apache/hadoop · warning · UnsupportedOperationException

Refresh not supported by " + getClass()

Error message

Refresh not supported by " + getClass()

What it means

BlockAliasMap.refresh() is the extension point for implementations that can reload their backing state without restarting. TextFileRegionAliasMap does not support it and always throws UnsupportedOperationException — its TextReader opens the text file on demand, so there is no cached state to refresh.

Solutions

1. Drop or skip the refresh() call when the implementation is the text alias map
2. To pick up a regenerated file, simply obtain a new Reader via getReader() — each reader re-opens the file
3. If runtime refresh is a hard requirement, use an implementation that supports it (e.g., InMemoryLevelDBAliasMap) instead of text

Example fix

// before
aliasMap.refresh(); // throws for TextFileRegionAliasMap

// after
if (aliasMap instanceof TextFileRegionAliasMap) {
  reader = aliasMap.getReader(null, bpid); // fresh reader re-opens the file
} else {
  aliasMap.refresh();
}

static boolean supportsRefresh(BlockAliasMap<?> map) {
  return !(map instanceof TextFileRegionAliasMap);
}

When it happens

Trigger: Invoking refresh() on a TextFileRegionAliasMap instance, typically through generic management/tooling code that calls refresh on whatever alias map dfs.provided.aliasmap.class selected.

Common situations: Switching the alias map implementation to text while retaining a refresh call; ops tooling that 'refreshes all alias maps' after regenerating the text file.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Invalid line: " + line
• Invalid options " + opts.getClass()
• A valid path needs to be specified for " +…
• Aliasmap archive ( ) does not exist
• Block pool id required to get aliasmap reader

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/5c7941fd40c03134. Report an issue: GitHub.

Appendix: source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/blockaliasmap/impl/TextFileRegionAliasMap.java:469

      out.append(Long.toString(psl.getLength())).append(delim);
      out.append(Long.toString(block.getGenerationStamp()));
      if (psl.getNonce().length > 0) {
        out.append(delim)
            .append(Base64.getEncoder().encodeToString(psl.getNonce()));
      }
      out.append("\n");
    }

    @Override
    public void close() throws IOException {
      out.close();
    }

  }

  @Override
  public void refresh() throws IOException {
    throw new UnsupportedOperationException(
        "Refresh not supported by " + getClass());
  }

  @Override
  public void close() throws IOException {
    // nothing to do;
  }

  @VisibleForTesting
  public static String blockPoolIDFromFileName(Path file) {
    if (file == null) {
      return "";
    }
    String fileName = file.getName();
    return fileName.substring("blocks_".length()).split("\\.")[0];
  }

  @VisibleForTesting

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