Current File : //proc/985914/root/www/varak.net/wiki.varak.net/includes/config/EtcdConfig.php
<?php
/**
* 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
*/
use Psr\Log\LoggerAwareInterface;
use Psr\Log\LoggerInterface;
use Wikimedia\ObjectFactory;
use Wikimedia\WaitConditionLoop;
/**
* Interface for configuration instances
*
* @since 1.29
*/
class EtcdConfig implements Config, LoggerAwareInterface {
/** @var MultiHttpClient */
private $http;
/** @var BagOStuff */
private $srvCache;
/** @var array */
private $procCache;
/** @var LoggerInterface */
private $logger;
/** @var string */
private $host;
/** @var string */
private $protocol;
/** @var string */
private $directory;
/** @var string */
private $encoding;
/** @var int */
private $baseCacheTTL;
/** @var int */
private $skewCacheTTL;
/** @var int */
private $timeout;
/**
* @param array $params Parameter map:
* - host: the host address and port
* - protocol: either http or https
* - directory: the etc "directory" were MediaWiki specific variables are located
* - encoding: one of ("JSON", "YAML"). Defaults to JSON. [optional]
* - cache: BagOStuff instance or ObjectFactory spec thereof for a server cache.
* The cache will also be used as a fallback if etcd is down. [optional]
* - cacheTTL: logical cache TTL in seconds [optional]
* - skewTTL: maximum seconds to randomly lower the assigned TTL on cache save [optional]
* - timeout: seconds to wait for etcd before throwing an error [optional]
*/
public function __construct( array $params ) {
$params += [
'protocol' => 'http',
'encoding' => 'JSON',
'cacheTTL' => 10,
'skewTTL' => 1,
'timeout' => 2
];
$this->host = $params['host'];
$this->protocol = $params['protocol'];
$this->directory = trim( $params['directory'], '/' );
$this->encoding = $params['encoding'];
$this->skewCacheTTL = $params['skewTTL'];
$this->baseCacheTTL = max( $params['cacheTTL'] - $this->skewCacheTTL, 0 );
$this->timeout = $params['timeout'];
if ( !isset( $params['cache'] ) ) {
$this->srvCache = new HashBagOStuff();
} elseif ( $params['cache'] instanceof BagOStuff ) {
$this->srvCache = $params['cache'];
} else {
$this->srvCache = ObjectFactory::getObjectFromSpec( $params['cache'] );
}
$this->logger = new Psr\Log\NullLogger();
$this->http = new MultiHttpClient( [
'connTimeout' => $this->timeout,
'reqTimeout' => $this->timeout,
'logger' => $this->logger
] );
}
public function setLogger( LoggerInterface $logger ) {
$this->logger = $logger;
$this->http->setLogger( $logger );
}
public function has( $name ) {
$this->load();
return array_key_exists( $name, $this->procCache['config'] );
}
public function get( $name ) {
$this->load();
if ( !array_key_exists( $name, $this->procCache['config'] ) ) {
throw new ConfigException( "No entry found for '$name'." );
}
return $this->procCache['config'][$name];
}
public function getModifiedIndex() {
$this->load();
return $this->procCache['modifiedIndex'];
}
/**
* @throws ConfigException
*/
private function load() {
if ( $this->procCache !== null ) {
return; // already loaded
}
$now = microtime( true );
$key = $this->srvCache->makeGlobalKey(
__CLASS__,
$this->host,
$this->directory
);
// Get the cached value or block until it is regenerated (by this or another thread)...
$data = null; // latest config info
$error = null; // last error message
$loop = new WaitConditionLoop(
function () use ( $key, $now, &$data, &$error ) {
// Check if the values are in cache yet...
$data = $this->srvCache->get( $key );
if ( is_array( $data ) && $data['expires'] > $now ) {
$this->logger->debug( "Found up-to-date etcd configuration cache." );
return WaitConditionLoop::CONDITION_REACHED;
}
// Cache is either empty or stale;
// refresh the cache from etcd, using a mutex to reduce stampedes...
if ( $this->srvCache->lock( $key, 0, $this->baseCacheTTL ) ) {
try {
$etcdResponse = $this->fetchAllFromEtcd();
$error = $etcdResponse['error'];
if ( is_array( $etcdResponse['config'] ) ) {
// Avoid having all servers expire cache keys at the same time
$expiry = microtime( true ) + $this->baseCacheTTL;
$expiry += mt_rand( 0, 1e6 ) / 1e6 * $this->skewCacheTTL;
$data = [
'config' => $etcdResponse['config'],
'expires' => $expiry,
'modifiedIndex' => $etcdResponse['modifiedIndex']
];
$this->srvCache->set( $key, $data, BagOStuff::TTL_INDEFINITE );
$this->logger->info( "Refreshed stale etcd configuration cache." );
return WaitConditionLoop::CONDITION_REACHED;
} else {
$this->logger->error( "Failed to fetch configuration: $error" );
if ( !$etcdResponse['retry'] ) {
// Fail fast since the error is likely to keep happening
return WaitConditionLoop::CONDITION_FAILED;
}
}
} finally {
$this->srvCache->unlock( $key ); // release mutex
}
}
if ( is_array( $data ) ) {
$this->logger->info( "Using stale etcd configuration cache." );
return WaitConditionLoop::CONDITION_REACHED;
}
return WaitConditionLoop::CONDITION_CONTINUE;
},
$this->timeout
);
if ( $loop->invoke() !== WaitConditionLoop::CONDITION_REACHED ) {
// No cached value exists and etcd query failed; throw an error
throw new ConfigException( "Failed to load configuration from etcd: $error" );
}
$this->procCache = $data;
}
/**
* @return array (containing the keys config, error, retry, modifiedIndex)
*/
public function fetchAllFromEtcd() {
// TODO: inject DnsSrvDiscoverer in order to be able to test this method
$dsd = new DnsSrvDiscoverer( $this->host );
$servers = $dsd->getServers();
if ( !$servers ) {
return $this->fetchAllFromEtcdServer( $this->host );
}
do {
// Pick a random etcd server from dns
$server = $dsd->pickServer( $servers );
$host = IP::combineHostAndPort( $server['target'], $server['port'] );
// Try to load the config from this particular server
$response = $this->fetchAllFromEtcdServer( $host );
if ( is_array( $response['config'] ) || $response['retry'] ) {
break;
}
// Avoid the server next time if that failed
$servers = $dsd->removeServer( $server, $servers );
} while ( $servers );
return $response;
}
/**
* @param string $address Host and port
* @return array (containing the keys config, error, retry, modifiedIndex)
*/
protected function fetchAllFromEtcdServer( $address ) {
// Retrieve all the values under the MediaWiki config directory
list( $rcode, $rdesc, /* $rhdrs */, $rbody, $rerr ) = $this->http->run( [
'method' => 'GET',
'url' => "{$this->protocol}://{$address}/v2/keys/{$this->directory}/?recursive=true",
'headers' => [ 'content-type' => 'application/json' ]
] );
$response = [ 'config' => null, 'error' => null, 'retry' => false, 'modifiedIndex' => 0 ];
static $terminalCodes = [ 404 => true ];
if ( $rcode < 200 || $rcode > 399 ) {
$response['error'] = strlen( $rerr ) ? $rerr : "HTTP $rcode ($rdesc)";
$response['retry'] = empty( $terminalCodes[$rcode] );
return $response;
}
try {
$parsedResponse = $this->parseResponse( $rbody );
} catch ( EtcdConfigParseError $e ) {
$parsedResponse = [ 'error' => $e->getMessage() ];
}
return array_merge( $response, $parsedResponse );
}
/**
* Parse a response body, throwing EtcdConfigParseError if there is a validation error
*
* @param string $rbody
* @return array
*/
protected function parseResponse( $rbody ) {
$info = json_decode( $rbody, true );
if ( $info === null ) {
throw new EtcdConfigParseError( "Error unserializing JSON response." );
}
if ( !isset( $info['node'] ) || !is_array( $info['node'] ) ) {
throw new EtcdConfigParseError(
"Unexpected JSON response: Missing or invalid node at top level." );
}
$config = [];
$lastModifiedIndex = $this->parseDirectory( '', $info['node'], $config );
return [ 'modifiedIndex' => $lastModifiedIndex, 'config' => $config ];
}
/**
* Recursively parse a directory node and populate the array passed by
* reference, throwing EtcdConfigParseError if there is a validation error
*
* @param string $dirName The relative directory name
* @param array $dirNode The decoded directory node
* @param array &$config The output array
* @return int lastModifiedIndex The maximum last modified index across all keys in the directory
*/
protected function parseDirectory( $dirName, $dirNode, &$config ) {
$lastModifiedIndex = 0;
if ( !isset( $dirNode['nodes'] ) ) {
throw new EtcdConfigParseError(
"Unexpected JSON response in dir '$dirName'; missing 'nodes' list." );
}
if ( !is_array( $dirNode['nodes'] ) ) {
throw new EtcdConfigParseError(
"Unexpected JSON response in dir '$dirName'; 'nodes' is not an array." );
}
foreach ( $dirNode['nodes'] as $node ) {
$baseName = basename( $node['key'] );
$fullName = $dirName === '' ? $baseName : "$dirName/$baseName";
if ( !empty( $node['dir'] ) ) {
$lastModifiedIndex = max(
$this->parseDirectory( $fullName, $node, $config ),
$lastModifiedIndex );
} else {
$value = $this->unserialize( $node['value'] );
if ( !is_array( $value ) || !array_key_exists( 'val', $value ) ) {
throw new EtcdConfigParseError( "Failed to parse value for '$fullName'." );
}
$lastModifiedIndex = max( $node['modifiedIndex'], $lastModifiedIndex );
$config[$fullName] = $value['val'];
}
}
return $lastModifiedIndex;
}
/**
* @param string $string
* @return mixed
*/
private function unserialize( $string ) {
if ( $this->encoding === 'YAML' ) {
return yaml_parse( $string );
} else { // JSON
return json_decode( $string, true );
}
}
}
Mini Shell