org.kitesdk.morphline.base.FaultTolerance Maven / Gradle / Ivy

/*
 * Copyright 2013 Cloudera Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.kitesdk.morphline.base;

import org.kitesdk.morphline.api.ExceptionHandler;
import org.kitesdk.morphline.api.MorphlineRuntimeException;
import org.kitesdk.morphline.api.Record;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Mission critical, large-scale online production systems need to make progress without downtime
 * despite some issues.
 * 
 * Some program exceptions tend to be transient, in which case the corresponding task can be
 * retried. Examples include network connection errors, timeouts, etc. These are called recoverable
 * exceptions.
 * 
 * The isIgnoringRecoverableExceptions should only be enabled if an exception misclassification bug
 * has been identified.
 */
public final class FaultTolerance implements ExceptionHandler {
    
  private final boolean isProductionMode; 
  private final boolean isIgnoringRecoverableExceptions;
  private final Class[] clazzes;
  
  public static final String IS_PRODUCTION_MODE = "isProductionMode";
  public static final String IS_IGNORING_RECOVERABLE_EXCEPTIONS = "isIgnoringRecoverableExceptions";
  public static final String RECOVERABLE_EXCEPTION_CLASSES = "recoverableExceptionClasses";

  private static final Logger LOG = LoggerFactory.getLogger(FaultTolerance.class);

  public FaultTolerance(boolean isProductionMode, boolean isIgnoringRecoverableExceptions) {
    this(isProductionMode, isIgnoringRecoverableExceptions, null);
  }
  
  public FaultTolerance(boolean isProductionMode, boolean isIgnoringRecoverableExceptions, 
      String recoverableExceptionClassNames) {
    
    this.isProductionMode = isProductionMode;
    this.isIgnoringRecoverableExceptions = isIgnoringRecoverableExceptions;    
    this.clazzes = parseRecoverableExceptionClassNames(recoverableExceptionClassNames);
  }

  @Override
  public void handleException(Throwable t, Record record) {
    if (t instanceof Error) {
      throw (Error) t; // never ignore errors
    }
    if (isProductionMode()) {
      if (!isRecoverableException(t)) {
        LOG.warn("Ignoring unrecoverable exception in production mode for record: " + record, t);
        return;
      } else if (isIgnoringRecoverableExceptions()) {
        LOG.warn("Ignoring recoverable exception in production mode for record: " + record, t);
        return;
      }
    }
    throw new MorphlineRuntimeException(t);
  }

  private boolean isProductionMode() {
    return isProductionMode;
  }
  
  private boolean isIgnoringRecoverableExceptions() {
    return isIgnoringRecoverableExceptions;
  }
  
  @SuppressWarnings("unchecked")
  private boolean isRecoverableException(Throwable t) {
    while (true) {
      for (Class clazz : clazzes) {
        if (clazz.isAssignableFrom(t.getClass())) {
          return true;
        }
      }      
      Throwable cause = t.getCause();
      if (cause == null || cause == t) {
        return false;
      }
      t = cause;
    } 

  }
   
  /* Input is a list of comma separated fully qualified class names */
  private Class[] parseRecoverableExceptionClassNames(String recoverableExceptionClassNames) {
    if (recoverableExceptionClassNames != null) {
      recoverableExceptionClassNames = recoverableExceptionClassNames.trim();
      if (recoverableExceptionClassNames.length() == 0) {
        recoverableExceptionClassNames = null;
      }
    }
    if (recoverableExceptionClassNames == null) {
      return new Class[0];
    } 
    String[] classNames = recoverableExceptionClassNames.split(",");
    Class[] classes = new Class[classNames.length];
    for (int i = 0; i < classNames.length; i++) {
      try {
        classes[i] = Class.forName(classNames[i].trim());
      } catch (ClassNotFoundException e) {
        throw new RuntimeException(e);
      }
    }
    return classes;
  }
  
}