NAME

Mail::SpamAssassin::BayesStore::Redis - Redis Bayesian Storage Module Implementation

DESCRIPTION

This module implements a Redis based bayesian storage module.

Apache SpamAssassin v3.4.0 introduces support for keeping a Bayes database on a Redis server, either running locally, or accessed over network. Similar to SQL backends, the database may be concurrently used by several hosts running SpamAssassin.

The current implementation only supports a global Bayes database, i.e. per-recipient sub-databases are not supported. The Redis 2.6.* server supports access over IPv4 or over a Unix socket, starting with Redis version 2.8.0 also IPv6 is supported. Bear in mind that Redis server only offers limited access controls, so it is advisable to let the Redis server bind to a loopback interface only, or to use other mechanisms to limit access, such as local firewall rules.

The Redis backend for Bayes can put a Lua scripting support in a Redis server to good use, improving performance. The Lua support is available in Redis server since version 2.6. In absence of a Lua support, the Redis backend uses batched (pipelined) traditional Redis commands, so it should work with a Redis server version 2.4 (untested), although this is not recommended for busy sites.

Expiration of token and 'seen' message id entries is left to the Redis server. There is no provision for manually expiring a database, so it is highly recommended to leave the setting bayes_auto_expire to its default value 1 (i.e. enabled).

Example configuration:

bayes_store_module  Mail::SpamAssassin::BayesStore::Redis
bayes_sql_dsn       server=127.0.0.1:6379;password=foo;database=2
bayes_token_ttl 21d
bayes_seen_ttl   8d
bayes_auto_expire 1

A redis server with a Lua support (2.6 or higher) is recommended for performance reasons.

The bayes_sql_dsn config variable has been hijacked for our purposes:

bayes_sql_dsn

  Optional config parameters affecting a connection to a redis server.

  This is a semicolon-separated list of option=value pairs, where an option
  can be: server, password, database. Unrecognized options are silently
  ignored.

  The 'server' option specifies a socket on which a redis server is
  listening. It can be an absolute path of a Unix socket, or a host:port
  pair, where a host can be an IPv4 or IPv6 address or a host name.
  An IPv6 address must be enclosed in brackets, e.g. [::1]:6379
  (IPv6 support in a redis server is available since version 2.8.0).
  A default is to connect to an INET socket at 127.0.0.1, port 6379.

  The value of a 'password' option is sent in an AUTH command to a redis
  server on connecting if a server requests authentication. A password is
  sent in plain text and a redis server only offers an optional rudimentary
  authentication. To limit access to a redis server use its 'bind' option
  to bind to a specific interface (typically to a loopback interface),
  or use a host-based firewall.

  The value of a 'database' option can be an non-negative (small) integer,
  which is passed to a redis server with a SELECT command on connecting,
  and chooses a sub-database index. A default database index is 0.

  Example: server=localhost:6379;password=foo;database=2

bayes_token_ttl

  Controls token expiry (ttl value in SECONDS, sent as-is to Redis)
  when bayes_auto_expire is true. Default value is 3 weeks (but check
  Mail::SpamAssassin::Conf.pm to make sure).

bayes_seen_ttl

  Controls 'seen' expiry (ttl value in SECONDS, sent as-is to Redis)
  when bayes_auto_expire is true. Default value is 8 days (but check
  Mail::SpamAssassin::Conf.pm to make sure).

Expiry is done internally in Redis using *_ttl settings mentioned above, but only if bayes_auto_expire is true (which is a default). This is why --force-expire etc does nothing, and token counts and atime values are shown as zero in statistics.

LIMITATIONS: Only global bayes storage is implemented, per-user bayes is not currently available. Dumping (sa-learn --backup, or --dump) of a huge database may not be possible if all keys do not fit into process memory.

METHODS

new

public class (Mail::SpamAssassin::BayesStore::Redis) new (Mail::Spamassassin::Plugin::Bayes $bayes)

Description: This methods creates a new instance of the Mail::SpamAssassin::BayesStore::Redis object. It expects to be passed an instance of the Mail::SpamAssassin:Bayes object which is passed into the Mail::SpamAssassin::BayesStore parent object.

prefork_init

public instance (Boolean) prefork_init ();

Description: This optional method is called in the parent process shortly before forking off child processes.

spamd_child_init

public instance (Boolean) spamd_child_init ();

Description: This optional method is called in a child process shortly after being spawned.

tie_db_readonly

public instance (Boolean) tie_db_readonly ();

Description: This method ensures that the database connection is properly setup and working.

tie_db_writable

public instance (Boolean) tie_db_writable ()

Description: This method ensures that the database connection is properly setup and working. If necessary it will initialize the database so that they can begin using the database immediately.

_open_db

private instance (Boolean) _open_db (Boolean $writable)

Description: This method ensures that the database connection is properly setup and working. It will initialize bayes variables so that they can begin using the database immediately.

untie_db

public instance () untie_db ()

Description: Closes any open db handles. You can safely call this at any time.

sync_due

public instance (Boolean) sync_due ()

Description: This method determines if a database sync is currently required.

Unused for Redis implementation.

expiry_due

public instance (Boolean) expiry_due ()

Description: This methods determines if an expire is due.

Unused for Redis implementation.

seen_get

public instance (String) seen_get (string $msgid)

Description: This method retrieves the stored value, if any, for $msgid. The return value is the stored string ('s' for spam and 'h' for ham) or undef if $msgid is not found.

seen_put

public (Boolean) seen_put (string $msgid, char $flag)

Description: This method records $msgid as the type given by $flag. $flag is one of two values 's' for spam and 'h' for ham.

seen_delete

public instance (Boolean) seen_delete (string $msgid)

Description: This method removes $msgid from the database.

get_storage_variables

public instance (@) get_storage_variables ()

Description: This method retrieves the various administrative variables used by the Bayes process and database.

The values returned in the array are in the following order:

0: scan count base 1: number of spam 2: number of ham 3: number of tokens in db 4: last expire atime 5: oldest token in db atime 6: db version value 7: last journal sync 8: last atime delta 9: last expire reduction count 10: newest token in db atime

Only 1,2,6 are used with Redis, others return zero always.

get_running_expire_tok

public instance (String $time) get_running_expire_tok ()

Description: This method determines if an expire is currently running and returns the last time set.

set_running_expire_tok

public instance (String $time) set_running_expire_tok ()

Description: This method sets the time that an expire starts running.

remove_running_expire_tok

public instance (Boolean) remove_running_expire_tok ()

Description: This method removes the row in the database that indicates that and expire is currently running.

tok_get

public instance (Integer, Integer, Integer) tok_get (String $token)

Description: This method retrieves a specified token ($token) from the database and returns its spam_count, ham_count and last access time.

tok_get_all

public instance (\@) tok_get (@ $tokens)

Description: This method retrieves the specified tokens ($tokens) from storage and returns a ref to arrays spam count, ham count and last access time.

tok_count_change

public instance (Boolean) tok_count_change ( Integer $dspam, Integer $dham, String $token, String $newatime)

Description: This method takes a $spam_count and $ham_count and adds it to $tok along with updating $toks atime with $atime.

multi_tok_count_change

public instance (Boolean) multi_tok_count_change ( Integer $dspam, Integer $dham, \% $tokens, String $newatime)

Description: This method takes a $dspam and $dham and adds it to all of the tokens in the $tokens hash ref along with updating each token's atime with $atime.

nspam_nham_get

public instance ($spam_count, $ham_count) nspam_nham_get ()

Description: This method retrieves the total number of spam and the total number of ham learned.

nspam_nham_change

public instance (Boolean) nspam_nham_change (Integer $num_spam, Integer $num_ham)

Description: This method updates the number of spam and the number of ham in the database.

tok_touch

public instance (Boolean) tok_touch (String $token, String $atime)

Description: This method updates the given tokens ($token) atime.

The assumption is that the token already exists in the database.

We will never update to an older atime

tok_touch_all

public instance (Boolean) tok_touch (\@ $tokens String $atime)

Description: This method does a mass update of the given list of tokens $tokens, if the existing token atime is < $atime.

cleanup

public instance (Boolean) cleanup ()

Description: This method performs any cleanup necessary before moving onto the next operation.

get_magic_re

public instance (String) get_magic_re ()

Description: This method returns a regexp which indicates a magic token.

sync

public instance (Boolean) sync (\% $opts)

Description: This method performs a sync of the database

perform_upgrade

public instance (Boolean) perform_upgrade (\% $opts);

Description: Performs an upgrade of the database from one version to another, not currently used in this implementation.

clear_database

public instance (Boolean) clear_database ()

Description: This method deletes all records for a particular user.

Callers should be aware that any errors returned by this method could causes the database to be inconsistent for the given user.

dump_db_toks

public instance () dump_db_toks (String $template, String $regex, Array @vars)

Description: This method loops over all tokens, computing the probability for the token and then printing it out according to the passed in token.

backup_database

public instance (Boolean) backup_database ()

Description: This method will dump the users database in a machine readable format.

restore_database

public instance (Boolean) restore_database (String $filename, Boolean $showdots)

Description: This method restores a database from the given filename, $filename.