apache/druid · error · RuntimeException

Compression failed

Error message

Compression failed

What it means

Pac4jSessionStore.compress wraps GZIP compression of serialized session data destined for a cookie. GZIPOutputStream.write only throws IOException in genuinely exceptional situations since the output is an in-memory ByteArrayOutputStream, so this RuntimeException signals an unexpected internal failure (e.g. JVM-level stream corruption or OOM-adjacent conditions) rather than bad user input.

Solutions

1. Inspect the cause chain (the IOException) to identify the underlying JVM resource problem
2. Reduce the size of the data being stored in the session/cookie
3. Check JVM heap availability and GC health at time of failure
4. Retry the request; this is almost never deterministic

try { byte[] compressed = store.compressEncryptBase64(obj); } catch (RuntimeException e) { LOGGER.error(e, "Session compression failed"); /* fail request or drop session */ }

When it happens

Trigger: Calling compressEncryptBase64 on a serialized session object while the internal GZIP write fails; practically only when the JVM is in a broken state (e.g. OutOfMemoryError surfaced as IOException) since both streams are in-memory.

Common situations: Very large session/profile objects stressing memory during cookie persistence; JVM resource exhaustion; rare JDK stream bugs.

Related errors

• Decompression failed
• Cannot list files in directory
• Column capacity exceeded
• Directory compression not supported for
• Directory decompression not supported for

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/b77aea8e8c3691d4. Report an issue: GitHub.

Appendix: source

Thrown at extensions-core/druid-pac4j/src/main/java/org/apache/druid/security/pac4j/Pac4jSessionStore.java:237

      }
      catch (Exception e) {
        LOGGER.debug("Failed to decrypt cookie value: %s", e.getMessage());
        throw InvalidInput.exception(e, "Decryption failed. Check service logs.");
      }
    }
    return null;
  }

  private byte[] compress(final byte[] data)
  {
    try (ByteArrayOutputStream byteStream = new ByteArrayOutputStream(data.length)) {
      try (GZIPOutputStream gzip = new GZIPOutputStream(byteStream)) {
        gzip.write(data);
      }
      return byteStream.toByteArray();
    }
    catch (IOException ex) {
      throw new RuntimeException("Compression failed", ex);
    }
  }

  private byte[] uncompress(final byte[] data)
  {
    try (ByteArrayInputStream inputStream = new ByteArrayInputStream(data);
         GZIPInputStream gzip = new GZIPInputStream(inputStream)) {
      return ByteStreams.toByteArray(gzip);
    }
    catch (IOException ex) {
      throw new RuntimeException("Decompression failed", ex);
    }
  }

  /**
   * Serialize object using standard Java serialization
   */
  private byte[] serializeToBytes(Serializable obj)

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