sendmail, 4th Edition

DelayLA

Add one second SMTP sleep on high load V8.12 and later

When the load average on a machine (the average number of processes in the run queue over the last 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 at which it will skip any scheduled queue runs, and the load at which scheduled runs will be skipped.

• The RefuseLA option (RefuseLA on page 1078) determines the load at which sendmail will begin to refuse connections rather than accepting them.

• The DelayLA option determines the load at which sendmail will begin to delay replies to SMTP commands.

The forms of the DelayLA option are as follows:

O DelayLA=load                ← configuration file (V8.12 and later)
-ODelayLA=load                ← command line (V8.12 and later)
define(`confDELAY_LA',load)   ← mc configuration (V8.12 and later)

The optional argument load, of type numeric, defaults to zero if it is missing. If the entire DelayLA option is missing, the default value given to load is zero. The default for the mc technique is to omit this option.

This DelayLA option is effective only if your sendmail binary was compiled with load-average support (LA_TYPE on page 118), which is almost universal these days. You can use the -d3.1 debugging switch to discover whether your binary includes the necessary support.

Should the load on the machine reach or exceed the limit, sendmail will begin to impose ...