Implement a more compact, general database-backed key-value cache

Summary:
See discussion in D4204. Facebook currently has a 314MB remarkup cache with a 55MB index, which is slow to access. Under the theory that this is an index size/quality problem (the current index is on a potentially-384-byte field, with many keys sharing prefixes), provide a more general index with fancy new features:

  - It implements PhutilKeyValueCache, so it can be a component in cache stacks and supports TTL.
  - It has a 12-byte hash-based key.
  - It automatically compresses large blocks of data (most of what we store is highly-compressible HTML).

Test Plan:
  - Basics:
    - Loaded /paste/, saw caches generate and save.
    - Reloaded /paste/, saw the page hit cache.
  - GC:
    - Ran GC daemon, saw nothing.
    - Set maximum lifetime to 1 second, ran GC daemon, saw it collect the entire cache.
  - Deflate:
    - Selected row formats from the database, saw a mixture of 'raw' and 'deflate' storage.
    - Used profiler to verify that 'deflate' is fast (12 calls @ 220us on my paste list).
  - Ran unit tests

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D4259

conf/default.conf.php

@@ -1130,6 +1130,13 @@ return array(
   'remarkup.enable-embedded-youtube' => false,
 
 
+// -- Cache ----------------------------------------------------------------- //
+
+  // Set this to false to disable the use of gzdeflate()-based compression in
+  // some caches. This may give you less performant (but more debuggable)
+  // caching.
+  'cache.enable-deflate' => true,
+
 // -- Garbage Collection ---------------------------------------------------- //
 
   // Phabricator generates various logs and caches in the database which can
@@ -1160,6 +1167,7 @@ return array(
   'gcdaemon.ttl.differential-parse-cache'   => 14 * (24 * 60 * 60),
   'gcdaemon.ttl.markup-cache'               => 30 * (24 * 60 * 60),
   'gcdaemon.ttl.task-archive'               => 14 * (24 * 60 * 60),
+  'gcdaemon.ttl.general-cache'              => 30 * (24 * 60 * 60),
 
 
 // -- Feed ------------------------------------------------------------------ //

resources/sql/patches/20121220.generalcache.sql

@@ -0,0 +1,11 @@
+CREATE TABLE {$NAMESPACE}_cache.cache_general (
+  id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  cacheKeyHash CHAR(12) BINARY NOT NULL,
+  cacheKey VARCHAR(128) NOT NULL COLLATE utf8_bin,
+  cacheFormat VARCHAR(16) NOT NULL COLLATE utf8_bin,
+  cacheData LONGBLOB NOT NULL,
+  cacheCreated INT UNSIGNED NOT NULL,
+  cacheExpires INT UNSIGNED,
+  KEY `key_cacheCreated` (cacheCreated),
+  UNIQUE KEY `key_cacheKeyHash` (cacheKeyHash)
+) ENGINE=InnoDB, COLLATE utf8_general_ci;

src/__phutil_library_map__.php

@@ -505,6 +505,7 @@ phutil_register_library_map(array(
     'JavelinUIExample' => 'applications/uiexample/examples/JavelinUIExample.php',
     'JavelinViewExample' => 'applications/uiexample/examples/JavelinViewExample.php',
     'JavelinViewExampleServerView' => 'applications/uiexample/examples/JavelinViewExampleServerView.php',
+    'LiskChunkTestCase' => 'infrastructure/storage/lisk/__tests__/LiskChunkTestCase.php',
     'LiskDAO' => 'infrastructure/storage/lisk/LiskDAO.php',
     'LiskDAOSet' => 'infrastructure/storage/lisk/LiskDAOSet.php',
     'LiskDAOTestCase' => 'infrastructure/storage/lisk/__tests__/LiskDAOTestCase.php',
@@ -835,6 +836,7 @@ phutil_register_library_map(array(
     'PhabricatorInlineSummaryView' => 'infrastructure/diff/view/PhabricatorInlineSummaryView.php',
     'PhabricatorJavelinLinter' => 'infrastructure/lint/linter/PhabricatorJavelinLinter.php',
     'PhabricatorJumpNavHandler' => 'applications/search/engine/PhabricatorJumpNavHandler.php',
+    'PhabricatorKeyValueDatabaseCache' => 'applications/cache/PhabricatorKeyValueDatabaseCache.php',
     'PhabricatorLDAPLoginController' => 'applications/auth/controller/PhabricatorLDAPLoginController.php',
     'PhabricatorLDAPProvider' => 'applications/auth/ldap/PhabricatorLDAPProvider.php',
     'PhabricatorLDAPRegistrationController' => 'applications/auth/controller/PhabricatorLDAPRegistrationController.php',
@@ -1789,6 +1791,7 @@ phutil_register_library_map(array(
     'JavelinUIExample' => 'PhabricatorUIExample',
     'JavelinViewExample' => 'PhabricatorUIExample',
     'JavelinViewExampleServerView' => 'AphrontView',
+    'LiskChunkTestCase' => 'PhabricatorTestCase',
     'LiskDAOTestCase' => 'PhabricatorTestCase',
     'LiskEphemeralObjectException' => 'Exception',
     'LiskFixtureTestCase' => 'PhabricatorTestCase',
@@ -2118,6 +2121,7 @@ phutil_register_library_map(array(
     'PhabricatorInlineCommentPreviewController' => 'PhabricatorController',
     'PhabricatorInlineSummaryView' => 'AphrontView',
     'PhabricatorJavelinLinter' => 'ArcanistLinter',
+    'PhabricatorKeyValueDatabaseCache' => 'PhutilKeyValueCache',
     'PhabricatorLDAPLoginController' => 'PhabricatorAuthController',
     'PhabricatorLDAPRegistrationController' => 'PhabricatorAuthController',
     'PhabricatorLDAPUnknownUserException' => 'Exception',

src/applications/cache/PhabricatorKeyValueDatabaseCache.php

@@ -0,0 +1,232 @@
+<?php
+
+final class PhabricatorKeyValueDatabaseCache
+  extends PhutilKeyValueCache {
+
+  const CACHE_FORMAT_RAW        = 'raw';
+  const CACHE_FORMAT_DEFLATE    = 'deflate';
+
+  public function setKeys(array $keys, $ttl = null) {
+    $call_id = null;
+    if ($this->getProfiler()) {
+      $call_id = $this->getProfiler()->beginServiceCall(
+        array(
+          'type' => 'kvcache-set',
+          'name' => 'phabricator-db',
+          'keys' => array_keys($keys),
+          'ttl'  => $ttl,
+        ));
+    }
+
+    if ($keys) {
+      $map = $this->digestKeys(array_keys($keys));
+      $conn_w = $this->establishConnection('w');
+
+      $sql = array();
+      foreach ($map as $key => $hash) {
+        $value = $keys[$key];
+
+        list($format, $storage_value) = $this->willWriteValue($key, $value);
+
+        $sql[] = qsprintf(
+          $conn_w,
+          '(%s, %s, %s, %s, %d, %nd)',
+          $hash,
+          $key,
+          $format,
+          $storage_value,
+          time(),
+          $ttl ? (time() + $ttl) : null);
+      }
+
+      $guard = AphrontWriteGuard::beginScopedUnguardedWrites();
+        foreach (PhabricatorLiskDAO::chunkSQL($sql) as $chunk) {
+            queryfx(
+              $conn_w,
+              'INSERT INTO %T
+                (cacheKeyHash, cacheKey, cacheFormat, cacheData,
+                  cacheCreated, cacheExpires) VALUES %Q
+                ON DUPLICATE KEY UPDATE
+                  cacheKey = VALUES(cacheKey),
+                  cacheFormat = VALUES(cacheFormat),
+                  cacheData = VALUES(cacheData),
+                  cacheCreated = VALUES(cacheCreated),
+                  cacheExpires = VALUES(cacheExpires)',
+              $this->getTableName(),
+              $chunk);
+        }
+      unset($guard);
+    }
+
+    if ($call_id) {
+      $this->getProfiler()->endServiceCall($call_id, array());
+    }
+
+    return $this;
+  }
+
+  public function getKeys(array $keys) {
+    $call_id = null;
+    if ($this->getProfiler()) {
+      $call_id = $this->getProfiler()->beginServiceCall(
+        array(
+          'type' => 'kvcache-get',
+          'name' => 'phabricator-db',
+          'keys' => $keys,
+        ));
+    }
+
+    $results = array();
+    if ($keys) {
+      $map = $this->digestKeys($keys);
+
+      $rows = queryfx_all(
+        $this->establishConnection('r'),
+        'SELECT * FROM %T WHERE cacheKeyHash IN (%Ls)',
+        $this->getTableName(),
+        $map);
+      $rows = ipull($rows, null, 'cacheKey');
+
+      foreach ($keys as $key) {
+        if (empty($rows[$key])) {
+          continue;
+        }
+
+        $row = $rows[$key];
+
+        if ($row['cacheExpires'] && ($row['cacheExpires'] < time())) {
+          continue;
+        }
+
+        try {
+          $results[$key] = $this->didReadValue(
+            $row['cacheFormat'],
+            $row['cacheData']);
+        } catch (Exception $ex) {
+          // Treat this as a cache miss.
+          phlog($ex);
+        }
+      }
+    }
+
+    if ($call_id) {
+      $this->getProfiler()->endServiceCall(
+        $call_id,
+        array(
+          'hits' => array_keys($results),
+        ));
+    }
+
+    return $results;
+  }
+
+  public function deleteKeys(array $keys) {
+    $call_id = null;
+    if ($this->getProfiler()) {
+      $call_id = $this->getProfiler()->beginServiceCall(
+        array(
+          'type' => 'kvcache-del',
+          'name' => 'phabricator-db',
+          'keys' => $keys,
+        ));
+    }
+
+    if ($keys) {
+      $map = $this->digestKeys($keys);
+      queryfx(
+        $this->establishConnection('w'),
+        'DELETE FROM %T WHERE cacheKeyHash IN (%Ls)',
+        $this->getTableName(),
+        $keys);
+    }
+
+    if ($call_id) {
+      $this->getProfiler()->endServiceCall($call_id, array());
+    }
+
+    return $this;
+  }
+
+  public function destroyCache() {
+    queryfx(
+      $this->establishConnection('w'),
+      'DELETE FROM %T',
+      $this->getTableName());
+    return $this;
+  }
+
+
+/* -(  Raw Cache Access  )--------------------------------------------------- */
+
+
+  public function establishConnection($mode) {
+    // TODO: This is the only concrete table we have on the database right
+    // now.
+    return id(new PhabricatorMarkupCache())->establishConnection($mode);
+  }
+
+  public function getTableName() {
+    return 'cache_general';
+  }
+
+
+/* -(  Implementation  )----------------------------------------------------- */
+
+
+  private function digestKeys(array $keys) {
+    $map = array();
+    foreach ($keys as $key) {
+      $map[$key] = PhabricatorHash::digestForIndex($key);
+    }
+    return $map;
+  }
+
+  private function willWriteValue($key, $value) {
+    if (!is_string($value)) {
+      throw new Exception("Only strings may be written to the DB cache!");
+    }
+
+    static $can_deflate;
+    if ($can_deflate === null) {
+      $can_deflate = function_exists('gzdeflate') &&
+                     PhabricatorEnv::getEnvConfig('cache.enable-deflate');
+    }
+
+    // If the value is larger than 1KB, we have gzdeflate(), we successfully
+    // can deflate it, and it benefits from deflation, store it deflated.
+    if ($can_deflate) {
+      $len = strlen($value);
+      if ($len > 1024) {
+        $deflated = gzdeflate($value);
+        if ($deflated !== false) {
+          $deflated_len = strlen($deflated);
+          if ($deflated_len < ($len / 2)) {
+            return array(self::CACHE_FORMAT_DEFLATE, $deflated);
+          }
+        }
+      }
+    }
+
+    return array(self::CACHE_FORMAT_RAW, $value);
+  }
+
+  private function didReadValue($format, $value) {
+    switch ($format) {
+      case self::CACHE_FORMAT_RAW:
+        return $value;
+      case self::CACHE_FORMAT_DEFLATE:
+        if (!function_exists('gzinflate')) {
+          throw new Exception("No gzinflate() to read deflated cache.");
+        }
+        $value = gzinflate($value);
+        if ($value === false) {
+          throw new Exception("Failed to deflate cache.");
+        }
+        return $value;
+      default:
+        throw new Exception("Unknown cache format.");
+    }
+  }
+
+
+}

src/applications/paste/query/PhabricatorPasteQuery.php

@@ -124,23 +124,22 @@ final class PhabricatorPasteQuery
   }
 
   private function loadContent(array $pastes) {
+    $cache = id(new PhabricatorKeyValueDatabaseCache())
+      ->setProfiler(PhutilServiceProfiler::getInstance());
+
     $keys = array();
     foreach ($pastes as $paste) {
       $keys[] = $this->getContentCacheKey($paste);
     }
 
-    // TODO: Move to a more appropriate/general cache once we have one? For
+
-    // now, this gets automatic GC.
+    $caches = $cache->getKeys($keys);
-    $caches = id(new PhabricatorMarkupCache())->loadAllWhere(
-      'cacheKey IN (%Ls)',
-      $keys);
-    $caches = mpull($caches, null, 'getCacheKey');
 
     $need_raw = array();
     foreach ($pastes as $paste) {
       $key = $this->getContentCacheKey($paste);
       if (isset($caches[$key])) {
-        $paste->attachContent($caches[$key]->getCacheData());
+        $paste->attachContent($caches[$key]);
       } else {
         $need_raw[] = $paste;
       }
@@ -150,18 +149,17 @@ final class PhabricatorPasteQuery
       return;
     }
 
+    $write_data = array();
+
     $this->loadRawContent($need_raw);
     foreach ($need_raw as $paste) {
       $content = $this->buildContent($paste);
       $paste->attachContent($content);
 
-      $guard = AphrontWriteGuard::beginScopedUnguardedWrites();
+      $write_data[$this->getContentCacheKey($paste)] = (string)$content;
-        id(new PhabricatorMarkupCache())
-          ->setCacheKey($this->getContentCacheKey($paste))
-          ->setCacheData($content)
-          ->replace();
-      unset($guard);
     }
+
+    $cache->setKeys($write_data);
   }
 
 

src/infrastructure/daemon/PhabricatorGarbageCollectorDaemon.php

@@ -49,6 +49,7 @@ final class PhabricatorGarbageCollectorDaemon extends PhabricatorDaemon {
       $n_parse  = $this->collectParseCaches();
       $n_markup = $this->collectMarkupCaches();
       $n_tasks  = $this->collectArchivedTasks();
+      $n_cache  = $this->collectGeneralCaches();
 
       $collected = array(
         'Herald Transcript'           => $n_herald,
@@ -56,6 +57,7 @@ final class PhabricatorGarbageCollectorDaemon extends PhabricatorDaemon {
         'Differential Parse Cache'    => $n_parse,
         'Markup Cache'                => $n_markup,
         'Archived Tasks'              => $n_tasks,
+        'General Cache Entries'       => $n_cache,
       );
       $collected = array_filter($collected);
 
@@ -200,4 +202,25 @@ final class PhabricatorGarbageCollectorDaemon extends PhabricatorDaemon {
     return count($task_ids);
   }
 
+
+  private function collectGeneralCaches() {
+    $key = 'gcdaemon.ttl.general-cache';
+    $ttl = PhabricatorEnv::getEnvConfig($key);
+    if ($ttl <= 0) {
+      return 0;
+    }
+
+    $cache = new PhabricatorKeyValueDatabaseCache();
+    $conn_w = $cache->establishConnection('w');
+
+    queryfx(
+      $conn_w,
+      'DELETE FROM %T WHERE cacheCreated < %d
+        ORDER BY cacheCreated ASC LIMIT 100',
+      $cache->getTableName(),
+      time() - $ttl);
+
+    return $conn_w->getAffectedRows();
+  }
+
 }

src/infrastructure/storage/lisk/PhabricatorLiskDAO.php

@@ -148,4 +148,63 @@ abstract class PhabricatorLiskDAO extends LiskDAO {
   protected function getConnectionNamespace() {
     return self::getStorageNamespace().'_'.$this->getApplicationName();
   }
+
+
+  /**
+   * Break a list of escaped SQL statement fragments (e.g., VALUES lists for
+   * INSERT, previously built with @{function:qsprintf}) into chunks which will
+   * fit under the MySQL 'max_allowed_packet' limit.
+   *
+   * Chunks are glued together with `$glue`, by default ", ".
+   *
+   * If a statement is too large to fit within the limit, it is broken into
+   * its own chunk (but might fail when the query executes).
+   */
+  public static function chunkSQL(
+    array $fragments,
+    $glue = ', ',
+    $limit = null) {
+
+    if ($limit === null) {
+      // NOTE: Hard-code this at 1MB for now, minus a 10% safety buffer.
+      // Eventually we could query MySQL or let the user configure it.
+      $limit = (int)((1024 * 1024) * 0.90);
+    }
+
+    $result = array();
+
+    $chunk = array();
+    $len = 0;
+    $glue_len = strlen($glue);
+    foreach ($fragments as $fragment) {
+      $this_len = strlen($fragment);
+
+      if ($chunk) {
+        // Chunks after the first also imply glue.
+        $this_len += $glue_len;
+      }
+
+      if ($len + $this_len <= $limit) {
+        $len += $this_len;
+        $chunk[] = $fragment;
+      } else {
+        if ($chunk) {
+          $result[] = $chunk;
+        }
+        $len = strlen($fragment);
+        $chunk = array($fragment);
+      }
+    }
+
+    if ($chunk) {
+      $result[] = $chunk;
+    }
+
+    foreach ($result as $key => $fragment_list) {
+      $result[$key] = implode($glue, $fragment_list);
+    }
+
+    return $result;
+  }
+
 }

src/infrastructure/storage/lisk/__tests__/LiskChunkTestCase.php

@@ -0,0 +1,55 @@
+<?php
+
+final class LiskChunkTestCase extends PhabricatorTestCase {
+
+  public function testSQLChunking() {
+    $fragments = array(
+      'a', 'a',
+      'b', 'b',
+      'ccc',
+      'dd',
+      'e',
+    );
+
+    $this->assertEqual(
+      array(
+        'aa',
+        'bb',
+        'ccc',
+        'dd',
+        'e',
+      ),
+      PhabricatorLiskDAO::chunkSQL($fragments, '', 2));
+
+
+    $fragments = array(
+      'a', 'a', 'a', 'XX', 'a', 'a', 'a', 'a'
+    );
+
+    $this->assertEqual(
+      array(
+        'a, a, a',
+        'XX, a, a',
+        'a, a',
+      ),
+      PhabricatorLiskDAO::chunkSQL($fragments, ', ', 8));
+
+
+    $fragments = array(
+      'xxxxxxxxxx',
+      'yyyyyyyyyy',
+      'a', 'b', 'c',
+      'zzzzzzzzzz',
+    );
+
+    $this->assertEqual(
+      array(
+        'xxxxxxxxxx',
+        'yyyyyyyyyy',
+        'a, b, c',
+        'zzzzzzzzzz',
+      ),
+      PhabricatorLiskDAO::chunkSQL($fragments, ', ', 8));
+  }
+
+}

src/infrastructure/storage/patch/PhabricatorBuiltinPatchList.php

@@ -1060,6 +1060,10 @@ final class PhabricatorBuiltinPatchList extends PhabricatorSQLPatchList {
         'type'    => 'sql',
         'name'    => $this->getPatchPath('20121209.xmacromigratekey.sql'),
       ),
+      '20121220.generalcache.sql' => array(
+        'type'    => 'sql',
+        'name'    => $this->getPatchPath('20121220.generalcache.sql'),
+      ),
     );
   }