Remove Java9VersionSpecific clock implementation (#7221)

Author: jack-berg

sdk/all/src/test/java/io/opentelemetry/sdk/common/SystemClockTest.java

@@ -9,26 +9,21 @@
 
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.DisabledOnJre;
-import org.junit.jupiter.api.condition.EnabledOnJre;
 import org.junit.jupiter.api.condition.JRE;
 
-// This test is placed in the all artifact instead of the common one so it uses the dependency jar
-// instead of the classes directly, which allows verifying mrjar behavior.
 class SystemClockTest {
 
-  @EnabledOnJre(JRE.JAVA_8)
   @Test
-  void now_millisPrecision() {
-    // If we test many times, we can be fairly sure we didn't just get lucky with having a rounded
-    // result on a higher than expected precision timestamp.
-    for (int i = 0; i < 100; i++) {
-      long now = SystemClock.getInstance().now();
-      assertThat(now % 1000000).isZero();
-    }
+  void now() {
+    assertThat(SystemClock.getInstance().now()).isNotZero();
+    assertThat(SystemClock.getInstance().now(true)).isNotZero();
+    assertThat(SystemClock.getInstance().now(false)).isNotZero();
   }
 
-  @DisabledOnJre(JRE.JAVA_8)
   @Test
+  // On java 8, the APIs used to produce micro precision are available but still only produce millis
+  // precision
+  @DisabledOnJre(JRE.JAVA_8)
   void now_microsPrecision() {
     // If we test many times, we can be fairly sure we get at least one timestamp that isn't
     // coincidentally rounded to millis precision.
@@ -52,8 +47,10 @@ void now_lowPrecision() {
     }
   }
 
-  @DisabledOnJre(JRE.JAVA_8)
   @Test
+  // On java 8, the APIs used to produce micro precision are available but still only produce millis
+  // precision
+  @DisabledOnJre(JRE.JAVA_8)
   void now_highPrecision() {
     // If we test many times, we can be fairly sure we get at least one timestamp that isn't
     // coincidentally rounded to millis precision.

sdk/common/build.gradle.kts

@@ -10,8 +10,6 @@ apply<OtelVersionClassPlugin>()
 description = "OpenTelemetry SDK Common"
 otelJava.moduleName.set("io.opentelemetry.sdk.common")
 
-val mrJarVersions = listOf(9)
-
 dependencies {
   api(project(":api:all"))
 
@@ -23,61 +21,9 @@ dependencies {
   testImplementation("com.google.guava:guava-testlib")
 }
 
-for (version in mrJarVersions) {
-  sourceSets {
-    create("java$version") {
-      java {
-        setSrcDirs(listOf("src/main/java$version"))
-      }
-    }
-  }
-
-  tasks {
-    named<JavaCompile>("compileJava${version}Java") {
-      sourceCompatibility = "$version"
-      targetCompatibility = "$version"
-      options.release.set(version)
-    }
-  }
-
-  configurations {
-    named("java${version}Implementation") {
-      extendsFrom(configurations["implementation"])
-    }
-  }
-
-  dependencies {
-    // Common to reference classes in main sourceset from Java 9 one (e.g., to return a common interface)
-    add("java${version}Implementation", files(sourceSets.main.get().output.classesDirs))
-  }
-}
-
 tasks {
-  withType(Jar::class) {
-    val sourcePathProvider = if (name.equals("jar")) {
-      { ss: SourceSet? -> ss?.output }
-    } else if (name.equals("sourcesJar")) {
-      { ss: SourceSet? -> ss?.java }
-    } else {
-      { _: SourceSet -> project.objects.fileCollection() }
-    }
-
-    for (version in mrJarVersions) {
-      into("META-INF/versions/$version") {
-        from(sourcePathProvider(sourceSets["java$version"]))
-      }
-    }
-    manifest.attributes(
-      "Multi-Release" to "true",
-    )
-  }
-
   test {
     // For checking version number included in Resource.
     systemProperty("otel.test.project-version", project.version.toString())
   }
-
-  check {
-    dependsOn(testing.suites)
-  }
 }

sdk/common/src/main/java/io/opentelemetry/sdk/common/SystemClock.java

@@ -5,13 +5,13 @@
 
 package io.opentelemetry.sdk.common;
 
-import io.opentelemetry.sdk.internal.JavaVersionSpecific;
+import java.time.Instant;
 import java.util.concurrent.TimeUnit;
 import javax.annotation.concurrent.ThreadSafe;
 
 /**
- * A {@link Clock} that uses {@link JavaVersionSpecific#currentTimeNanos()} and {@link
- * System#nanoTime()}.
+ * A {@link Clock} that uses {@link java.time.Clock#systemUTC()}, {@link
+ * System#currentTimeMillis()}, and {@link System#nanoTime()}.
  */
 @ThreadSafe
 final class SystemClock implements Clock {
@@ -33,7 +33,8 @@ public long now() {
   @Override
   public long now(boolean highPrecision) {
     if (highPrecision) {
-      return JavaVersionSpecific.get().currentTimeNanos();
+      Instant now = java.time.Clock.systemUTC().instant();
+      return TimeUnit.SECONDS.toNanos(now.getEpochSecond()) + now.getNano();
     }
     return TimeUnit.MILLISECONDS.toNanos(System.currentTimeMillis());
   }