Allow events to be emitted with timestamp

api/events/src/main/java/io/opentelemetry/api/events/DefaultEventEmitter.java

@@ -17,6 +17,9 @@ static EventEmitter getInstance() {
     return INSTANCE;
   }
 
+  @Override
+  public void emit(long epochNanos, String eventName, Attributes attributes) {}
+
   @Override
   public void emit(String eventName, Attributes attributes) {}
 }

api/events/src/main/java/io/opentelemetry/api/events/EventEmitter.java

@@ -32,6 +32,17 @@
 @ThreadSafe
 public interface EventEmitter {
 
+  /**
+   * Emit an event.
+   *
+   * @param epochNanos The time at which the event happened, in epoch nanoseconds.
+   * @param eventName the event name, which acts as a classifier for events. Within a particular
+   *     event domain, event name defines a particular class or type of event.
+   * @param attributes attributes associated with the event
+   */
+  @SuppressWarnings("InconsistentOverloads")
+  void emit(long epochNanos, String eventName, Attributes attributes);
+
   /**
    * Emit an event.
    *

api/events/src/test/java/io/opentelemetry/api/events/DefaultEventEmitterTest.java

@@ -22,4 +22,11 @@ void emit() {
                     .emit("event-name", Attributes.builder().put("key1", "value1").build()))
         .doesNotThrowAnyException();
   }
+
+  @Test
+  void emitWithTimestamp() {
+    EventEmitter emitter = DefaultEventEmitter.getInstance();
+    Attributes attributes = Attributes.builder().put("key1", "value1").build();
+    assertThatCode(() -> emitter.emit(System.nanoTime(), "event-name", attributes));
+  }
 }

sdk/logs/src/main/java/io/opentelemetry/sdk/logs/internal/SdkEventEmitterProvider.java

@@ -113,9 +113,14 @@ private SdkEventEmitter(Clock clock, Logger delegateLogger, String eventDomain)
 
     @Override
     public void emit(String eventName, Attributes attributes) {
+      emit(clock.now(), eventName, attributes);
+    }
+
+    @Override
+    public void emit(long epochNanos, String eventName, Attributes attributes) {
       delegateLogger
           .logRecordBuilder()
-          .setTimestamp(clock.now(), TimeUnit.NANOSECONDS)
+          .setTimestamp(epochNanos, TimeUnit.NANOSECONDS)
           .setAllAttributes(attributes)
           .setAttribute(EVENT_DOMAIN, eventDomain)
           .setAttribute(EVENT_NAME, eventName)

sdk/logs/src/test/java/io/opentelemetry/sdk/logs/internal/SdkEventEmitterProviderTest.java

@@ -5,16 +5,19 @@
 
 package io.opentelemetry.sdk.logs.internal;
 
+import static io.opentelemetry.api.common.AttributeKey.stringKey;
 import static io.opentelemetry.sdk.testing.assertj.OpenTelemetryAssertions.assertThat;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
 import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.events.EventEmitter;
 import io.opentelemetry.sdk.common.Clock;
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
 import io.opentelemetry.sdk.logs.ReadWriteLogRecord;
 import io.opentelemetry.sdk.logs.SdkLoggerProvider;
 import io.opentelemetry.sdk.resources.Resource;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 import org.junit.jupiter.api.Test;
 
@@ -91,4 +94,24 @@ void emit_NoDomain() {
                 .put("event.name", "event-name")
                 .build());
   }
+
+  @Test
+  void emit_withTimestamp() {
+    long yesterday = System.nanoTime() - TimeUnit.DAYS.toNanos(1);
+    Attributes attributes = Attributes.of(stringKey("foo"), "bar");
+
+    EventEmitter emitter = eventEmitterProvider.eventEmitterBuilder("test-scope").build();
+
+    emitter.emit(yesterday, "testing", attributes);
+
+    assertThat(seenLog.get().toLogRecordData())
+        .hasResource(RESOURCE)
+        .hasInstrumentationScope(InstrumentationScopeInfo.create("test-scope"))
+        .hasTimestamp(yesterday)
+        .hasAttributes(
+            attributes.toBuilder()
+                .put("event.domain", "unknown")
+                .put("event.name", "testing")
+                .build());
+  }
 }