Change CachelessHystrixPropertiesStrategy to a normal class

Apparently you can only register a strategy once inside a single Java process and
subsequent attempts will cause exceptions to be thrown.

Instead of registering in Global, which, depending on libs/other singletons/w/e,
may already be too late, use the hystrix.plugin.HystrixPropertiesStrategy.implementation
system property and name our class.

app/com/m3/octoparts/Global.scala

@@ -7,11 +7,10 @@ import _root_.controllers.ControllersModule
 import com.kenshoo.play.metrics.MetricsFilter
 import com.m3.octoparts.cache.CacheModule
 import com.m3.octoparts.http.HttpModule
-import com.m3.octoparts.hystrix.{ CachelessHystrixPropertiesStrategy, HystrixMetricsLogger, HystrixModule }
+import com.m3.octoparts.hystrix.{ HystrixMetricsLogger, HystrixModule }
 import com.m3.octoparts.logging.PartRequestLogger
 import com.beachape.logging.LTSVLogger
 import com.m3.octoparts.repository.RepositoriesModule
-import com.netflix.hystrix.strategy.HystrixPlugins
 import com.typesafe.config.ConfigFactory
 import com.wordnik.swagger.config.{ ConfigFactory => SwaggerConfigFactory }
 import com.wordnik.swagger.model.ApiInfo
@@ -82,7 +81,6 @@ object Global extends WithFilters(MetricsFilter) with ScaldiSupport {
 
   override def onStart(app: Application) = {
     super.onStart(app)
-    HystrixPlugins.getInstance().registerPropertiesStrategy(CachelessHystrixPropertiesStrategy)
     startPeriodicTasks(app)
   }
 

app/com/m3/octoparts/hystrix/CachelessHystrixPropertiesStrategy.scala

@@ -8,6 +8,6 @@ import com.netflix.hystrix.strategy.properties.HystrixPropertiesStrategy
  * to return null so that [[com.netflix.hystrix.strategy.properties.HystrixPropertiesFactory]] will always
  * generate a new [[HystrixCommandProperties]] for each new [[com.netflix.hystrix.HystrixCommand]] instantiation
  */
-object CachelessHystrixPropertiesStrategy extends HystrixPropertiesStrategy {
+class CachelessHystrixPropertiesStrategy extends HystrixPropertiesStrategy {
   override def getCommandPropertiesCacheKey(commandKey: HystrixCommandKey, builder: HystrixCommandProperties.Setter): String = null
 }

project/Build.scala

@@ -72,6 +72,7 @@ object OctopartsBuild extends Build {
       sonatypeSettings ++
       coverallsSettings ++
       Seq(
+        javaOptions += "-Dhystrix.plugin.HystrixPropertiesStrategy.implementation=com.m3.octoparts.hystrix.CachelessHystrixPropertiesStrategy",
         publishArtifact := false,
         libraryDependencies ++= Seq(
           // Logging

test/com/m3/octoparts/hystrix/CachelessHystrixPropertiesStrategySpec.scala

@@ -7,19 +7,23 @@ import org.scalatest.{ Matchers, FunSpec }
 
 class CachelessHystrixPropertiesStrategySpec extends FunSpec with Matchers {
 
+  val subject = new CachelessHystrixPropertiesStrategy
   val commandKey = HystrixCommandKey.Factory.asKey("hello")
   val commandProps = HystrixCommandProperties.Setter()
   describe("getCommandPropertiesCacheKey") {
     it("should return null") {
-      val r = CachelessHystrixPropertiesStrategy.getCommandPropertiesCacheKey(commandKey, commandProps)
+      val r = subject.getCommandPropertiesCacheKey(commandKey, commandProps)
       r should be(null)
     }
   }
 
+  // The following works if this test is run by itself, but
   describe("after registering with HystrixPlugins") {
 
     it("should allow HystrixPropertiesFactory.getCommandProperties to instantiate different HystrixCommandProperties for the same command key") {
-      HystrixPlugins.getInstance().registerPropertiesStrategy(CachelessHystrixPropertiesStrategy)
+      if (HystrixPlugins.getInstance().getPropertiesStrategy.getClass != subject.getClass) {
+        fail("HystrixPlugins.getPropertiesStrategy did not return CachelessHystrixPropertiesStrategy")
+      }
       val properties1 = HystrixPropertiesFactory.getCommandProperties(
         commandKey,
         HystrixCommandProperties.Setter().withExecutionIsolationThreadTimeoutInMilliseconds(300))