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PhabricatorDatabaseHealthRecord.php
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Wed, Nov 27, 02:55

PhabricatorDatabaseHealthRecord.php
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<?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 $this->downEventCount;
}
/**
* Number of failures or successes we need to see in a row before we change
* the state.
*/
public function getRequiredEventCount() {
// NOTE: If you change this value, update the "Cluster: Databases" docs.
return 5;
}
/**
* Seconds to wait between health checks.
*/
public function getHealthCheckFrequency() {
// NOTE: If you change this value, update the "Cluster: Databases" docs.
return 3;
}
public function didHealthCheck($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);
}
}

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