Differential D15677 Diff 37783 src/infrastructure/cluster/PhabricatorDatabaseHealthRecord.php

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src/infrastructure/cluster/PhabricatorDatabaseHealthRecord.php

This file was added.

				<?php

				final class PhabricatorDatabaseHealthRecord
				extends Phobject {

				private $ref;
				private $shouldCheck;
				private $isHealthy;
				private $upEventCount;
				private $downEventCount;

				public function __construct(PhabricatorDatabaseRef $ref) {
				$this->ref = $ref;
				$this->readState();
				}


				/**
				* Is the database currently healthy?
				*/
				public function getIsHealthy() {
				return $this->isHealthy;
				}


				/**
				* Should this request check database health?
				*/
				public function getShouldCheck() {
				return $this->shouldCheck;
				}


				/**
				* How many recent health checks were successful?
				*/
				public function getUpEventCount() {
				return $this->upEventCount;
				}


				/**
				* How many recent health checks failed?
				*/
				public function getDownEventCount() {
				return $this->downEventCount;
				}


				/**
				* Number of failures or successes we need to see in a row before we change
				* the state.
				*/
				public function getRequiredEventCount() {
				return 5;
				}


				/**
				* Seconds to wait between health checks.
				*/
				public function getHealthCheckFrequency() {
				return 3;
				}


				public function didHealthCheck($result) {
				$now = microtime(true);
				$check_frequency = $this->getHealthCheckFrequency();
				$event_count = $this->getRequiredEventCount();

				$record = $this->readHealthRecord();

				$log = $record['log'];
				foreach ($log as $key => $event) {
				$when = idx($event, 'timestamp');

				// If the log already has another nearby event, just ignore this one.
				// We raced with another process and our result can just be thrown away.
				if (($now - $when) <= $check_frequency) {
				return $this;
				}
				}

				$log[] = array(
				'timestamp' => $now,
				'up' => $result,
				);

				// Throw away older events which are now obsolete.
				$log = array_slice($log, -$event_count);

				$count_up = 0;
				$count_down = 0;
				foreach ($log as $event) {
				if ($event['up']) {
				$count_up++;
				} else {
				$count_down++;
				}
				}

				// If all of the events are the same, change the state.
				if ($count_up == $event_count) {
				$record['up'] = true;
				} else if ($count_down == $event_count) {
				$record['up'] = false;
				}

				$record['log'] = $log;

				$this->writeHealthRecord($record);

				$this->isHealthy = $record['up'];
				$this->shouldCheck = false;
				$this->updateStatistics($record);

				return $this;
				}


				private function readState() {
				$now = microtime(true);
				$check_frequency = $this->getHealthCheckFrequency();

				$record = $this->readHealthRecord();

				$last_check = $record['lastCheck'];

				if (($now - $last_check) >= $check_frequency) {
				$record['lastCheck'] = $now;
				$this->writeHealthRecord($record);
				$this->shouldCheck = true;
				} else {
				$this->shouldCheck = false;
				}

				$this->isHealthy = $record['up'];
				$this->updateStatistics($record);
				}

				private function updateStatistics(array $record) {
				$this->upEventCount = 0;
				$this->downEventCount = 0;
				foreach ($record['log'] as $event) {
				if ($event['up']) {
				$this->upEventCount++;
				} else {
				$this->downEventCount++;
				}
				}
				}

				private function getHealthRecordCacheKey() {
				$ref = $this->ref;

				$host = $ref->getHost();
				$port = $ref->getPort();

				return "cluster.db.health({$host}, {$port})";
				}

				private function readHealthRecord() {
				$cache = PhabricatorCaches::getSetupCache();
				$cache_key = $this->getHealthRecordCacheKey();
				$health_record = $cache->getKey($cache_key);

				if (!is_array($health_record)) {
				$health_record = array(
				'up' => true,
				'lastCheck' => 0,
				'log' => array(),
				);
				}

				return $health_record;
				}

				private function writeHealthRecord(array $record) {
				$cache = PhabricatorCaches::getSetupCache();
				$cache_key = $this->getHealthRecordCacheKey();
				$cache->setKey($cache_key, $record);
				}

				}