Provided by: libcache-memcached-fast-perl_0.25-1_amd64 
NAME
Cache::Memcached::Fast - Perl client for memcached, in C language
VERSION
Version 0.25.
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.memcached.org/>). 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.
"touch"
$memd->touch($key, $expiration_time);
Update the expiration time of $key without fetching it.
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.
touch command first appeared in memcached 1.4.8.
"touch_multi"
$memd->touch_multi(
[$key],
[$key, $expiration_time],
...
);
Like "touch", but operates on more than one key. Takes the list of references to
arrays each holding $key 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 "touch" to
learn what the result value is.
touch command first appeared in memcached 1.4.8.
"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
<https://github.com/kroki/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.memcached.org/> - 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.