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Commit 828c6515 authored by root's avatar root Committed by lucha
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switch to new hashing algorithm for hyperdb

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README 0 → 100644
Uso di HyperDB con il piano R di A/I
------------------------------------
I database di noblogs sono distribuiti su piu' di un backend, utilizzando
un sistema di consistent hashing che associa ogni blog_id ad un backend
specifico.
L'elenco dei backend e' specificato nel file /etc/noblogs/backends.
Lo schema e' molto semplice e si basa sull'ID pubblico di ciascun server
(es, latitanza:1, confino:3, etc). Ogni server ha un database 'noblogs_ID'
(in /opt/noblogs/mysql), cui puo' accedere l'utente 'noblogsdb'.
<?php
function noblogs_load_backends($db_config_file, &$hashptr) {
global $wpdb;
$backend_map = array();
$fp = @fopen($db_config_file, "r");
if (!$fp) {
die("Database backends not configured!");
}
while (($line = fgets($fp, 1024)) !== false) {
if ($line[0] == '#') {
continue;
}
$line_parts = explode(" ", rtrim($line));
$server_id = $line_parts[0];
$dataset = "backend_" . $server_id;
$backend_url = $line_parts[2];
$backend_url_data = parse_url($backend_url);
$backend = array(
"host" => $backend_url_data["host"] . ":" . $backend_url_data["port"],
"user" => $backend_url_data["user"],
"password" => $backend_url_data["pass"],
"name" => substr($backend_url_data["path"], 1),
"dataset" => $dataset,
"read" => 1, "write" => 1, "timeout" => 2
);
$wpdb->add_database($backend);
$hashptr->addTarget($dataset);
$backend_map[$dataset] = $backend;
}
fclose($fp);
return $backend_map;
}
<?php
require_once('flexihash.php');
$wpdb_hash = new Flexihash();
/* Hashing function to map blogs to databases.
*
* Implements a consistent hashing scheme using Flexihash.
*/
function noblogs_db_callback($query, $wpdb) {
global $wpdb_hash;
if (preg_match("/^{$wpdb->base_prefix}(\d+)_/", $wpdb->table, $matches)) {
$blog_id = $matches[1];
return $wpdb_hash->lookup($blog_id);
}
}
$wpdb->add_callback('noblogs_db_callback');
<?php
/**
* Flexihash - A simple consistent hashing implementation for PHP.
*
* The MIT License
*
* Copyright (c) 2008 Paul Annesley
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
* @author Paul Annesley
* @link http://paul.annesley.cc/
* @copyright Paul Annesley, 2008
*/
/**
* A simple consistent hashing implementation with pluggable hash algorithms.
*
* @author Paul Annesley
* @package Flexihash
* @licence http://www.opensource.org/licenses/mit-license.php
*/
class Flexihash
{
/**
* The number of positions to hash each target to.
*
* @var int
*/
private $_replicas = 64;
/**
* The hash algorithm, encapsulated in a Flexihash_Hasher implementation.
* @var object Flexihash_Hasher
*/
private $_hasher;
/**
* Internal counter for current number of targets.
* @var int
*/
private $_targetCount = 0;
/**
* Internal map of positions (hash outputs) to targets
* @var array { position => target, ... }
*/
private $_positionToTarget = array();
/**
* Internal map of targets to lists of positions that target is hashed to.
* @var array { target => [ position, position, ... ], ... }
*/
private $_targetToPositions = array();
/**
* Whether the internal map of positions to targets is already sorted.
* @var boolean
*/
private $_positionToTargetSorted = false;
/**
* Constructor
* @param object $hasher Flexihash_Hasher
* @param int $replicas Amount of positions to hash each target to.
*/
public function __construct(Flexihash_Hasher $hasher = null, $replicas = null)
{
$this->_hasher = $hasher ? $hasher : new Flexihash_Crc32Hasher();
if (!empty($replicas)) $this->_replicas = $replicas;
}
/**
* Add a target.
* @param string $target
* @param float $weight
* @chainable
*/
public function addTarget($target, $weight=1)
{
if (isset($this->_targetToPositions[$target]))
{
throw new Flexihash_Exception("Target '$target' already exists.");
}
$this->_targetToPositions[$target] = array();
// hash the target into multiple positions
for ($i = 0; $i < round($this->_replicas*$weight); $i++)
{
$position = $this->_hasher->hash($target . $i);
$this->_positionToTarget[$position] = $target; // lookup
$this->_targetToPositions[$target] []= $position; // target removal
}
$this->_positionToTargetSorted = false;
$this->_targetCount++;
return $this;
}
/**
* Add a list of targets.
* @param array $targets
* @param float $weight
* @chainable
*/
public function addTargets($targets, $weight=1)
{
foreach ($targets as $target)
{
$this->addTarget($target,$weight);
}
return $this;
}
/**
* Remove a target.
* @param string $target
* @chainable
*/
public function removeTarget($target)
{
if (!isset($this->_targetToPositions[$target]))
{
throw new Flexihash_Exception("Target '$target' does not exist.");
}
foreach ($this->_targetToPositions[$target] as $position)
{
unset($this->_positionToTarget[$position]);
}
unset($this->_targetToPositions[$target]);
$this->_targetCount--;
return $this;
}
/**
* A list of all potential targets
* @return array
*/
public function getAllTargets()
{
return array_keys($this->_targetToPositions);
}
/**
* Looks up the target for the given resource.
* @param string $resource
* @return string
*/
public function lookup($resource)
{
$targets = $this->lookupList($resource, 1);
if (empty($targets)) throw new Flexihash_Exception('No targets exist');
return $targets[0];
}
/**
* Get a list of targets for the resource, in order of precedence.
* Up to $requestedCount targets are returned, less if there are fewer in total.
*
* @param string $resource
* @param int $requestedCount The length of the list to return
* @return array List of targets
*/
public function lookupList($resource, $requestedCount)
{
if (!$requestedCount)
throw new Flexihash_Exception('Invalid count requested');
// handle no targets
if (empty($this->_positionToTarget))
return array();
// optimize single target
if ($this->_targetCount == 1)
return array_unique(array_values($this->_positionToTarget));
// hash resource to a position
$resourcePosition = $this->_hasher->hash($resource);
$results = array();
$collect = false;
$this->_sortPositionTargets();
// search values above the resourcePosition
foreach ($this->_positionToTarget as $key => $value)
{
// start collecting targets after passing resource position
if (!$collect && $key > $resourcePosition)
{
$collect = true;
}
// only collect the first instance of any target
if ($collect && !in_array($value, $results))
{
$results []= $value;
}
// return when enough results, or list exhausted
if (count($results) == $requestedCount || count($results) == $this->_targetCount)
{
return $results;
}
}
// loop to start - search values below the resourcePosition
foreach ($this->_positionToTarget as $key => $value)
{
if (!in_array($value, $results))
{
$results []= $value;
}
// return when enough results, or list exhausted
if (count($results) == $requestedCount || count($results) == $this->_targetCount)
{
return $results;
}
}
// return results after iterating through both "parts"
return $results;
}
public function __toString()
{
return sprintf(
'%s{targets:[%s]}',
get_class($this),
implode(',', $this->getAllTargets())
);
}
// ----------------------------------------
// private methods
/**
* Sorts the internal mapping (positions to targets) by position
*/
private function _sortPositionTargets()
{
// sort by key (position) if not already
if (!$this->_positionToTargetSorted)
{
ksort($this->_positionToTarget, SORT_REGULAR);
$this->_positionToTargetSorted = true;
}
}
}
/**
* Hashes given values into a sortable fixed size address space.
*
* @author Paul Annesley
* @package Flexihash
* @licence http://www.opensource.org/licenses/mit-license.php
*/
interface Flexihash_Hasher
{
/**
* Hashes the given string into a 32bit address space.
*
* Note that the output may be more than 32bits of raw data, for example
* hexidecimal characters representing a 32bit value.
*
* The data must have 0xFFFFFFFF possible values, and be sortable by
* PHP sort functions using SORT_REGULAR.
*
* @param string
* @return mixed A sortable format with 0xFFFFFFFF possible values
*/
public function hash($string);
}
/**
* Uses CRC32 to hash a value into a signed 32bit int address space.
* Under 32bit PHP this (safely) overflows into negatives ints.
*
* @author Paul Annesley
* @package Flexihash
* @licence http://www.opensource.org/licenses/mit-license.php
*/
class Flexihash_Crc32Hasher
implements Flexihash_Hasher
{
/* (non-phpdoc)
* @see Flexihash_Hasher::hash()
*/
public function hash($string)
{
return crc32($string);
}
}
/**
* Uses CRC32 to hash a value into a 32bit binary string data address space.
*
* @author Paul Annesley
* @package Flexihash
* @licence http://www.opensource.org/licenses/mit-license.php
*/
class Flexihash_Md5Hasher
implements Flexihash_Hasher
{
/* (non-phpdoc)
* @see Flexihash_Hasher::hash()
*/
public function hash($string)
{
return substr(md5($string), 0, 8); // 8 hexits = 32bit
// 4 bytes of binary md5 data could also be used, but
// performance seems to be the same.
}
}
/**
* An exception thrown by Flexihash.
*
* @author Paul Annesley
* @package Flexihash
* @licence http://www.opensource.org/licenses/mit-license.php
*/
class Flexihash_Exception extends Exception
{
}
#!/opt/noblogs/cron/php-noblogs
<?php
// Load wordpress api.
define('WP_CACHE',false);
/** Setup WordPress environment */
require_once('wp-load.php');
require_once('db-config-new.php');
function old_hash($dbid) {
if (($dbid % 2) == 0) {
return array('host' => '172.16.1.3',
'port' => '3307',
'user' => 'noblogs',
'password' => 'n0bl0gst3st',
'db' => 'noblogs_2');
} else {
return array('host' => '172.16.1.8',
'port' => '3307',
'user' => 'noblogsusr',
'password' => 'n0bl0gsdb4xpw!',
'db' => 'noblogs');
}
}
function new_hash($dbid) {
global $wpdb_hash;
global $wpdb_reverse_backend_map;
$lookup = $wpdb_hash->lookup($dbid);
$backend = $wpdb_reverse_backend_map[$lookup];
$result = array();
if (preg_match('/^(.*):([0-9]*)$/', $backend['host'], $matches)) {
$result['host'] = $matches[1];
$result['port'] = $matches[2];
}
$result['user'] = $backend['user'];
$result['password'] = $backend['password'];
$result['db'] = $backend['name'];
return $result;
}
function mysqlopts(&$attrs) {
return ("-h" . $attrs['host'] . " -P" . $attrs['port'] . " -u" . $attrs['user']
. " '-p" . $attrs['password'] . "'");
}
function mysqlurl(&$attrs) {
return ("mysql://" . $attrs['user'] . "@" . $attrs['host']
. ":" . $attrs['port'] . "/" . $attrs['db']);
}
function get_all_blogs()
{
global $wpdb;
$sql = "SELECT blog_id, domain, path FROM $wpdb->blogs WHERE public = 1 AND deleted = 0 AND archived = '0' ORDER BY domain, path";
$result = $wpdb->get_results($sql);
return ($result);
}
$new_counts = array();
$moved_count = 0;
$blogs = get_all_blogs();
foreach ($blogs as $blog) {
$blog_id = $blog->blog_id;
$old_params = old_hash($blog_id);
$old_dburi = mysqlurl($old_params);
$new_params = new_hash($blog_id);
$new_dburi = mysqlurl($new_params);
if ($new_counts[$new_params['host']]) {
$new_counts[$new_params['host']] += 1;
} else {
$new_counts[$new_params['host']] = 1;
}
if ($old_dburi != $new_dburi) {
echo "echo moving blog $blog_id from " . $old_params['host'] . " to " . $new_params['host'] . "\n";
echo "tables=\$(mysql " . mysqlopts($old_params) . " " . $old_params['db'] . " -NBe \"show tables like 'wp\\_" . $blog_id . "\\_%'\")\n";
echo "mysqldump --opt " . mysqlopts($old_params) . " " . $old_params['db'] . " \${tables} \\\n";
echo " | mysql " . mysqlopts($new_params) . " " . $new_params['db'] . "\n";
$moved_count += 1;
} else {
echo "echo blog $blog_id stays on " . $old_params['host'] . "\n";
}
}
echo "\n\n\nBlog distribution:\n";
print_r($new_counts);
print "\n $moved_count blogs moved\n";
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