prestodb/presto · critical · RuntimeException

EMR File System class not found:

Error message

EMR File System class not found: 

What it means

HiveS3Module.validateEmrFsClass (called from setup when hive.s3-file-system-type=EMRFS) loads com.amazon.ws.emr.hadoop.fs.EmrFileSystem via Class.forName; a ClassNotFoundException is rethrown as RuntimeException 'EMR File System class not found: ...'. The connector requires the EMRFS jar on the classpath to use EMR's S3 FileSystem, and startup fails fast when it is missing.

Solutions

1. Either add the EMRFS connector jar (emrfs-hadoop-connector-*.jar from /usr/share/aws/emr/emrfs/lib on EMR) to the Presto plugin/hive classpath on every node.
2. Or change hive.s3-file-system-type back to PRESTO (or HADOOP_DEFAULT) if you don't actually need EMRFS features (consistent view, S3 encryption defaults).
3. Ensure the same classpath fix is applied to ALL coordinator/worker nodes, then restart Presto.
4. Verify with: java -cp <presto-classpath> Class.forName check or simply grep the plugin dir for emrfs jars.

Example fix

// before: etc/catalog/hive.properties on non-EMR host
hive.s3-file-system-type=EMRFS
// after
hive.s3-file-system-type=PRESTO
hive.s3.endpoint=s3.us-east-1.amazonaws.com

// before enabling EMRFS, ensure the class is on the plugin classpath on this node
try {
    Class.forName("com.amazon.ws.emr.hadoop.fs.EmrFileSystem", true, Thread.currentThread().getContextClassLoader());
} catch (ClassNotFoundException e) {
    throw new IllegalStateException("EMRFS jar missing; add emrfs-hadoop-connector to the hive plugin dir or use PRESTO type");
}

boolean emrFsAvailable() {
    try { Class.forName("com.amazon.ws.emr.hadoop.fs.EmrFileSystem", false, JavaUtils.getClassLoader()); return true; }
    catch (ClassNotFoundException e) { return false; }
}

try {
    return pluginManager.loadCatalog("hive", props);
} catch (RuntimeException e) {
    if (e.getMessage() != null && e.getMessage().startsWith("EMR File System class not found:")) {
        throw new ConfigException("Deploy EMRFS jars to all nodes or set hive.s3-file-system-type=PRESTO");
    }
    throw e;
}

When it happens

Trigger: Configuring hive.s3-file-system-type=EMRFS in the Hive catalog on a non-EMR cluster (or Presto distribution) that does not bundle the EMRFS libraries (emrfs-hadoop-connector jar), so Class.forName fails during connector plugin initialization.

Common situations: Running Presto on a plain EC2/AMI instead of EMR while copying EMR-style hive.properties; upgrading Presto where EMRFS jars are no longer bundled; missing hive.jar-path/classpath entry pointing at /usr/share/aws/emr/emrfs/lib; deploying the catalog config to all nodes when only some have the EMR jars.

Related errors

• JDBC driver class not found
• Unable to load or create S3 encryption materials provider
• Unknown file system type:
• Configured staging path is not a directory:
• Could not create hudi connector for catalog

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/9e41cf52434d73b2. Report an issue: GitHub.

Appendix: source

Thrown at presto-hive/src/main/java/com/facebook/presto/hive/s3/HiveS3Module.java:99

    }

    private void bindSecurityMapping(Binder binder)
    {
        if (buildConfigObject(AWSSecurityMappingConfig.class).getConfigFile().isPresent() &&
                buildConfigObject(AWSSecurityMappingConfig.class).getMappingType().equals(S3)) {
            newSetBinder(binder, DynamicConfigurationProvider.class).addBinding()
                    .to(AWSS3SecurityMappingConfigurationProvider.class).in(Scopes.SINGLETON);
        }
    }

    private static void validateEmrFsClass()
    {
        // verify that the class exists
        try {
            Class.forName(EMR_FS_CLASS_NAME, true, JavaUtils.getClassLoader());
        }
        catch (ClassNotFoundException e) {
            throw new RuntimeException("EMR File System class not found: " + EMR_FS_CLASS_NAME, e);
        }
    }

    public static class EmrFsS3ConfigurationUpdater
            implements S3ConfigurationUpdater
    {
        @Override
        public void updateConfiguration(Configuration config)
        {
            // re-map filesystem schemes to use the Amazon EMR file system
            config.set("fs.s3.impl", EMR_FS_CLASS_NAME);
            config.set("fs.s3a.impl", EMR_FS_CLASS_NAME);
            config.set("fs.s3n.impl", EMR_FS_CLASS_NAME);
        }
    }

    public static class HadoopDefaultConfigurationUpdater
            implements S3ConfigurationUpdater

View on GitHub (pinned to 55bb57d202)