hadoop AuditingFunctions 源码

haddop AuditingFunctions 代码

文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/store/audit/AuditingFunctions.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.hadoop.fs.store.audit;

import javax.annotation.Nullable;
import java.util.concurrent.Callable;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.util.functional.CallableRaisingIOE;
import org.apache.hadoop.util.functional.FunctionRaisingIOE;
import org.apache.hadoop.util.functional.InvocationRaisingIOE;

/**
 * Static methods to assist in working with Audit Spans.
 * the {@code withinX} calls take a span and a closure/function etc.
 * and return a new function of the same types but which will
 * activate and the span.
 * They do not deactivate it afterwards to avoid accidentally deactivating
 * the already-active span during a chain of operations in the same thread.
 * All they do is ensure that the given span is guaranteed to be
 * active when the passed in callable/function/invokable is evaluated.
 */
@InterfaceAudience.Private
@InterfaceStability.Unstable
public final class AuditingFunctions {

  private AuditingFunctions() {
  }

  /**
   * Given a callable, return a new callable which
   * activates and deactivates the span around the inner invocation.
   * @param auditSpan audit span
   * @param operation operation
   * @param <T> type of result
   * @return a new invocation.
   */
  public static <T> CallableRaisingIOE<T> withinAuditSpan(
      @Nullable AuditSpan auditSpan,
      CallableRaisingIOE<T> operation) {
    return auditSpan == null
        ? operation
        : () -> {
          auditSpan.activate();
          return operation.apply();
        };
  }

  /**
   * Given an invocation, return a new invocation which
   * activates and deactivates the span around the inner invocation.
   * @param auditSpan audit span
   * @param operation operation
   * @return a new invocation.
   */
  public static InvocationRaisingIOE withinAuditSpan(
      @Nullable AuditSpan auditSpan,
      InvocationRaisingIOE operation) {
    return auditSpan == null
        ? operation
        : () -> {
          auditSpan.activate();
          operation.apply();
        };
  }

  /**
   * Given a function, return a new function which
   * activates and deactivates the span around the inner one.
   * @param auditSpan audit span
   * @param operation operation
   * @param <T> Generics Type T.
   * @param <R> Generics Type R.
   * @return a new invocation.
   */
  public static <T, R> FunctionRaisingIOE<T, R> withinAuditSpan(
      @Nullable AuditSpan auditSpan,
      FunctionRaisingIOE<T, R> operation) {
    return auditSpan == null
        ? operation
        : (x) -> {
          auditSpan.activate();
          return operation.apply(x);
        };
  }

  /**
   * Given a callable, return a new callable which
   * activates and deactivates the span around the inner invocation.
   * @param auditSpan audit span
   * @param operation operation
   * @param <T> type of result
   * @return a new invocation.
   */
  public static <T> Callable<T> callableWithinAuditSpan(
      @Nullable AuditSpan auditSpan,
      Callable<T> operation) {
    return auditSpan == null
        ? operation
        : () -> {
          auditSpan.activate();
          return operation.call();
        };
  }

}

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