apache/hadoop · error · IllegalArgumentException

No class configured for {}

Error message

No class configured for {}

What it means

Same lookup in FSEditLog.getJournalClass, but conf.getClass returned null: the key dfs.namenode.edits.journal-plugin.<scheme> is absent. An edits URI uses a scheme for which no JournalManager implementation is registered, so getJournalClass throws IllegalArgumentException('No class configured for <scheme>') after logging a warning that names the missing key.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java:1864

   * @return the class of the journal implementation
   * @throws IllegalArgumentException if no class is configured for uri
   */
  static Class<? extends JournalManager> getJournalClass(Configuration conf,
                               String uriScheme) {
    String key
      = DFSConfigKeys.DFS_NAMENODE_EDITS_PLUGIN_PREFIX + "." + uriScheme;
    Class <? extends JournalManager> clazz = null;
    try {
      clazz = conf.getClass(key, null, JournalManager.class);
    } catch (RuntimeException re) {
      throw new IllegalArgumentException(
          "Invalid class specified for " + uriScheme, re);
    }
      
    if (clazz == null) {
      LOG.warn("No class configured for " +uriScheme
               + ", " + key + " is empty");
      throw new IllegalArgumentException(
          "No class configured for " + uriScheme);
    }
    return clazz;
  }

  /**
   * Construct a custom journal manager.
   * The class to construct is taken from the configuration.
   * @param uri Uri to construct
   * @return The constructed journal manager
   * @throws IllegalArgumentException if no class is configured for uri
   */
  @VisibleForTesting
  JournalManager createJournal(URI uri) {
    Class<? extends JournalManager> clazz
      = getJournalClass(conf, uri.getScheme());

    try {

View on GitHub (pinned to 2add963021)

Solutions

1. Add dfs.namenode.edits.journal-plugin.<scheme>=<fully-qualified JournalManager class> to hdfs-site.xml
2. Fix the scheme in dfs.namenode.edits.dir / dfs.namenode.shared.edits.dir: file:// for local edits, qjm://HOST:PORT;HOST:PORT;HOST:PORT/JOURNALNAME for QuorumJournalManager
3. Verify the effective value on the failing host with 'hdfs getconf -confKey dfs.namenode.edits.dir' to confirm the property is loaded

Example fix

<!-- before: myj:// URI present, no plugin registered -->
<property><name>dfs.namenode.edits.dir</name><value>myj://journalhost:8220/nn</value></property>

<!-- after: register the scheme handler -->
<property><name>dfs.namenode.edits.journal-plugin.myj</name><value>com.example.storage.MyJournalManager</value></property>

// every scheme used in edits dirs must be built-in or have a plugin entry
Set<String> builtin = new HashSet<>(Arrays.asList("file", "qjm", "hftp", "https"));
for (URI u : FSNamesystem.getNamespaceEditsDirs(conf)) {
  String scheme = u.getScheme();
  boolean known = scheme == null || builtin.contains(scheme)
      || conf.get("dfs.namenode.edits.journal-plugin." + scheme) != null;
  if (!known) {
    throw new IllegalStateException(
        "No dfs.namenode.edits.journal-plugin." + scheme + " configured for " + u);
  }
}

try {
  // NameNode / FSEditLog construction
} catch (IllegalArgumentException e) {
  if (e.getMessage() != null && e.getMessage().startsWith("No class configured for")) {
    // e.getMessage() names the scheme: add dfs.namenode.edits.journal-plugin.<scheme>
  }
  throw e;
}

When it happens

Trigger: dfs.namenode.edits.dir or dfs.namenode.shared.edits.dir contains a URI whose scheme has no built-in handler (not file or qjm) and no dfs.namenode.edits.journal-plugin.<scheme> property exists. Also hit when a scheme is misspelled, so it resolves to no plugin at all.

Common situations: Typo in the edits URI scheme (for example 'qjm3:' instead of 'qjm:'); plugin property deleted during config cleanup while the URI stayed; property placed in a config file the failing host does not load; config migration dropping custom journal entries.

Related errors

• Invalid class specified for {}
• Unable to construct journal, {}
• Multiple shared edits directories are not yet supported
• Remote NameNodes not correctly configured!
• Unknown nameservice: {}

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/c0c43234b40daf95. Report an issue: GitHub.