Active Queue Test

The queue manager is a delivery agent scheduler which ensures fast and fair delivery of mail to all destinations within designated resource limits. By default, the active queue accommodates a maximum of 20000 messages. The messages to the active queue are from the incoming queue where new mails arrive and the deferred queue where old mails are retried. The messages in the active queue are ready to be sent, but are not necessarily in the process of being sent. In reality, the active queue is a set of data structures within the memory of the queue manager process. The envelope information for messages in the active queue is managed in memory, allowing the queue manager to do global scheduling, allocating available delivery agent processes to an appropriate message in the active queue. Within the active queue, the messages are broken up into groups of recipients that share the same transport/nexthop combination; the group size is capped by the transport's recipient concurrency limit. Multiple recipient groups (from one or more messages) are queued for delivery grouped by transport/nexthop combination. An active queue will be empty only when a queue manager marks a destination as dead (this may be due to the destination being down) and defers all the mails assigned to that destination to the deferred queue. An active queue may be overflowing if the destination is slow or if there is a problem in the destination which has caused excessive arrival of mails leading to a sudden surge in the active queue as well as congesting the destination. A destination may also be congested if the entire deferred queue undergoes an unwarranted flush. When messages reside in the active queue for a prolonged period, then the active queue may grow indefinitely and may not hold the space to accommodate all the messages. This will lead to a drastic degradation of the performance of the Postfix mail server. To avoid such unpleasant degradation and to keep track of the performance of the Postfix mail server, it is necessary to continuously track the messages in the active queue. The Active Queue test helps administrators in this regard!

This test periodically monitors the active queue of the target Postfix mail server and reports the total size of the queue as well as the split up of the message count in terms of time duration i.e., the number of messages that were in the queue for a specified time duration.

Target of the test : A Postfix mail server

Agent deploying the test : A remote agent

Outputs of the test : One set of results for the target Postfix mail server being monitored

Configurable parameters for the test
Parameters Description

Test period

How often should the test be executed

Host

The host for which the test is to be configured.

Port

The port at which the specified host listens. By default, this is NULL.

UseSUDO

By default, this flag is set to False indicating that the test does not collect the queue related statistics, by default. If this flag is set to True, then the test uses the sudo command to collect the queue related statistics.

Timeout

Specify the duration (in seconds) beyond which this test should time out in the TIMEOUT text box. The default is 30 seconds.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise suite embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measures made by the test
Measurement Description Measurement Unit Interpretation

Queue size

Indicates the total size of the queue.

Number

Ideally, a low value is desired for this measure.

An unusually high number of messages in the queue is indicative of any problem with the corresponding queue or its end points.

The Detailed diagnosis of this measure lists the message count for each domain to which the mails are destined to.

Less than 5 mins

Indicates the number of messages that were in the queue for less than 5 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

Between 5-10 mins

Indicates the number of messages that were in the queue for a time duration between 5 to 10 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

Between 10-20 mins

Indicates the number of messages that were in the queue for a time duration between 10 to 20 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

Between 20-40 mins

Indicates the number of messages that were in the queue for a time duration between 20 to 40 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

Between 40-80 mins

Indicates the number of messages that were in the queue for a time duration between 40 to 80 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

Between 80-160 mins

Indicates the number of messages that were in the queue for a time duration between 80 to 160 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

Between 160-320 mins

Indicates the number of messages that were in the queue for a time duration between 160 to 320 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

Between 320-640 mins

Indicates the number of messages that were in the queue for a time duration between 320 to 640 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

Between 640-1280 mins

Indicates the number of messages that were in the queue for a time duration between 640 to 1280 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

More than 1280 mins

Indicates the number of messages that were in the queue for more than 1280 minutes.

Number

Under normal conditions, the active queue should be empty i.e., the mail should leave the system to the destination as quickly as it comes in.

An unusually high value of this measure may indicate that the active queue is congested. Administrators should therefore investigate the real reason for congestion and should take necessary steps to send the mails to the deferred queue or should set a rule intimating the users to try sending mails to the problematic domain later. Some of the possible reasons for congestion may be either the unavailability of the domain to which the mails are destined to or the domain may be slow.