chore(x-goog-spanner-request-id): plumb for BatchCreateSessions

This change plumbs x-goog-spanner-request-id into BatchCreateSessions
and asserts that the header is present for that method.

Updates #3537

Author: odeke-em

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SessionClient.java

@@ -206,6 +206,8 @@ interface SessionConsumer {
     this.executorFactory = executorFactory;
     this.executor = executorFactory.get();
     this.commonAttributes = spanner.getTracer().createCommonAttributes(db);
+    this.nthId = SessionClient.NTH_ID.incrementAndGet();
+    this.nthRequest = new AtomicInteger(0);
   }
 
   @Override
@@ -239,6 +241,7 @@ SessionImpl createSession() {
     XGoogSpannerRequestId reqId = nextRequestId(channelId, 1);
     ISpan span = spanner.getTracer().spanBuilder(SpannerImpl.CREATE_SESSION, this.commonAttributes);
     try (IScope s = spanner.getTracer().withSpan(span)) {
+      XGoogSpannerRequestId reqId = this.nextRequestId(channelId, 1);
       com.google.spanner.v1.Session session =
           spanner
               .getRpc()

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SessionImpl.java

@@ -305,6 +305,8 @@ public CommitResponse writeAtLeastOnceWithOptions(
     try (IScope s = tracer.withSpan(span)) {
       return SpannerRetryHelper.runTxWithRetriesOnAborted(
           () -> {
+            // TODO: Detect an abort and then refresh the reqId.
+            reqId.incrementAttempt();
             return new CommitResponse(
                 spanner.getRpc().commit(request, reqId.withOptions(getOptions())));
           });

google-cloud-spanner/src/main/java/com/google/cloud/spanner/XGoogSpannerRequestId.java

@@ -159,4 +159,26 @@ public XGoogSpannerRequestId nextRequestId(long channelId, int attempt) {
       return XGoogSpannerRequestId.of(1, 1, 1, 0);
     }
   }
+
+  public static void assertMonotonicityOfIds(String prefix, List<XGoogSpannerRequestId> reqIds) {
+    int size = reqIds.size();
+
+    List<String> violations = new ArrayList<>();
+    for (int i = 1; i < size; i++) {
+      XGoogSpannerRequestId prev = reqIds.get(i - 1);
+      XGoogSpannerRequestId curr = reqIds.get(i);
+      if (prev.isGreaterThan(curr)) {
+        violations.add(String.format("#%d(%s) > #%d(%s)", i - 1, prev, i, curr));
+      }
+    }
+
+    if (violations.size() == 0) {
+      return;
+    }
+
+    throw new IllegalStateException(
+        prefix
+            + " monotonicity violation:"
+            + String.join("\n\t", violations.toArray(new String[0])));
+  }
 }