func TestQueryRowsScanned(t *testing.T) {
	t.Parallel()
	htraceBld := &MiniHTracedBuilder{Name: "TestQueryRowsScanned",
		WrittenSpans: common.NewSemaphore(0),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		panic(err)
	}
	defer ht.Close()
	createSpans(SIMPLE_TEST_SPANS, ht.Store)
	assertNumWrittenEquals(t, ht.Store.msink, len(SIMPLE_TEST_SPANS))
	testQueryExt(t, ht, &common.Query{
		Predicates: []common.Predicate{
			common.Predicate{
				Op:    common.EQUALS,
				Field: common.SPAN_ID,
				Val:   common.TestId("00000000000000000000000000000001").String(),
			},
		},
		Lim:  100,
		Prev: nil,
	}, []common.Span{SIMPLE_TEST_SPANS[0]},
		[]int{2, 1})
}
Example #2
0
// Test queries on the datastore.
func TestSimpleQuery(t *testing.T) {
	t.Parallel()
	htraceBld := &MiniHTracedBuilder{Name: "TestSimpleQuery",
		Cnf: map[string]string{
			conf.HTRACE_DATASTORE_HEARTBEAT_PERIOD_MS: "30000",
		},
		WrittenSpans: common.NewSemaphore(0),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		panic(err)
	}
	defer ht.Close()
	createSpans(SIMPLE_TEST_SPANS, ht.Store)

	assertNumWrittenEquals(t, ht.Store.msink, len(SIMPLE_TEST_SPANS))

	testQuery(t, ht, &common.Query{
		Predicates: []common.Predicate{
			common.Predicate{
				Op:    common.GREATER_THAN_OR_EQUALS,
				Field: common.BEGIN_TIME,
				Val:   "125",
			},
		},
		Lim: 5,
	}, []common.Span{SIMPLE_TEST_SPANS[1], SIMPLE_TEST_SPANS[2]})
}
func TestDumpAll(t *testing.T) {
	htraceBld := &MiniHTracedBuilder{Name: "TestDumpAll",
		DataDirs:     make([]string, 2),
		WrittenSpans: common.NewSemaphore(0),
		Cnf: map[string]string{
			conf.HTRACE_LOG_LEVEL: "INFO",
		},
	}
	ht, err := htraceBld.Build()
	if err != nil {
		t.Fatalf("failed to create datastore: %s", err.Error())
	}
	defer ht.Close()
	var hcl *htrace.Client
	hcl, err = htrace.NewClient(ht.ClientConf(), nil)
	if err != nil {
		t.Fatalf("failed to create client: %s", err.Error())
	}
	defer hcl.Close()

	NUM_TEST_SPANS := 100
	allSpans := createRandomTestSpans(NUM_TEST_SPANS)
	sort.Sort(allSpans)
	err = hcl.WriteSpans(allSpans)
	if err != nil {
		t.Fatalf("WriteSpans failed: %s\n", err.Error())
	}
	ht.Store.WrittenSpans.Waits(int64(NUM_TEST_SPANS))
	out := make(chan *common.Span, NUM_TEST_SPANS)
	var dumpErr error
	go func() {
		dumpErr = hcl.DumpAll(3, out)
	}()
	var numSpans int
	nextLogTime := time.Now().Add(time.Millisecond * 5)
	for {
		span, channelOpen := <-out
		if !channelOpen {
			break
		}
		common.ExpectSpansEqual(t, allSpans[numSpans], span)
		numSpans++
		if testing.Verbose() {
			now := time.Now()
			if !now.Before(nextLogTime) {
				nextLogTime = now
				nextLogTime = nextLogTime.Add(time.Millisecond * 5)
				fmt.Printf("read back %d span(s)...\n", numSpans)
			}
		}
	}
	if numSpans != len(allSpans) {
		t.Fatalf("expected to read %d spans... but only read %d\n",
			len(allSpans), numSpans)
	}
	if dumpErr != nil {
		t.Fatalf("got dump error %s\n", dumpErr.Error())
	}
}
func TestReapingOldSpans(t *testing.T) {
	const NUM_TEST_SPANS = 20
	testSpans := make([]*common.Span, NUM_TEST_SPANS)
	rnd := rand.New(rand.NewSource(2))
	now := common.TimeToUnixMs(time.Now().UTC())
	for i := range testSpans {
		testSpans[i] = test.NewRandomSpan(rnd, testSpans[0:i])
		testSpans[i].Begin = now - int64(NUM_TEST_SPANS-1-i)
		testSpans[i].Description = fmt.Sprintf("Span%02d", i)
	}
	htraceBld := &MiniHTracedBuilder{Name: "TestReapingOldSpans",
		Cnf: map[string]string{
			conf.HTRACE_SPAN_EXPIRY_MS:                fmt.Sprintf("%d", 60*60*1000),
			conf.HTRACE_REAPER_HEARTBEAT_PERIOD_MS:    "1",
			conf.HTRACE_DATASTORE_HEARTBEAT_PERIOD_MS: "1",
		},
		WrittenSpans: common.NewSemaphore(0),
		DataDirs:     make([]string, 2),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		t.Fatalf("failed to create mini htraced cluster: %s\n", err.Error())
	}
	ing := ht.Store.NewSpanIngestor(ht.Store.lg, "127.0.0.1", "")
	for spanIdx := range testSpans {
		ing.IngestSpan(testSpans[spanIdx])
	}
	ing.Close(time.Now())
	// Wait the spans to be created
	ht.Store.WrittenSpans.Waits(NUM_TEST_SPANS)
	// Set a reaper date that will remove all the spans except final one.
	ht.Store.rpr.SetReaperDate(now)

	common.WaitFor(5*time.Minute, time.Millisecond, func() bool {
		for i := 0; i < NUM_TEST_SPANS-1; i++ {
			span := ht.Store.FindSpan(testSpans[i].Id)
			if span != nil {
				ht.Store.lg.Debugf("Waiting for %s to be removed...\n",
					testSpans[i].Description)
				return false
			}
		}
		span := ht.Store.FindSpan(testSpans[NUM_TEST_SPANS-1].Id)
		if span == nil {
			ht.Store.lg.Debugf("Did not expect %s to be removed\n",
				testSpans[NUM_TEST_SPANS-1].Description)
			return false
		}
		return true
	})
	defer ht.Close()
}
// Tests that HRPC limits the number of simultaneous connections being processed.
func TestHrpcAdmissionsControl(t *testing.T) {
	var wg sync.WaitGroup
	wg.Add(TEST_NUM_WRITESPANS)
	var numConcurrentHrpcCalls int32
	testHooks := &hrpcTestHooks{
		HandleAdmission: func() {
			defer wg.Done()
			n := atomic.AddInt32(&numConcurrentHrpcCalls, 1)
			if n > TEST_NUM_HRPC_HANDLERS {
				t.Fatalf("The number of concurrent HRPC calls went above "+
					"%d: it's at %d\n", TEST_NUM_HRPC_HANDLERS, n)
			}
			time.Sleep(1 * time.Millisecond)
			n = atomic.AddInt32(&numConcurrentHrpcCalls, -1)
			if n >= TEST_NUM_HRPC_HANDLERS {
				t.Fatalf("The number of concurrent HRPC calls went above "+
					"%d: it was at %d\n", TEST_NUM_HRPC_HANDLERS, n+1)
			}
		},
	}
	htraceBld := &MiniHTracedBuilder{Name: "TestHrpcAdmissionsControl",
		DataDirs: make([]string, 2),
		Cnf: map[string]string{
			conf.HTRACE_NUM_HRPC_HANDLERS: fmt.Sprintf("%d", TEST_NUM_HRPC_HANDLERS),
		},
		WrittenSpans:  common.NewSemaphore(0),
		HrpcTestHooks: testHooks,
	}
	ht, err := htraceBld.Build()
	if err != nil {
		t.Fatalf("failed to create datastore: %s", err.Error())
	}
	defer ht.Close()
	var hcl *htrace.Client
	hcl, err = htrace.NewClient(ht.ClientConf(), nil)
	if err != nil {
		t.Fatalf("failed to create client: %s", err.Error())
	}
	// Create some random trace spans.
	allSpans := createRandomTestSpans(TEST_NUM_WRITESPANS)
	for iter := 0; iter < TEST_NUM_WRITESPANS; iter++ {
		go func(i int) {
			err = hcl.WriteSpans(allSpans[i : i+1])
			if err != nil {
				t.Fatalf("WriteSpans failed: %s\n", err.Error())
			}
		}(iter)
	}
	wg.Wait()
	ht.Store.WrittenSpans.Waits(int64(TEST_NUM_WRITESPANS))
}
Example #6
0
func TestQueries5(t *testing.T) {
	t.Parallel()
	htraceBld := &MiniHTracedBuilder{Name: "TestQueries5",
		WrittenSpans: common.NewSemaphore(0),
		DataDirs:     make([]string, 1),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		panic(err)
	}
	defer ht.Close()
	createSpans(TEST_QUERIES5_SPANS, ht.Store)

	testQuery(t, ht, &common.Query{
		Predicates: []common.Predicate{
			common.Predicate{
				Op:    common.GREATER_THAN,
				Field: common.BEGIN_TIME,
				Val:   "123",
			},
		},
		Lim: 5,
	}, []common.Span{TEST_QUERIES5_SPANS[2]})
	testQuery(t, ht, &common.Query{
		Predicates: []common.Predicate{
			common.Predicate{
				Op:    common.GREATER_THAN,
				Field: common.END_TIME,
				Val:   "200",
			},
		},
		Lim: 500,
	}, []common.Span{TEST_QUERIES5_SPANS[0], TEST_QUERIES5_SPANS[2]})

	testQuery(t, ht, &common.Query{
		Predicates: []common.Predicate{
			common.Predicate{
				Op:    common.LESS_THAN_OR_EQUALS,
				Field: common.END_TIME,
				Val:   "999",
			},
		},
		Lim: 500,
	}, []common.Span{TEST_QUERIES5_SPANS[2],
		TEST_QUERIES5_SPANS[0],
		TEST_QUERIES5_SPANS[1],
	})
}
Example #7
0
// Test creating a datastore and adding some spans.
func TestDatastoreWriteAndRead(t *testing.T) {
	t.Parallel()
	htraceBld := &MiniHTracedBuilder{Name: "TestDatastoreWriteAndRead",
		Cnf: map[string]string{
			conf.HTRACE_DATASTORE_HEARTBEAT_PERIOD_MS: "30000",
		},
		WrittenSpans: common.NewSemaphore(0),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		panic(err)
	}
	defer ht.Close()
	createSpans(SIMPLE_TEST_SPANS, ht.Store)

	span := ht.Store.FindSpan(common.TestId("00000000000000000000000000000001"))
	if span == nil {
		t.Fatal()
	}
	if !span.Id.Equal(common.TestId("00000000000000000000000000000001")) {
		t.Fatal()
	}
	common.ExpectSpansEqual(t, &SIMPLE_TEST_SPANS[0], span)
	children := ht.Store.FindChildren(common.TestId("00000000000000000000000000000001"), 1)
	if len(children) != 1 {
		t.Fatalf("expected 1 child, but got %d\n", len(children))
	}
	children = ht.Store.FindChildren(common.TestId("00000000000000000000000000000001"), 2)
	if len(children) != 2 {
		t.Fatalf("expected 2 children, but got %d\n", len(children))
	}
	sort.Sort(common.SpanIdSlice(children))
	if !children[0].Equal(common.TestId("00000000000000000000000000000002")) {
		t.Fatal()
	}
	if !children[1].Equal(common.TestId("00000000000000000000000000000003")) {
		t.Fatal()
	}
}
Example #8
0
func BenchmarkDatastoreWrites(b *testing.B) {
	htraceBld := &MiniHTracedBuilder{Name: "BenchmarkDatastoreWrites",
		Cnf: map[string]string{
			conf.HTRACE_DATASTORE_HEARTBEAT_PERIOD_MS: "30000",
			conf.HTRACE_LOG_LEVEL:                     "INFO",
		},
		WrittenSpans: common.NewSemaphore(0),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		b.Fatalf("Error creating MiniHTraced: %s\n", err.Error())
	}
	ht.Store.lg.Infof("BenchmarkDatastoreWrites: b.N = %d\n", b.N)
	defer func() {
		if r := recover(); r != nil {
			ht.Store.lg.Infof("panic: %s\n", r.(error))
		}
		ht.Close()
	}()
	rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
	allSpans := make([]*common.Span, b.N)
	for n := range allSpans {
		allSpans[n] = test.NewRandomSpan(rnd, allSpans[0:n])
	}

	// Reset the timer to avoid including the time required to create new
	// random spans in the benchmark total.
	b.ResetTimer()

	// Write many random spans.
	ing := ht.Store.NewSpanIngestor(ht.Store.lg, "127.0.0.1", "")
	for n := 0; n < b.N; n++ {
		ing.IngestSpan(allSpans[n])
	}
	ing.Close(time.Now())
	// Wait for all the spans to be written.
	ht.Store.WrittenSpans.Waits(int64(b.N))
	assertNumWrittenEquals(b, ht.Store.msink, b.N)
}
Example #9
0
func TestQueriesWithContinuationTokens1(t *testing.T) {
	t.Parallel()
	htraceBld := &MiniHTracedBuilder{Name: "TestQueriesWithContinuationTokens1",
		Cnf: map[string]string{
			conf.HTRACE_DATASTORE_HEARTBEAT_PERIOD_MS: "30000",
		},
		WrittenSpans: common.NewSemaphore(0),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		panic(err)
	}
	defer ht.Close()
	createSpans(SIMPLE_TEST_SPANS, ht.Store)
	assertNumWrittenEquals(t, ht.Store.msink, len(SIMPLE_TEST_SPANS))
	// Adding a prev value to this query excludes the first result that we
	// would normally get.
	testQuery(t, ht, &common.Query{
		Predicates: []common.Predicate{
			common.Predicate{
				Op:    common.GREATER_THAN,
				Field: common.BEGIN_TIME,
				Val:   "120",
			},
		},
		Lim:  5,
		Prev: &SIMPLE_TEST_SPANS[0],
	}, []common.Span{SIMPLE_TEST_SPANS[1], SIMPLE_TEST_SPANS[2]})

	// There is only one result from an EQUALS query on SPAN_ID.
	testQuery(t, ht, &common.Query{
		Predicates: []common.Predicate{
			common.Predicate{
				Op:    common.EQUALS,
				Field: common.SPAN_ID,
				Val:   common.TestId("00000000000000000000000000000001").String(),
			},
		},
		Lim:  100,
		Prev: &SIMPLE_TEST_SPANS[0],
	}, []common.Span{})

	// When doing a LESS_THAN_OR_EQUALS search, we still don't get back the
	// span we pass as a continuation token. (Primary index edition).
	testQuery(t, ht, &common.Query{
		Predicates: []common.Predicate{
			common.Predicate{
				Op:    common.LESS_THAN_OR_EQUALS,
				Field: common.SPAN_ID,
				Val:   common.TestId("00000000000000000000000000000002").String(),
			},
		},
		Lim:  100,
		Prev: &SIMPLE_TEST_SPANS[1],
	}, []common.Span{SIMPLE_TEST_SPANS[0]})

	// When doing a GREATER_THAN_OR_EQUALS search, we still don't get back the
	// span we pass as a continuation token. (Secondary index edition).
	testQuery(t, ht, &common.Query{
		Predicates: []common.Predicate{
			common.Predicate{
				Op:    common.GREATER_THAN,
				Field: common.DURATION,
				Val:   "0",
			},
		},
		Lim:  100,
		Prev: &SIMPLE_TEST_SPANS[1],
	}, []common.Span{SIMPLE_TEST_SPANS[2], SIMPLE_TEST_SPANS[0]})
}
Example #10
0
func TestReloadDataStore(t *testing.T) {
	htraceBld := &MiniHTracedBuilder{Name: "TestReloadDataStore",
		Cnf: map[string]string{
			conf.HTRACE_DATASTORE_HEARTBEAT_PERIOD_MS: "30000",
		},
		DataDirs:            make([]string, 2),
		KeepDataDirsOnClose: true,
		WrittenSpans:        common.NewSemaphore(0),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		t.Fatalf("failed to create datastore: %s", err.Error())
	}
	dataDirs := make([]string, len(ht.DataDirs))
	copy(dataDirs, ht.DataDirs)
	defer func() {
		if ht != nil {
			ht.Close()
		}
		for i := range dataDirs {
			os.RemoveAll(dataDirs[i])
		}
	}()
	var hcl *htrace.Client
	hcl, err = htrace.NewClient(ht.ClientConf(), nil)
	if err != nil {
		t.Fatalf("failed to create client: %s", err.Error())
	}
	hcnf := ht.Cnf.Clone()

	// Create some random trace spans.
	NUM_TEST_SPANS := 5
	allSpans := createRandomTestSpans(NUM_TEST_SPANS)
	err = hcl.WriteSpans(allSpans)
	if err != nil {
		t.Fatalf("WriteSpans failed: %s\n", err.Error())
	}
	ht.Store.WrittenSpans.Waits(int64(NUM_TEST_SPANS))

	// Look up the spans we wrote.
	var span *common.Span
	for i := 0; i < NUM_TEST_SPANS; i++ {
		span, err = hcl.FindSpan(allSpans[i].Id)
		if err != nil {
			t.Fatalf("FindSpan(%d) failed: %s\n", i, err.Error())
		}
		common.ExpectSpansEqual(t, allSpans[i], span)
	}
	hcl.Close()
	ht.Close()
	ht = nil

	// Verify that we can reload the datastore, even if we configure the data
	// directories in a different order.
	verifySuccessfulLoad(t, allSpans, []string{dataDirs[1], dataDirs[0]})

	// If we try to reload the datastore with only one directory, it won't work
	// (we need both).
	verifyFailedLoad(t, []string{dataDirs[1]},
		"The TotalShards field of all shards is 2, but we have 1 shards.")

	// Test that we give an intelligent error message when 0 directories are
	// configured.
	verifyFailedLoad(t, []string{}, "No shard directories found.")

	// Can't specify the same directory more than once... will get "lock
	// already held by process"
	verifyFailedLoad(t, []string{dataDirs[0], dataDirs[1], dataDirs[1]},
		" already held by process.")

	// Open the datastore and modify it to have the wrong DaemonId
	dld := NewDataStoreLoader(hcnf)
	defer func() {
		if dld != nil {
			dld.Close()
			dld = nil
		}
	}()
	dld.LoadShards()
	sinfo, err := dld.shards[0].readShardInfo()
	if err != nil {
		t.Fatalf("error reading shard info for shard %s: %s\n",
			dld.shards[0].path, err.Error())
	}
	newDaemonId := sinfo.DaemonId + 1
	dld.lg.Infof("Read %s from shard %s.  Changing daemonId to 0x%016x\n.",
		asJson(sinfo), dld.shards[0].path, newDaemonId)
	sinfo.DaemonId = newDaemonId
	err = dld.shards[0].writeShardInfo(sinfo)
	if err != nil {
		t.Fatalf("error writing shard info for shard %s: %s\n",
			dld.shards[0].path, err.Error())
	}
	dld.Close()
	dld = nil
	verifyFailedLoad(t, dataDirs, "DaemonId mismatch.")

	// Open the datastore and modify it to have the wrong TotalShards
	dld = NewDataStoreLoader(hcnf)
	dld.LoadShards()
	sinfo, err = dld.shards[0].readShardInfo()
	if err != nil {
		t.Fatalf("error reading shard info for shard %s: %s\n",
			dld.shards[0].path, err.Error())
	}
	newDaemonId = sinfo.DaemonId - 1
	dld.lg.Infof("Read %s from shard %s.  Changing daemonId to 0x%016x, "+
		"TotalShards to 3\n.",
		asJson(sinfo), dld.shards[0].path, newDaemonId)
	sinfo.DaemonId = newDaemonId
	sinfo.TotalShards = 3
	err = dld.shards[0].writeShardInfo(sinfo)
	if err != nil {
		t.Fatalf("error writing shard info for shard %s: %s\n",
			dld.shards[0].path, err.Error())
	}
	dld.Close()
	dld = nil
	verifyFailedLoad(t, dataDirs, "TotalShards mismatch.")

	// Open the datastore and modify it to have the wrong LayoutVersion
	dld = NewDataStoreLoader(hcnf)
	dld.LoadShards()
	for shardIdx := range dld.shards {
		sinfo, err = dld.shards[shardIdx].readShardInfo()
		if err != nil {
			t.Fatalf("error reading shard info for shard %s: %s\n",
				dld.shards[shardIdx].path, err.Error())
		}
		dld.lg.Infof("Read %s from shard %s.  Changing TotalShards to 2, "+
			"LayoutVersion to 2\n", asJson(sinfo), dld.shards[shardIdx].path)
		sinfo.TotalShards = 2
		sinfo.LayoutVersion = 2
		err = dld.shards[shardIdx].writeShardInfo(sinfo)
		if err != nil {
			t.Fatalf("error writing shard info for shard %s: %s\n",
				dld.shards[0].path, err.Error())
		}
	}
	dld.Close()
	dld = nil
	verifyFailedLoad(t, dataDirs, "The layout version of all shards is 2, "+
		"but we only support")

	// It should work with data.store.clear set.
	htraceBld = &MiniHTracedBuilder{
		Name:                "TestReloadDataStore#clear",
		DataDirs:            dataDirs,
		KeepDataDirsOnClose: true,
		Cnf:                 map[string]string{conf.HTRACE_DATA_STORE_CLEAR: "true"},
	}
	ht, err = htraceBld.Build()
	if err != nil {
		t.Fatalf("failed to create datastore: %s", err.Error())
	}
}
func TestClientOperations(t *testing.T) {
	htraceBld := &MiniHTracedBuilder{Name: "TestClientOperations",
		DataDirs:     make([]string, 2),
		WrittenSpans: common.NewSemaphore(0),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		t.Fatalf("failed to create datastore: %s", err.Error())
	}
	defer ht.Close()
	var hcl *htrace.Client
	hcl, err = htrace.NewClient(ht.ClientConf(), nil)
	if err != nil {
		t.Fatalf("failed to create client: %s", err.Error())
	}
	defer hcl.Close()

	// Create some random trace spans.
	NUM_TEST_SPANS := 30
	allSpans := createRandomTestSpans(NUM_TEST_SPANS)

	// Write half of the spans to htraced via the client.
	err = hcl.WriteSpans(allSpans[0 : NUM_TEST_SPANS/2])
	if err != nil {
		t.Fatalf("WriteSpans(0:%d) failed: %s\n", NUM_TEST_SPANS/2,
			err.Error())
	}
	ht.Store.WrittenSpans.Waits(int64(NUM_TEST_SPANS / 2))

	// Look up the first half of the spans.  They should be found.
	var span *common.Span
	for i := 0; i < NUM_TEST_SPANS/2; i++ {
		span, err = hcl.FindSpan(allSpans[i].Id)
		if err != nil {
			t.Fatalf("FindSpan(%d) failed: %s\n", i, err.Error())
		}
		common.ExpectSpansEqual(t, allSpans[i], span)
	}

	// Look up the second half of the spans.  They should not be found.
	for i := NUM_TEST_SPANS / 2; i < NUM_TEST_SPANS; i++ {
		span, err = hcl.FindSpan(allSpans[i].Id)
		if err != nil {
			t.Fatalf("FindSpan(%d) failed: %s\n", i, err.Error())
		}
		if span != nil {
			t.Fatalf("Unexpectedly found a span we never write to "+
				"the server: FindSpan(%d) succeeded\n", i)
		}
	}

	// Test FindChildren
	childSpan := allSpans[1]
	parentId := childSpan.Parents[0]
	var children []common.SpanId
	children, err = hcl.FindChildren(parentId, 1)
	if err != nil {
		t.Fatalf("FindChildren(%s) failed: %s\n", parentId, err.Error())
	}
	if len(children) != 1 {
		t.Fatalf("FindChildren(%s) returned an invalid number of "+
			"children: expected %d, got %d\n", parentId, 1, len(children))
	}
	if !children[0].Equal(childSpan.Id) {
		t.Fatalf("FindChildren(%s) returned an invalid child id: expected %s, "+
			" got %s\n", parentId, childSpan.Id, children[0])
	}

	// Test FindChildren on a span that has no children
	childlessSpan := allSpans[NUM_TEST_SPANS/2]
	children, err = hcl.FindChildren(childlessSpan.Id, 10)
	if err != nil {
		t.Fatalf("FindChildren(%d) failed: %s\n", childlessSpan.Id, err.Error())
	}
	if len(children) != 0 {
		t.Fatalf("FindChildren(%d) returned an invalid number of "+
			"children: expected %d, got %d\n", childlessSpan.Id, 0, len(children))
	}

	// Test Query
	var query common.Query
	query = common.Query{Lim: 10}
	spans, err := hcl.Query(&query)
	if err != nil {
		t.Fatalf("Query({lim: %d}) failed: %s\n", 10, err.Error())
	}
	if len(spans) != 10 {
		t.Fatalf("Query({lim: %d}) returned an invalid number of "+
			"children: expected %d, got %d\n", 10, 10, len(spans))
	}
}
func doWriteSpans(name string, N int, maxSpansPerRpc uint32, b *testing.B) {
	htraceBld := &MiniHTracedBuilder{Name: "doWriteSpans",
		Cnf: map[string]string{
			conf.HTRACE_LOG_LEVEL:         "INFO",
			conf.HTRACE_NUM_HRPC_HANDLERS: "20",
		},
		WrittenSpans: common.NewSemaphore(int64(1 - N)),
	}
	ht, err := htraceBld.Build()
	if err != nil {
		panic(err)
	}
	defer ht.Close()
	rnd := rand.New(rand.NewSource(1))
	allSpans := make([]*common.Span, N)
	for n := 0; n < N; n++ {
		allSpans[n] = test.NewRandomSpan(rnd, allSpans[0:n])
	}
	// Determine how many calls to WriteSpans we should make.  Each writeSpans
	// message should be small enough so that it doesn't exceed the max RPC
	// body length limit.  TODO: a production-quality golang client would do
	// this internally rather than needing us to do it here in the unit test.
	bodyLen := (4 * common.MAX_HRPC_BODY_LENGTH) / 5
	reqs := make([][]*common.Span, 0, 4)
	curReq := -1
	curReqLen := bodyLen
	var curReqSpans uint32
	mh := new(codec.MsgpackHandle)
	mh.WriteExt = true
	var mbuf [8192]byte
	buf := mbuf[:0]
	enc := codec.NewEncoderBytes(&buf, mh)
	for n := 0; n < N; n++ {
		span := allSpans[n]
		if (curReqSpans >= maxSpansPerRpc) ||
			(curReqLen >= bodyLen) {
			reqs = append(reqs, make([]*common.Span, 0, 16))
			curReqLen = 0
			curReq++
			curReqSpans = 0
		}
		buf = mbuf[:0]
		enc.ResetBytes(&buf)
		err := enc.Encode(span)
		if err != nil {
			panic(fmt.Sprintf("Error encoding span %s: %s\n",
				span.String(), err.Error()))
		}
		bufLen := len(buf)
		if bufLen > (bodyLen / 5) {
			panic(fmt.Sprintf("Span too long at %d bytes\n", bufLen))
		}
		curReqLen += bufLen
		reqs[curReq] = append(reqs[curReq], span)
		curReqSpans++
	}
	ht.Store.lg.Infof("num spans: %d.  num WriteSpansReq calls: %d\n", N, len(reqs))
	var hcl *htrace.Client
	hcl, err = htrace.NewClient(ht.ClientConf(), nil)
	if err != nil {
		panic(fmt.Sprintf("failed to create client: %s", err.Error()))
	}
	defer hcl.Close()

	// Reset the timer to avoid including the time required to create new
	// random spans in the benchmark total.
	if b != nil {
		b.ResetTimer()
	}

	// Write many random spans.
	for reqIdx := range reqs {
		go func(i int) {
			err = hcl.WriteSpans(reqs[i])
			if err != nil {
				panic(fmt.Sprintf("failed to send WriteSpans request %d: %s",
					i, err.Error()))
			}
		}(reqIdx)
	}
	// Wait for all the spans to be written.
	ht.Store.WrittenSpans.Wait()
}