108 lines
2.6 KiB
Go
108 lines
2.6 KiB
Go
package fetch
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import (
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"context"
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"errors"
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"fmt"
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"io"
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"net/http"
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"time"
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)
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const (
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maxRetriesWithoutProgress = 8
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retryBaseDelay = 2 * time.Second
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retryMaxDelay = 30 * time.Second
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)
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type segmentWorker struct {
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session *session
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segment *liveSegment
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failedAttempts int
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}
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func (worker *segmentWorker) run(ctx context.Context, response *http.Response) error {
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var err error
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if response == nil {
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response, err = worker.open(ctx)
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}
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for {
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if err != nil {
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response, err = worker.reconnect(ctx, err)
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if err != nil {
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return err
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}
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}
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doneBefore := worker.segment.done.Load()
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err = worker.copyFrom(response)
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if err == nil {
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return nil
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}
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if worker.segment.done.Load() > doneBefore {
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worker.failedAttempts = 0
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}
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}
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}
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func (worker *segmentWorker) open(ctx context.Context) (*http.Response, error) {
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return worker.session.downloader.open(ctx, worker.session.source, worker.segment.position(), worker.segment.end)
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}
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func (worker *segmentWorker) copyFrom(response *http.Response) error {
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defer response.Body.Close()
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writer := io.NewOffsetWriter(worker.session.file, worker.segment.position())
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if err := copyBody(writer, response.Body, worker.segment.remaining(), worker.record); err != nil {
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return err
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}
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if worker.segment.bounded() && !worker.segment.complete() {
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return ErrIncomplete
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}
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return nil
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}
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func (worker *segmentWorker) record(count int64) error {
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worker.segment.done.Add(count)
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return worker.session.record(count)
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}
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func (worker *segmentWorker) reconnect(ctx context.Context, cause error) (*http.Response, error) {
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progress := worker.session.request.Progress
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for {
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worker.failedAttempts++
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if ctx.Err() != nil || !isRetryable(cause) || worker.failedAttempts > maxRetriesWithoutProgress {
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return nil, cause
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}
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progress.SetNotice(fmt.Sprintf("Connection lost, reconnecting (attempt %d of %d)", worker.failedAttempts, maxRetriesWithoutProgress))
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if err := waitBeforeRetry(ctx, worker.failedAttempts); err != nil {
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return nil, err
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}
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response, err := worker.open(ctx)
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if err == nil {
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progress.SetNotice("")
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return response, nil
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}
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cause = err
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}
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}
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func isRetryable(err error) bool {
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return errors.Is(err, errConnectionFailed) ||
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errors.Is(err, errServerUnavailable) ||
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errors.Is(err, ErrStalled) ||
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errors.Is(err, ErrIncomplete)
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}
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func waitBeforeRetry(ctx context.Context, attempt int) error {
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delay := min(retryBaseDelay*time.Duration(attempt), retryMaxDelay)
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timer := time.NewTimer(delay)
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defer timer.Stop()
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select {
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case <-ctx.Done():
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return ctx.Err()
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case <-timer.C:
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return nil
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}
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}
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