NAME

Mail::SpamAssassin::AsyncLoop - scanner asynchronous event loop

DESCRIPTION

An asynchronous event loop used for long-running operations, performed "in the background" during the Mail::SpamAssassin::check() scan operation, such as DNS blocklist lookups.

METHODS

$obj = $async->start_lookup($obj)

Register the start of a long-running asynchronous lookup operation. $obj is a hash reference containing the following items:

key (required)

A key string, unique to this lookup. This is what is reported in debug messages, used as the key for get_lookup(), etc.

id (required)

An ID string, also unique to this lookup. Typically, this is the DNS packet ID as returned by DnsResolver's bgsend method. Sadly, the Net::DNS architecture forces us to keep a separate ID string for this task instead of reusing key -- if you are not using DNS lookups through DnsResolver, it should be OK to just reuse key.

type (required)

A string, typically one word, used to describe the type of lookup in log messages, such as DNSBL, MX, TXT.

poll_callback (optional)

A code reference, which will be called periodically during the background-processing period. If you will be performing an async lookup on a non-DNS-based service, you will need to implement this so that it checks for new responses and calls set_response_packet() or report_id_complete() as appropriate. DNS-based lookups can leave it undefined, since DnsResolver::poll_responses() will be called automatically anyway.

The code reference will be called with one argument, the $ent object.

completed_callback (optional)

A code reference which will be called when an asynchronous task (e.g. a DNS lookup) is completed, either normally, or aborted, e.g. by a timeout.

When a task has been reported as completed via set_response_packet() the response (as provided to set_response_packet()) is stored in $ent->{response_packet} (possibly undef, its semantics is defined by the caller). When completion is reported via report_id_complete() or a task was aborted, the $ent->{response_packet} is guaranteed to be undef. If it is necessary to distinguish between the last two cases, the $ent->{status} may be examined for a string 'ABORTING' or 'FINISHED'.

The code reference will be called with one argument, the $ent object.

zone (optional)

A zone specification (typically a DNS zone name - e.g. host, domain, or RBL) which may be used as a key to look up per-zone settings. No semantics on this parameter is imposed by this module. Currently used to fetch by-zone timeouts.

timeout_initial (optional)

An initial value of elapsed time for which we are willing to wait for a response (time in seconds, floating point value is allowed). When elapsed time since a query started exceeds the timeout value and there are no other queries to wait for, the query is aborted. The actual timeout value ranges from timeout_initial and gradually approaches timeout_min (see next parameter) as the number of already completed queries approaches the number of all queries started.

If a caller does not explicitly provide this parameter or its value is undefined, a default initial timeout value is settable by a configuration variable rbl_timeout.

If a value of the timeout_initial parameter is below timeout_min, the initial timeout is set to timeout_min.

timeout_min (optional)

A lower bound (in seconds) to which the actual timeout approaches as the number of queries completed approaches the number of all queries started. Defaults to 0.2 * timeout_initial.

$obj is returned by this method.

$obj = $async->get_lookup($key)

Retrieve the pending-lookup object for the given key $key.

If the lookup is complete, this will return undef.

Note that a lookup is still considered "pending" until complete_lookups() is called, even if it has been reported as complete via set_response_packet() or report_id_complete().

@objs = $async->get_pending_lookups()

Retrieve the lookup objects for all pending lookups.

Note that a lookup is still considered "pending" until complete_lookups() is called, even if it has been reported as complete via set_response_packet() or report_id_complete().

$async->log_lookups_timing()

Log sorted timing for all completed lookups.

$alldone = $async->complete_lookups()

Perform a poll of the pending lookups, to see if any are completed; if they are, their <completed_callback> is called with the entry object for that lookup.

If there are no lookups remaining, or if too long has elapsed since any results were returned, 1 is returned, otherwise 0.

$async->abort_remaining_lookups()

Abort any remaining lookups.

$async->set_response_packet($id, $pkt, $key, $timestamp)

Register a "response packet" for a given query. $id is the ID for the query, and must match the id supplied in start_lookup(). $pkt is the packet object for the response. A parameter $key identifies an entry in a hash %{$self->{pending_lookups}} where the object which spawned this query can be found, and through which futher information about the query is accessible.

If this was called, $pkt will be available in the completed_callback function as $ent-<gt{response_packet}>.

One or the other of set_response_packet() or report_id_complete() should be called, but not both.

$async->report_id_complete($id,$key,$key,$timestamp)

Register that a query has completed, and is no longer "pending". $id is the ID for the query, and must match the id supplied in start_lookup().

One or the other of set_response_packet() or report_id_complete() should be called, but not both.

$time = $async->last_poll_responses_time()

Get the time of the last call to poll_responses() (which is called from complete_lookups(). If poll_responses() was never called or abort_remaining_lookups() has been called last_poll_responses_time() will return undef.