prometheus/tsdb/example_test.go

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Add basic initial developer docs for TSDB (#9451) * Add basic initial developer docs for TSDB There's a decent amount of content already out there (blog posts, conference talks, etc), but: * when they get stale, they don't tend to get updated * they still leave me with questions that I'ld like to answer for developers (like me) who want to use, or work with, TSDB What I propose is developer docs inside the prometheus repository. Easy to find and harness the power of the community to expand it and keep it up to date. * perfect is the enemy of good. Let's have a base and incrementally improve * Markdown docs should be broad but not too deep. Source code comments can complement them, and are the ideal place for implementation details. Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * use example code that works out of the box Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * Apply suggestions from code review Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com> Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * PR feedback Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * more docs Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * PR feedback Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * Apply suggestions from code review Signed-off-by: Dieter Plaetinck <dieter@grafana.com> Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com> * Apply suggestions from code review Signed-off-by: Dieter Plaetinck <dieter@grafana.com> Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com> * feedback Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * Update tsdb/docs/usage.md Signed-off-by: Dieter Plaetinck <dieter@grafana.com> Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com> * final tweaks Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * workaround docs versioning issue Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * Move example code to real executable, testable example. Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * cleanup example test and make sure it always reproduces Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * obtain temp dir in a way that works with older Go versions Signed-off-by: Dieter Plaetinck <dieter@grafana.com> * Fix Ganesh's comments Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com> Co-authored-by: Ganesh Vernekar <15064823+codesome@users.noreply.github.com> Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com> Co-authored-by: Ganesh Vernekar <ganeshvern@gmail.com>
2021-11-17 02:21:27 -08:00
// Copyright 2021 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package tsdb
import (
"context"
"fmt"
"math"
"testing"
"time"
"github.com/stretchr/testify/require"
"github.com/prometheus/prometheus/model/labels"
)
func TestExample(t *testing.T) {
// 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()
// Open a TSDB for reading and/or writing.
db, err := Open(dir, nil, nil, DefaultOptions(), nil)
require.NoError(t, err)
// Open an appender for writing.
app := db.Appender(context.Background())
lbls := labels.FromStrings("foo", "bar")
var appendedSamples []sample
// 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})
// 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})
// Commit to storage.
err = app.Commit()
require.NoError(t, err)
// In case you want to do more appends after app.Commit(),
// you need a new appender.
// 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)
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})
}
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)
// Clean up any last resources when done.
err = db.Close()
require.NoError(t, err)
require.Equal(t, appendedSamples, queriedSamples)
// Output:
// series: {foo="bar"}
// sample <ts1> 123
// sample <ts2> 124
// it.Err(): <nil>
// ss.Err(): <nil>
}