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Mail::SpamAssassin::AsyncLoop.3pm

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.