--- /dev/null
+<?php
+/**
+ * Wait loop that reaches a condition or times out.
+ *
+ * Copyright (C) 2016 Aaron Schulz <aschulz@wikimedia.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @author Aaron Schulz
+ */
+
+namespace Wikimedia;
+
+/**
+ * Wait loop that reaches a condition or times out
+ */
+class WaitConditionLoop {
+ /** @var callable */
+ private $condition;
+ /** @var callable[] */
+ private $busyCallbacks = [];
+ /** @var float Seconds */
+ private $timeout;
+ /** @var float Seconds */
+ private $lastWaitTime;
+ /** @var integer|null */
+ private $rusageMode;
+
+ const CONDITION_REACHED = 1;
+ const CONDITION_CONTINUE = 0; // evaluates as falsey
+ const CONDITION_FAILED = -1;
+ const CONDITION_TIMED_OUT = -2;
+ const CONDITION_ABORTED = -3;
+
+ /**
+ * @param callable $condition Callback that returns a WaitConditionLoop::CONDITION_ constant
+ * @param float $timeout Timeout in seconds
+ * @param array &$busyCallbacks List of callbacks to do useful work (by reference)
+ */
+ public function __construct( callable $condition, $timeout = 5.0, &$busyCallbacks = [] ) {
+ $this->condition = $condition;
+ $this->timeout = $timeout;
+ $this->busyCallbacks =& $busyCallbacks;
+
+ if ( defined( 'HHVM_VERSION' ) && PHP_OS === 'Linux' ) {
+ $this->rusageMode = 2; // RUSAGE_THREAD
+ } elseif ( function_exists( 'getrusage' ) ) {
+ $this->rusageMode = 0; // RUSAGE_SELF
+ }
+ }
+
+ /**
+ * Invoke the loop and continue until either:
+ * - a) The condition callback returns neither CONDITION_CONTINUE nor false
+ * - b) The timeout is reached
+ * This a condition callback can return true (stop) or false (continue) for convenience.
+ * In such cases, the halting result of "true" will be converted to CONDITION_REACHED.
+ *
+ * If $timeout is 0, then only the condition callback will be called (no busy callbacks),
+ * and this will immediately return CONDITION_FAILED if the condition was not met.
+ *
+ * Exceptions in callbacks will be caught and the callback will be swapped with
+ * one that simply rethrows that exception back to the caller when invoked.
+ *
+ * @return integer WaitConditionLoop::CONDITION_* constant
+ * @throws \Exception Any error from the condition callback
+ */
+ public function invoke() {
+ $elapsed = 0.0; // seconds
+ $sleepUs = 0; // microseconds to sleep each time
+ $lastCheck = false;
+ $finalResult = self::CONDITION_TIMED_OUT;
+ do {
+ $checkStartTime = $this->getWallTime();
+ // Check if the condition is met yet
+ $realStart = $this->getWallTime();
+ $cpuStart = $this->getCpuTime();
+ $checkResult = call_user_func( $this->condition );
+ $cpu = $this->getCpuTime() - $cpuStart;
+ $real = $this->getWallTime() - $realStart;
+ // Exit if the condition is reached, an error occurs, or this is non-blocking
+ if ( $this->timeout <= 0 ) {
+ $finalResult = $checkResult ? self::CONDITION_REACHED : self::CONDITION_FAILED;
+ break;
+ } elseif ( (int)$checkResult !== self::CONDITION_CONTINUE ) {
+ if ( is_int( $checkResult ) ) {
+ $finalResult = $checkResult;
+ } else {
+ $finalResult = self::CONDITION_REACHED;
+ }
+ break;
+ } elseif ( $lastCheck ) {
+ break; // timeout reached
+ }
+ // Detect if condition callback seems to block or if justs burns CPU
+ $conditionUsesInterrupts = ( $real > 0.100 && $cpu <= $real * .03 );
+ if ( !$this->popAndRunBusyCallback() && !$conditionUsesInterrupts ) {
+ // 10 queries = 10(10+100)/2 ms = 550ms, 14 queries = 1050ms
+ $sleepUs = min( $sleepUs + 10 * 1e3, 1e6 ); // stop incrementing at ~1s
+ $this->usleep( $sleepUs );
+ }
+ $checkEndTime = $this->getWallTime();
+ // The max() protects against the clock getting set back
+ $elapsed += max( $checkEndTime - $checkStartTime, 0.010 );
+ // Do not let slow callbacks timeout without checking the condition one more time
+ $lastCheck = ( $elapsed >= $this->timeout );
+ } while ( true );
+
+ $this->lastWaitTime = $elapsed;
+
+ return $finalResult;
+ }
+
+ /**
+ * @return float Seconds
+ */
+ public function getLastWaitTime() {
+ return $this->lastWaitTime;
+ }
+
+ /**
+ * @param integer $microseconds
+ */
+ protected function usleep( $microseconds ) {
+ usleep( $microseconds );
+ }
+
+ /**
+ * @return float
+ */
+ protected function getWallTime() {
+ return microtime( true );
+ }
+
+ /**
+ * @return float Returns 0.0 if not supported (Windows on PHP < 7)
+ */
+ protected function getCpuTime() {
+ if ( $this->rusageMode === null ) {
+ return microtime( true ); // assume worst case (all time is CPU)
+ }
+
+ $ru = getrusage( $this->rusageMode );
+ $time = $ru['ru_utime.tv_sec'] + $ru['ru_utime.tv_usec'] / 1e6;
+ $time += $ru['ru_stime.tv_sec'] + $ru['ru_stime.tv_usec'] / 1e6;
+
+ return $time;
+ }
+
+ /**
+ * Run one of the callbacks that does work ahead of time for another caller
+ *
+ * @return bool Whether a callback was executed
+ */
+ private function popAndRunBusyCallback() {
+ if ( $this->busyCallbacks ) {
+ reset( $this->busyCallbacks );
+ $key = key( $this->busyCallbacks );
+ /** @var callable $workCallback */
+ $workCallback =& $this->busyCallbacks[$key];
+ try {
+ $workCallback();
+ } catch ( \Exception $e ) {
+ $workCallback = function () use ( $e ) {
+ throw $e;
+ };
+ }
+ unset( $this->busyCallbacks[$key] ); // consume
+
+ return true;
+ }
+
+ return false;
+ }
+}
scripts.mit.edu / autoinstallsdev / mediawiki.git / blobdiff