main class of your application.
+ *
+ * This trait can be mixed into a [[com.twitter.app.App]] type and will attempt to install the
+ * `SLF4JBridgeHandler` via the [[Slf4jBridgeUtility]] as part of the constructor of the resultant
+ * class.
+ * @see [[Slf4jBridgeUtility]]
+ * @see [[org.slf4j.bridge.SLF4JBridgeHandler]]
+ * @see [[https://www.slf4j.org/legacy.html Bridging legacy APIs]]
+ */
+trait Slf4jBridge { self: App =>
+
+  /** Attempt Slf4jBridgeHandler installation */
+  Slf4jBridgeUtility.attemptSlf4jBridgeHandlerInstallation()
+}

Diff for: util-slf4j-jul-bridge/src/main/scala/com/twitter/util/logging/Slf4jBridgeUtility.scala

@@ -17,6 +17,8 @@ import org.slf4j.bridge.SLF4JBridgeHandler
  * manner. However, using the [[https://logback.qos.ch/manual/configuration.html#LevelChangePropagator Logback LevelChangePropagator]]
  * (> 0.9.25) can eliminate this performance impact.
  *
+ * @see [[org.slf4j.bridge.SLF4JBridgeHandler]]
+ * @see [[https://www.slf4j.org/legacy.html Bridging legacy APIs]]
  * @see [[https://www.slf4j.org/legacy.html#jul-to-slf4j SLF4J: jul-to-slf4j bridge]]
  */
 object Slf4jBridgeUtility extends Logging {
@@ -30,7 +32,7 @@ object Slf4jBridgeUtility extends Logging {
 
   /* Private */
 
-  private val install = Once {
+  private[this] val install = Once {
     if (!SLF4JBridgeHandler.isInstalled && canInstallBridgeHandler) {
       SLF4JBridgeHandler.removeHandlersForRootLogger()
       SLF4JBridgeHandler.install()
@@ -42,7 +44,7 @@ object Slf4jBridgeUtility extends Logging {
    * We do not want to install the bridge handler if the
    * `org.slf4j.impl.JDK14LoggerFactory` exists on the classpath.
    */
-  private def canInstallBridgeHandler: Boolean = {
+  private[this] def canInstallBridgeHandler: Boolean = {
     try {
       Class.forName("org.slf4j.impl.JDK14LoggerFactory", false, this.getClass.getClassLoader)
       LoggerFactory
@@ -53,7 +55,7 @@ object Slf4jBridgeUtility extends Logging {
         )
       false
     } catch {
-      case e: ClassNotFoundException =>
+      case _: ClassNotFoundException =>
         true
     }
   }