hashicorp/nomad · error

error streaming previous alloc %q for new alloc %q: %w

Error message

error streaming previous alloc %q for new alloc %q: %w

What it means

streamAllocDir reads the tar snapshot of the previous allocation directory from the HTTP response body, extracting each entry. If the tar reader or body read returns a non-EOF error mid-stream, the error is wrapped as 'error streaming previous alloc %q for new alloc %q: %w'. This means the snapshot transfer broke partway through, not that it failed to start.

Source

Thrown at client/allocwatcher/alloc_watcher.go:592

			return false
		}
	}

	// if we see this file, there was an error on the remote side
	errorFilename := allocdir.SnapshotErrorFilename(p.prevAllocID)

	buf := make([]byte, 1024)
	for !canceled() {
		// Get the next header
		hdr, err := tr.Next()

		// Snapshot has ended
		if err == io.EOF {
			return nil
		}

		if err != nil {
			return fmt.Errorf("error streaming previous alloc %q for new alloc %q: %w",
				p.prevAllocID, p.allocID, err)
		}

		if escapes, err := escapingfs.PathEscapesAllocDir(dest, "", hdr.Name); err != nil {
			return fmt.Errorf("error evaluating object: %w", err)
		} else if escapes {
			return fmt.Errorf("archive contains object that escapes alloc dir")
		}

		if hdr.Name == errorFilename {
			// Error snapshotting on the remote side, try to read
			// the message out of the file and return it.
			errBuf := make([]byte, int(hdr.Size))
			if _, err := tr.Read(errBuf); err != nil && err != io.EOF {
				return fmt.Errorf("error streaming previous alloc %q for new alloc %q; failed reading error message: %w",
					p.prevAllocID, p.allocID, err)
			}
			return fmt.Errorf("error streaming previous alloc %q for new alloc %q: %s",

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Check network stability between the two client nodes (packet loss, conntrack/proxy timeouts); retry the allocation so migration restarts
2. Inspect the previous node's agent logs for snapshot-side errors during the transfer window
3. Avoid draining/restarting the source node while its allocations are migrating
4. Retry migration during lower network load or reduce alloc dir size (large task logs/data) to shorten the transfer

err := p.streamAllocDir(ctx, resp, allocDirPath)
if err != nil && !errors.Is(err, io.EOF) {
	if strings.Contains(err.Error(), "error streaming previous alloc") {
		// transfer broke mid-stream: safe to retry migration from scratch
	}
	return err
}

When it happens

Trigger: During extraction loop, reading the next tar header or entry data returns an error other than io.EOF: the HTTP response body is truncated (connection reset mid-transfer), the remote node errors while reading the snapshot stream, gzip corruption, or a malformed/incomplete tar payload.

Common situations: Network interruption between nodes during a large allocation migration; previous node's agent crashes or is drained mid-stream; load balancer/proxy idle-timeout cutting a long-lived response; disk errors on the source node while snapshotting.

Related errors

• error getting snapshot from previous alloc %q: %w
• archive contains object that escapes alloc dir
• error streaming previous alloc %q for new alloc %q; failed r
• network namespace already exists but was misconfigured
• network already configured but not found in state

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/a51ccca21d43c5f1. Report an issue: GitHub.