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diagnostics.go
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diagnostics.go
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// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You 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 diagnostics is a beam internal package that contains code for writing and uploading
// diagnostic info (e.g. heap profiles) about the worker process.
// This package is not intended for end user use and can change at any time.
package diagnostics
import (
"bufio"
"context"
"errors"
"os"
"runtime"
"runtime/pprof"
"time"
"github.com/apache/beam/sdks/v2/go/pkg/beam/io/filesystem"
"github.com/apache/beam/sdks/v2/go/pkg/beam/log"
)
const (
hProfLoc = "/tmp/hProf"
tempHProfLoc = "/tmp/hProf.tmp"
)
// SampleForHeapProfile checks every second if it should take a heap profile, and if so
// it takes one and saves it to hProfLoc. A profile will be taken if either:
// (1) the amount of memory allocated has increased since the last heap profile was taken or
// (2) it has been 60 seconds since the last heap profile was taken
func SampleForHeapProfile(ctx context.Context, samplingFrequencySeconds, maxTimeBetweenDumpsSeconds int) {
var maxAllocatedSoFar uint64
samplesSkipped := 0
for {
var m runtime.MemStats
runtime.ReadMemStats(&m)
if m.Alloc > maxAllocatedSoFar || (samplesSkipped+1)*samplingFrequencySeconds > maxTimeBetweenDumpsSeconds {
samplesSkipped = 0
maxAllocatedSoFar = m.Alloc
err := saveHeapProfile()
if err != nil {
log.Warnf(ctx, "Failed to save heap profile. This will not affect pipeline execution, but may make it harder to diagnose memory issues: %v", err)
}
} else {
samplesSkipped++
}
time.Sleep(time.Duration(samplingFrequencySeconds) * time.Second)
}
}
func saveHeapProfile() error {
// Write to a .tmp file before moving to final location to ensure
// that OOM doesn't disrupt this flow.
// Try removing temp file in case we ran into an error previously
if err := os.Remove(tempHProfLoc); err != nil && !errors.Is(err, os.ErrNotExist) {
return err
}
fd, err := os.Create(tempHProfLoc)
if err != nil {
return err
}
defer fd.Close()
buf := bufio.NewWriterSize(fd, 1<<20) // use 1MB buffer
if err := pprof.WriteHeapProfile(buf); err != nil {
return err
}
if err := buf.Flush(); err != nil {
return err
}
if err := os.Remove(hProfLoc); err != nil && !errors.Is(err, os.ErrNotExist) {
return err
}
return os.Rename(tempHProfLoc, hProfLoc)
}
// UploadHeapProfile checks if a heap profile is available and, if so, uploads it to dest.
// It will first check hProfLoc for the heap profile and then it will
// check tempHProfLoc if no file exists at hProfLoc.
//
// To examine, download the file and run: `go tool pprof -http=:8082 path/to/profile`
func UploadHeapProfile(ctx context.Context, dest string) error {
hProf, err := os.Open(hProfLoc)
if err != nil {
if errors.Is(err, os.ErrNotExist) {
hProf, err = os.Open(tempHProfLoc)
if err != nil {
if errors.Is(err, os.ErrNotExist) {
return nil
}
return err
}
}
}
defer hProf.Close()
hProfReader := bufio.NewReader(hProf)
fs, err := filesystem.New(ctx, dest)
if err != nil {
return err
}
defer fs.Close()
fd, err := fs.OpenWrite(ctx, dest)
if err != nil {
return err
}
buf := bufio.NewWriterSize(fd, 1<<20) // use 1MB buffer
_, err = hProfReader.WriteTo(buf)
if err != nil {
return err
}
if err := buf.Flush(); err != nil {
return err
}
return fd.Close()
}