error writing files to upload to Docker instance into a temp

Error message

error writing files to upload to Docker instance into a temporary tar blob: %s

What it means

Thrown by DockerVM.Start when building the in-memory tar archive of TLS files (addFiles or tar.Writer.Close) fails before it is uploaded to the chaincode container via CopyToContainer. The tar holds the client key/cert (some base64-encoded for historical reasons) and root cert needed for mutual TLS. A failure here means TLS material could not be staged and the container is not started.

Source

Thrown at core/container/dockercontroller/dockercontroller.go:289

	// upload TLS files to the container before starting it if needed
	if peerConnection.TLSConfig != nil {
		// the docker upload API takes a tar file, so we need to first
		// consolidate the file entries to a tar
		payload := bytes.NewBuffer(nil)
		gw := gzip.NewWriter(payload)
		tw := tar.NewWriter(gw)

		// Note, we goofily base64 encode 2 of the TLS artifacts but not the other for strange historical reasons
		err = addFiles(tw, map[string][]byte{
			TLSClientKeyPath:      []byte(base64.StdEncoding.EncodeToString(peerConnection.TLSConfig.ClientKey)),
			TLSClientCertPath:     []byte(base64.StdEncoding.EncodeToString(peerConnection.TLSConfig.ClientCert)),
			TLSClientKeyFile:      peerConnection.TLSConfig.ClientKey,
			TLSClientCertFile:     peerConnection.TLSConfig.ClientCert,
			TLSClientRootCertFile: peerConnection.TLSConfig.RootCert,
		})
		if err != nil {
			return fmt.Errorf("error writing files to upload to Docker instance into a temporary tar blob: %s", err)
		}

		// Write the tar file out
		if err = tw.Close(); err != nil {
			return fmt.Errorf("error writing files to upload to Docker instance into a temporary tar blob: %s", err)
		}

		gw.Close()

		_, err = vm.Client.CopyToContainer(context.Background(), containerName, dcli.CopyToContainerOptions{
			DestinationPath:           "/",
			Content:                   bytes.NewReader(payload.Bytes()),
			AllowOverwriteDirWithFile: true,
		})
		if err != nil {
			return fmt.Errorf("Error uploading files to the container instance %s: %s", containerName, err)
		}
	}

View on GitHub (pinned to 2736b63f8f)

Solutions

Check the embedded %s error in the peer log for the underlying tar/gzip failure and fix accordingly.
Verify the TLSConfig fields (ClientKey, ClientCert, RootCert) are fully populated before Start; re-establish the chaincode connection if certs are nil.
Retry Start — tar staging is in-memory and transient resource failures resolve after retry.
If on a fork, review modifications to addFiles/tar writer usage; upstream code assumes valid byte slices for all five entries.

Example fix

// before: partial TLS config
peerConn.TLSConfig = &ccintf.TLSConfig{ClientCert: cert} // ClientKey missing
// after
peerConn.TLSConfig = &ccintf.TLSConfig{ClientKey: key, ClientCert: cert, RootCert: root}

Defensive patterns

Strategy: validation

Validate before calling

func validateTLSConfig(tls *ccintf.TLSConfig) error {
	if tls == nil {
		return nil // TLS disabled, tar staging will be skipped
	}
	if len(tls.ClientKey) == 0 || len(tls.ClientCert) == 0 || len(tls.RootCert) == 0 {
		return errors.New("TLS config incomplete: key, cert and root cert are required")
	}
	return nil
}

Type guard

func hasCompleteTLS(tls *ccintf.TLSConfig) bool {
	return tls != nil && len(tls.ClientKey) > 0 && len(tls.ClientCert) > 0 && len(tls.RootCert) > 0
}

Try / catch

if err := vm.Start(ccid, ccType, peerConn); err != nil {
	if strings.Contains(err.Error(), "temporary tar blob") {
		// TLS staging failed — verify TLSConfig fields and retry
	}
	return err
}

Prevention

Ensure the full TLS key/cert/root-cert set is populated on PeerConnection before Start.
Validate PEM material at connection setup, not at container start time.
Run Start under sufficient memory; the tar staging is buffered entirely in memory.

When it happens

Trigger: Calling Start with a non-nil PeerConnection.TLSConfig while addFiles fails writing one of the five TLS entries (gzip/tar writer errors are rare — typically an internal I/O or state error), or tw.Close() fails flushing the gzip stream.

Common situations: Rare in practice; usually seen under memory pressure or when TLSConfig fields are nil/empty causing downstream write problems; also when the gzip/tar writer stack is misused by modified code paths in forks.

Related errors

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/f2c5db55dd62bea2. Report an issue: GitHub.