metrics: remove delayed implementation of timers interface (elastic#1…

…4815)

The delayed implementation `AfterCompletionTimerMetric` of the `TimerMetric`
interface, introduced along-side that interface's introduction to replicate
the previous (undesired) behaviour, is superceded by an already-merged live-
tracking implementation that is effectively as performant when not under
concurrent contention and still reasonably performant when a single timer is
contended across multiple threads.

The `metric.timers` setting removed here has not been a part of any Logstash
release and can safely be removed without going through the normal deprecation
path; from the user's perspective this removal combined with the previously-
merged work is simply an improvement to the accuracy of the existing timer
metrics exposed via our API.

docker/data/logstash/env2yaml/env2yaml.go

@@ -95,7 +95,6 @@ func normalizeSetting(setting string) (string, error) {
 		"log.format",
 		"modules",
 		"metric.collect",
-		"metric.timers",
 		"path.logs",
 		"path.plugins",
 		"api.auth.type",

logstash-core/lib/logstash/environment.rb

@@ -52,7 +52,6 @@ module Environment
            Setting::Boolean.new("config.support_escapes", false),
             Setting::String.new("config.field_reference.escape_style", "none", true, %w(none percent ampersand)),
            Setting::Boolean.new("metric.collect", true),
-            Setting::String.new("metric.timers", "delayed", true, %w(delayed live)),
             Setting::String.new("pipeline.id", "main"),
            Setting::Boolean.new("pipeline.system", false),
    Setting::PositiveInteger.new("pipeline.workers", LogStash::Config::CpuCoreStrategy.maximum),
@@ -128,7 +127,6 @@ module Environment
     java.lang.System.setProperty("ls.log.format", settings.get("log.format"))
     java.lang.System.setProperty("ls.log.level", settings.get("log.level"))
     java.lang.System.setProperty("ls.pipeline.separate_logs", settings.get("pipeline.separate_logs").to_s)
-    java.lang.System.setProperty("ls.metric.timers", settings.get("metric.timers"))
     unless java.lang.System.getProperty("log4j.configurationFile")
       log4j_config_location = ::File.join(settings.get("path.settings"), "log4j2.properties")
 

logstash-core/src/main/java/org/logstash/instrument/metrics/timer/TimerMetricFactory.java

@@ -13,12 +13,6 @@ public TimerMetric create(final String name) {
     }
 
     TimerMetric create(final String name, final LongSupplier nanoTimeSupplier) {
-        // INTERNAL-ONLY system property escape hatch, set with `metric.timers` config in logstash.yml
-        final String timerType = System.getProperty("ls.metric.timers", "delayed");
-        switch (timerType) {
-            case "live"   : return new ConcurrentLiveTimerMetric(name, nanoTimeSupplier);
-            case "delayed": return new AfterCompletionTimerMetric(name, nanoTimeSupplier);
-            default       : throw new IllegalStateException(String.format("Unknown timer type `%s`", timerType));
-        }
+        return new ConcurrentLiveTimerMetric(name, nanoTimeSupplier);
     }
 }

logstash-core/src/test/java/org/logstash/instrument/metrics/timer/TestTimerMetricFactory.java

@@ -23,10 +23,6 @@ public TestTimerMetricFactory(final LongSupplier nanoTimeSupplier) {
         this.nanoTimeSupplier = nanoTimeSupplier;
     }
 
-    public AfterCompletionTimerMetric newAfterCompletionTimerMetric(final String name) {
-        return new AfterCompletionTimerMetric(name, this.nanoTimeSupplier);
-    }
-
     public ConcurrentLiveTimerMetric newConcurrentLiveTimerMetric(final String name) {
         return new ConcurrentLiveTimerMetric(name, this.nanoTimeSupplier);
     }