feat: (observability) trace Database.batchCreateSessions + SessionPoo…

…l.createSessions

This change adds tracing for Database.batchCreateSessions
as well as SessionPool.createSessions which was raised
as a big need.
This change is a premise to finishing up tracing Transaction.

While here, also folded in the async/await fix to avoid day+ long
code review lag and then 3+ hours just to run tests per PR:
OpenTelemetry cannot work correctly for async/await if there isn't
a set AsyncHooksManager, but we should not burden our customers with
this type of specialist knowledge, their code should just work and
this change performs such a check. Later on we shall file a feature
request with the OpenTelemetry-JS API group to give us a hook to detect
if we've got a live asyncHooksManager instead of this mandatory
comparison to ROOT_CONTEXT each time.

Fixes #2146
Updates #2079
Spun out of PR #2122
Supersedes PR #2147

observability-test/database.ts

@@ -375,6 +375,115 @@ describe('Database', () => {
     });
   });
 
+  describe('batchCreateSessions', () => {
+    it('without error', done => {
+      const ARGS = [null, [{}]];
+      database.request = (config, callback) => {
+        callback(...ARGS);
+      };
+
+      database.batchCreateSessions(10, (err, sessions) => {
+        assert.ifError(err);
+        assert.ok(sessions);
+
+        traceExporter.forceFlush();
+        const spans = traceExporter.getFinishedSpans();
+
+        const actualSpanNames: string[] = [];
+        const actualEventNames: string[] = [];
+        spans.forEach(span => {
+          actualSpanNames.push(span.name);
+          span.events.forEach(event => {
+            actualEventNames.push(event.name);
+          });
+        });
+
+        const expectedSpanNames = ['CloudSpanner.Database.batchCreateSessions'];
+        assert.deepStrictEqual(
+          actualSpanNames,
+          expectedSpanNames,
+          `span names mismatch:\n\tGot:  ${actualSpanNames}\n\tWant: ${expectedSpanNames}`
+        );
+
+        // Ensure that the span didn't encounter an error.
+        const firstSpan = spans[0];
+        assert.strictEqual(
+          SpanStatusCode.UNSET,
+          firstSpan.status.code,
+          'Unexpected span status code'
+        );
+        assert.strictEqual(
+          undefined,
+          firstSpan.status.message,
+          'Mismatched span status message'
+        );
+
+        // We don't expect events.
+        const expectedEventNames = [];
+        assert.deepStrictEqual(
+          actualEventNames,
+          expectedEventNames,
+          `Unexpected events:\n\tGot:  ${actualEventNames}\n\tWant: ${expectedEventNames}`
+        );
+
+        done();
+      });
+    });
+
+    it('with error', done => {
+      const ARGS = [new Error('batchCreateSessions.error'), null];
+      database.request = (config, callback) => {
+        callback(...ARGS);
+      };
+
+      database.batchCreateSessions(10, (err, sessions) => {
+        assert.ok(err);
+        assert.ok(!sessions);
+        traceExporter.forceFlush();
+        const spans = traceExporter.getFinishedSpans();
+
+        const actualSpanNames: string[] = [];
+        const actualEventNames: string[] = [];
+        spans.forEach(span => {
+          actualSpanNames.push(span.name);
+          span.events.forEach(event => {
+            actualEventNames.push(event.name);
+          });
+        });
+
+        const expectedSpanNames = ['CloudSpanner.Database.batchCreateSessions'];
+        assert.deepStrictEqual(
+          actualSpanNames,
+          expectedSpanNames,
+          `span names mismatch:\n\tGot:  ${actualSpanNames}\n\tWant: ${expectedSpanNames}`
+        );
+
+        // Ensure that the span actually produced an error that was recorded.
+        const firstSpan = spans[0];
+        assert.strictEqual(
+          SpanStatusCode.ERROR,
+          firstSpan.status.code,
+          'Expected an ERROR span status'
+        );
+        assert.strictEqual(
+          'batchCreateSessions.error',
+          firstSpan.status.message,
+          'Mismatched span status message'
+        );
+
+        // We don't expect events.
+        const expectedEventNames = [];
+        assert.deepStrictEqual(
+          actualEventNames,
+          expectedEventNames,
+          `Unexpected events:\n\tGot:  ${actualEventNames}\n\tWant: ${expectedEventNames}`
+        );
+
+        done();
+      });
+    });
+  });
+
   describe('getSnapshot', () => {
     let fakePool: FakeSessionPool;
     let fakeSession: FakeSession;