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

       $ent = $async->start_lookup($ent, $master_deadline)
           Register the start of a long-running asynchronous lookup operation.  $ent 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".

           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.

           $ent is returned by this method, with its contents augmented by additional
           information.

       $ent = $async->bgsend_and_start_lookup($domain, $type, $class, $ent, $cb, %options)
           A common idiom: calls "bgsend", followed by a call to "start_lookup", returning the
           argument $ent object as modified by "start_lookup" and filled-in with a query ID.

       $ent = $async->get_lookup($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()".

       $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.  Callbacks on
           completed queries will be called from poll_responses().

           If there are no lookups remaining, or if too much time 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.

           $pkt may be undef, indicating that no response packet is available, but a query has
           completed (e.g. was aborted or dismissed) and is no longer "pending".

           The DNS resolver's response packet $pkt will be made available to a callback
           subroutine through its argument as well as in "$ent-<gt"{response_packet}>.

       $async->report_id_complete($id,$key,$key,$timestamp)
           Legacy. Equivalent to $self->set_response_packet($id,undef,$key,$timestamp), i.e.
           providing undef as a response packet. 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.