chore: add transaction.retried attribute to traces (#3148)

Adds a 'transaction.retried' attribute to Connection API read/write
transaction spans if it was retried. This makes it easier to search
for transactions that were retried.

Author: olavloite

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/ReadWriteTransaction.java

@@ -57,6 +57,7 @@
 import com.google.common.collect.Iterables;
 import com.google.common.util.concurrent.MoreExecutors;
 import com.google.spanner.v1.SpannerGrpc;
+import io.opentelemetry.api.common.AttributeKey;
 import io.opentelemetry.context.Scope;
 import java.time.Duration;
 import java.util.ArrayList;
@@ -80,6 +81,8 @@
  * exact same results as the original transaction.
  */
 class ReadWriteTransaction extends AbstractMultiUseTransaction {
+  private static final AttributeKey<Boolean> TRANSACTION_RETRIED =
+      AttributeKey.booleanKey("transaction.retried");
   private static final Logger logger = Logger.getLogger(ReadWriteTransaction.class.getName());
   private static final AtomicLong ID_GENERATOR = new AtomicLong();
   private static final String MAX_INTERNAL_RETRIES_EXCEEDED =
@@ -990,6 +993,7 @@ private void handleAborted(AbortedException aborted) {
         long delay = aborted.getRetryDelayInMillis();
         span.addEvent(
             "Transaction aborted. Backing off for " + delay + " milliseconds and retrying.");
+        span.setAttribute(TRANSACTION_RETRIED, true);
         try {
           if (delay > 0L) {
             //noinspection BusyWait

google-cloud-spanner/src/test/java/com/google/cloud/spanner/connection/OpenTelemetryTracingTest.java

@@ -447,6 +447,9 @@ public void testMultiUseReadWriteAborted() {
             .filter(span -> span.getName().equals("CloudSpannerJdbc.ReadWriteTransaction"))
             .findFirst()
             .orElseThrow(IllegalStateException::new);
+    assertEquals(
+        Boolean.TRUE,
+        transactionSpan.getAttributes().get(AttributeKey.booleanKey("transaction.retried")));
     assertEquals(1, transactionSpan.getTotalRecordedEvents());
     EventData event = transactionSpan.getEvents().get(0);
     assertEquals(