argoproj/argo-workflows · error

plugin stream error

Error message

plugin %s stream error: %s

What it means

This error surfaces when the artifact plugin itself reports an error message inside an otherwise-healthy OpenStream gRPC response: the driver is receiving chunks from the plugin's stream and a response carries a non-empty resp.Error field. The driver wraps the plugin's own error string and injects it into the io.Pipe via CloseWithError, so the caller of Load/any reader of the returned ReadCloser sees it as a read error. It means the plugin started streaming but failed on its side (e.g. could not read the source storage).

Solutions

1. Read the embedded plugin error message after 'stream error: ' — it is the plugin's own diagnosis and names the real cause
2. Check the plugin's logs (kubectl logs on the plugin container) for the corresponding failure
3. Verify the artifact's source location/credentials are valid and accessible from the plugin pod
4. Retry the artifact load once storage issues are fixed

// No pre-call validation can predict plugin-internal failures; ensure the plugin is reachable first:
if _, err := os.Stat(socketPath); err != nil {
    return fmt.Errorf("plugin socket %s missing before OpenStream: %w", socketPath, err)
}

func pluginStreamError(err error) (string, bool) {
    var pe *io.PipeError // or match on message prefix
    if errors.As(err, &pe) && strings.Contains(err.Error(), "stream error: ") {
        return err.Error(), true
    }
    return "", false
}

reader, err := driver.OpenStream(ctx, artifact)
if err != nil { return err }
if _, copyErr := io.Copy(dst, reader); copyErr != nil {
    if strings.Contains(copyErr.Error(), "stream error: ") {
        // plugin-reported failure: inspect plugin logs, fix storage creds/config, retry
    }
    reader.Close()
    return copyErr
}
reader.Close()

When it happens

Trigger: Calling Driver.OpenStream (artifact plugin driver, workflow/artifacts/plugin/plugin.go:163) where the plugin's stream.Recv returns a response with resp.Error set — i.e. the plugin's gRPC server hit an error mid-stream and reported it in-band rather than as a gRPC status.

Common situations: Plugin cannot access the backing storage (bad S3/GCS credentials configured on the plugin), artifact key does not exist, plugin-side timeout while reading a large artifact, or plugin misconfigured storage backend.

Related errors

• plugin save stream failed
• plugin save stream failed to open
• plugin save stream failed
• plugin delete failed
• plugin get capabilities failed

AI-assisted analysis of argoproj/argo-workflows@35bff19146 (2026-09-03). Data as JSON: /api/errors/82addf8083f994d2. Report an issue: GitHub.

Appendix: source

Thrown at workflow/artifacts/plugin/plugin.go:186

	if err != nil {
		return nil, fmt.Errorf("plugin %s open stream failed: %w", d.pluginName, err)
	}

	reader, writer := io.Pipe()

	go func() {
		defer writer.Close()
		for {
			resp, err := stream.Recv()
			if errors.Is(err, io.EOF) {
				break
			}
			if err != nil {
				writer.CloseWithError(fmt.Errorf("plugin %s stream receive failed: %w", d.pluginName, err))
				return
			}
			if resp.Error != "" {
				writer.CloseWithError(fmt.Errorf("plugin %s stream error: %s", d.pluginName, resp.Error))
				return
			}
			if resp.IsEnd {
				break
			}
			if len(resp.Data) > 0 {
				if _, writeErr := writer.Write(resp.Data); writeErr != nil {
					writer.CloseWithError(fmt.Errorf("plugin %s stream write failed: %w", d.pluginName, writeErr))
					return
				}
			}
		}
	}()

	return reader, nil
}

// Save implements ArtifactDriver.Save by calling the plugin service

View on GitHub (pinned to 35bff19146)