code: /*
   * Copyright © 2014-2017 EntIT Software LLC, a Micro Focus company (L.P.)
   *
   * 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 io.cloudslang.runtime.impl.python.external;
  
  import io.cloudslang.runtime.api.python.PythonEvaluationResult;
  import io.cloudslang.runtime.api.python.PythonExecutionResult;
  import io.cloudslang.runtime.api.python.PythonRuntimeService;
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  
  import javax.annotation.Resource;
  import java.io.Serializable;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.Semaphore;
  import java.util.concurrent.TimeUnit;
  
  public class ExternalPythonRuntimeServiceImpl implements PythonRuntimeService {
      private static final Logger logger = LogManager.getLogger(ExternalPythonRuntimeServiceImpl.class);
  
      private final Semaphore executionControlSemaphore;
  
      private final Semaphore testingControlSemaphore;
  
      public ExternalPythonRuntimeServiceImpl(Semaphore executionControlSemaphore, Semaphore testingControlSemaphore) {
          this.executionControlSemaphore = executionControlSemaphore;
          this.testingControlSemaphore = testingControlSemaphore;
      }
  
      @Resource(name = "externalPythonExecutionEngine")
      private ExternalPythonExecutionEngine externalPythonExecutionEngine;
  
      @Override
      public PythonExecutionResult exec(Set<String> dependencies, String script, Map<String, Serializable> vars) {
          try {
              if (executionControlSemaphore.tryAcquire(1L, TimeUnit.SECONDS)) {
                  try {
                      return externalPythonExecutionEngine.exec(dependencies, script, vars);
                  } finally {
                      executionControlSemaphore.release();
                  }
              } else {
                  logger.warn("Maximum number of python processes has been reached. Waiting for a python process to finish. " +
                          "You can configure the number of concurrent python executions by setting " +
                          "'python.concurrent.execution.permits' system property.");
                  executionControlSemaphore.acquire();
                  try {
                      logger.info("Acquired a permit for a new python process. Continuing with execution...");
                      return externalPythonExecutionEngine.exec(dependencies, script, vars);
                  } finally {
                      executionControlSemaphore.release();
                  }
              }
          } catch (InterruptedException ie) {
              throw new ExternalPythonScriptException("Execution was interrupted while waiting for a python permit.");
          }
      }
  
      @Override
      public PythonEvaluationResult test(String prepareEnvironmentScript, String script, Map<String, Serializable> vars, long timeout) {
          try {
              if (testingControlSemaphore.tryAcquire(1L, TimeUnit.SECONDS)) {
                  try {
                      return externalPythonExecutionEngine.test(prepareEnvironmentScript, script, vars, timeout);
                  } finally {
                      testingControlSemaphore.release();
                  }
              } else {
                  logger.warn("Maximum number of python processes has been reached. Waiting for a python process to finish. " +
                          "You can configure the number of concurrent python executions by setting " +
                          "'python.testing.concurrent.execution.permits' system property.");
                  testingControlSemaphore.acquire();
                  try {
                      logger.info("Acquired a permit for a new python process. Continuing with execution...");
                      return externalPythonExecutionEngine.test(prepareEnvironmentScript, script, vars, timeout);
                  } finally {
                      testingControlSemaphore.release();
                  }
              }
          } catch (InterruptedException ie) {
              throw new ExternalPythonScriptException("Execution was interrupted while waiting for a python permit.");
          }
      }
  
      @Override
      public PythonEvaluationResult eval(String prepareEnvironmentScript, String script, Map<String, Serializable> vars) {
          try {
              if (executionControlSemaphore.tryAcquire(1L, TimeUnit.SECONDS)) {
                  try {
                      return externalPythonExecutionEngine.eval(prepareEnvironmentScript, script, vars);
                  } finally {
                      executionControlSemaphore.release();
                  }
              } else {
                  logger.warn("Maximum number of python processes has been reached. Waiting for a python process to finish. " +
                          "You can configure the number of concurrent python executions by setting " +
                          "'python.concurrent.execution.permits' system property.");
                  executionControlSemaphore.acquire();
                  try {
                      logger.info("Acquired a permit for a new python process. Continuing with execution...");
                      return externalPythonExecutionEngine.eval(prepareEnvironmentScript, script, vars);
                  } finally {
                      executionControlSemaphore.release();
                  }
              }
          } catch (InterruptedException ie) {
              throw new ExternalPythonScriptException("Execution was interrupted while waiting for a python permit.");
          }
      }
  
  }
  