Fix Example() function in TSDB (#10153)

* Fix Example() function in TSDB

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>

* Fix tests

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>

tsdb/chunks/chunk_write_queue.go

@@ -163,3 +163,22 @@ func (c *chunkWriteQueue) stop() {
 
 	c.workerWg.Wait()
 }
+
+func (c *chunkWriteQueue) queueIsEmpty() bool {
+	return c.queueSize() == 0
+}
+
+func (c *chunkWriteQueue) queueIsFull() bool {
+	// When the queue is full and blocked on the writer the chunkRefMap has one more job than the cap of the jobCh
+	// because one job is currently being processed and blocked in the writer.
+	return c.queueSize() == cap(c.jobs)+1
+}
+
+func (c *chunkWriteQueue) queueSize() int {
+	c.chunkRefMapMtx.Lock()
+	defer c.chunkRefMapMtx.Unlock()
+
+	// Looking at chunkRefMap instead of jobCh because the job is popped from the chan before it has
+	// been fully processed, it remains in the chunkRefMap until the processing is complete.
+	return len(c.chunkRefMap)
+}

tsdb/chunks/chunk_write_queue_test.go

@@ -146,7 +146,7 @@ func TestChunkWriteQueue_WrappingAroundSizeLimit(t *testing.T) {
 	}
 
 	// The queue should be full.
-	require.True(t, queueIsFull(q))
+	require.True(t, q.queueIsFull())
 
 	// Adding another job should block as long as no job from the queue gets consumed.
 	addedJob := atomic.NewBool(false)
@@ -166,19 +166,19 @@ func TestChunkWriteQueue_WrappingAroundSizeLimit(t *testing.T) {
 	require.Eventually(t, func() bool { return addedJob.Load() }, time.Second, time.Millisecond*10)
 
 	// The queue should be full again.
-	require.True(t, queueIsFull(q))
+	require.True(t, q.queueIsFull())
 
 	// Consume <sizeLimit>+1 jobs from the queue.
 	// To drain the queue we need to consume <sizeLimit>+1 jobs because 1 job
 	// is already in the state of being processed.
 	for job := 0; job < sizeLimit+1; job++ {
-		require.False(t, queueIsEmpty(q))
+		require.False(t, q.queueIsEmpty())
 		unblockChunkWriter()
 	}
 
 	// Wait until all jobs have been processed.
 	callbackWg.Wait()
-	require.True(t, queueIsEmpty(q))
+	require.True(t, q.queueIsEmpty())
 }
 
 func TestChunkWriteQueue_HandlerErrorViaCallback(t *testing.T) {
@@ -266,22 +266,3 @@ func BenchmarkChunkWriteQueue_addJob(b *testing.B) {
 		})
 	}
 }
-
-func queueIsEmpty(q *chunkWriteQueue) bool {
-	return queueSize(q) == 0
-}
-
-func queueIsFull(q *chunkWriteQueue) bool {
-	// When the queue is full and blocked on the writer the chunkRefMap has one more job than the cap of the jobCh
-	// because one job is currently being processed and blocked in the writer.
-	return queueSize(q) == cap(q.jobs)+1
-}
-
-func queueSize(q *chunkWriteQueue) int {
-	q.chunkRefMapMtx.Lock()
-	defer q.chunkRefMapMtx.Unlock()
-
-	// Looking at chunkRefMap instead of jobCh because the job is popped from the chan before it has
-	// been fully processed, it remains in the chunkRefMap until the processing is complete.
-	return len(q.chunkRefMap)
-}

tsdb/chunks/head_chunks.go

@@ -473,6 +473,10 @@ func (cdm *ChunkDiskMapper) CutNewFile() {
 	cdm.evtlPos.cutFileOnNextChunk()
 }
 
+func (cdm *ChunkDiskMapper) IsQueueEmpty() bool {
+	return cdm.writeQueue.queueIsEmpty()
+}
+
 // cutAndExpectRef creates a new m-mapped file.
 // The write lock should be held before calling this.
 // It ensures that the position in the new file matches the given chunk reference, if not then it errors.

tsdb/db_test.go

@@ -1461,6 +1461,10 @@ func TestSizeRetention(t *testing.T) {
 	}
 	require.NoError(t, headApp.Commit())
 
+	require.Eventually(t, func() bool {
+		return db.Head().chunkDiskMapper.IsQueueEmpty()
+	}, 2*time.Second, 100*time.Millisecond)
+
 	// Test that registered size matches the actual disk size.
 	require.NoError(t, db.reloadBlocks())                               // Reload the db to register the new db size.
 	require.Equal(t, len(blocks), len(db.Blocks()))                     // Ensure all blocks are registered.

tsdb/example_test.go

@@ -16,97 +16,89 @@ package tsdb
 import (
 	"context"
 	"fmt"
+	"io/ioutil"
 	"math"
-	"testing"
+	"os"
 	"time"
 
-	"github.com/stretchr/testify/require"
-
 	"github.com/prometheus/prometheus/model/labels"
 )
 
-func TestExample(t *testing.T) {
+func Example() {
 	// Create a random dir to work in.  Open() doesn't require a pre-existing dir, but
 	// we want to make sure not to make a mess where we shouldn't.
-	dir := t.TempDir()
+	dir, err := ioutil.TempDir("", "tsdb-test")
+	noErr(err)
 
 	// Open a TSDB for reading and/or writing.
 	db, err := Open(dir, nil, nil, DefaultOptions(), nil)
-	require.NoError(t, err)
+	noErr(err)
 
 	// Open an appender for writing.
 	app := db.Appender(context.Background())
 
-	lbls := labels.FromStrings("foo", "bar")
-	var appendedSamples []sample
+	series := labels.FromStrings("foo", "bar")
 
 	// Ref is 0 for the first append since we don't know the reference for the series.
-	ts, v := time.Now().Unix(), 123.0
-	ref, err := app.Append(0, lbls, ts, v)
-	require.NoError(t, err)
-	appendedSamples = append(appendedSamples, sample{ts, v})
+	ref, err := app.Append(0, series, time.Now().Unix(), 123)
+	noErr(err)
 
 	// Another append for a second later.
 	// Re-using the ref from above since it's the same series, makes append faster.
 	time.Sleep(time.Second)
-	ts, v = time.Now().Unix(), 124
-	_, err = app.Append(ref, lbls, ts, v)
-	require.NoError(t, err)
-	appendedSamples = append(appendedSamples, sample{ts, v})
+	_, err = app.Append(ref, series, time.Now().Unix(), 124)
+	noErr(err)
 
 	// Commit to storage.
 	err = app.Commit()
-	require.NoError(t, err)
+	noErr(err)
 
 	// In case you want to do more appends after app.Commit(),
 	// you need a new appender.
-	// app = db.Appender(context.Background())
-	//
+	app = db.Appender(context.Background())
 	// ... adding more samples.
-	//
-	// Commit to storage.
-	// err = app.Commit()
-	// require.NoError(t, err)
 
 	// Open a querier for reading.
 	querier, err := db.Querier(context.Background(), math.MinInt64, math.MaxInt64)
-	require.NoError(t, err)
-
+	noErr(err)
 	ss := querier.Select(false, nil, labels.MustNewMatcher(labels.MatchEqual, "foo", "bar"))
-	var queriedSamples []sample
+
 	for ss.Next() {
 		series := ss.At()
 		fmt.Println("series:", series.Labels().String())
 
 		it := series.Iterator()
 		for it.Next() {
-			ts, v := it.At()
-			fmt.Println("sample", ts, v)
-			queriedSamples = append(queriedSamples, sample{ts, v})
+			_, v := it.At() // We ignore the timestamp here, only to have a predictable output we can test against (below)
+			fmt.Println("sample", v)
 		}
 
-		require.NoError(t, it.Err())
 		fmt.Println("it.Err():", it.Err())
 	}
-	require.NoError(t, ss.Err())
 	fmt.Println("ss.Err():", ss.Err())
 	ws := ss.Warnings()
 	if len(ws) > 0 {
 		fmt.Println("warnings:", ws)
 	}
 	err = querier.Close()
-	require.NoError(t, err)
+	noErr(err)
 
 	// Clean up any last resources when done.
 	err = db.Close()
-	require.NoError(t, err)
-
-	require.Equal(t, appendedSamples, queriedSamples)
+	noErr(err)
+	err = os.RemoveAll(dir)
+	noErr(err)
 
 	// Output:
 	// series: {foo="bar"}
-	// sample <ts1> 123
-	// sample <ts2> 124
+	// sample 123
+	// sample 124
 	// it.Err(): <nil>
 	// ss.Err(): <nil>
 }
+
+func noErr(err error) {
+	if err != nil {
+		panic(err)
+	}
+}