Expose the latest modified index seen by EtcdConfig

[lhc/web/wiklou.git] / includes / config / EtcdConfig.php

diff --git a/includes/config/EtcdConfig.php b/includes/config/EtcdConfig.php
index 3811da3..7020159 100644 (file)
--- a/includes/config/EtcdConfig.php
+++ b/includes/config/EtcdConfig.php
@@ -119,6 +119,11 @@ class EtcdConfig implements Config, LoggerAwareInterface {
                return $this->procCache['config'][$name];
        }
 
+       public function getModifiedIndex() {
+               $this->load();
+               return $this->procCache['modifiedIndex'];
+       }
+
        /**
         * @throws ConfigException
         */
@@ -151,13 +156,17 @@ class EtcdConfig implements Config, LoggerAwareInterface {
                                // refresh the cache from etcd, using a mutex to reduce stampedes...
                                if ( $this->srvCache->lock( $key, 0, $this->baseCacheTTL ) ) {
                                        try {
-                                               list( $config, $error, $retry ) = $this->fetchAllFromEtcd();
-                                               if ( is_array( $config ) ) {
+                                               $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' => $config, 'expires' => $expiry ];
+                                                       $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." );
@@ -165,7 +174,7 @@ class EtcdConfig implements Config, LoggerAwareInterface {
                                                        return WaitConditionLoop::CONDITION_REACHED;
                                                } else {
                                                        $this->logger->error( "Failed to fetch configuration: $error" );
-                                                       if ( !$retry ) {
+                                                       if ( !$etcdResponse['retry'] ) {
                                                                // Fail fast since the error is likely to keep happening
                                                                return WaitConditionLoop::CONDITION_FAILED;
                                                        }
@@ -195,9 +204,10 @@ class EtcdConfig implements Config, LoggerAwareInterface {
        }
 
        /**
-        * @return array (config array or null, error string, allow retries)
+        * @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 ) {
@@ -209,8 +219,8 @@ class EtcdConfig implements Config, LoggerAwareInterface {
                        $server = $dsd->pickServer( $servers );
                        $host = IP::combineHostAndPort( $server['target'], $server['port'] );
                        // Try to load the config from this particular server
-                       list( $config, $error, $retry ) = $this->fetchAllFromEtcdServer( $host );
-                       if ( is_array( $config ) || !$retry ) {
+                       $response = $this->fetchAllFromEtcdServer( $host );
+                       if ( is_array( $response['config'] ) || $response['retry'] ) {
                                break;
                        }
 
@@ -218,12 +228,12 @@ class EtcdConfig implements Config, LoggerAwareInterface {
                        $servers = $dsd->removeServer( $server, $servers );
                } while ( $servers );
 
-               return [ $config, $error, $retry ];
+               return $response;
        }
 
        /**
         * @param string $address Host and port
-        * @return array (config array or null, error string, whether to allow retries)
+        * @return array (containing the keys config, error, retry, modifiedIndex)
         */
        protected function fetchAllFromEtcdServer( $address ) {
                // Retrieve all the values under the MediaWiki config directory
@@ -233,19 +243,21 @@ class EtcdConfig implements Config, LoggerAwareInterface {
                        'headers' => [ 'content-type' => 'application/json' ]
                ] );
 
+               $response = [ 'config' => null, 'error' => null, 'retry' => false, 'modifiedIndex' => 0 ];
+
                static $terminalCodes = [ 404 => true ];
                if ( $rcode < 200 || $rcode > 399 ) {
-                       return [
-                               null,
-                               strlen( $rerr ) ? $rerr : "HTTP $rcode ($rdesc)",
-                               empty( $terminalCodes[$rcode] )
-                       ];
+                       $response['error'] = strlen( $rerr ) ? $rerr : "HTTP $rcode ($rdesc)";
+                       $response['retry'] = empty( $terminalCodes[$rcode] );
+                       return $response;
                }
+
                try {
-                       return [ $this->parseResponse( $rbody ), null, false ];
+                       $parsedResponse = $this->parseResponse( $rbody );
                } catch ( EtcdConfigParseError $e ) {
-                       return [ null, $e->getMessage(), false ];
+                       $parsedResponse = [ 'error' => $e->getMessage() ];
                }
+               return array_merge( $response, $parsedResponse );
        }
 
        /**
@@ -264,8 +276,8 @@ class EtcdConfig implements Config, LoggerAwareInterface {
                                "Unexpected JSON response: Missing or invalid node at top level." );
                }
                $config = [];
-               $this->parseDirectory( '', $info['node'], $config );
-               return $config;
+               $lastModifiedIndex = $this->parseDirectory( '', $info['node'], $config );
+               return [ 'modifiedIndex' => $lastModifiedIndex, 'config' => $config ];
        }
 
        /**
@@ -275,8 +287,10 @@ class EtcdConfig implements Config, LoggerAwareInterface {
         * @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." );
@@ -290,16 +304,19 @@ class EtcdConfig implements Config, LoggerAwareInterface {
                        $baseName = basename( $node['key'] );
                        $fullName = $dirName === '' ? $baseName : "$dirName/$baseName";
                        if ( !empty( $node['dir'] ) ) {
-                               $this->parseDirectory( $fullName, $node, $config );
+                               $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;
        }
 
        /**