[ClusterLabs] Antw: Interacting with Pacemaker from my code
kwenning at redhat.com
Tue Jul 16 02:39:13 EDT 2019
On 7/16/19 8:03 AM, Ulrich Windl wrote:
>>>> Nishant Nakate <technonsquare at gmail.com> schrieb am 16.07.2019 um 05:37 in
> <CANTAVSkfNnx=ZQv+UftaKs76Htk3VU+kO=bqHrOj4ssZx+Ou4A at mail.gmail.com>:
>> Hi All,
>> I am new to this community and HA tools. Need some guidance on my current
>> handling pacemaker.
>> For one of my projects, I am using pacekmaker for high availability.
>> Following the instructions provided in setup document, I am able to create
>> a new cluster with three nodes. Tested the failover and it works as
>> expected. Now, I need to run our own code on this nodes. I am going to use
>> Active-Pasive topology for our system architecture.
>> I would like to know, how can I detect from my code if DC has changed ? So
>> that tools running on new DC can take over the controll of application
> Why would you need that? crm_mon shows where ther DC is.
DC is actually a pacemaker-internal role and it would really have
to be checked carefully if an application role should be tied to that
If you are looking for the possibility of giving a single instance of your
application on one of the nodes a special role you might have a
look at promotable-resources (master/slave-resources historically).
If you still want to know which node has the DC role you can of
course use the same interface crm_mon is using
(read the cib - some kind of cluster-database holding both
configuration and live-data). There are new interfaces in the works
apart from this C-API but I'm not sure if anything is already available
As a last resort - or your method of choice depending on how often you
need the information and how quickly you need to be updated - you can
of course consider parsing the output ofsome existing cmdline-tool
(e.g. xml-output of crm_mon).
>> Also, how to configure my processes (tools) as resources so that Pacemaker
>> can make them HA.
> You'll have to write an RA (resource agent) at least, but more importantly the application has the be designed for HA to be effective.
>> Please let me know if you need any clarification or any other information.
>> Thanks in advance !!!
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