roachtest: backup2TB writes perf artifacts for roachperf

The backup2TB roachtest now writes a histogram with the
time taken by the backup to the artifacts directory. This
change will be followed by teaching roachperf to read this
value, parse the backup size and number of nodes from the
test name, and plot the rate of backup per node.

Release note: None

Informs: #49813

pkg/cmd/roachtest/backup.go

@@ -12,15 +12,19 @@ package main
 
 import (
  "context"
+ "encoding/json"
  "fmt"
  "net/url"
  "os"
+ "path/filepath"
  "strings"
  "time"
 
  "github.com/cockroachdb/cockroach/pkg/storage/cloudimpl"
+ "github.com/cockroachdb/cockroach/pkg/util/log"
  "github.com/cockroachdb/cockroach/pkg/util/timeutil"
  "github.com/cockroachdb/cockroach/pkg/util/version"
+ "github.com/cockroachdb/cockroach/pkg/workload/histogram"
  "github.com/cockroachdb/errors"
 )
 
@@ -149,11 +153,44 @@ func registerBackup(r *testRegistry) {
  rows = 100
  }
  dest := importBankData(ctx, rows, t, c)
+
+ // Register a named histogram to track the total time the backup took.
+ // Roachperf uses this information to display information about this
+ // roachtest.
+ reg := histogram.NewRegistry(2 * time.Hour)
+ reg.GetHandle().Get("backup/2TB")
+
+ // Create the stats file where the roachtest will write perf artifacts.
+ // We probably don't want to fail the roachtest if we are unable to
+ // collect perf stats.
+ statsFile := perfArtifactsDir + "/stats.json"
+ err := os.MkdirAll(filepath.Dir(statsFile), 0755)
+ if err != nil {
+ log.Errorf(ctx, "backup/2TB failed to create perf artifacts directory %s: %s", statsFile,
+ err.Error())
+ }
+ jsonF, err := os.Create(statsFile)
+ if err != nil {
+ log.Errorf(ctx, "backup/2TB failed to create perf artifacts directory %s: %s", statsFile,
+ err.Error())
+ }
+ jsonEnc := json.NewEncoder(jsonF)
+ tick := func() {
+ reg.Tick(func(tick histogram.Tick) {
+ _ = jsonEnc.Encode(tick.Snapshot())
+ })
+ }
+
  m := newMonitor(ctx, c)
  m.Go(func(ctx context.Context) error {
  t.Status(`running backup`)
+ // Tick once before starting the backup, and once after to capture the
+ // total elapsed time. This is used by roachperf to compute and display
+ // the average MB/sec per node.
+ tick()
  c.Run(ctx, c.Node(1), `./cockroach sql --insecure -e "
  BACKUP bank.bank TO 'gs://cockroachdb-backup-testing/`+dest+`'"`)
+ tick()
  return nil
  })
  m.Wait()