apache/beam · error · RuntimeException

Unexpected IOException closing ByteArrayInputStream

Error message

Unexpected IOException closing ByteArrayInputStream

What it means

ExposedByteArrayInputStream.close() delegates to ByteArrayInputStream.close(), which is documented to never throw IOException. This RuntimeException is a defensive guard: if an IOException somehow surfaces while closing the in-memory stream, it indicates a JVM/library-level bug, so it is rethrown unchecked with this message.

Source

Thrown at sdks/java/core/src/main/java/org/apache/beam/sdk/util/ExposedByteArrayInputStream.java:50

  }

  /** Read all remaining bytes. */
  public byte[] readAll() throws IOException {
    if (pos == 0 && count == buf.length) {
      pos = count;
      return buf;
    }
    byte[] ret = new byte[count - pos];
    super.read(ret);
    return ret;
  }

  @Override
  public void close() {
    try {
      super.close();
    } catch (IOException exn) {
      throw new RuntimeException("Unexpected IOException closing ByteArrayInputStream", exn);
    }
  }
}

View on GitHub (pinned to 12126d8942)

Solutions

1. Treat it as an internal invariant violation: report it to the Beam project with the full stack trace
2. Check whether a custom or instrumented stream/JVM version is replacing the JDK ByteArrayInputStream behavior
3. If it appears in cleanup code, inspect the cause — the message is always secondary to the underlying IOException

try {
  stream.close();
} catch (RuntimeException e) {
  if (e.getCause() instanceof IOException) {
    LOG.error("Impossible IOException closing byte stream; JVM/stream anomaly", e);
  }
  throw e;
}

When it happens

Trigger: Calling close() on an ExposedByteArrayInputStream in a code path where ByteArrayInputStream.close() unexpectedly throws IOException — theoretically impossible per the JDK contract, so effectively only via exotic stream subclassing or JVM anomalies.

Common situations: Extremely rare; encountered only when stream implementations are swapped, instrumented, or when running under a JVM with a broken/patched java.io implementation. Practically a 'this should never happen' assertion.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• Stream has been finished. Can not add any more elements.
• Stream has been finished. Can not write any more data.
• Caller does not own the underlying input stream and should
• Caller does not own the underlying output stream and should
• No block has been successfully read from " + getCurrentSourc

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/1876403bb469e04e. Report an issue: GitHub.