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MDL-19711 dml: Enable use of readonly slave database handles

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Implemented with moodle_read_slave_trait

Functionality is triggered by supplying config dboption['readonly'].
See config-dist.php for more info on supported dboptions.

pgsql and mysqli drivers are using this feature. Also added support for
connection timeout for these two drivers.
This commit is contained in:
Srdjan
2020-05-19 11:50:42 +10:00
parent d85118369d
commit 46cfde3d95
19 changed files with 2422 additions and 28 deletions
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lib/dml/pgsql_native_moodle_database.php
+78 -8
View File
@@ -25,6 +25,7 @@
defined('MOODLE_INTERNAL') || die();
require_once(__DIR__.'/moodle_database.php');
require_once(__DIR__.'/moodle_read_slave_trait.php');
require_once(__DIR__.'/pgsql_native_moodle_recordset.php');
require_once(__DIR__.'/pgsql_native_moodle_temptables.php');
@@ -36,6 +37,14 @@ require_once(__DIR__.'/pgsql_native_moodle_temptables.php');
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class pgsql_native_moodle_database extends moodle_database {
use moodle_read_slave_trait {
select_db_handle as read_slave_select_db_handle;
can_use_readonly as read_slave_can_use_readonly;
query_start as read_slave_query_start;
}
/** @var array $dbhcursor keep track of open cursors */
private $dbhcursor = [];
/** @var resource $pgsql database resource */
protected $pgsql = null;
@@ -110,7 +119,6 @@ class pgsql_native_moodle_database extends moodle_database {
/**
* Connect to db
* Must be called before other methods.
* @param string $dbhost The database host.
* @param string $dbuser The database username.
* @param string $dbpass The database username's password.
@@ -120,7 +128,7 @@ class pgsql_native_moodle_database extends moodle_database {
* @return bool true
* @throws dml_connection_exception if error
*/
public function connect($dbhost, $dbuser, $dbpass, $dbname, $prefix, array $dboptions=null) {
public function raw_connect(string $dbhost, string $dbuser, string $dbpass, string $dbname, $prefix, array $dboptions=null): bool {
if ($prefix == '' and !$this->external) {
//Enforce prefixes for everybody but mysql
throw new dml_exception('prefixcannotbeempty', $this->get_dbfamily());
@@ -160,6 +168,10 @@ class pgsql_native_moodle_database extends moodle_database {
$connection = "host='$this->dbhost' $port user='$this->dbuser' password='$pass' dbname='$this->dbname'";
}
if (!empty($this->dboptions['connecttimeout'])) {
$connection .= " connect_timeout=".$this->dboptions['connecttimeout'];
}
if (empty($this->dboptions['dbhandlesoptions'])) {
// ALTER USER and ALTER DATABASE are overridden by these settings.
$options = array('--client_encoding=utf8', '--standard_conforming_strings=on');
@@ -232,6 +244,64 @@ class pgsql_native_moodle_database extends moodle_database {
}
}
/**
* Gets db handle currently used with queries
* @return resource
*/
protected function get_db_handle() {
return $this->pgsql;
}
/**
* Sets db handle to be used with subsequent queries
* @param resource $dbh
* @return void
*/
protected function set_db_handle($dbh): void {
$this->pgsql = $dbh;
}
/**
* Select appropriate db handle - readwrite or readonly
* @param int $type type of query
* @param string $sql
* @return void
*/
protected function select_db_handle(int $type, string $sql): void {
$this->read_slave_select_db_handle($type, $sql);
if (preg_match('/^DECLARE (crs\w*) NO SCROLL CURSOR/', $sql, $match)) {
$cursor = $match[1];
$this->dbhcursor[$cursor] = $this->pgsql;
}
if (preg_match('/^(?:FETCH \d+ FROM|CLOSE) (crs\w*)\b/', $sql, $match)) {
$cursor = $match[1];
$this->pgsql = $this->dbhcursor[$cursor];
}
}
/**
* Check if The query qualifies for readonly connection execution
* Logging queries are exempt, those are write operations that circumvent
* standard query_start/query_end paths.
* @param int $type type of query
* @param string $sql
* @return bool
*/
protected function can_use_readonly(int $type, string $sql): bool {
// ... pg_*lock queries always go to master.
if (preg_match('/\bpg_\w*lock/', $sql)) {
return false;
}
// ... a nuisance - temptables use this.
if (preg_match('/\bpg_constraint/', $sql) && $this->temptables->get_temptables()) {
return false;
}
return $this->read_slave_can_use_readonly($type, $sql);
}
/**
* Called before each db query.
@@ -242,8 +312,8 @@ class pgsql_native_moodle_database extends moodle_database {
* @return void
*/
protected function query_start($sql, array $params=null, $type, $extrainfo=null) {
parent::query_start($sql, $params, $type, $extrainfo);
// pgsql driver tents to send debug to output, we do not need that ;-)
$this->read_slave_query_start($sql, $params, $type, $extrainfo);
// pgsql driver tends to send debug to output, we do not need that.
$this->last_error_reporting = error_reporting(0);
}
@@ -733,8 +803,6 @@ class pgsql_native_moodle_database extends moodle_database {
list($sql, $params, $type) = $this->fix_sql_params($sql, $params);
$this->query_start($sql, $params, SQL_QUERY_SELECT);
// For any query that doesn't explicitly specify a limit, we must use cursors to stop it
// loading the entire thing (unless the config setting is turned off).
$usecursors = !$limitnum && ($this->get_fetch_buffer_size() > 0);
@@ -747,12 +815,14 @@ class pgsql_native_moodle_database extends moodle_database {
// Do the query to a cursor.
$sql = 'DECLARE ' . $cursorname . ' NO SCROLL CURSOR WITH HOLD FOR ' . $sql;
$result = pg_query_params($this->pgsql, $sql, $params);
} else {
$result = pg_query_params($this->pgsql, $sql, $params);
$cursorname = '';
}
$this->query_start($sql, $params, SQL_QUERY_SELECT);
$result = pg_query_params($this->pgsql, $sql, $params);
$this->query_end($result);
if ($usecursors) {
pg_free_result($result);