Hi,
While trying to analyze the second half (duplicate alarms) of the bug 1794430,
I got stuck with a basic question.
Why do we need to store the DAT entries in persistent memory?
Please correct me if I'm wrong.
According to SAF HPI spec, DAT contains the entries for active alarm.
The DAT stores the active alarms and deletes when alarms get cleared.
Below is the extraction for SAF HPI B.02.01 spec (section 6.6):
The domain controller maintains a Domain Alarm Table (DAT) which contains
entries for each active alarm in the domain. Alarms are added to and deleted
from the DAT by the HPI implementation as the presence or absence of the
corresponding conditions are detected by the domain controller.
Storing the entries in persistent memory is required for marinating the history.
This is true for Domain Event Log (DEL) and not correct for DAT.
I'll try to explain with examples.
Scenario 1
-------------
1. The user has enabled option of saving DAT entries to persistent memory.
2. The openhpi daemon is started.
3. A resource (say) R1, reports an alarm related to temperature sensor.
4. An entry is created in the DAT and same is stored into the DAT file.
5. The openhpi daemon is brought down (for any reason).
6. Before the openhpi daemon is restarted, the resource R1 got resolved problem
and temperature alarm got cleared.
7. openhpi daemon is restarted.
Domain controller (openhpi daemon) reads the DAT file and creates an alarm
entry for the temperature sensor in the DAT.
This entry is a wrong as the temperature sensor alarm of resource R1 is not
active anymore.
Since the domain controller alarm entries added by reading DAT file, openhpi
plugin (which is managing resource R1) will not be aware of these entries.
Hence, alarm entries whose state is already cleared will never get deleted from
DAT.
Scenario 2
------------
Let us take the same situation as explained in scenario 1 till step 5.
6. The alarm condition in resource R1 still persists.
7. The openhpi daemon is restarted.
Domain controller (openhpi daemon) reads the DAT file and creates an alarm
entry for the temperature sensor in the DAT.
8. Since the openhpi plugin (which is managing the resource R1) is not aware of
the alarm added by the domain controller, plugin detects the temperature sensor
alarm condition and reports the same into DAT.
Scenario 2 is root cause of the duplicate alarms as reported in bug 1794430.
I'm not able to find a reference in SAF HPI spec for storing the DAT entries in
persistent memory.
Regards,
Raghavendra PG
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