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cloud_io.go
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cloud_io.go
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// Copyright 2021 The Cockroach Authors.
//
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.
package cloud
import (
"context"
"crypto/tls"
"crypto/x509"
"fmt"
"io"
"net/http"
"strconv"
"strings"
"time"
"github.com/cockroachdb/cockroach/pkg/base"
"github.com/cockroachdb/cockroach/pkg/roachpb"
"github.com/cockroachdb/cockroach/pkg/settings"
"github.com/cockroachdb/cockroach/pkg/settings/cluster"
"github.com/cockroachdb/cockroach/pkg/util/ctxgroup"
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/retry"
"github.com/cockroachdb/cockroach/pkg/util/sysutil"
"github.com/cockroachdb/cockroach/pkg/util/tracing"
"github.com/cockroachdb/errors"
)
// Timeout is a cluster setting used for cloud storage interactions.
var Timeout = settings.RegisterDurationSetting(
settings.TenantWritable,
"cloudstorage.timeout",
"the timeout for import/export storage operations",
10*time.Minute,
).WithPublic()
var httpCustomCA = settings.RegisterStringSetting(
settings.TenantWritable,
"cloudstorage.http.custom_ca",
"custom root CA (appended to system's default CAs) for verifying certificates when interacting with HTTPS storage",
"",
).WithPublic()
// HTTPRetryOptions defines the tunable settings which control the retry of HTTP
// operations.
var HTTPRetryOptions = retry.Options{
InitialBackoff: 100 * time.Millisecond,
MaxBackoff: 2 * time.Second,
MaxRetries: 32,
Multiplier: 4,
}
// MakeHTTPClient makes an http client configured with the common settings used
// for interacting with cloud storage (timeouts, retries, CA certs, etc).
func MakeHTTPClient(settings *cluster.Settings) (*http.Client, error) {
var tlsConf *tls.Config
if pem := httpCustomCA.Get(&settings.SV); pem != "" {
roots, err := x509.SystemCertPool()
if err != nil {
return nil, errors.Wrap(err, "could not load system root CA pool")
}
if !roots.AppendCertsFromPEM([]byte(pem)) {
return nil, errors.Errorf("failed to parse root CA certificate from %q", pem)
}
tlsConf = &tls.Config{RootCAs: roots}
}
t := http.DefaultTransport.(*http.Transport).Clone()
// Add our custom CA.
t.TLSClientConfig = tlsConf
return &http.Client{Transport: t}, nil
}
// MaxDelayedRetryAttempts is the number of times the delayedRetry method will
// re-run the provided function.
const MaxDelayedRetryAttempts = 3
// DelayedRetry runs fn and re-runs it a limited number of times if it
// fails. It knows about specific kinds of errors that need longer retry
// delays than normal.
func DelayedRetry(
ctx context.Context, opName string, customDelay func(error) time.Duration, fn func() error,
) error {
span := tracing.SpanFromContext(ctx)
attemptNumber := int32(1)
return retry.WithMaxAttempts(ctx, base.DefaultRetryOptions(), MaxDelayedRetryAttempts, func() error {
err := fn()
if err == nil {
return nil
}
retryEvent := &roachpb.RetryTracingEvent{
Operation: opName,
AttemptNumber: attemptNumber,
RetryError: tracing.RedactAndTruncateError(err),
}
span.RecordStructured(retryEvent)
if customDelay != nil {
if d := customDelay(err); d > 0 {
select {
case <-time.After(d):
case <-ctx.Done():
}
}
}
// See https:github.com/GoogleCloudPlatform/google-cloudimpl-go/issues/1012#issuecomment-393606797
// which suggests this GCE error message could be due to auth quota limits
// being reached.
if strings.Contains(err.Error(), "net/http: timeout awaiting response headers") {
select {
case <-time.After(time.Second * 5):
case <-ctx.Done():
}
}
attemptNumber++
return err
})
}
// IsResumableHTTPError returns true if we can
// resume download after receiving an error 'err'.
// We can attempt to resume download if the error is ErrUnexpectedEOF.
// In particular, we should not worry about a case when error is io.EOF.
// The reason for this is two-fold:
// 1. The underlying http library converts io.EOF to io.ErrUnexpectedEOF
// if the number of bytes transferred is less than the number of
// bytes advertised in the Content-Length header. So if we see
// io.ErrUnexpectedEOF we can simply request the next range.
// 2. If the server did *not* advertise Content-Length, then
// there is really nothing we can do: http standard says that
// the stream ends when the server terminates connection.
// In addition, we treat connection reset by peer errors (which can
// happen if we didn't read from the connection too long due to e.g. load),
// the same as unexpected eof errors.
func IsResumableHTTPError(err error) bool {
return errors.Is(err, io.ErrUnexpectedEOF) ||
sysutil.IsErrConnectionReset(err) ||
sysutil.IsErrConnectionRefused(err)
}
// Maximum number of times we can attempt to retry reading from external storage,
// without making any progress.
const maxNoProgressReads = 3
// ReaderOpenerAt describes a function that opens a ReadCloser at the passed
// offset.
type ReaderOpenerAt func(ctx context.Context, pos int64) (io.ReadCloser, error)
// ResumingReader is a reader which retries reads in case of a transient errors.
type ResumingReader struct {
Ctx context.Context // Reader context
Opener ReaderOpenerAt // Get additional content
Reader io.ReadCloser // Currently opened reader
Pos int64 // How much data was received so far
RetryOnErrFn func(error) bool // custom retry-on-error function
ErrFn func(error) time.Duration // custom error delay picker
}
var _ io.ReadCloser = &ResumingReader{}
// NewResumingReader returns a ResumingReader instance.
func NewResumingReader(
ctx context.Context,
opener ReaderOpenerAt,
reader io.ReadCloser,
pos int64,
retryOnErrFn func(error) bool,
errFn func(error) time.Duration,
) *ResumingReader {
r := &ResumingReader{
Ctx: ctx,
Opener: opener,
Reader: reader,
Pos: pos,
RetryOnErrFn: retryOnErrFn,
ErrFn: errFn,
}
if r.RetryOnErrFn == nil {
log.Warning(ctx, "no RetryOnErrFn specified when configuring ResumingReader, setting to default value")
r.RetryOnErrFn = sysutil.IsErrConnectionReset
}
return r
}
// Open opens the reader at its current offset.
func (r *ResumingReader) Open() error {
return DelayedRetry(r.Ctx, "ResumingReader.Opener", r.ErrFn, func() error {
var readErr error
r.Reader, readErr = r.Opener(r.Ctx, r.Pos)
return readErr
})
}
// Read implements io.Reader.
func (r *ResumingReader) Read(p []byte) (int, error) {
var lastErr error
for retries := 0; lastErr == nil; retries++ {
if r.Reader == nil {
lastErr = r.Open()
}
if lastErr == nil {
n, readErr := r.Reader.Read(p)
if readErr == nil || readErr == io.EOF {
r.Pos += int64(n)
return n, readErr
}
lastErr = readErr
}
if !errors.IsAny(lastErr, io.EOF, io.ErrUnexpectedEOF) {
log.Errorf(r.Ctx, "Read err: %s", lastErr)
}
// Use the configured retry-on-error decider to check for a resumable error.
if r.RetryOnErrFn(lastErr) {
span := tracing.SpanFromContext(r.Ctx)
retryEvent := &roachpb.RetryTracingEvent{
Operation: "ResumingReader.Reader.Read",
AttemptNumber: int32(retries + 1),
RetryError: tracing.RedactAndTruncateError(lastErr),
}
span.RecordStructured(retryEvent)
if retries >= maxNoProgressReads {
return 0, errors.Wrap(lastErr, "multiple Read calls return no data")
}
log.Errorf(r.Ctx, "Retry IO: error %s", lastErr)
lastErr = nil
r.Reader.Close()
r.Reader = nil
}
}
// NB: Go says Read() callers need to expect n > 0 *and* non-nil error, and do
// something with what was read before the error, but this mostly applies to
// err = EOF case which we handle above, so likely OK that we're discarding n
// here and pretending it was zero.
return 0, lastErr
}
// Close implements io.Closer.
func (r *ResumingReader) Close() error {
if r.Reader != nil {
return r.Reader.Close()
}
return nil
}
// CheckHTTPContentRangeHeader parses Content-Range header and ensures that
// range start offset is the same as the expected 'pos'. It returns the total
// size of the remote object as extracted from the header.
// See https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Range
func CheckHTTPContentRangeHeader(h string, pos int64) (int64, error) {
if len(h) == 0 {
return 0, errors.New("http server does not honor download resume")
}
h = strings.TrimPrefix(h, "bytes ")
dash := strings.IndexByte(h, '-')
if dash <= 0 {
return 0, errors.Errorf("malformed Content-Range header: %s", h)
}
resume, err := strconv.ParseInt(h[:dash], 10, 64)
if err != nil {
return 0, errors.Errorf("malformed start offset in Content-Range header: %s", h)
}
if resume != pos {
return 0, errors.Errorf(
"expected resume position %d, found %d instead in Content-Range header: %s",
pos, resume, h)
}
slash := strings.IndexByte(h, '/')
if slash <= 0 {
return 0, errors.Errorf("malformed Content-Range header: %s", h)
}
size, err := strconv.ParseInt(h[slash+1:], 10, 64)
if err != nil {
return 0, errors.Errorf("malformed slash offset in Content-Range header: %s", h)
}
return size, nil
}
// BackgroundPipe is a helper for providing a Writer that is backed by a pipe
// that has a background process reading from it. It *must* be Closed().
func BackgroundPipe(
ctx context.Context, fn func(ctx context.Context, pr io.Reader) error,
) io.WriteCloser {
pr, pw := io.Pipe()
w := &backgroundPipe{w: pw, grp: ctxgroup.WithContext(ctx), ctx: ctx}
w.grp.GoCtx(func(ctc context.Context) error {
err := fn(ctx, pr)
if err != nil {
closeErr := pr.CloseWithError(err)
err = errors.CombineErrors(err, closeErr)
} else {
err = pr.Close()
}
return err
})
return w
}
type backgroundPipe struct {
w *io.PipeWriter
grp ctxgroup.Group
ctx context.Context
}
// Write writes to the writer.
func (s *backgroundPipe) Write(p []byte) (int, error) {
return s.w.Write(p)
}
// Close closes the writer, finishing the write operation.
func (s *backgroundPipe) Close() error {
err := s.w.CloseWithError(s.ctx.Err())
return errors.CombineErrors(err, s.grp.Wait())
}
// WriteFile is a helper for writing the content of a Reader to the given path
// of an ExternalStorage.
func WriteFile(ctx context.Context, dest ExternalStorage, basename string, src io.Reader) error {
var span *tracing.Span
ctx, span = tracing.ChildSpan(ctx, fmt.Sprintf("%s.WriteFile", dest.Conf().Provider.String()))
defer span.Finish()
var cancel context.CancelFunc
ctx, cancel = context.WithCancel(ctx)
defer cancel()
w, err := dest.Writer(ctx, basename)
if err != nil {
return errors.Wrap(err, "opening object for writing")
}
if _, err := io.Copy(w, src); err != nil {
cancel()
return errors.CombineErrors(w.Close(), err)
}
return errors.Wrap(w.Close(), "closing object")
}