MemcachedClient.php
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MemcachedClient.php
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	<?php
	// phpcs:ignoreFile -- It's an external lib and it isn't. Let's not bother.
	/**
	* Memcached client for PHP.
	*
	* +---------------------------------------------------------------------------+
	* \| memcached client, PHP \|
	* +---------------------------------------------------------------------------+
	* \| Copyright (c) 2003 Ryan T. Dean <rtdean@cytherianage.net> \|
	* \| All rights reserved. \|
	* \| \|
	* \| Redistribution and use in source and binary forms, with or without \|
	* \| modification, are permitted provided that the following conditions \|
	* \| are met: \|
	* \| \|
	* \| 1. Redistributions of source code must retain the above copyright \|
	* \| notice, this list of conditions and the following disclaimer. \|
	* \| 2. Redistributions in binary form must reproduce the above copyright \|
	* \| notice, this list of conditions and the following disclaimer in the \|
	* \| documentation and/or other materials provided with the distribution. \|
	* \| \|
	* \| THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR \|
	* \| IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES \|
	* \| OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. \|
	* \| IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, \|
	* \| INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT \|
	* \| NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, \|
	* \| DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY \|
	* \| THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT \|
	* \| (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF \|
	* \| THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. \|
	* +---------------------------------------------------------------------------+
	* \| Author: Ryan T. Dean <rtdean@cytherianage.net> \|
	* \| Heavily influenced by the Perl memcached client by Brad Fitzpatrick. \|
	* \| Permission granted by Brad Fitzpatrick for relicense of ported Perl \|
	* \| client logic under 2-clause BSD license. \|
	* +---------------------------------------------------------------------------+
	*
	* @file
	* $TCAnet$
	*/

	/**
	* This is a PHP client for memcached - a distributed memory cache daemon.
	*
	* More information is available at http://www.danga.com/memcached/
	*
	* Usage example:
	*
	* $mc = new MemcachedClient(array(
	* 'servers' => array(
	* '127.0.0.1:10000',
	* array( '192.0.0.1:10010', 2 ),
	* '127.0.0.1:10020'
	* ),
	* 'debug' => false,
	* 'compress_threshold' => 10240,
	* 'persistent' => true
	* ));
	*
	* $mc->add( 'key', array( 'some', 'array' ) );
	* $mc->replace( 'key', 'some random string' );
	* $val = $mc->get( 'key' );
	*
	* @author Ryan T. Dean <rtdean@cytherianage.net>
	* @version 0.1.2
	*/

	use Psr\Log\LoggerInterface;
	use Psr\Log\NullLogger;
	use Wikimedia\AtEase\AtEase;
	use Wikimedia\IPUtils;
	use Wikimedia\LightweightObjectStore\StorageAwareness;

	/**
	* memcached client class implemented using (p)fsockopen()
	*
	* @author Ryan T. Dean <rtdean@cytherianage.net>
	* @ingroup Cache
	*/
	class MemcachedClient implements StorageAwareness {
	// {{{ properties
	// {{{ public

	// {{{ constants
	// {{{ flags

	/**
	* Flag: indicates data is serialized
	*/
	const SERIALIZED = 1;

	/**
	* Flag: indicates data is compressed
	*/
	const COMPRESSED = 2;

	/**
	* Flag: indicates data is an integer
	*/
	const INTVAL = 4;

	// }}}

	/**
	* Minimum savings to store data compressed
	*/
	const COMPRESSION_SAVINGS = 0.20;

	// }}}

	/**
	* Command statistics
	*
	* @var array
	* @access public
	*/
	public $stats;

	// }}}
	// {{{ private

	/**
	* Cached Sockets that are connected
	*
	* @var array
	* @access private
	*/
	public $_cache_sock;

	/**
	* Current debug status; 0 - none to 9 - profiling
	*
	* @var bool
	* @access private
	*/
	public $_debug;

	/**
	* Dead hosts, assoc array, 'host'=>'unixtime when ok to check again'
	*
	* @var array
	* @access private
	*/
	public $_host_dead;

	/**
	* Is compression available?
	*
	* @var bool
	* @access private
	*/
	public $_have_zlib;

	/**
	* Do we want to use compression?
	*
	* @var bool
	* @access private
	*/
	public $_compress_enable;

	/**
	* At how many bytes should we compress?
	*
	* @var int
	* @access private
	*/
	public $_compress_threshold;

	/**
	* Are we using persistent links?
	*
	* @var bool
	* @access private
	*/
	public $_persistent;

	/**
	* If only using one server; contains ip:port to connect to
	*
	* @var string
	* @access private
	*/
	public $_single_sock;

	/**
	* Array containing ip:port or array(ip:port, weight)
	*
	* @var array
	* @access private
	*/
	public $_servers;

	/**
	* Our bit buckets
	*
	* @var array
	* @access private
	*/
	public $_buckets;

	/**
	* Total # of bit buckets we have
	*
	* @var int
	* @access private
	*/
	public $_bucketcount;

	/**
	* # of total servers we have
	*
	* @var int
	* @access private
	*/
	public $_active;

	/**
	* Stream timeout in seconds. Applies for example to fread()
	*
	* @var int
	* @access private
	*/
	public $_timeout_seconds;

	/**
	* Stream timeout in microseconds
	*
	* @var int
	* @access private
	*/
	public $_timeout_microseconds;

	/**
	* Connect timeout in seconds
	*/
	public $_connect_timeout;

	/**
	* Number of connection attempts for each server
	*/
	public $_connect_attempts;

	/** @var int StorageAwareness:ERR_* constant of the last cache command */
	public $_last_cmd_status = self::ERR_NONE;

	/**
	* @var LoggerInterface
	*/
	private $_logger;


	// }}}
	// }}}
	// {{{ methods
	// {{{ public functions
	// {{{ memcached()

	/**
	* Memcache initializer
	*
	* @param array $args Associative array of settings
	*/
	public function __construct( $args ) {
	$this->set_servers( $args['servers'] ?? array() );
	$this->_debug = $args['debug'] ?? false;
	$this->stats = array();
	$this->_compress_threshold = $args['compress_threshold'] ?? 0;
	$this->_persistent = $args['persistent'] ?? false;
	$this->_compress_enable = true;
	$this->_have_zlib = function_exists( 'gzcompress' );

	$this->_cache_sock = array();
	$this->_host_dead = array();

	$this->_timeout_seconds = 0;
	$this->_timeout_microseconds = $args['timeout'] ?? 500_000;

	$this->_connect_timeout = $args['connect_timeout'] ?? 0.1;
	$this->_connect_attempts = 2;

	$this->_logger = $args['logger'] ?? new NullLogger();
	}

	// }}}

	/**
	* @param mixed $value
	* @return string\|integer
	*/
	public function serialize( $value ) {
	return serialize( $value );
	}

	/**
	* @param string $value
	* @return mixed
	*/
	public function unserialize( $value ) {
	return unserialize( $value );
	}

	// {{{ add()

	/**
	* Adds a key/value to the memcache server if one isn't already set with
	* that key
	*
	* @param string $key Key to set with data
	* @param mixed $val Value to store
	* @param int $exp (optional) Expiration time. This can be a number of seconds
	* to cache for (up to 30 days inclusive). Any timespans of 30 days + 1 second or
	* longer must be the timestamp of the time at which the mapping should expire. It
	* is safe to use timestamps in all cases, regardless of expiration
	* eg: strtotime("+3 hour")
	*
	* @return bool
	*/
	public function add( $key, $val, $exp = 0 ) {
	$this->_last_cmd_status = self::ERR_NONE;

	return $this->_set( 'add', $key, $val, $exp );
	}

	// }}}
	// {{{ decr()

	/**
	* Decrease a value stored on the memcache server
	*
	* @param string $key Key to decrease
	* @param int $amt (optional) amount to decrease
	*
	* @return mixed False on failure, value on success
	*/
	public function decr( $key, $amt = 1 ) {
	$this->_last_cmd_status = self::ERR_NONE;

	return $this->_incrdecr( 'decr', $key, $amt );
	}

	// }}}
	// {{{ delete()

	/**
	* Deletes a key from the server, optionally after $time
	*
	* @param string $key Key to delete
	* @param int $time (optional) how long to wait before deleting
	*
	* @return bool True on success, false on failure
	*/
	public function delete( $key, $time = 0 ) {
	$this->_last_cmd_status = self::ERR_NONE;

	if ( !$this->_active ) {
	return false;
	}

	$sock = $this->get_sock( $key );
	if ( !$sock ) {
	return false;
	}

	$key = is_array( $key ) ? $key[1] : $key;

	if ( isset( $this->stats['delete'] ) ) {
	$this->stats['delete']++;
	} else {
	$this->stats['delete'] = 1;
	}
	$cmd = "delete $key $time\r\n";
	if ( !$this->_fwrite( $sock, $cmd ) ) {
	return false;
	}
	$res = $this->_fgets( $sock );

	if ( $this->_debug ) {
	$this->_debugprint( sprintf( "MemCache: delete %s (%s)", $key, $res ) );
	}

	if ( $res == "DELETED" \|\| $res == "NOT_FOUND" ) {
	return true;
	}

	$this->_last_cmd_status = self::ERR_UNEXPECTED;

	return false;
	}

	/**
	* Changes the TTL on a key from the server to $time
	*
	* @param string $key
	* @param int $time TTL in seconds
	*
	* @return bool True on success, false on failure
	*/
	public function touch( $key, $time = 0 ) {
	$this->_last_cmd_status = self::ERR_NONE;

	if ( !$this->_active ) {
	return false;
	}

	$sock = $this->get_sock( $key );
	if ( !$sock ) {
	return false;
	}

	$key = is_array( $key ) ? $key[1] : $key;

	if ( isset( $this->stats['touch'] ) ) {
	$this->stats['touch']++;
	} else {
	$this->stats['touch'] = 1;
	}
	$cmd = "touch $key $time\r\n";
	if ( !$this->_fwrite( $sock, $cmd ) ) {
	return false;
	}
	$res = $this->_fgets( $sock );

	if ( $this->_debug ) {
	$this->_debugprint( sprintf( "MemCache: touch %s (%s)", $key, $res ) );
	}

	if ( $res == "TOUCHED" ) {
	return true;
	}

	return false;
	}

	// }}}
	// {{{ disconnect_all()

	/**
	* Disconnects all connected sockets
	*/
	public function disconnect_all() {
	foreach ( $this->_cache_sock as $sock ) {
	fclose( $sock );
	}

	$this->_cache_sock = array();
	}

	// }}}
	// {{{ enable_compress()

	/**
	* Enable / Disable compression
	*
	* @param bool $enable True to enable, false to disable
	*/
	public function enable_compress( $enable ) {
	$this->_compress_enable = $enable;
	}

	// }}}
	// {{{ forget_dead_hosts()

	/**
	* Forget about all of the dead hosts
	*/
	public function forget_dead_hosts() {
	$this->_host_dead = array();
	}

	// }}}
	// {{{ get()

	/**
	* Retrieves the value associated with the key from the memcache server
	*
	* @param array\|string $key key to retrieve
	* @param float $casToken [optional]
	*
	* @return mixed
	*/
	public function get( $key, &$casToken = null ) {
	$getToken = ( func_num_args() >= 2 );

	$this->_last_cmd_status = self::ERR_NONE;

	if ( $this->_debug ) {
	$this->_debugprint( "get($key)" );
	}

	if ( !is_array( $key ) && strval( $key ) === '' ) {
	$this->_last_cmd_status = self::ERR_UNEXPECTED;
	$this->_debugprint( "Skipping key which equals to an empty string" );
	return false;
	}

	if ( !$this->_active ) {
	$this->_last_cmd_status = self::ERR_UNEXPECTED;

	return false;
	}

	$sock = $this->get_sock( $key );

	if ( !$sock ) {
	$this->_last_cmd_status = self::ERR_UNREACHABLE;

	return false;
	}

	$key = is_array( $key ) ? $key[1] : $key;
	if ( isset( $this->stats['get'] ) ) {
	$this->stats['get']++;
	} else {
	$this->stats['get'] = 1;
	}

	$cmd = $getToken ? "gets" : "get";
	$cmd .= " $key\r\n";
	if ( !$this->_fwrite( $sock, $cmd ) ) {
	$this->_last_cmd_status = self::ERR_NO_RESPONSE;

	return false;
	}

	$val = array();
	if ( !$this->_load_items( $sock, $val, $casToken ) ) {
	$this->_last_cmd_status = self::ERR_NO_RESPONSE;
	}

	if ( $this->_debug ) {
	foreach ( $val as $k => $v ) {
	$this->_debugprint(
	sprintf( "MemCache: sock %s got %s", $this->serialize( $sock ), $k ) );
	}
	}

	$value = false;
	if ( isset( $val[$key] ) ) {
	$value = $val[$key];
	}
	return $value;
	}

	// }}}
	// {{{ get_multi()

	/**
	* Get multiple keys from the server(s)
	*
	* @param array $keys Keys to retrieve
	*
	* @return array
	*/
	public function get_multi( $keys ) {
	$this->_last_cmd_status = self::ERR_NONE;

	if ( !$this->_active ) {
	$this->_last_cmd_status = self::ERR_UNEXPECTED;

	return array();
	}

	if ( isset( $this->stats['get_multi'] ) ) {
	$this->stats['get_multi']++;
	} else {
	$this->stats['get_multi'] = 1;
	}
	$sock_keys = array();
	$socks = array();
	foreach ( $keys as $key ) {
	$sock = $this->get_sock( $key );
	if ( !$sock ) {
	$this->_last_cmd_status = self::ERR_UNREACHABLE;
	continue;
	}
	$key = is_array( $key ) ? $key[1] : $key;
	$sockValue = intval( $sock );

	if ( !isset( $sock_keys[$sockValue] ) ) {
	$sock_keys[$sockValue] = array();
	$socks[] = $sock;
	}
	$sock_keys[$sockValue][] = $key;
	}

	$gather = array();
	// Send out the requests
	foreach ( $socks as $sock ) {
	$cmd = 'get';
	foreach ( $sock_keys[intval( $sock )] as $key ) {
	$cmd .= ' ' . $key;
	}
	$cmd .= "\r\n";

	if ( $this->_fwrite( $sock, $cmd ) ) {
	$gather[] = $sock;
	} else {
	$this->_last_cmd_status = self::ERR_NO_RESPONSE;
	}
	}

	// Parse responses
	$val = array();
	foreach ( $gather as $sock ) {
	if ( !$this->_load_items( $sock, $val ) ) {
	$this->_last_cmd_status = self::ERR_NO_RESPONSE;
	}
	}

	if ( $this->_debug ) {
	foreach ( $val as $k => $v ) {
	$this->_debugprint( sprintf( "MemCache: got %s", $k ) );
	}
	}

	return $val;
	}

	// }}}
	// {{{ incr()

	/**
	* Increments $key (optionally) by $amt
	*
	* @param string $key Key to increment
	* @param int $amt (optional) amount to increment
	*
	* @return int\|null Null if the key does not exist yet (this does NOT
	* create new mappings if the key does not exist). If the key does
	* exist, this returns the new value for that key.
	*/
	public function incr( $key, $amt = 1 ) {
	return $this->_incrdecr( 'incr', $key, $amt );
	}

	// }}}
	// {{{ replace()

	/**
	* Overwrites an existing value for key; only works if key is already set
	*
	* @param string $key Key to set value as
	* @param mixed $value Value to store
	* @param int $exp (optional) Expiration time. This can be a number of seconds
	* to cache for (up to 30 days inclusive). Any timespans of 30 days + 1 second or
	* longer must be the timestamp of the time at which the mapping should expire. It
	* is safe to use timestamps in all cases, regardless of expiration
	* eg: strtotime("+3 hour")
	*
	* @return bool
	*/
	public function replace( $key, $value, $exp = 0 ) {
	return $this->_set( 'replace', $key, $value, $exp );
	}

	// }}}
	// {{{ run_command()

	/**
	* Passes through $cmd to the memcache server connected by $sock; returns
	* output as an array (null array if no output)
	*
	* @param Resource $sock Socket to send command on
	* @param string $cmd Command to run
	*
	* @return array Output array
	*/
	public function run_command( $sock, $cmd ) {
	if ( !$sock ) {
	return array();
	}

	if ( !$this->_fwrite( $sock, $cmd ) ) {
	return array();
	}

	$ret = array();
	while ( true ) {
	$res = $this->_fgets( $sock );
	$ret[] = $res;
	if ( preg_match( '/^END/', $res ) ) {
	break;
	}
	if ( strlen( $res ) == 0 ) {
	break;
	}
	}
	return $ret;
	}

	// }}}
	// {{{ set()

	/**
	* Unconditionally sets a key to a given value in the memcache. Returns true
	* if set successfully.
	*
	* @param string $key Key to set value as
	* @param mixed $value Value to set
	* @param int $exp (optional) Expiration time. This can be a number of seconds
	* to cache for (up to 30 days inclusive). Any timespans of 30 days + 1 second or
	* longer must be the timestamp of the time at which the mapping should expire. It
	* is safe to use timestamps in all cases, regardless of expiration
	* eg: strtotime("+3 hour")
	*
	* @return bool True on success
	*/
	public function set( $key, $value, $exp = 0 ) {
	return $this->_set( 'set', $key, $value, $exp );
	}

	// }}}
	// {{{ cas()

	/**
	* Sets a key to a given value in the memcache if the current value still corresponds
	* to a known, given value. Returns true if set successfully.
	*
	* @param float $casToken Current known value
	* @param string $key Key to set value as
	* @param mixed $value Value to set
	* @param int $exp (optional) Expiration time. This can be a number of seconds
	* to cache for (up to 30 days inclusive). Any timespans of 30 days + 1 second or
	* longer must be the timestamp of the time at which the mapping should expire. It
	* is safe to use timestamps in all cases, regardless of expiration
	* eg: strtotime("+3 hour")
	*
	* @return bool True on success
	*/
	public function cas( $casToken, $key, $value, $exp = 0 ) {
	return $this->_set( 'cas', $key, $value, $exp, $casToken );
	}

	// }}}
	// {{{ set_compress_threshold()

	/**
	* Set the compression threshold
	*
	* @param int $thresh Threshold to compress if larger than
	*/
	public function set_compress_threshold( $thresh ) {
	$this->_compress_threshold = $thresh;
	}

	// }}}
	// {{{ set_debug()

	/**
	* Set the debug flag
	*
	* @see __construct()
	* @param bool $dbg True for debugging, false otherwise
	*/
	public function set_debug( $dbg ) {
	$this->_debug = $dbg;
	}

	// }}}
	// {{{ set_servers()

	/**
	* Set the server list to distribute key gets and puts between
	*
	* @see __construct()
	* @param array $list Array of servers to connect to
	*/
	public function set_servers( $list ) {
	$this->_servers = $list;
	$this->_active = count( $list );
	$this->_buckets = null;
	$this->_bucketcount = 0;

	$this->_single_sock = null;
	if ( $this->_active == 1 ) {
	$this->_single_sock = $this->_servers[0];
	}
	}

	/**
	* Sets the timeout for new connections
	*
	* @param int $seconds Number of seconds
	* @param int $microseconds Number of microseconds
	*/
	public function set_timeout( $seconds, $microseconds ) {
	$this->_timeout_seconds = $seconds;
	$this->_timeout_microseconds = $microseconds;
	}

	// }}}
	// }}}
	// {{{ private methods
	// {{{ _close_sock()

	/**
	* Close the specified socket
	*
	* @param string $sock Socket to close
	*
	* @access private
	*/
	function _close_sock( $sock ) {
	$host = array_search( $sock, $this->_cache_sock );
	fclose( $this->_cache_sock[$host] );
	unset( $this->_cache_sock[$host] );
	}

	// }}}
	// {{{ _connect_sock()

	/**
	* Connects $sock to $host, timing out after $timeout
	*
	* @param int $sock Socket to connect
	* @param string $host Host:IP to connect to
	*
	* @return bool
	* @access private
	*/
	function _connect_sock( &$sock, $host ) {
	$port = null;
	$hostAndPort = IPUtils::splitHostAndPort( $host );
	if ( $hostAndPort ) {
	$ip = $hostAndPort[0];
	if ( $hostAndPort[1] ) {
	$port = $hostAndPort[1];
	}
	} else {
	$ip = $host;
	}
	$sock = false;
	$timeout = $this->_connect_timeout;
	$errno = $errstr = null;
	for ( $i = 0; !$sock && $i < $this->_connect_attempts; $i++ ) {
	AtEase::suppressWarnings();
	if ( $this->_persistent == 1 ) {
	$sock = pfsockopen( $ip, $port, $errno, $errstr, $timeout );
	} else {
	$sock = fsockopen( $ip, $port, $errno, $errstr, $timeout );
	}
	AtEase::restoreWarnings();
	}
	if ( !$sock ) {
	$this->_error_log( "Error connecting to $host: $errstr" );
	$this->_dead_host( $host );
	return false;
	}

	// Initialise timeout
	stream_set_timeout( $sock, $this->_timeout_seconds, $this->_timeout_microseconds );

	// If the connection was persistent, flush the read buffer in case there
	// was a previous incomplete request on this connection
	if ( $this->_persistent ) {
	$this->_flush_read_buffer( $sock );
	}
	return true;
	}

	// }}}
	// {{{ _dead_sock()

	/**
	* Marks a host as dead until 30-40 seconds in the future
	*
	* @param string $sock Socket to mark as dead
	*
	* @access private
	*/
	function _dead_sock( $sock ) {
	$host = array_search( $sock, $this->_cache_sock );
	$this->_dead_host( $host );
	}

	/**
	* @param string $host
	*/
	function _dead_host( $host ) {
	$hostAndPort = IPUtils::splitHostAndPort( $host );
	if ( $hostAndPort ) {
	$ip = $hostAndPort[0];
	} else {
	$ip = $host;
	}
	$this->_host_dead[$ip] = time() + 30 + intval( rand( 0, 10 ) );
	$this->_host_dead[$host] = $this->_host_dead[$ip];
	unset( $this->_cache_sock[$host] );
	}

	// }}}
	// {{{ get_sock()

	/**
	* get_sock
	*
	* @param string $key Key to retrieve value for;
	*
	* @return Resource\|bool Resource on success, false on failure
	* @access private
	*/
	function get_sock( $key ) {
	if ( !$this->_active ) {
	return false;
	}

	if ( $this->_single_sock !== null ) {
	return $this->sock_to_host( $this->_single_sock );
	}

	$hv = is_array( $key ) ? intval( $key[0] ) : $this->_hashfunc( $key );
	if ( $this->_buckets === null ) {
	$bu = array();
	foreach ( $this->_servers as $v ) {
	if ( is_array( $v ) ) {
	for ( $i = 0; $i < $v[1]; $i++ ) {
	$bu[] = $v[0];
	}
	} else {
	$bu[] = $v;
	}
	}
	$this->_buckets = $bu;
	$this->_bucketcount = count( $bu );
	}

	$realkey = is_array( $key ) ? $key[1] : $key;
	for ( $tries = 0; $tries < 20; $tries++ ) {
	$host = $this->_buckets[$hv % $this->_bucketcount];
	$sock = $this->sock_to_host( $host );
	if ( $sock ) {
	return $sock;
	}
	$hv = $this->_hashfunc( $hv . $realkey );
	}

	return false;
	}

	// }}}
	// {{{ _hashfunc()

	/**
	* Creates a hash integer based on the $key
	*
	* @param string $key Key to hash
	*
	* @return int Hash value
	* @access private
	*/
	function _hashfunc( $key ) {
	# Hash function must be in [0,0x7ffffff]
	# We take the first 31 bits of the MD5 hash, which unlike the hash
	# function used in a previous version of this client, works
	return hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
	}

	// }}}
	// {{{ _incrdecr()

	/**
	* Perform increment/decrement on $key
	*
	* @param string $cmd Command to perform
	* @param string\|array $key Key to perform it on
	* @param int $amt Amount to adjust
	*
	* @return int New value of $key
	* @access private
	*/
	function _incrdecr( $cmd, $key, $amt = 1 ) {
	$this->_last_cmd_status = self::ERR_NONE;

	if ( !$this->_active ) {
	$this->_last_cmd_status = self::ERR_UNEXPECTED;

	return null;
	}

	$sock = $this->get_sock( $key );
	if ( !$sock ) {
	$this->_last_cmd_status = self::ERR_UNREACHABLE;

	return null;
	}

	$key = is_array( $key ) ? $key[1] : $key;
	if ( isset( $this->stats[$cmd] ) ) {
	$this->stats[$cmd]++;
	} else {
	$this->stats[$cmd] = 1;
	}
	if ( !$this->_fwrite( $sock, "$cmd $key $amt\r\n" ) ) {
	$this->_last_cmd_status = self::ERR_NO_RESPONSE;

	return null;
	}

	$line = $this->_fgets( $sock );
	if ( $this->_debug ) {
	$this->_debugprint( "$cmd($key): $line" );
	}

	$match = array();
	if ( !preg_match( '/^(\d+)/', $line, $match ) ) {
	$this->_last_cmd_status = self::ERR_NO_RESPONSE;

	return null;
	}

	return (int)$match[1];
	}

	// }}}
	// {{{ _load_items()

	/**
	* Load items into $ret from $sock
	*
	* @param Resource $sock Socket to read from
	* @param array $ret returned values
	* @param float $casToken [optional]
	* @return bool True for success, false for failure
	*
	* @access private
	*/
	function _load_items( $sock, &$ret, &$casToken = null ) {
	$results = array();

	while ( 1 ) {
	$decl = $this->_fgets( $sock );

	if ( $decl === false ) {
	/*
	* If nothing can be read, something is wrong because we know exactly when
	* to stop reading (right after "END") and we return right after that.
	*/
	return false;
	} elseif ( preg_match( '/^VALUE (\S+) (\d+) (\d+)(?: (\d+))?$/', $decl, $match ) ) {
	/*
	* Read all data returned. This can be either one or multiple values.
	* Save all that data (in an array) to be processed later: we'll first
	* want to continue reading until "END" before doing anything else,
	* to make sure that we don't leave our client in a state where it's
	* output is not yet fully read.
	*/
	$results[] = array(
	$match[1], // rkey
	$match[2], // flags
	$match[3], // len
	$match[4] ?? null, // casToken (appears with "gets" but not "get")
	$this->_fread( $sock, $match[3] + 2 ), // data
	);
	} elseif ( $decl == "END" ) {
	/**
	* All data has been read, time to process the data and build
	* meaningful return values.
	*/
	foreach ( $results as [ $rkey, $flags, /* length */, $casToken, $data ] ) {
	if ( $data === false \|\| substr( $data, -2 ) !== "\r\n" ) {
	$this->_handle_error( $sock,
	'line ending missing from data block from $1' );
	return false;
	}
	$data = substr( $data, 0, -2 );
	$ret[$rkey] = $data;

	if ( $this->_have_zlib && $flags & self::COMPRESSED ) {
	$ret[$rkey] = gzuncompress( $ret[$rkey] );
	}

	/*
	* This unserialize is the exact reason that we only want to
	* process data after having read until "END" (instead of doing
	* this right away): "unserialize" can trigger outside code:
	* in the event that $ret[$rkey] is a serialized object,
	* unserializing it will trigger __wakeup() if present. If that
	* function attempted to read from memcached (while we did not
	* yet read "END"), these 2 calls would collide.
	*/
	if ( $flags & self::SERIALIZED ) {
	$ret[$rkey] = $this->unserialize( $ret[$rkey] );
	} elseif ( $flags & self::INTVAL ) {
	$ret[$rkey] = intval( $ret[$rkey] );
	}
	}

	return true;
	} else {
	$this->_handle_error( $sock, 'Error parsing response from $1' );
	return false;
	}
	}
	}

	// }}}
	// {{{ _set()

	/**
	* Performs the requested storage operation to the memcache server
	*
	* @param string $cmd Command to perform
	* @param string $key Key to act on
	* @param mixed $val What we need to store
	* @param int $exp (optional) Expiration time. This can be a number of seconds
	* to cache for (up to 30 days inclusive). Any timespans of 30 days + 1 second or
	* longer must be the timestamp of the time at which the mapping should expire. It
	* is safe to use timestamps in all cases, regardless of expiration
	* eg: strtotime("+3 hour")
	* @param float $casToken [optional]
	*
	* @return bool
	* @access private
	*/
	function _set( $cmd, $key, $val, $exp, $casToken = null ) {
	$this->_last_cmd_status = self::ERR_NONE;

	if ( !$this->_active ) {
	$this->_last_cmd_status = self::ERR_UNEXPECTED;

	return false;
	}

	$sock = $this->get_sock( $key );
	if ( !$sock ) {
	$this->_last_cmd_status = self::ERR_UNREACHABLE;

	return false;
	}

	if ( isset( $this->stats[$cmd] ) ) {
	$this->stats[$cmd]++;
	} else {
	$this->stats[$cmd] = 1;
	}

	$flags = 0;

	if ( is_int( $val ) ) {
	$flags \|= self::INTVAL;
	} elseif ( !is_scalar( $val ) ) {
	$val = $this->serialize( $val );
	$flags \|= self::SERIALIZED;
	if ( $this->_debug ) {
	$this->_debugprint( "client: serializing data as it is not scalar" );
	}
	}

	$len = strlen( $val );

	if ( $this->_have_zlib && $this->_compress_enable
	&& $this->_compress_threshold && $len >= $this->_compress_threshold
	) {
	$c_val = gzcompress( $val, 9 );
	$c_len = strlen( $c_val );

	if ( $c_len < $len * ( 1 - self::COMPRESSION_SAVINGS ) ) {
	if ( $this->_debug ) {
	$this->_debugprint( sprintf( "client: compressing data; was %d bytes is now %d bytes", $len, $c_len ) );
	}
	$val = $c_val;
	$len = $c_len;
	$flags \|= self::COMPRESSED;
	}
	}

	$command = "$cmd $key $flags $exp $len";
	if ( $casToken ) {
	$command .= " $casToken";
	}

	if ( !$this->_fwrite( $sock, "$command\r\n$val\r\n" ) ) {
	$this->_last_cmd_status = self::ERR_NO_RESPONSE;

	return false;
	}

	$line = $this->_fgets( $sock );
	if ( $this->_debug ) {
	$this->_debugprint( sprintf( "%s %s (%s)", $cmd, $key, $line ) );
	}

	if ( $line === "STORED" ) {
	return true;
	} elseif ( $line === "NOT_STORED" && $cmd === "set" ) {
	// "Not stored" is always used as the mcrouter response with AllAsyncRoute
	return true;
	}

	if ( $line === false ) {
	$this->_last_cmd_status = self::ERR_NO_RESPONSE;
	}

	return false;
	}

	// }}}
	// {{{ sock_to_host()

	/**
	* Returns the socket for the host
	*
	* @param string $host Host:IP to get socket for
	*
	* @return Resource\|bool IO Stream or false
	* @access private
	*/
	function sock_to_host( $host ) {
	if ( isset( $this->_cache_sock[$host] ) ) {
	return $this->_cache_sock[$host];
	}

	$sock = null;
	$now = time();
	$hostAndPort = IPUtils::splitHostAndPort( $host );
	if ( $hostAndPort ) {
	$ip = $hostAndPort[0];
	} else {
	$ip = $host;
	}
	if ( isset( $this->_host_dead[$host] ) && $this->_host_dead[$host] > $now \|\|
	isset( $this->_host_dead[$ip] ) && $this->_host_dead[$ip] > $now
	) {
	return null;
	}

	if ( !$this->_connect_sock( $sock, $host ) ) {
	return null;
	}

	// Do not buffer writes
	stream_set_write_buffer( $sock, 0 );

	$this->_cache_sock[$host] = $sock;

	return $this->_cache_sock[$host];
	}

	/**
	* @param string $text
	*/
	function _debugprint( $text ) {
	$this->_logger->debug( $text );
	}

	/**
	* @param string $text
	*/
	function _error_log( $text ) {
	$this->_logger->error( "Memcached error: $text" );
	}

	/**
	* Write to a stream. If there is an error, mark the socket dead.
	*
	* @param Resource $sock The socket
	* @param string $buf The string to write
	* @return bool True on success, false on failure
	*/
	function _fwrite( $sock, $buf ) {
	$bytesWritten = 0;
	$bufSize = strlen( $buf );
	while ( $bytesWritten < $bufSize ) {
	$result = fwrite( $sock, $buf );
	$data = stream_get_meta_data( $sock );
	if ( $data['timed_out'] ) {
	$this->_handle_error( $sock, 'timeout writing to $1' );
	return false;
	}
	// Contrary to the documentation, fwrite() returns zero on error in PHP 5.3.
	if ( $result === false \|\| $result === 0 ) {
	$this->_handle_error( $sock, 'error writing to $1' );
	return false;
	}
	$bytesWritten += $result;
	}

	return true;
	}

	/**
	* Handle an I/O error. Mark the socket dead and log an error.
	*
	* @param Resource $sock
	* @param string $msg
	*/
	function _handle_error( $sock, $msg ) {
	$peer = stream_socket_get_name( $sock, true / remote / );
	if ( strval( $peer ) === '' ) {
	$peer = array_search( $sock, $this->_cache_sock );
	if ( $peer === false ) {
	$peer = '[unknown host]';
	}
	}
	$msg = str_replace( '$1', $peer, $msg );
	$this->_error_log( "$msg" );
	$this->_dead_sock( $sock );
	}

	/**
	* Read the specified number of bytes from a stream. If there is an error,
	* mark the socket dead.
	*
	* @param Resource $sock The socket
	* @param int $len The number of bytes to read
	* @return string\|bool The string on success, false on failure.
	*/
	function _fread( $sock, $len ) {
	$buf = '';
	while ( $len > 0 ) {
	$result = fread( $sock, $len );
	$data = stream_get_meta_data( $sock );
	if ( $data['timed_out'] ) {
	$this->_handle_error( $sock, 'timeout reading from $1' );
	return false;
	}
	if ( $result === false ) {
	$this->_handle_error( $sock, 'error reading buffer from $1' );
	return false;
	}
	if ( $result === '' ) {
	// This will happen if the remote end of the socket is shut down
	$this->_handle_error( $sock, 'unexpected end of file reading from $1' );
	return false;
	}
	$len -= strlen( $result );
	$buf .= $result;
	}
	return $buf;
	}

	/**
	* Read a line from a stream. If there is an error, mark the socket dead.
	* The \r\n line ending is stripped from the response.
	*
	* @param Resource $sock The socket
	* @return string\|bool The string on success, false on failure
	*/
	function _fgets( $sock ) {
	$result = fgets( $sock );
	// fgets() may return a partial line if there is a select timeout after
	// a successful recv(), so we have to check for a timeout even if we
	// got a string response.
	$data = stream_get_meta_data( $sock );
	if ( $data['timed_out'] ) {
	$this->_handle_error( $sock, 'timeout reading line from $1' );
	return false;
	}
	if ( $result === false ) {
	$this->_handle_error( $sock, 'error reading line from $1' );
	return false;
	}
	if ( substr( $result, -2 ) === "\r\n" ) {
	$result = substr( $result, 0, -2 );
	} elseif ( substr( $result, -1 ) === "\n" ) {
	$result = substr( $result, 0, -1 );
	} else {
	$this->_handle_error( $sock, 'line ending missing in response from $1' );
	return false;
	}
	return $result;
	}

	/**
	* Flush the read buffer of a stream
	* @param Resource $f
	*/
	function _flush_read_buffer( $f ) {
	if ( !$f ) {
	return;
	}
	$r = array( $f );
	$w = null;
	$e = null;
	$n = stream_select( $r, $w, $e, 0, 0 );
	while ( $n == 1 && !feof( $f ) ) {
	fread( $f, 1024 );
	$r = array( $f );
	$w = null;
	$e = null;
	$n = stream_select( $r, $w, $e, 0, 0 );
	}
	}

	// }}}
	// }}}
	// }}}
	}

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