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Add a generic multistep Markup cache

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Summary:
The immediate issue this addresses is T1366, adding a rendering cache to Phriction. For wiki pages with code blocks especially, rerendering them each time is expensive.

The broader issue is that out markup caches aren't very good right now. They have three major problems:

**Problem 1: the data is stored in the wrong place.** We currently store remarkup caches on objects. This means we're always loading it and passing it around even when we don't need it, can't genericize cache management code (e.g., have one simple script to drop/GC caches), need to update authoritative rows to clear caches, and can't genericize rendering code since each object is different.

To solve this, I created a dedicated cache database that I plan to move all markup caches to use.

**Problem 2: time-variant rules break when cached.** Some rules like `**bold**` are time-invariant and always produce the same output, but some rules like `{Tnnn}` and `@username` are variant and may render differently (because a task was closed or a user is on vacation). Currently, we cache the raw output, so these time-variant rules get locked at whatever values they had when they were first rendered. This is the main reason Phriction doesn't have a cache right now -- I wanted `{Tnnn}` rules to reflect open/closed tasks.

To solve this, I split markup into a "preprocessing" phase (which does all the parsing and evaluates all time-invariant rules) and a "postprocessing" phase (which evaluates time-variant rules only). The preprocessing phase is most of the expense (and, notably, includes syntax highlighting) so this is nearly as good as caching the final output. I did most of the work here in D737 / D738, but we never moved to use it in Phabricator -- we currently just do the two operations serially in all cases.

This diff splits them apart and caches the output of preprocessing only, so we benefit from caching but also get accurate time-variant rendering.

**Problem 3: cache access isn't batched/pipelined optimally.** When we're rendering a list of markup blocks, we should be able to batch datafetching better than we do. D738 helped with this (fetching is batched within a single hunk of markup) and this improves batching on cache access. We could still do better here, but this is at least a step forward.

Also fixes a bug with generating a link in the Phriction history interface ($uri gets clobbered).

I'm using PHP serialization instead of JSON serialization because Remarkup does some stuff with non-ascii characters that might not survive JSON.

Test Plan:
  - Created a Phriction document and verified that previews don't go to cache (no rows appear in the cache table).
  - Verified that published documents come out of cache.
  - Verified that caches generate/regenerate correctly, time-variant rules render properly and old documents hit the right caches.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1366

Differential Revision: https://secure.phabricator.com/D2945
This commit is contained in:
epriestley
2012-07-09 15:20:56 -07:00
parent 918ac5755c
commit 2b0b9a1573
10 changed files with 534 additions and 20 deletions
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291
src/infrastructure/markup/PhabricatorMarkupEngine.php
View File

@@ -16,41 +16,268 @@
* limitations under the License.
*/
class PhabricatorMarkupEngine {
/**
* Manages markup engine selection, configuration, application, caching and
* pipelining.
*
* @{class:PhabricatorMarkupEngine} can be used to render objects which
* implement @{interface:PhabricatorMarkupInterface} in a batched, cache-aware
* way. For example, if you have a list of comments written in remarkup (and
* the objects implement the correct interface) you can render them by first
* building an engine and adding the fields with @{method:addObject}.
*
* $field = 'field:body'; // Field you want to render. Each object exposes
* // one or more fields of markup.
*
* $engine = new PhabricatorMarkupEngine();
* foreach ($comments as $comment) {
* $engine->addObject($comment, $field);
* }
*
* Now, call @{method:process} to perform the actual cache/rendering
* step. This is a heavyweight call which does batched data access and
* transforms the markup into output.
*
* $engine->process();
*
* Finally, do something with the results:
*
* $results = array();
* foreach ($comments as $comment) {
* $results[] = $engine->getOutput($comment, $field);
* }
*
* If you have a single object to render, you can use the convenience method
* @{method:renderOneObject}.
*
* @task markup Markup Pipeline
* @task engine Engine Construction
*/
final class PhabricatorMarkupEngine {
public static function extractPHIDsFromMentions(array $content_blocks) {
$mentions = array();
private $objects = array();
$engine = self::newDifferentialMarkupEngine();
foreach ($content_blocks as $content_block) {
$engine->markupText($content_block);
$phids = $engine->getTextMetadata(
PhabricatorRemarkupRuleMention::KEY_MENTIONED,
array());
$mentions += $phids;
}
/* -( Markup Pipeline )---------------------------------------------------- */
return $mentions;
/**
* Convenience method for pushing a single object through the markup
* pipeline.
*
* @param PhabricatorMarkupInterface The object to render.
* @param string The field to render.
* @return string Marked up output.
* @task markup
*/
public static function renderOneObject(
PhabricatorMarkupInterface $object,
$field) {
return id(new PhabricatorMarkupEngine())
->addObject($object, $field)
->process()
->getOutput($object, $field);
}
/**
* Queue an object for markup generation when @{method:process} is
* called. You can retrieve the output later with @{method:getOutput}.
*
* @param PhabricatorMarkupInterface The object to render.
* @param string The field to render.
* @return this
* @task markup
*/
public function addObject(PhabricatorMarkupInterface $object, $field) {
$key = $this->getMarkupFieldKey($object, $field);
$this->objects[$key] = array(
'object' => $object,
'field' => $field,
);
return $this;
}
/**
* Process objects queued with @{method:addObject}. You can then retrieve
* the output with @{method:getOutput}.
*
* @return this
* @task markup
*/
public function process() {
$keys = array();
foreach ($this->objects as $key => $info) {
if (!isset($info['markup'])) {
$keys[] = $key;
}
}
if (!$keys) {
return;
}
$objects = array_select_keys($this->objects, $keys);
// Build all the markup engines. We need an engine for each field whether
// we have a cache or not, since we still need to postprocess the cache.
$engines = array();
foreach ($objects as $key => $info) {
$engines[$key] = $info['object']->newMarkupEngine($info['field']);
}
// Load or build the preprocessor caches.
$blocks = $this->loadPreprocessorCaches($engines, $objects);
// Finalize the output.
foreach ($objects as $key => $info) {
$data = $blocks[$key]->getCacheData();
$engine = $engines[$key];
$field = $info['field'];
$object = $info['object'];
$output = $engine->postprocessText($data);
$output = $object->didMarkupText($field, $output, $engine);
$this->objects[$key]['output'] = $output;
}
return $this;
}
/**
* Get the output of markup processing for a field queued with
* @{method:addObject}. Before you can call this method, you must call
* @{method:process}.
*
* @param PhabricatorMarkupInterface The object to retrieve.
* @param string The field to retrieve.
* @return string Processed output.
* @task markup
*/
public function getOutput(PhabricatorMarkupInterface $object, $field) {
$key = $this->getMarkupFieldKey($object, $field);
if (empty($this->objects[$key])) {
throw new Exception(
"Call addObject() before getOutput() (key = '{$key}').");
}
if (!isset($this->objects[$key]['output'])) {
throw new Exception(
"Call process() before getOutput().");
}
return $this->objects[$key]['output'];
}
/**
* @task markup
*/
private function getMarkupFieldKey(
PhabricatorMarkupInterface $object,
$field) {
return $object->getMarkupFieldKey($field);
}
/**
* @task markup
*/
private function loadPreprocessorCaches(array $engines, array $objects) {
$blocks = array();
$use_cache = array();
foreach ($objects as $key => $info) {
if ($info['object']->shouldUseMarkupCache($info['field'])) {
$use_cache[$key] = true;
}
}
if ($use_cache) {
$blocks = id(new PhabricatorMarkupCache())->loadAllWhere(
'cacheKey IN (%Ls)',
array_keys($use_cache));
$blocks = mpull($blocks, null, 'getCacheKey');
}
foreach ($objects as $key => $info) {
if (isset($blocks[$key])) {
// If we already have a preprocessing cache, we don't need to rebuild
// it.
continue;
}
$text = $info['object']->getMarkupText($info['field']);
$data = $engines[$key]->preprocessText($text);
// NOTE: This is just debugging information to help sort out cache issues.
// If one machine is misconfigured and poisoning caches you can use this
// field to hunt it down.
$metadata = array(
'host' => php_uname('n'),
);
$blocks[$key] = id(new PhabricatorMarkupCache())
->setCacheKey($key)
->setCacheData($data)
->setMetadata($metadata);
if (isset($use_cache[$key])) {
// This is just filling a cache and always safe, even on a read pathway.
$unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
try {
$blocks[$key]->save();
} catch (AphrontQueryDuplicateKeyException $ex) {
// Ignore this, we just raced to write the cache.
}
unset($unguarded);
}
}
return $blocks;
}
/* -( Engine Construction )------------------------------------------------ */
/**
* @task engine
*/
public static function newManiphestMarkupEngine() {
return self::newMarkupEngine(array(
));
}
/**
* @task engine
*/
public static function newPhrictionMarkupEngine() {
return self::newMarkupEngine(array(
'header.generate-toc' => true,
));
}
/**
* @task engine
*/
public static function newPhameMarkupEngine() {
return self::newMarkupEngine(array(
'macros' => false,
));
}
/**
* @task engine
*/
public static function newFeedMarkupEngine() {
return self::newMarkupEngine(
array(
@@ -61,6 +288,10 @@ class PhabricatorMarkupEngine {
));
}
/**
* @task engine
*/
public static function newDifferentialMarkupEngine(array $options = array()) {
return self::newMarkupEngine(array(
'custom-inline' => PhabricatorEnv::getEnvConfig(
@@ -71,21 +302,37 @@ class PhabricatorMarkupEngine {
));
}
/**
* @task engine
*/
public static function newDiffusionMarkupEngine(array $options = array()) {
return self::newMarkupEngine(array(
));
}
/**
* @task engine
*/
public static function newProfileMarkupEngine() {
return self::newMarkupEngine(array(
));
}
/**
* @task engine
*/
public static function newSlowvoteMarkupEngine() {
return self::newMarkupEngine(array(
));
}
/**
* @task engine
*/
private static function getMarkupEngineDefaultConfiguration() {
return array(
'pygments' => PhabricatorEnv::getEnvConfig('pygments.enabled'),
@@ -104,6 +351,10 @@ class PhabricatorMarkupEngine {
);
}
/**
* @task engine
*/
private static function newMarkupEngine(array $options) {
$options += self::getMarkupEngineDefaultConfiguration();
@@ -198,4 +449,20 @@ class PhabricatorMarkupEngine {
return $engine;
}
public static function extractPHIDsFromMentions(array $content_blocks) {
$mentions = array();
$engine = self::newDifferentialMarkupEngine();
foreach ($content_blocks as $content_block) {
$engine->markupText($content_block);
$phids = $engine->getTextMetadata(
PhabricatorRemarkupRuleMention::KEY_MENTIONED,
array());
$mentions += $phids;
}
return $mentions;
}
}