>>> Nishant Nakate <[email protected]> schrieb am 16.07.2019 um 08:58 in Nachricht <cantavsneyduvqrs4twiocpuc+huc4ypwrzu5psixpradvgb...@mail.gmail.com>: > On Tue, Jul 16, 2019 at 11:33 AM Ulrich Windl < > [email protected]> wrote: > >> >>> Nishant Nakate <[email protected]> schrieb am 16.07.2019 um >> 05:37 in >> Nachricht >> <CANTAVSkfNnx=ZQv+UftaKs76Htk3VU+kO=bqhroj4sszx+o...@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 >> > logic. >> >> Why would you need that? crm_mon shows where ther DC is. >> >> Thanks you Ulrich for your quick response. > > I will give you a quick overview of the system. There would be 3 nodes > configured in a cluster. One would act as a leader and others as followers. > Our system would be actively running on all the three nodes and serve > external services assigned to them. On top of that, the Leader would have > some services running. In case the leader node (DC) fails, load of failed > leader needs to be distributed among followers. One should get elected as > next leader and start the additional services the previous leader was > running. > > In this case, a our system daemon running on the next node (designated as > new coordinater) needs to know that DC has changed and start the additional > services. Hope this clarifies my need. > > AFAIK, crm_mon (or dcs) needs to be run from command line. Are you > suggesting that I create a service which runs crm_mon and parse the ourput > in a loop to check changes in DC/resources ?
Hi! Still I don't see the dependency on the cluster's DC: You could put your coordinator resources in a group (for example) and place the other resources on different nodes. That group could run on any node, DC or not. > > >> > 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. >> > We are currently designing the services which are all stateless. If you > have any quick suggestions to be considered, please let me know. Also, what > type of RA would be helpful in this case. My services would be written in > C++. C++ will give you top performance and great control, but usually RAs are written as shell scripts, being able to use a library of convenience functions like ocf_log: ocf_log info "$1: activating crontab $crontab" > >> >> > >> > Please let me know if you need any clarification or any other >> information. >> > >> > Thanks in advance !!! >> >> >> >> >> _______________________________________________ >> Manage your subscription: >> https://lists.clusterlabs.org/mailman/listinfo/users >> >> ClusterLabs home: https://www.clusterlabs.org/ >> _______________________________________________ Manage your subscription: https://lists.clusterlabs.org/mailman/listinfo/users ClusterLabs home: https://www.clusterlabs.org/
