apache/hadoop · error · NoNamenodesAvailableException

No namenodes available under nameservice {}

Error message

No namenodes available under nameservice {}

What it means

Error "No namenodes available under nameservice {}" thrown in apache/hadoop.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcClient.java:488

   * @param ioe IOException reported.
   * @param retryCount Number of retries.
   * @param nsId Nameservice ID.
   * @param namenode namenode context.
   * @param listObserverFirst Observer read case, observer NN will be ranked first.
   * @return Retry decision.
   * @throws IOException An IO Error occurred.
   */
  protected RetryDecision shouldRetry(
      final IOException ioe, final int retryCount, final String nsId,
      final FederationNamenodeContext namenode,
      final boolean listObserverFirst) throws IOException {
    // check for the case of cluster unavailable state
    if (isClusterUnAvailable(nsId, namenode, listObserverFirst)) {
      // we allow to retry once if cluster is unavailable
      if (retryCount == 0) {
        return RetryDecision.RETRY;
      } else {
        throw new NoNamenodesAvailableException(nsId, ioe);
      }
    }

    try {
      final RetryPolicy.RetryAction a =
          this.retryPolicy.shouldRetry(ioe, retryCount, 0, true);
      return a.action;
    } catch (Exception ex) {
      LOG.error("Re-throwing API exception, no more retries", ex);
      throw toIOException(ex);
    }
  }

  /**
   * Invokes a method against the ClientProtocol proxy server. If a standby
   * exception is generated by the call to the client, retries using the
   * alternate server.
   * <p>

View on GitHub (pinned to 2add963021)

Solutions

1. Check that namenodes for the nameservice have registered with the State Store (Router admin: dfsrouteradmin -ls <nsId>).
2. Verify the namenode heartbeats are reaching the Router and the registrations are not expired/disabled.
3. Confirm dfs.federation.router.nameservices / resolver configuration includes the nameservice.

When it happens

Trigger: The namenode resolver returned an empty list of active namenodes for the requested nameservice.

Common situations: All namenodes of a subcluster are down/unregistered, in safe mode/standby-only, or the nameservice was disabled in the State Store.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/c318f0e86db6c9f2. Report an issue: GitHub.