OpenFeign/feign · error · IOException

Mark not supported

Error message

Mark not supported

What it means

The metrics5 CountingInputStream.reset() throws IOException("Mark not supported") when the wrapped stream does not support mark/reset. Behavior is identical to the metrics4 variant; mark support is delegated to the underlying stream.

Solutions

  1. Wrap the source in a BufferedInputStream before CountingInputStream
  2. Check markSupported() before resetting
  3. Call mark() before reading

Example fix

// before
new CountingInputStream(connection.getInputStream(), clock);
// after
new CountingInputStream(new BufferedInputStream(connection.getInputStream()), clock);
Defensive patterns

Strategy: validation

Validate before calling

if (in.markSupported()) { /* safe to reset */ }

Try / catch

try {
  in.reset();
} catch (IOException e) {
  // fall back to re-requesting the resource
}

Prevention

When it happens

Trigger: Calling reset() on a feign.metrics5 CountingInputStream whose underlying stream has markSupported() == false.

Common situations: Re-reading response bodies for retries/metrics when the source is an unbuffered network stream.

Related errors

AI-assisted analysis of OpenFeign/feign@e2a1e27560 (2026-09-10). Data as JSON: /api/errors/2825b2758aa68b55. Report an issue: GitHub.

Appendix: source

Thrown at dropwizard-metrics5/src/main/java/feign/metrics5/CountingInputStream.java:85

  @Override
  public long skip(long n) throws IOException {
    final long result = in.skip(n);
    count += result;
    return result;
  }

  @Override
  public synchronized void mark(int readlimit) {
    in.mark(readlimit);
    mark = count;
    // it's okay to mark even if mark isn't supported, as reset won't work
  }

  @Override
  public synchronized void reset() throws IOException {
    if (!in.markSupported()) {
      throw new IOException("Mark not supported");
    }
    if (mark == -1) {
      throw new IOException("Mark not set");
    }

    in.reset();
    count = mark;
  }
}

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