What causes "Error reading stream." in quarkusio/quarkus?

Investigate the cause (the wrapped IOException is attached) — check the child process logs and exit code.

quarkusio/quarkus · error · RuntimeException

Error reading stream.

Error message

Error reading stream.

What it means

OutputFilter reads a process/log stream line by line; if reading throws an IOException other than the tolerated 'Stream closed' case, it wraps it in a RuntimeException 'Error reading stream.' This usually indicates the underlying stream broke unexpectedly rather than a normal end-of-stream.

Source

Thrown at core/deployment/src/main/java/io/quarkus/deployment/OutputFilter.java:29

public class OutputFilter implements Function<InputStream, Runnable> {
    private final StringBuilder builder = new StringBuilder();
    private static final Logger log = Logger.getLogger(OutputFilter.class);

    @Override
    public Runnable apply(InputStream is) {
        return () -> {

            try (InputStreamReader isr = new InputStreamReader(is);
                    BufferedReader reader = new BufferedReader(isr)) {

                for (String line = reader.readLine(); line != null; line = reader.readLine()) {
                    builder.append(line);
                }
            } catch (IOException e) {
                if (e.getMessage().contains("Stream closed")) {
                    log.warn("Stream is closed, ignoring and trying to continue");
                } else {
                    throw new RuntimeException("Error reading stream.", e);
                }
            }
        };
    }

    public String getOutput() {
        return builder.toString();
    }
}

View on GitHub (pinned to e1c734241f)

Solutions

Investigate the cause (the wrapped IOException is attached) — check the child process logs and exit code.
Ensure the process whose output is filtered is not being forcibly killed before it finishes.
Catch the RuntimeException around the augmentation/run call and handle it if reading child output is best-effort in your tooling.

Example fix

null

Defensive patterns

Strategy: try-catch

Try / catch

try {
    augmentor.run();
} catch (RuntimeException e) {
    if ("Error reading stream.".equals(e.getMessage())) {
        log.warn("Child output stream broke; cause: " + e.getCause(), e);
    } else {
        throw e;
    }
}

Prevention

Ensure child processes are not killed mid-run (check CI timeouts / OOM killers).
Capture child process exit codes and logs to diagnose abrupt termination.
Treat stream filtering as best-effort in tooling and degrade gracefully.

When it happens

Trigger: The monitored process is killed abruptly or the pipe is closed mid-read; an IOException occurs while BufferedReader.readLine() whose message does not contain 'Stream closed'.

Common situations: Forked build/test processes dying unexpectedly; platform pipe breakage in CI; a child process terminating while Quarkus still reads its output.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/291bc8c69af087c3. Report an issue: GitHub.