sendmail, 4th Edition

RefuseLA

Refuse connections on high load All versions

When the load average on a machine (the average number of processes in the run queue over the past minute) becomes too high, sendmail can compensate in three different ways:

• The QueueLA option (QueueLA on page 1072) determines the load at which sendmail will begin to queue messages rather than delivering them, and the load at which scheduled queue runs will be skipped.

• This RefuseLA option determines the load at which sendmail will begin to refuse connections^[414] rather than accepting them.

• The DelayLA option (DelayLA on page 1002) determines the load at which sendmail will begin to delay replies to SMTP commands.

Some experts consider refusing connections with the RefuseLA option a more serious problem than the queuing caused by the QueueLA option (QueueLA on page 1072), so prior to the introduction of V8.7 sendmail, they generally recommended that the load specified for this RefuseLA option should be the higher of the two. Others take the opposite stand. Paul Vixie, for one, believes that the RefuseLA option should be lower than the QueueLA option so that you stop accepting mail before you stop processing it. Under V8.7, the two options have been decoupled, and you can now tune them according to your personal philosophy.

The forms of the RefuseLA option are as follows:

O RefuseLA=limit                ← configuration file (V8.7 and later)
-ORefuseLA=limit                ← command line (V8.7 and later)
define(`confREFUSE_LA',limit)   ← mc configuration (V8.7 and ...