NAME¶
Cache::Memcached::Fast - Perl client for memcached, in C language
VERSION¶
Version 0.22.
SYNOPSIS¶
use Cache::Memcached::Fast;
my $memd = new Cache::Memcached::Fast({
servers => [ { address => 'localhost:11211', weight => 2.5 },
'192.168.254.2:11211',
{ address => '/path/to/unix.sock', noreply => 1 } ],
namespace => 'my:',
connect_timeout => 0.2,
io_timeout => 0.5,
close_on_error => 1,
compress_threshold => 100_000,
compress_ratio => 0.9,
compress_methods => [ \&IO::Compress::Gzip::gzip,
\&IO::Uncompress::Gunzip::gunzip ],
max_failures => 3,
failure_timeout => 2,
ketama_points => 150,
nowait => 1,
hash_namespace => 1,
serialize_methods => [ \&Storable::freeze, \&Storable::thaw ],
utf8 => ($^V ge v5.8.1 ? 1 : 0),
max_size => 512 * 1024,
});
# Get server versions.
my $versions = $memd->server_versions;
while (my ($server, $version) = each %$versions) {
#...
}
# Store scalars.
$memd->add('skey', 'text');
$memd->add_multi(['skey2', 'text2'], ['skey3', 'text3', 10]);
$memd->replace('skey', 'val');
$memd->replace_multi(['skey2', 'val2'], ['skey3', 'val3']);
$memd->set('nkey', 5);
$memd->set_multi(['nkey2', 10], ['skey3', 'text', 5]);
# Store arbitrary Perl data structures.
my %hash = (a => 1, b => 2);
my @list = (1, 2);
$memd->set('hash', \%hash);
$memd->set_multi(['scalar', 1], ['list', \@list]);
# Add to strings.
$memd->prepend('skey', 'This is a ');
$memd->prepend_multi(['skey2', 'This is a '], ['skey3', 'prefix ']);
$memd->append('skey', 'ue.');
$memd->append_multi(['skey2', 'ue.'], ['skey3', ' suffix']);
# Do arithmetic.
$memd->incr('nkey', 10);
print "OK\n" if $memd->decr('nkey', 3) == 12;
my @counters = qw(c1 c2);
$memd->set_multi(map { [$_, 0] } @counters, 'c3', 'c4');
$memd->incr_multi(['c3', 2], @counters, ['c4', 10]);
# Retrieve values.
my $val = $memd->get('skey');
print "OK\n" if $val eq 'This is a value.';
my $href = $memd->get_multi('hash', 'nkey');
print "OK\n" if $href->{hash}->{b} == 2 and $href->{nkey} == 12;
# Do atomic test-and-set operations.
my $cas_val = $memd->gets('nkey');
$$cas_val[1] = 0 if $$cas_val[1] == 12;
if ($memd->cas('nkey', @$cas_val)) {
print "OK, value updated\n";
} else {
print "Update failed, probably another client"
. " has updated the value\n";
}
# Delete some data.
$memd->delete('skey');
my @keys = qw(k1 k2 k3);
$memd->delete_multi(@keys);
# Wait for all commands that were executed in nowait mode.
$memd->nowait_push;
# Wipe out all cached data.
$memd->flush_all;
DESCRIPTION¶
Cache::Memcached::Fast is a Perl client for
memcached, a memory
cache daemon (<
http://www.danga.com/memcached/>). Module core is
implemented in C and tries hard to minimize number of system calls and to
avoid any key/value copying for speed. As a result, it has very low CPU
consumption.
API is largely compatible with Cache::Memcached, original pure Perl client, most
users of the original module may start using this module by installing it and
adding
"::Fast" to the old name in their scripts (see
"Compatibility with Cache::Memcached" below for full details).
CONSTRUCTOR¶
- "new"
-
my $memd = new Cache::Memcached::Fast($params);
Create new client object. $params is a reference to a
hash with client parameters. Currently recognized keys are:
- servers
-
servers => [ { address => 'localhost:11211', weight => 2.5 },
'192.168.254.2:11211',
{ address => '/path/to/unix.sock', noreply => 1 } ],
(default: none)
The value is a reference to an array of server addresses. Each address is
either a scalar, a hash reference, or an array reference (for
compatibility with Cache::Memcached, deprecated). If hash reference, the
keys are address (scalar), weight (positive rational
number), and noreply (boolean flag). The server address is in the
form host:port for network TCP connections, or
/path/to/unix.sock for local Unix socket connections. When weight
is not given, 1 is assumed. Client will distribute keys across servers
proportionally to server weights.
If you want to get key distribution compatible with Cache::Memcached, all
server weights should be integer, and their sum should be less than 32768.
When noreply is enabled, commands executed in a void context will
instruct the server to not send the reply. Compare with "nowait"
below. memcached server implements noreply starting with
version 1.2.5. If you enable noreply for earlier server versions,
things will go wrongly, and the client will eventually block. Use with
care.
- namespace
-
namespace => 'my::'
(default: '')
The value is a scalar that will be prepended to all key names passed to the
memcached server. By using different namespaces clients avoid
interference with each other.
- hash_namespace
-
hash_namespace => 1
(default: disabled)
The value is a boolean which enables (true) or disables (false) the hashing
of the namespace key prefix. By default for compatibility with
Cache::Memcached namespace prefix is not hashed along with the key.
Thus
namespace => 'prefix/',
...
$memd->set('key', $val);
may use different memcached server than
namespace => '',
...
$memd->set('prefix/key', $val);
because hash values of 'key' and 'prefix/key' may be
different.
However sometimes is it necessary to hash the namespace prefix, for instance
for interoperability with other clients that do not have the notion of the
namespace. When hash_namespace is enabled, both examples above will
use the same server, the one that 'prefix/key' is mapped to. Note
that there's no performance penalty then, as namespace prefix is hashed
only once. See "namespace".
- nowait
-
nowait => 1
(default: disabled)
The value is a boolean which enables (true) or disables (false)
nowait mode. If enabled, when you call a method that only returns
its success status (like "set"), in a void
context , it sends the request to the server and returns
immediately, not waiting the reply. This avoids the round-trip latency at
a cost of uncertain command outcome.
Internally there is a counter of how many outstanding replies there should
be, and on any command the client reads and discards any replies that have
already arrived. When you later execute some method in a non-void context,
all outstanding replies will be waited for, and then the reply for this
command will be read and returned.
- connect_timeout
-
connect_timeout => 0.7
(default: 0.25 seconds)
The value is a non-negative rational number of seconds to wait for
connection to establish. Applies only to network connections. Zero
disables timeout, but keep in mind that operating systems have their own
heuristic connect timeout.
Note that network connect process consists of several steps: destination
host address lookup, which may return several addresses in general case
(especially for IPv6, see
<http://people.redhat.com/drepper/linux-rfc3484.html> and
<http://people.redhat.com/drepper/userapi-ipv6.html>), then the
attempt to connect to one of those addresses. connect_timeout
applies only to one such connect, i.e. to one
connect(2) call. Thus overall connect process may
take longer than connect_timeout seconds, but this is
unavoidable.
- io_timeout (or deprecated select_timeout)
-
io_timeout => 0.5
(default: 1.0 seconds)
The value is a non-negative rational number of seconds to wait before giving
up on communicating with the server(s). Zero disables timeout.
Note that for commands that communicate with more than one server (like
"get_multi") the timeout applies per server set, not per each
server. Thus it won't expire if one server is quick enough to communicate,
even if others are silent. But if some servers are dead those alive will
finish communication, and then dead servers would timeout.
- close_on_error
-
close_on_error => 0
(default: enabled)
The value is a boolean which enables (true) or disables (false)
close_on_error mode. When enabled, any error response from the
memcached server would make client close the connection. Note that
such "error response" is different from "negative
response". The latter means the server processed the command and
yield negative result. The former means the server failed to process the
command for some reason. close_on_error is enabled by default for
safety. Consider the following scenario:
- 1 Client want to set some value, but mistakenly sends malformed command
(this can't happen with current module of course ;)):
-
set key 10\r\n
value_data\r\n
- 2 Memcached server reads first line, 'set key 10', and can't parse it,
because there's wrong number of tokens in it. So it sends
-
ERROR\r\n
- 3 Then the server reads 'value_data' while it is in accept-command state!
It can't parse it either (hopefully), and sends another
-
ERROR\r\n
But the client expects one reply per command, so after sending the next command
it will think that the second 'ERROR' is a reply for this new command. This
means that all replies will shift, including replies for "get"
commands! By closing the connection we eliminate such possibility.
When connection dies, or the client receives the reply that it can't understand,
it closes the socket regardless the
close_on_error setting.
- compress_threshold
-
compress_threshold => 10_000
(default: -1)
The value is an integer. When positive it denotes the threshold size in
bytes: data with the size equal or larger than this should be compressed.
See "compress_ratio" and "compress_methods" below.
Negative value disables compression.
- compress_ratio
-
compress_ratio => 0.9
(default: 0.8)
The value is a fractional number between 0 and 1. When
"compress_threshold" triggers the compression, compressed size
should be less or equal to (original-size *
compress_ratio). Otherwise the data will be stored
uncompressed.
- compress_methods
-
compress_methods => [ \&IO::Compress::Gzip::gzip,
\&IO::Uncompress::Gunzip::gunzip ]
(default: [ sub { ${$_[1]} = Compress::Zlib::memGzip(${$_[0]}) },
sub { ${$_[1]} = Compress::Zlib::memGunzip(${$_[0]}) } ]
when Compress::Zlib is available)
The value is a reference to an array holding two code references for
compression and decompression routines respectively.
Compression routine is called when the size of the
$value passed to "set" method family is
greater than or equal to "compress_threshold" (also see
"compress_ratio"). The fact that compression was performed is
remembered along with the data, and decompression routine is called on
data retrieval with "get" method family. The interface of these
routines should be the same as for IO::Compress family (for
instance see IO::Compress::Gzip::gzip and IO::Uncompress::Gunzip::gunzip).
I.e. compression routine takes a reference to scalar value and a reference
to scalar where compressed result will be stored. Decompression routine
takes a reference to scalar with compressed data and a reference to scalar
where uncompressed result will be stored. Both routines should return true
on success, and false on error.
By default we use Compress::Zlib because as of this writing it appears to be
much faster than IO::Uncompress::Gunzip.
- max_failures
-
max_failures => 3
(default: 0)
The value is a non-negative integer. When positive, if there happened
max_failures in failure_timeout seconds, the client does not
try to connect to this particular server for another
failure_timeout seconds. Value of zero disables this
behaviour.
- failure_timeout
-
failure_timeout => 30
(default: 10 seconds)
The value is a positive integer number of seconds. See
"max_failures".
- ketama_points
-
ketama_points => 150
(default: 0)
The value is a non-negative integer. When positive, enables the
Ketama consistent hashing algorithm
(<http://www.last.fm/user/RJ/journal/2007/04/10/392555/>), and
specifies the number of points the server with weight 1 will be mapped to.
Thus each server will be mapped to
ketama_points * weight points in continuum.
Larger value will result in more uniform distribution. Note that the
number of internal bucket structures, and hence memory consumption, will
be proportional to sum of such products. But bucket structures themselves
are small (two integers each), so you probably shouldn't worry.
Zero value disables the Ketama algorithm. See also server weight in
"servers" above.
- serialize_methods
-
serialize_methods => [ \&Storable::freeze, \&Storable::thaw ],
(default: [ \&Storable::nfreeze, \&Storable::thaw ])
The value is a reference to an array holding two code references for
serialization and deserialization routines respectively.
Serialization routine is called when the $value passed
to "set" method family is a reference. The fact that
serialization was performed is remembered along with the data, and
deserialization routine is called on data retrieval with "get"
method family. The interface of these routines should be the same as for
Storable::nfreeze and Storable::thaw. I.e. serialization routine takes a
reference and returns a scalar string; it should not fail. Deserialization
routine takes scalar string and returns a reference; if deserialization
fails (say, wrong data format) it should throw an exception (call
die). The exception will be caught by the module and
"get" will then pretend that the key hasn't been found.
- utf8
-
utf8 => 1
(default: disabled)
The value is a boolean which enables (true) or disables (false) the
conversion of Perl character strings to octet sequences in UTF-8 encoding
on store, and the reverse conversion on fetch (when the retrieved data is
marked as being UTF-8 octet sequence). See perlunicode.
- max_size
-
max_size => 512 * 1024
(default: 1024 * 1024)
The value is a maximum size of an item to be stored in memcached. When
trying to set a key to a value longer than max_size bytes (after
serialization and compression) nothing is sent to the server, and
set methods return undef.
Note that the real maximum on the server is less than 1MB, and depends on
key length among other things. So some values in the range
[1MB - N bytes, 1MB], where N is
several hundreds, will still be sent to the server, and rejected there.
You may set max_size to a smaller value to avoid this.
- check_args
-
check_args => 'skip'
(default: not 'skip')
The value is a string. Currently the only recognized string is
'skip'.
By default all constructor parameter names are checked to be recognized, and
a warning is given for unknown parameter. This will catch spelling errors
that otherwise might go unnoticed.
When set to 'skip', the check will be bypassed. This may be desired
when you share the same argument hash among different client versions, or
among different clients.
METHODS¶
- "enable_compress"
-
$memd->enable_compress($enable);
Enable compression when boolean $enable is true,
disable when false.
Note that you can enable compression only when you set
"compress_threshold" to some positive value and
"compress_methods" is set.
Return: none.
- "namespace"
-
$memd->namespace;
$memd->namespace($string);
Without the argument return the current namespace prefix. With the argument
set the namespace prefix to $string, and return the
old prefix.
Return: scalar, the namespace prefix that was in effect before the
call.
- "set"
-
$memd->set($key, $value);
$memd->set($key, $value, $expiration_time);
Store the $value on the server under the
$key . $key should be a scalar.
$value should be defined and may be of any Perl data
type. When it is a reference, the referenced Perl data structure will be
transparently serialized by routines specified with
"serialize_methods", which see.
Optional $expiration_time is a positive integer number
of seconds after which the value will expire and wouldn't be accessible
any longer.
Return: boolean, true for positive server reply, false for negative
server reply, or undef in case of some error.
- "set_multi"
-
$memd->set_multi(
[$key, $value],
[$key, $value, $expiration_time],
...
);
Like "set", but operates on more than one key. Takes the list of
references to arrays each holding $key,
$value and optional
$expiration_time.
Note that multi commands are not all-or-nothing, some operations may
succeed, while others may fail.
Return: in list context returns the list of results, each
$list [$index] is the result value corresponding to
the argument at position $index. In scalar context,
hash reference is returned, where $href->{$key}
holds the result value. See "set" to learn what the result value
is.
- "cas"
-
$memd->cas($key, $cas, $value);
$memd->cas($key, $cas, $value, $expiration_time);
Store the $value on the server under the
$key , but only if CAS ( Consistent Access
Storage) value associated with this key is equal to
$cas. $cas is an opaque object
returned with "gets" or "gets_multi".
See "set" for $key,
$value, $expiration_time
parameters description.
Return: boolean, true for positive server reply, false for negative
server reply, or undef in case of some error. Thus if the key
exists on the server, false would mean that some other client has updated
the value, and "gets", "cas" command sequence should
be repeated.
cas command first appeared in memcached 1.2.4.
- "cas_multi"
-
$memd->cas_multi(
[$key, $cas, $value],
[$key, $cas, $value, $expiration_time],
...
);
Like "cas", but operates on more than one key. Takes the list of
references to arrays each holding $key,
$cas , $value and optional
$expiration_time.
Note that multi commands are not all-or-nothing, some operations may
succeed, while others may fail.
Return: in list context returns the list of results, each
$list [$index] is the result value corresponding to
the argument at position $index. In scalar context,
hash reference is returned, where $href->{$key}
holds the result value. See "cas" to learn what the result value
is.
cas command first appeared in memcached 1.2.4.
- "add"
-
$memd->add($key, $value);
$memd->add($key, $value, $expiration_time);
Store the $value on the server under the
$key , but only if the key doesn't exists on
the server.
See "set" for $key,
$value, $expiration_time
parameters description.
Return: boolean, true for positive server reply, false for negative
server reply, or undef in case of some error.
- "add_multi"
-
$memd->add_multi(
[$key, $value],
[$key, $value, $expiration_time],
...
);
Like "add", but operates on more than one key. Takes the list of
references to arrays each holding $key,
$value and optional
$expiration_time.
Note that multi commands are not all-or-nothing, some operations may
succeed, while others may fail.
Return: in list context returns the list of results, each
$list [$index] is the result value corresponding to
the argument at position $index. In scalar context,
hash reference is returned, where $href->{$key}
holds the result value. See "add" to learn what the result value
is.
- "replace"
-
$memd->replace($key, $value);
$memd->replace($key, $value, $expiration_time);
Store the $value on the server under the
$key , but only if the key does exists on the
server.
See "set" for $key,
$value, $expiration_time
parameters description.
Return: boolean, true for positive server reply, false for negative
server reply, or undef in case of some error.
- "replace_multi"
-
$memd->replace_multi(
[$key, $value],
[$key, $value, $expiration_time],
...
);
Like "replace", but operates on more than one key. Takes the list
of references to arrays each holding $key,
$value and optional
$expiration_time.
Note that multi commands are not all-or-nothing, some operations may
succeed, while others may fail.
Return: in list context returns the list of results, each
$list [$index] is the result value corresponding to
the argument at position $index. In scalar context,
hash reference is returned, where $href->{$key}
holds the result value. See "replace" to learn what the result
value is.
- "append"
-
$memd->append($key, $value);
Append the $value to the current value on the
server under the $key.
$key and $value should be
scalars, as well as current value on the server. "append"
doesn't affect expiration time of the value.
Return: boolean, true for positive server reply, false for negative
server reply, or undef in case of some error.
append command first appeared in memcached 1.2.4.
- "append_multi"
-
$memd->append_multi(
[$key, $value],
...
);
Like "append", but operates on more than one key. Takes the list
of references to arrays each holding $key,
$value .
Note that multi commands are not all-or-nothing, some operations may
succeed, while others may fail.
Return: in list context returns the list of results, each
$list [$index] is the result value corresponding to
the argument at position $index. In scalar context,
hash reference is returned, where $href->{$key}
holds the result value. See "append" to learn what the result
value is.
append command first appeared in memcached 1.2.4.
- "prepend"
-
$memd->prepend($key, $value);
Prepend the $value to the current value on the
server under the $key.
$key and $value should be
scalars, as well as current value on the server. "prepend"
doesn't affect expiration time of the value.
Return: boolean, true for positive server reply, false for negative
server reply, or undef in case of some error.
prepend command first appeared in memcached 1.2.4.
- "prepend_multi"
-
$memd->prepend_multi(
[$key, $value],
...
);
Like "prepend", but operates on more than one key. Takes the list
of references to arrays each holding $key,
$value .
Note that multi commands are not all-or-nothing, some operations may
succeed, while others may fail.
Return: in list context returns the list of results, each
$list [$index] is the result value corresponding to
the argument at position $index. In scalar context,
hash reference is returned, where $href->{$key}
holds the result value. See "prepend" to learn what the result
value is.
prepend command first appeared in memcached 1.2.4.
- "get"
-
$memd->get($key);
Retrieve the value for a $key.
$key should be a scalar.
Return: value associated with the $key, or
nothing.
- "get_multi"
-
$memd->get_multi(@keys);
Retrieve several values associated with @keys.
@keys should be an array of scalars.
Return: reference to hash, where
$href->{$key} holds corresponding value.
- "gets"
-
$memd->gets($key);
Retrieve the value and its CAS for a $key.
$key should be a scalar.
Return: reference to an array [$cas, $value],
or nothing. You may conveniently pass it back to "cas" with
@$res:
my $cas_val = $memd->gets($key);
# Update value.
if (defined $cas_val) {
$$cas_val[1] = 3;
$memd->cas($key, @$cas_val);
}
gets command first appeared in memcached 1.2.4.
- "gets_multi"
-
$memd->gets_multi(@keys);
Retrieve several values and their CASs associated with
@keys. @keys should be an array
of scalars.
Return: reference to hash, where
$href->{$key} holds a reference to an array
[$cas, $value]. Compare with "gets".
gets command first appeared in memcached 1.2.4.
- "incr"
-
$memd->incr($key);
$memd->incr($key, $increment);
Increment the value for the $key. Starting with
memcached 1.3.3 $key should be set to a number
or the command will fail. An optional $increment
should be a positive integer, when not given 1 is assumed. Note that the
server doesn't check for overflow.
Return: unsigned integer, new value for the
$key, or false for negative server reply, or
undef in case of some error.
- "incr_multi"
-
$memd->incr_multi(
@keys,
[$key],
[$key, $increment],
...
);
Like "incr", but operates on more than one key. Takes the list of
keys and references to arrays each holding $key and
optional $increment.
Note that multi commands are not all-or-nothing, some operations may
succeed, while others may fail.
Return: in list context returns the list of results, each
$list [$index] is the result value corresponding to
the argument at position $index. In scalar context,
hash reference is returned, where $href->{$key}
holds the result value. See "incr" to learn what the result
value is.
- "decr"
-
$memd->decr($key);
$memd->decr($key, $decrement);
Decrement the value for the $key. Starting with
memcached 1.3.3 $key should be set to a number
or the command will fail. An optional $decrement
should be a positive integer, when not given 1 is assumed. Note that the
server does check for underflow, attempt to decrement the value
below zero would set the value to zero. Similar to DBI, zero is returned
as "0E0", and evaluates to true in a boolean context.
Return: unsigned integer, new value for the
$key, or false for negative server reply, or
undef in case of some error.
- "decr_multi"
-
$memd->decr_multi(
@keys,
[$key],
[$key, $decrement],
...
);
Like "decr", but operates on more than one key. Takes the list of
keys and references to arrays each holding $key and
optional $decrement.
Note that multi commands are not all-or-nothing, some operations may
succeed, while others may fail.
Return: in list context returns the list of results, each
$list [$index] is the result value corresponding to
the argument at position $index. In scalar context,
hash reference is returned, where $href->{$key}
holds the result value. See "decr" to learn what the result
value is.
- "delete"
-
$memd->delete($key);
Delete $key and its value from the cache.
Return: boolean, true for positive server reply, false for negative
server reply, or undef in case of some error.
- "remove" (deprecated)
- Alias for "delete", for compatibility with
Cache::Memcached.
- "delete_multi"
-
$memd->delete_multi(@keys);
Like "delete", but operates on more than one key. Takes the list
of keys.
Note that multi commands are not all-or-nothing, some operations may
succeed, while others may fail.
Return: in list context returns the list of results, each
$list [$index] is the result value corresponding to
the argument at position $index. In scalar context,
hash reference is returned, where $href->{$key}
holds the result value. See "delete" to learn what the result
value is.
- "flush_all"
-
$memd->flush_all;
$memd->flush_all($delay);
Flush all caches the client knows about. This command invalidates all items
in the caches, none of them will be returned on subsequent retrieval
command. $delay is an optional non-negative integer
number of seconds to delay the operation. The delay will be distributed
across the servers. For instance, when you have three servers, and call
"flush_all(30)", the servers would get 30, 15, 0 seconds delays
respectively. When omitted, zero is assumed, i.e. flush immediately.
Return: reference to hash, where
$href->{$server} holds corresponding result value.
$server is either host:port or
/path/to/unix.sock, as described in "servers". Result
value is a boolean, true for positive server reply, false for negative
server reply, or undef in case of some error.
- "nowait_push"
-
$memd->nowait_push;
Push all pending requests to the server(s), and wait for all replies. When
"nowait" mode is enabled, the requests issued in a void context
may not reach the server(s) immediately (because the reply is not waited
for). Instead they may stay in the send queue on the local host, or in the
receive queue on the remote host(s), for quite a long time. This method
ensures that they are delivered to the server(s), processed there, and the
replies have arrived (or some error has happened that caused some
connection(s) to be closed).
Destructor will call this method to ensure that all requests are processed
before the connection is closed.
Return: nothing.
- "server_versions"
-
$memd->server_versions;
Get server versions.
Return: reference to hash, where
$href->{$server} holds corresponding server
version. $server is either host:port or
/path/to/unix.sock, as described in "servers".
- "disconnect_all"
-
$memd->disconnect_all;
Closes all open sockets to memcached servers. Must be called after
"fork" in perlfunc if the parent process has open sockets to
memcacheds (as the child process inherits the socket and thus two
processes end up using the same socket which leads to protocol errors.)
Return: nothing.
Compatibility with Cache::Memcached¶
This module is designed to be a drop in replacement for Cache::Memcached. Where
constructor parameters are the same as in Cache::Memcached, the default values
are also the same, and new parameters are disabled by default (the exception
is "close_on_error", which is absent in Cache::Memcached and enabled
by default in this module, and "check_args", which see). Internally
Cache::Memcached::Fast uses the same hash function as Cache::Memcached, and
thus should distribute the keys across several servers the same way. So both
modules may be used interchangeably. Most users of the original module should
be able to use this module after replacing
"Cache::Memcached"
with
"Cache::Memcached::Fast", without further code
modifications. However, as of this release, the following features of
Cache::Memcached are not supported by Cache::Memcached::Fast (and some of them
will never be):
Constructor parameters¶
- no_rehash
- Current implementation never rehashes keys, instead
"max_failures" and "failure_timeout" are used.
If the client would rehash the keys, a consistency problem would arise: when
the failure occurs the client can't tell whether the server is down, or
there's a (transient) network failure. While some clients might fail to
reach a particular server, others may still reach it, so some clients will
start rehashing, while others will not, and they will no longer agree
which key goes where.
- readonly
- Not supported. Easy to add. However I'm not sure about the demand for it,
and it will slow down things a bit (because from design point of view it's
better to add it on Perl side rather than on XS side).
- debug
- Not supported. Since the implementation is different, there can't be any
compatibility on debug level.
Methods¶
- Passing keys
- Every key should be a scalar. The syntax when key is a reference to an
array [$precomputed_hash, $key] is not
supported.
- "set_servers"
- Not supported. Server set should not change after client object
construction.
- "set_debug"
- Not supported. See "debug".
- "set_readonly"
- Not supported. See "readonly".
- "set_norehash"
- Not supported. See "no_rehash".
- "set_compress_threshold"
- Not supported. Easy to add. Currently you specify
compress_threshold during client object construction.
- "stats"
- Not supported. Perhaps will appear in the future releases.
Tainted data¶
In current implementation tainted flag is neither tested nor preserved, storing
tainted data and retrieving it back would clear tainted flag. See perlsec.
Threads¶
This module is thread-safe when used with Perl >= 5.7.2. As with other Perl
data each thread gets its own copy of Cache::Memcached::Fast object that is in
scope when the thread is created. Such copies share no state, and may be used
concurrently. For example:
use threads;
my $memd = new Cache::Memcached::Fast({...});
sub thread_job {
$memd->set("key", "thread value");
}
threads->new(\&thread_job);
$memd->set("key", "main value");
Here both "set"s will be executed concurrently, and the value of
key will be either
main value or
thread value, depending
on the timing of operations. Note that $memd inside "thread_job"
internally refers to a different Cache::Memcached::Fast object than $memd from
the outer scope. Each object has its own connections to servers, its own
counter of outstanding replies for "nowait" mode, etc.
New object copy is created with the same constructor arguments, but initially is
not connected to any server (even when master copy has open connections). No
file descriptor is allocated until the command is executed through this new
object.
You may safely create Cache::Memcached::Fast object from threads other than main
thread, and/or pass them as parameters to
threads::new(). However you
can't return the object from top-level thread function. I.e., the following
won't work:
use threads;
sub thread_job {
return new Cache::Memcached::Fast({...});
}
my $thread = threads->new(\&thread_job);
my $memd = $thread->join; # The object will be destroyed here.
This is a Perl limitation (see "BUGS AND LIMITATIONS" in threads).
BUGS¶
Please report any bugs or feature requests to "bug-cache-memcached-fast at
rt.cpan.org", or through the web interface at
<
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Cache-Memcached-Fast>. I
will be notified, and then you'll automatically be notified of progress on
your bug as I make changes.
SUPPORT¶
You can find documentation for this module with the perldoc command.
perldoc Cache::Memcached::Fast
You can also look for information at:
- •
- Project home
<http://openhack.ru/Cache-Memcached-Fast>
- •
- RT: CPAN's request tracker
<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Cache-Memcached-Fast>
- •
- AnnoCPAN: Annotated CPAN documentation
<http://annocpan.org/dist/Cache-Memcached-Fast>
- •
- CPAN Ratings
<http://cpanratings.perl.org/d/Cache-Memcached-Fast>
- •
- Search CPAN
<http://search.cpan.org/dist/Cache-Memcached-Fast>
SEE ALSO¶
<
https://github.com/kroki/Cache-Memcached-Fast> - project home. Latest
development tree can be found there.
<
http://openhack.ru/Cache-Memcached-Fast> - old project home.
Cache::Memcached - original pure Perl
memcached client.
<
http://www.danga.com/memcached/> -
memcached website.
AUTHORS¶
Tomash Brechko, "<tomash.brechko at gmail.com>" - design
and implementation.
Michael Monashev, "<postmaster at softsearch.ru>" -
project management, design suggestions, testing.
ACKNOWLEDGEMENTS¶
Development of this module was sponsored by Monashev Co. Ltd.
Thanks to Peter J. Holzer for enlightening on UTF-8 support.
Thanks to Yasuhiro Matsumoto for initial Win32 patch.
WARRANTY¶
There's
NONE, neither explicit nor implied. But you knew it already ;).
COPYRIGHT AND LICENSE¶
Copyright (C) 2007-2010 Tomash Brechko. All rights reserved.
This library is free software; you can redistribute it and/or modify it under
the same terms as Perl itself, either Perl version 5.8.8 or, at your option,
any later version of Perl 5 you may have available.