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phorge-phorge/support/startup/PhabricatorClientLimit.php
epriestley 3f53718d10 Modularize rate/connection limits in Phabricator
Summary:
Depends on D18702. Ref T13008. This replaces the old hard-coded single rate limit with multiple flexible limits, and defines two types of limits:

  - Rate: reject requests if a client has completed too many requests recently.
  - Connection: reject requests if a client has too many more connections than disconnections recently.

The connection limit adds +1 to the score for each connection, then adds -1 for each disconnection. So the overall number is how many open connections they have, at least approximately.

Supporting multiple limits will let us do limiting by Hostname and by remote address (e.g., a specific IP can't exceed a low limit, and all requests to a hostname can't exceed a higher limit).

Configuring the new limits looks something like this:

```
PhabricatorStartup::addRateLimit(new PhabricatorClientRateLimit())
  ->setLimitKey('rate')
  ->setClientKey($_SERVER['REMOTE_ADDR'])
  ->setLimit(5);

PhabricatorStartup::addRateLimit(new PhabricatorClientConnectionLimit())
  ->setLimitKey('conn')
  ->setClientKey($_SERVER['REMOTE_ADDR'])
  ->setLimit(2);
```

Test Plan:
  - Configured limits as above.
  - Made a lot of requests, got cut off by the rate limit.
  - Used `curl --limit-rate -F 'data=@the_letter_m.txt' ...` to upload files really slowly. Got cut off by the connection limit. With `enable_post_data_reading` off, this correctly killed the connections //before// the uploads finished.
  - I'll send this stuff to `secure` before production to give it more of a chance.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13008

Differential Revision: https://secure.phabricator.com/D18703
2017-10-13 13:12:05 -07:00

291 lines
7.1 KiB
PHP

<?php
abstract class PhabricatorClientLimit {
private $limitKey;
private $clientKey;
private $limit;
final public function setLimitKey($limit_key) {
$this->limitKey = $limit_key;
return $this;
}
final public function getLimitKey() {
return $this->limitKey;
}
final public function setClientKey($client_key) {
$this->clientKey = $client_key;
return $this;
}
final public function getClientKey() {
return $this->clientKey;
}
final public function setLimit($limit) {
$this->limit = $limit;
return $this;
}
final public function getLimit() {
return $this->limit;
}
final public function didConnect() {
// NOTE: We can not use pht() here because this runs before libraries
// load.
if (!function_exists('apc_fetch') && !function_exists('apcu_fetch')) {
throw new Exception(
'You can not configure connection rate limits unless APC/APCu are '.
'available. Rate limits rely on APC/APCu to track clients and '.
'connections.');
}
if ($this->getClientKey() === null) {
throw new Exception(
'You must configure a client key when defining a rate limit.');
}
if ($this->getLimitKey() === null) {
throw new Exception(
'You must configure a limit key when defining a rate limit.');
}
if ($this->getLimit() === null) {
throw new Exception(
'You must configure a limit when defining a rate limit.');
}
$points = $this->getConnectScore();
if ($points) {
$this->addScore($points);
}
$score = $this->getScore();
if (!$this->shouldRejectConnection($score)) {
// Client has not hit the limit, so continue processing the request.
return null;
}
$penalty = $this->getPenaltyScore();
if ($penalty) {
$this->addScore($penalty);
$score += $penalty;
}
return $this->getRateLimitReason($score);
}
final public function didDisconnect(array $request_state) {
$score = $this->getDisconnectScore($request_state);
if ($score) {
$this->addScore($score);
}
}
/**
* Get the number of seconds for each rate bucket.
*
* For example, a value of 60 will create one-minute buckets.
*
* @return int Number of seconds per bucket.
*/
abstract protected function getBucketDuration();
/**
* Get the total number of rate limit buckets to retain.
*
* @return int Total number of rate limit buckets to retain.
*/
abstract protected function getBucketCount();
/**
* Get the score to add when a client connects.
*
* @return double Connection score.
*/
abstract protected function getConnectScore();
/**
* Get the number of penalty points to add when a client hits a rate limit.
*
* @return double Penalty score.
*/
abstract protected function getPenaltyScore();
/**
* Get the score to add when a client disconnects.
*
* @return double Connection score.
*/
abstract protected function getDisconnectScore(array $request_state);
/**
* Get a human-readable explanation of why the client is being rejected.
*
* @return string Brief rejection message.
*/
abstract protected function getRateLimitReason($score);
/**
* Determine whether to reject a connection.
*
* @return bool True to reject the connection.
*/
abstract protected function shouldRejectConnection($score);
/**
* Get the APC key for the smallest stored bucket.
*
* @return string APC key for the smallest stored bucket.
* @task ratelimit
*/
private function getMinimumBucketCacheKey() {
$limit_key = $this->getLimitKey();
return "limit:min:{$limit_key}";
}
/**
* Get the current bucket ID for storing rate limit scores.
*
* @return int The current bucket ID.
*/
private function getCurrentBucketID() {
return (int)(time() / $this->getBucketDuration());
}
/**
* Get the APC key for a given bucket.
*
* @param int Bucket to get the key for.
* @return string APC key for the bucket.
*/
private function getBucketCacheKey($bucket_id) {
$limit_key = $this->getLimitKey();
return "limit:bucket:{$limit_key}:{$bucket_id}";
}
/**
* Add points to the rate limit score for some client.
*
* @param string Some key which identifies the client making the request.
* @param float The cost for this request; more points pushes them toward
* the limit faster.
* @return this
*/
private function addScore($score) {
$is_apcu = (bool)function_exists('apcu_fetch');
$current = $this->getCurrentBucketID();
$bucket_key = $this->getBucketCacheKey($current);
// There's a bit of a race here, if a second process reads the bucket
// before this one writes it, but it's fine if we occasionally fail to
// record a client's score. If they're making requests fast enough to hit
// rate limiting, we'll get them soon enough.
if ($is_apcu) {
$bucket = apcu_fetch($bucket_key);
} else {
$bucket = apc_fetch($bucket_key);
}
if (!is_array($bucket)) {
$bucket = array();
}
$client_key = $this->getClientKey();
if (empty($bucket[$client_key])) {
$bucket[$client_key] = 0;
}
$bucket[$client_key] += $score;
if ($is_apcu) {
apcu_store($bucket_key, $bucket);
} else {
apc_store($bucket_key, $bucket);
}
return $this;
}
/**
* Get the current rate limit score for a given client.
*
* @return float The client's current score.
* @task ratelimit
*/
private function getScore() {
$is_apcu = (bool)function_exists('apcu_fetch');
// Identify the oldest bucket stored in APC.
$min_key = $this->getMinimumBucketCacheKey();
if ($is_apcu) {
$min = apcu_fetch($min_key);
} else {
$min = apc_fetch($min_key);
}
// If we don't have any buckets stored yet, store the current bucket as
// the oldest bucket.
$cur = $this->getCurrentBucketID();
if (!$min) {
if ($is_apcu) {
apcu_store($min_key, $cur);
} else {
apc_store($min_key, $cur);
}
$min = $cur;
}
// Destroy any buckets that are older than the minimum bucket we're keeping
// track of. Under load this normally shouldn't do anything, but will clean
// up an old bucket once per minute.
$count = $this->getBucketCount();
for ($cursor = $min; $cursor < ($cur - $count); $cursor++) {
$bucket_key = $this->getBucketCacheKey($cursor);
if ($is_apcu) {
apcu_delete($bucket_key);
apcu_store($min_key, $cursor + 1);
} else {
apc_delete($bucket_key);
apc_store($min_key, $cursor + 1);
}
}
$client_key = $this->getClientKey();
// Now, sum up the client's scores in all of the active buckets.
$score = 0;
for (; $cursor <= $cur; $cursor++) {
$bucket_key = $this->getBucketCacheKey($cursor);
if ($is_apcu) {
$bucket = apcu_fetch($bucket_key);
} else {
$bucket = apc_fetch($bucket_key);
}
if (isset($bucket[$client_key])) {
$score += $bucket[$client_key];
}
}
return $score;
}
}