12.5.3 Specifying the Retry Frequency for Messages that Failed Delivery

Keywords: backoff, nonurgentbackoff, normalbackoff, urgentbackoff, notices

By default, the frequency of delivery retries for messages that have had delivery failures depends on the message’s priority. The default intervals between delivery attempts (in minutes) is shown below. The first number after the priority indicates the number of minutes after the initial delivery failure that the first delivery retry is attempted:

urgent: 30, 60, 60, 120, 120, 120, 240
normal: 60, 120, 120, 240, 240, 240, 480
nonurgent: 120, 240, 240, 480, 480, 480, 960

For urgent messages, a retry is attempted 30 minutes after the initial delivery failure, 60 minutes after the first delivery retry, 60 minutes after the second retry, 120 minutes after the third and so on. Retries after the last specified attempt repeat at the same interval. Thus, for urgent messages, retries occur every 240 minutes.

Delivery attempts continue for a period of time specified by the notices, nonurgentnotices, normalnotices, or urgentnotices keywords. If a successful delivery cannot be made, a delivery failure notification is generated and the message is returned to sender. (For details on the notices keyword, see 10.10.4.3 To Set Notification Message Delivery Intervals

The backoff keywords allow you to specify customized sets of delivery retry intervals for messages of varying priorities. nonurgentbackoff specifies the intervals for nonurgent messages. normalbackoff specifies the intervals for normal messages. urgentbackoff specifies the intervals for urgent messages. If none of these keywords is specified, backoff specifies the intervals for all messages regardless of priority.

An example, is shown below:

urgentbackoff "pt30m" "pt1h" "pt2h" "pt3h" "pt4h" "pt5h" "pt8h" "pt16h"

Here, delivery retries of urgent messages is attempted 30 minutes after the initial delivery failure, one hour after the first delivery attempt (1 hour 30 minutes after initial failure), two hours after the second delivery attempt, three hours after the third, four hours after the fourth, five hours after the fifth, eight hours after the sixth, 16 hours after the seventh delivery attempt. Subsequent attempts are made every 16 hours until the period of time specified by the notices keyword. If a successful delivery cannot be made, a delivery failure notification is generated and the message is returned to sender. Note that the interval syntax is in ISO 8601P and is described in the Sun Java System Messaging Server Administration Reference.

In this next example,

normalbackoff "pt30m" "pt1h" "pt8h" "p1d" "p2d” "p1w"

a delivery retry of normal messages is attempted 30 minutes after the initial delivery failure, one hour after the first delivery attempt, eight hours after the second attempt, one day after the third, two days after the fourth, one week after the fifth and repeating each week until the period of time specified by the notices keyword. If a successful delivery cannot be made, a delivery failure notification is generated and the message is returned to sender.

In this final example,

backoff "pt30m" "pt120m" "pt16h" "pt36h" "p3d"

all failed message deliveries, regardless of message priority—unless overridden by nonurgentbackoff, normalbackoff, or urgentbackoff—will be retried 30 minutes after the initial delivery failure, two hours after the first retry attempt, 16 hours after the second attempt, 36 hours after the third, three days after the fourth and repeating every three days until the period of time specified by the notices keyword. If a successful delivery cannot be made, a delivery failure notification is generated and the message is returned to sender.