ambari/hmc/php/util/lock.php

<?php
/*
 *
 * 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.
 *
*/


$logger = new HMCLogger("Lock");
$lockFile = $GLOBALS['HMC_CLUSTER_PATH']."/lockfile";
$GLOBALS['fileHdl'] = 0;


function LockAcquire($suffixT = "") {
  global $lockFile;
  global $logger;
  $suffix = strtolower($suffixT);

  $suffixLockFile = $lockFile;
  if ($suffix != "") {
    $suffixLockFile = $lockFile.".".$suffix;
  }

  if ($suffix != "" && !file_exists($suffixLockFile)) {
    $h = fopen($suffixLockFile, "x");
    if ($h !== FALSE) {
      fclose($h);
    }
  }

  $logger->log_trace("About to acquire lock using $suffixLockFile for pid: " .
    json_encode(posix_getpid()));
  $fileHdl = fopen($suffixLockFile, "r");
  $GLOBALS['fileHdl'.$suffix] = $fileHdl;
  $retval = flock($fileHdl, LOCK_EX);
  /* Uncomment for debugging purposes
  $e = new Exception;
  $logger->log_trace("Acquired Lock Status for Process: "
    . json_encode(posix_getpid()). " : ". json_encode($retval) . " backtrace: ".
  $e->getTraceAsString());
  unset($e);
   */
  return;
}

function LockRelease($suffixT = "") {
  global $lockFile;
  global $logger;
  $suffix = strtolower($suffixT);

  $suffixLockFile = $lockFile;
  if ($suffix != "") {
    $suffixLockFile = $lockFile.".".$suffix;
  }

  $logger->log_trace("Trying to release lock using $suffixLockFile for process: "
     . json_encode(posix_getpid()));
  $fileHdl = $GLOBALS['fileHdl'.$suffix];
  $retval = flock($fileHdl, LOCK_UN);
  /* Uncomment for debugging purposes
  $e = new Exception;
  $logger->log_trace("Released Lock Status for Process: "
  . json_encode(posix_getpid()). " : ". json_encode($retval) . " backtrace: ".
  $e->getTraceAsString());
  unset($e);
   */
}

?>