Suppressing composite alarm actions
Because composite alarms allow you to get an aggregated view of your health across multiple alarms, there are common situations where it is expected for those alarms to trigger. For example, during a maintenance window of your application or when you investigate an ongoing incident. In such situations, you may want to suppress the actions of your composite alarms, to prevent unwanted notifications or the creation of new incident tickets
With composite alarm action suppression, you define alarms as suppressor alarms. Suppressor alarms prevent composite alarms from taking actions. For example, you can specify a suppressor alarm that represents the status of a supporting resource. If the supporting resource is down, the suppressor alarm prevents the composite alarm from sending notifications. Composite alarm action suppression helps you reduce alarm noise, so you spend less time managing your alarms and more time focusing on your operations.
You specify suppressor alarms
when you configure composite alarms.
Any alarm can function
as a suppressor alarm.
When a suppressor alarm changes states
from OK
to ALARM,
its composite alarm stops taking actions.
When a suppressor alarm changes states
from ALARM
to OK,
its composite alarm resumes taking actions.
WaitPeriod and ExtensionPeriod
When you specify a suppressor alarm,
you set the parameters WaitPeriod and ExtensionPeriod.
These parameters prevent composite alarms
from taking actions unexpectedly
while suppressor alarms change states.
Use WaitPeriod
to compensate for any delays
that can occur
when a suppressor alarm changes
from OK
to ALARM.
For example,
if a suppressor alarm changes
from OK to ALARM
within 60 seconds,
set WaitPeriod to 60 seconds.
In the image,
the composite alarm changes
from OK to ALARM
at t2.
A WaitPeriod starts
at t2
and ends
at t8.
This gives the suppressor alarm time
to change states
from OK
to ALARM
at t4
before it suppresses the composite alarm's actions
when the WaitPeriod expires
at t8.
Use ExtensionPeriod
to compensate
for any delays
that can occur
when a composite alarm changes
to OK
following a suppressor alarm changing
to OK.
For example,
if a composite alarm changes
to OK
within 60 seconds
of a suppressor alarm changing
to OK,
set ExtensionPeriod
to 60 seconds.
In the image,
the suppressor alarm changes
from ALARM
to OK
at t2.
An ExtensionPeriod starts
at t2
and ends
at t8.
This gives the composite alarm time
to change
from ALARM
to OK
before the ExtensionPeriod expires
at t8.
Composite alarms don't take actions
when WaitPeriod and ExtensionPeriod become active.
Composite alarms take actions
that are based
on their currents states
when ExtensionPeriod and WaitPeriod become inactive.
We recommend
that you set the value
for each parameter
to 60 seconds,
as CloudWatch evaluates metric alarms every minute.
You can set the parameters
to any integer
in seconds.
The following examples describe
in more detail
how WaitPeriod and ExtensionPeriod prevent composite alarms
from taking actions unexpectedly.
Note
In the following examples,
WaitPeriod is configured
as 2 time units,
and ExtensionPeriod is configured
as 3 time units.
Examples
Example 1:
Actions are not suppressed
after WaitPeriod
In the image,
the composite alarm changes states
from OK
to ALARM
at t2.
A WaitPeriod starts
at t2
and ends
at t4,
so it can prevent the composite alarm
from taking actions.
After the WaitPeriod expires
at t4,
the composite alarm takes its actions
because the suppressor alarm is still
in OK.
Example 2:
Actions are suppressed
by alarm
before WaitPeriod expires
In the image,
the composite alarm changes states
from OK
to ALARM
at t2.
A WaitPeriod starts
at t2
and ends
at t4.
This gives the suppressor alarm time
to change states
from OK
to ALARM
at t3.
Because the suppressor alarm changes states
from OK
to ALARM
at t3,
the WaitPeriod
that started
at t2
is discarded,
and the suppressor alarm now stops the composite alarm
from taking actions.
Example 3:
State transition
when actions are suppressed
by WaitPeriod
In the image,
the composite alarm changes states
from OK
to ALARM
at t2.
A WaitPeriod starts
at t2
and ends
at t4.
This gives the suppressor alarm time
to change states.
The composite alarm changes back
to OK
at t3,
so the WaitPeriod
that started
at t2
is discarded.
A new WaitPeriod starts
at t3
and ends
at t5.
After the new WaitPeriod expires
at t5,
the composite alarm takes its actions.
Example 4: State transition when actions are suppressed by alarm
In the image,
the composite alarm changes states
from OK to ALARM
at t2.
The suppressor alarm is already
in ALARM.
The suppressor alarm stops the composite alarm
from taking actions.
Example 5:
Actions are not suppressed
after ExtensionPeriod
In the image,
the composite alarm changes states
from OK
to ALARM
at t2.
A WaitPeriod starts
at t2
and ends
at t4.
This gives the suppressor alarm time
to change states
from OK
to ALARM
at t3
before it suppresses the composite alarm's actions
until t6.
Because the suppressor alarm changes states
from OK
to ALARM
at t3,
the WaitPeriod
that started
at t2
is discarded.
At t6,
the suppressor alarm changes
to OK.
An ExtensionPeriod starts
at t6
and ends
at t9.
After the ExtensionPeriod expires,
the composite alarm takes its actions.
Example 6:
State transition
when actions are suppressed
by ExtensionPeriod
In the image,
the composite alarm changes states
from OK
to ALARM
at t2.
A WaitPeriod starts
at t2
and ends
at t4.
This gives the suppressor alarm time
to change states
from OK
to ALARM
at t3
before it suppresses the composite alarm's actions
until t6.
Because the suppressor alarm changes states
from OK
to ALARM
at t3,
the WaitPeriod
that started
at t2
is discarded.
At t6,
the suppressor alarm changes back
to OK.
An ExtensionPeriod
starts
at t6
and ends
at t9.
When the composite alarm changes back
to OK
at t7,
the ExtensionPeriod is discarded,
and a new WaitPeriod
starts
at t7
and ends
at t9.
Tip
If you replace the action suppressor alarm,
any active WaitPeriod or ExtensionPeriod
is discarded.
