Added VirtualRESTServiceClient/VirtualRESTService classes
authorAaron Schulz <aschulz@wikimedia.org>
Tue, 28 Jan 2014 20:21:29 +0000 (12:21 -0800)
committerAaron Schulz <aschulz@wikimedia.org>
Wed, 30 Apr 2014 00:01:25 +0000 (17:01 -0700)
* Reference handling cleanup for loops in MultiHttpClient
* Support a slightly more convenient request array format for MultiHttpClient
* Added missing license header to MultiHttpClient

Change-Id: Icc86ed9e4c2ac78363aa7b6f3147253bb59e2afb

includes/AutoLoader.php
includes/libs/MultiHttpClient.php
includes/libs/virtualrest/SwiftVirtualRESTService.php [new file with mode: 0644]
includes/libs/virtualrest/VirtualRESTService.php [new file with mode: 0644]
includes/libs/virtualrest/VirtualRESTServiceClient.php [new file with mode: 0644]

index 077c72c..1f05ef6 100644 (file)
@@ -697,6 +697,9 @@ $wgAutoloadLocalClasses = array(
        'RunningStat' => 'includes/libs/RunningStat.php',
        'ScopedCallback' => 'includes/libs/ScopedCallback.php',
        'ScopedPHPTimeout' => 'includes/libs/ScopedPHPTimeout.php',
+       'SwiftVirtualRESTService' => 'includes/libs/virtualrest/SwiftVirtualRESTService.php',
+       'VirtualRESTService' => 'includes/libs/virtualrest/VirtualRESTService.php',
+       'VirtualRESTServiceClient' => 'includes/libs/virtualrest/VirtualRESTServiceClient.php',
        'XmlTypeCheck' => 'includes/libs/XmlTypeCheck.php',
 
        # includes/libs/lessphp
index 340e7f4..671e812 100644 (file)
@@ -86,7 +86,7 @@ class MultiHttpClient {
         *   - err     : Any cURL error string
         * The map also stores integer-indexed copies of these values. This lets callers do:
         *      <code>
-        *              list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $req;
+        *              list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $http->run( $req );
         *  </code>
         * @param array $req HTTP request array
         * @param array $opts
@@ -110,7 +110,7 @@ class MultiHttpClient {
         *   - err     : Any cURL error string
         * The map also stores integer-indexed copies of these values. This lets callers do:
         *      <code>
-        *              list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $req;
+        *              list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $req['response'];
         *  </code>
         * All headers in the 'headers' field are normalized to use lower case names.
         * This is true for the request headers and the response headers. Integer-indexed
diff --git a/includes/libs/virtualrest/SwiftVirtualRESTService.php b/includes/libs/virtualrest/SwiftVirtualRESTService.php
new file mode 100644 (file)
index 0000000..011dabe
--- /dev/null
@@ -0,0 +1,175 @@
+<?php
+/**
+ * Virtual HTTP service client for Swift
+ *
+ * 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
+ */
+
+/**
+ * Example virtual rest service for OpenStack Swift
+ * @TODO: caching support (APC/memcached)
+ * @since 1.23
+ */
+class SwiftVirtualRESTService extends VirtualRESTService {
+       /** @var array */
+       protected $authCreds;
+       /** @var int UNIX timestamp */
+       protected $authSessionTimestamp = 0;
+       /** @var int UNIX timestamp */
+       protected $authErrorTimestamp = null;
+       /** @var int */
+       protected $authCachedStatus = null;
+       /** @var string */
+       protected $authCachedReason = null;
+
+       /**
+        * @param array $params Key/value map
+        *   - swiftAuthUrl       : Swift authentication server URL
+        *   - swiftUser          : Swift user used by MediaWiki (account:username)
+        *   - swiftKey           : Swift authentication key for the above user
+        *   - swiftAuthTTL       : Swift authentication TTL (seconds)
+        */
+       public function __construct( array $params ) {
+               parent::__construct( $params );
+       }
+
+       /**
+        * @return int|bool HTTP status on cached failure
+        */
+       protected function needsAuthRequest() {
+               if ( !$this->authCreds ) {
+                       return true;
+               }
+               if ( $this->authErrorTimestamp !== null ) {
+                       if ( ( time() - $this->authErrorTimestamp ) < 60 ) {
+                               return $this->authCachedStatus; // failed last attempt; don't bother
+                       } else { // actually retry this time
+                               $this->authErrorTimestamp = null;
+                       }
+               }
+               // Session keys expire after a while, so we renew them periodically
+               return ( ( time() - $this->authSessionTimestamp ) > $this->params['swiftAuthTTL'] );
+       }
+
+       protected function applyAuthResponse( array $req ) {
+               $this->authSessionTimestamp = 0;
+               list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $req['response'];
+               if ( $rcode >= 200 && $rcode <= 299 ) { // OK
+                       $this->authCreds = array(
+                               'auth_token'  => $rhdrs['x-auth-token'],
+                               'storage_url' => $rhdrs['x-storage-url']
+                       );
+                       $this->authSessionTimestamp = time();
+                       return true;
+               } elseif ( $rcode === 403 ) {
+                       $this->authCachedStatus = 401;
+                       $this->authCachedReason = 'Authorization Required';
+                       $this->authErrorTimestamp = time();
+                       return false;
+               } else {
+                       $this->authCachedStatus = $rcode;
+                       $this->authCachedReason = $rdesc;
+                       $this->authErrorTimestamp = time();
+                       return null;
+               }
+       }
+
+       public function onRequests( array $reqs, Closure $idGeneratorFunc ) {
+               $result = array();
+               $firstReq = reset( $reqs );
+               if ( $firstReq && count( $reqs ) == 1 && isset( $firstReq['isAuth'] ) ) {
+                       // This was an authentication request for work requests...
+                       $result = $reqs; // no change
+               } else {
+                       // These are actual work requests...
+                       $needsAuth = $this->needsAuthRequest();
+                       if ( $needsAuth === true ) {
+                               // These are work requests and we don't have any token to use.
+                               // Replace the work requests with an authentication request.
+                               $result = array(
+                                       $idGeneratorFunc() => array(
+                                               'method'  => 'GET',
+                                               'url'     => $this->params['swiftAuthUrl'] . "/v1.0",
+                                               'headers' => array(
+                                                       'x-auth-user' => $this->params['swiftUser'],
+                                                       'x-auth-key'  => $this->params['swiftKey'] ),
+                                               'isAuth'  => true,
+                                               'chain'   => $reqs
+                                       )
+                               );
+                       } elseif ( $needsAuth !== false ) {
+                               // These are work requests and authentication has previously failed.
+                               // It is most efficient to just give failed pseudo responses back for
+                               // the original work requests.
+                               foreach ( $reqs as $key => $req ) {
+                                       $req['response'] = array(
+                                               'code'     => $this->authCachedStatus,
+                                               'reason'   => $this->authCachedReason,
+                                               'headers'  => array(),
+                                               'body'     => '',
+                                               'error'    => ''
+                                       );
+                                       $result[$key] = $req;
+                               }
+                       } else {
+                               // These are work requests and we have a token already.
+                               // Go through and mangle each request to include a token.
+                               foreach ( $reqs as $key => $req ) {
+                                       // The default encoding treats the URL as a REST style path that uses
+                                       // forward slash as a hierarchical delimiter (and never otherwise).
+                                       // Subclasses can override this, and should be documented in any case.
+                                       $parts = array_map( 'rawurlencode', explode( '/', $req['url'] ) );
+                                       $req['url'] = $this->authCreds['storage_url'] . '/' . implode( '/', $parts );
+                                       $req['headers']['x-auth-token'] = $this->authCreds['auth_token'];
+                                       $result[$key] = $req;
+                                       // @TODO: add ETag/Content-Length and such as needed
+                               }
+                       }
+               }
+               return $result;
+       }
+
+       public function onResponses( array $reqs, Closure $idGeneratorFunc ) {
+               $firstReq = reset( $reqs );
+               if ( $firstReq && count( $reqs ) == 1 && isset( $firstReq['isAuth'] ) ) {
+                       $result = array();
+                       // This was an authentication request for work requests...
+                       if ( $this->applyAuthResponse( $firstReq ) ) {
+                               // If it succeeded, we can subsitute the work requests back.
+                               // Call this recursively in order to munge and add headers.
+                               $result = $this->onRequests( $firstReq['chain'], $idGeneratorFunc );
+                       } else {
+                               // If it failed, it is most efficient to just give failing
+                               // pseudo-responses back for the actual work requests.
+                               foreach ( $firstReq['chain'] as $key => $req ) {
+                                       $req['response'] = array(
+                                               'code'     => $this->authCachedStatus,
+                                               'reason'   => $this->authCachedReason,
+                                               'headers'  => array(),
+                                               'body'     => '',
+                                               'error'    => ''
+                                       );
+                                       $result[$key] = $req;
+                               }
+                       }
+               } else {
+                       $result = $reqs; // no change
+               }
+               return $result;
+       }
+}
diff --git a/includes/libs/virtualrest/VirtualRESTService.php b/includes/libs/virtualrest/VirtualRESTService.php
new file mode 100644 (file)
index 0000000..05c2afc
--- /dev/null
@@ -0,0 +1,107 @@
+<?php
+/**
+ * Virtual HTTP service client
+ *
+ * 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
+ */
+
+/**
+ * Virtual HTTP service instance that can be mounted on to a VirtualRESTService
+ *
+ * Sub-classes manage the logic of either:
+ *   - a) Munging virtual HTTP request arrays to have qualified URLs and auth headers
+ *   - b) Emulating the execution of virtual HTTP requests (e.g. brokering)
+ *
+ * Authentication information can be cached in instances of the class for performance.
+ * Such information should also be cached locally on the server and auth requests should
+ * have reasonable timeouts.
+ *
+ * @since 1.23
+ */
+abstract class VirtualRESTService {
+       /** @var array Key/value map */
+       protected $params = array();
+
+       /**
+        * @param array $params Key/value map
+        */
+       public function __construct( array $params ) {
+               $this->params = $params;
+       }
+
+       /**
+        * Prepare virtual HTTP(S) requests (for this service) for execution
+        *
+        * This method should mangle any of the $reqs entry fields as needed:
+        *   - url      : munge the URL to have an absolute URL with a protocol
+        *                and encode path components as needed by the backend [required]
+        *   - query    : include any authentication signatures/parameters [as needed]
+        *   - headers  : include any authentication tokens/headers [as needed]
+        *
+        * The incoming URL parameter will be relative to the service mount point.
+        *
+        * This method can also remove some of the requests as well as add new ones
+        * (using $idGenerator to set each of the entries' array keys). For any existing
+        * or added request, the 'response' array can be filled in, which will prevent the
+        * client from executing it. If an original request is removed, at some point it
+        * must be added back (with the same key) in onRequests() or onResponses();
+        * it's reponse may be filled in as with other requests.
+        *
+        * @param array $reqs Map of Virtual HTTP request arrays
+        * @param Closure $idGeneratorFunc Method to generate unique keys for new requests
+        * @return array Modified HTTP request array map
+        */
+       public function onRequests( array $reqs, Closure $idGeneratorFunc ) {
+               $result = array();
+               foreach ( $reqs as $key => $req ) {
+                       // The default encoding treats the URL as a REST style path that uses
+                       // forward slash as a hierarchical delimiter (and never otherwise).
+                       // Subclasses can override this, and should be documented in any case.
+                       $parts = array_map( 'rawurlencode', explode( '/', $req['url'] ) );
+                       $req['url'] = $this->params['baseUrl'] . '/' . implode( '/', $parts );
+                       $result[$key] = $req;
+               }
+               return $result;
+       }
+
+       /**
+        * Mangle or replace virtual HTTP(S) requests which have been responded to
+        *
+        * This method may mangle any of the $reqs entry 'response' fields as needed:
+        *   - code    : perform any code normalization [as needed]
+        *   - reason  : perform any reason normalization [as needed]
+        *   - headers : perform any header normalization [as needed]
+        *
+        * This method can also remove some of the requests as well as add new ones
+        * (using $idGenerator to set each of the entries' array keys). For any existing
+        * or added request, the 'response' array can be filled in, which will prevent the
+        * client from executing it. If an original request is removed, at some point it
+        * must be added back (with the same key) in onRequests() or onResponses();
+        * it's reponse may be filled in as with other requests. All requests added to $reqs
+        * will be passed through onRequests() to handle any munging required as normal.
+        *
+        * The incoming URL parameter will be relative to the service mount point.
+        *
+        * @param array $reqs Map of Virtual HTTP request arrays with 'response' set
+        * @param Closure $idGeneratorFunc Method to generate unique keys for new requests
+        * @return array Modified HTTP request array map
+        */
+       public function onResponses( array $reqs, Closure $idGeneratorFunc ) {
+               return $reqs;
+       }
+}
diff --git a/includes/libs/virtualrest/VirtualRESTServiceClient.php b/includes/libs/virtualrest/VirtualRESTServiceClient.php
new file mode 100644 (file)
index 0000000..2d21d3c
--- /dev/null
@@ -0,0 +1,289 @@
+<?php
+/**
+ * Virtual HTTP service client
+ *
+ * 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
+ */
+
+/**
+ * Virtual HTTP service client loosely styled after a Virtual File System
+ *
+ * Services can be mounted on path prefixes so that virtual HTTP operations
+ * against sub-paths will map to those services. Operations can actually be
+ * done using HTTP messages over the wire or may simple be emulated locally.
+ *
+ * Virtual HTTP request maps are arrays that use the following format:
+ *   - method   : GET/HEAD/PUT/POST/DELETE
+ *   - url      : HTTP/HTTPS URL or virtual service path with a registered prefix
+ *   - query    : <query parameter field/value associative array> (uses RFC 3986)
+ *   - headers  : <header name/value associative array>
+ *   - body     : source to get the HTTP request body from;
+ *                this can simply be a string (always), a resource for
+ *                PUT requests, and a field/value array for POST request;
+ *                array bodies are encoded as multipart/form-data and strings
+ *                use application/x-www-form-urlencoded (headers sent automatically)
+ *   - stream   : resource to stream the HTTP response body to
+ * Request maps can use integer index 0 instead of 'method' and 1 instead of 'url'.
+ *
+ * @author Aaron Schulz
+ * @since 1.23
+ */
+class VirtualRESTServiceClient {
+       /** @var MultiHttpClient */
+       protected $http;
+       /** @var Array Map of (prefix => VirtualRESTService) */
+       protected $instances = array();
+
+       const VALID_MOUNT_REGEX = '#^/[0-9a-z]+/([0-9a-z]+/)*$#';
+
+       /**
+        * @param MultiHttpClient $http
+        */
+       public function __construct( MultiHttpClient $http ) {
+               $this->http = $http;
+       }
+
+       /**
+        * Map a prefix to service handler
+        *
+        * @param string $prefix Virtual path
+        * @param VirtualRESTService $instance
+        */
+       public function mount( $prefix, VirtualRESTService $instance ) {
+               if ( !preg_match( self::VALID_MOUNT_REGEX, $prefix ) ) {
+                       throw new UnexpectedValueException( "Invalid service mount point '$prefix'." );
+               } elseif ( isset( $this->instances[$prefix] ) ) {
+                       throw new UnexpectedValueException( "A service is already mounted on '$prefix'." );
+               }
+               $this->instances[$prefix] = $instance;
+       }
+
+       /**
+        * Unmap a prefix to service handler
+        *
+        * @param string $prefix Virtual path
+        */
+       public function unmount( $prefix ) {
+               if ( !preg_match( self::VALID_MOUNT_REGEX, $prefix ) ) {
+                       throw new UnexpectedValueException( "Invalid service mount point '$prefix'." );
+               } elseif ( !isset( $this->instances[$prefix] ) ) {
+                       throw new UnexpectedValueException( "No service is mounted on '$prefix'." );
+               }
+               unset( $this->instances[$prefix] );
+       }
+
+       /**
+        * Get the prefix and service that a virtual path is serviced by
+        *
+        * @param string $path
+        * @return array (prefix,VirtualRESTService) or (null,null) if none found
+        */
+       public function getMountAndService( $path ) {
+               $cmpFunc = function( $a, $b ) {
+                       $al = substr_count( $a, '/' );
+                       $bl = substr_count( $b, '/' );
+                       if ( $al === $bl ) {
+                               return 0; // should not actually happen
+                       }
+                       return ( $al < $bl ) ? 1 : -1; // largest prefix first
+               };
+
+               $matches = array(); // matching prefixes (mount points)
+               foreach ( $this->instances as $prefix => $service ) {
+                       if ( strpos( $path, $prefix ) === 0 ) {
+                               $matches[] = $prefix;
+                       }
+               }
+               usort( $matches, $cmpFunc );
+
+               // Return the most specific prefix and corresponding service
+               return isset( $matches[0] )
+                       ? array( $matches[0], $this->instances[$matches[0]] )
+                       : array( null, null );
+       }
+
+       /**
+        * Execute a virtual HTTP(S) request
+        *
+        * This method returns a response map of:
+        *   - code    : HTTP response code or 0 if there was a serious cURL error
+        *   - reason  : HTTP response reason (empty if there was a serious cURL error)
+        *   - headers : <header name/value associative array>
+        *   - body    : HTTP response body or resource (if "stream" was set)
+        *   - err     : Any cURL error string
+        * The map also stores integer-indexed copies of these values. This lets callers do:
+        *      <code>
+        *              list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $client->run( $req );
+        *  </code>
+        * @param array $req Virtual HTTP request array
+        * @return array Response array for request
+        */
+       public function run( array $req ) {
+               $req = $this->runMulti( array( $req ) );
+               return $req[0]['response'];
+       }
+
+       /**
+        * Execute a set of virtual HTTP(S) requests concurrently
+        *
+        * A map of requests keys to response maps is returned. Each response map has:
+        *   - code    : HTTP response code or 0 if there was a serious cURL error
+        *   - reason  : HTTP response reason (empty if there was a serious cURL error)
+        *   - headers : <header name/value associative array>
+        *   - body    : HTTP response body or resource (if "stream" was set)
+        *   - err     : Any cURL error string
+        * The map also stores integer-indexed copies of these values. This lets callers do:
+        *      <code>
+        *              list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $responses[0];
+        *  </code>
+        *
+        * @param array $req Map of Virtual HTTP request arrays
+        * @return array $reqs Map of corresponding response values with the same keys/order
+        */
+       public function runMulti( array $reqs ) {
+               foreach ( $reqs as $index => &$req ) {
+                       if ( isset( $req[0] ) ) {
+                               $req['method'] = $req[0]; // short-form
+                               unset( $req[0] );
+                       }
+                       if ( isset( $req[1] ) ) {
+                               $req['url'] = $req[1]; // short-form
+                               unset( $req[1] );
+                       }
+                       $req['chain'] = array(); // chain or list of replaced requests
+               }
+               unset( $req ); // don't assign over this by accident
+
+               $curUniqueId = 0;
+               $armoredIndexMap = array(); // (original index => new index)
+
+               $doneReqs = array(); // (index => request)
+               $executeReqs = array(); // (index => request)
+               $replaceReqsByService = array(); // (prefix => index => request)
+               $origPending = array(); // (index => 1) for original requests
+
+               foreach ( $reqs as $origIndex => $req ) {
+                       // Re-index keys to consecutive integers (they will be swapped back later)
+                       $index = $curUniqueId++;
+                       $armoredIndexMap[$origIndex] = $index;
+                       $origPending[$index] = 1;
+                       if ( preg_match( '#^(http|ftp)s?://#', $req['url'] ) ) {
+                               // Absolute FTP/HTTP(S) URL, run it as normal
+                               $executeReqs[$index] = $req;
+                       } else {
+                               // Must be a virtual HTTP URL; resolve it
+                               list( $prefix, $service ) = $this->getMountAndService( $req['url'] );
+                               if ( !$service ) {
+                                       throw new UnexpectedValueException( "Path '{$req['url']}' has no service." );
+                               }
+                               // Set the URL to the mount-relative portion
+                               $req['url'] = substr( $req['url'], strlen( $prefix ) );
+                               $replaceReqsByService[$prefix][$index] = $req;
+                       }
+               }
+
+               // Function to get IDs that won't collide with keys in $armoredIndexMap
+               $idFunc = function() use ( &$curUniqueId ) {
+                       return $curUniqueId++;
+               };
+
+               $rounds = 0;
+               do {
+                       if ( ++$rounds > 5 ) { // sanity
+                               throw new Exception( "Too many replacement rounds detected. Aborting." );
+                       }
+                       // Resolve the virtual URLs valid and qualified HTTP(S) URLs
+                       // and add any required authentication headers for the backend.
+                       // Services can also replace requests with new ones, either to
+                       // defer the original or to set a proxy response to the original.
+                       $newReplaceReqsByService = array();
+                       foreach ( $replaceReqsByService as $prefix => $servReqs ) {
+                               $service = $this->instances[$prefix];
+                               foreach ( $service->onRequests( $servReqs, $idFunc ) as $index => $req ) {
+                                       // Services use unique IDs for replacement requests
+                                       if ( isset( $servReqs[$index] ) || isset( $origPending[$index] ) ) {
+                                               // A current or original request which was not modified
+                                       } else {
+                                               // Replacement requests with pre-set responses should not execute
+                                               $newReplaceReqsByService[$prefix][$index] = $req;
+                                       }
+                                       if ( isset( $req['response'] ) ) {
+                                               // Replacement requests with pre-set responses should not execute
+                                               unset( $executeReqs[$index] );
+                                               unset( $origPending[$index] );
+                                               $doneReqs[$index] = $req;
+                                       } else {
+                                               // Original or mangled request included
+                                               $executeReqs[$index] = $req;
+                                       }
+                               }
+                       }
+                       // Update index of requests to inspect for replacement
+                       $replaceReqsByService = $newReplaceReqsByService;
+                       // Run the actual work HTTP requests
+                       foreach ( $this->http->runMulti( $executeReqs ) as $index => $ranReq ) {
+                               $doneReqs[$index] = $ranReq;
+                               unset( $origPending[$index] );
+                       }
+                       $executeReqs = array();
+                       // Services can also replace requests with new ones, either to
+                       // defer the original or to set a proxy response to the original.
+                       // Any replacement requests executed above will need to be replaced
+                       // with new requests (eventually the original). The responses can be
+                       // forced instead of having the request sent over the wire.
+                       $newReplaceReqsByService = array();
+                       foreach ( $replaceReqsByService as $prefix => $servReqs ) {
+                               $service = $this->instances[$prefix];
+                               // Only the request copies stored in $doneReqs actually have the response
+                               $servReqs = array_intersect_key( $doneReqs, $servReqs );
+                               foreach ( $service->onResponses( $servReqs, $idFunc ) as $index => $req ) {
+                                       // Services use unique IDs for replacement requests
+                                       if ( isset( $servReqs[$index] ) || isset( $origPending[$index] ) ) {
+                                               // A current or original request which was not modified
+                                       } else {
+                                               // Replacement requests with pre-set responses should not execute
+                                               $newReplaceReqsByService[$prefix][$index] = $req;
+                                       }
+                                       if ( isset( $req['response'] ) ) {
+                                               // Replacement requests with pre-set responses should not execute
+                                               unset( $origPending[$index] );
+                                               $doneReqs[$index] = $req;
+                                       } else {
+                                               // Update the request in case it was mangled
+                                               $executeReqs[$index] = $req;
+                                       }
+                               }
+                       }
+                       // Update index of requests to inspect for replacement
+                       $replaceReqsByService = $newReplaceReqsByService;
+               } while ( count( $origPending ) );
+
+               $responses = array();
+               // Update $reqs to include 'response' and normalized request 'headers'.
+               // This maintains the original order of $reqs.
+               foreach ( $reqs as $origIndex => $req ) {
+                       $index = $armoredIndexMap[$origIndex];
+                       if ( !isset( $doneReqs[$index] ) ) {
+                               throw new UnexpectedValueException( "Response for request '$index' is NULL." );
+                       }
+                       $responses[$origIndex] = $doneReqs[$index]['response'];
+               }
+
+               return $responses;
+       }
+}