Can flowable support cluster?
What do you mean by this?
Have a look at the Process Engine API and services. It has a section saying
All services are stateless. This means that you can easily run Flowable on multiple nodes in a cluster, each going to the same database, without having to worry about which machine actually executed previous calls. Any call to any service is idempotent regardless of where it is executed.
So yes Flowable can run in a clustered environment.
What about Timer Events? For example I have cluster with several flowable servers looking into same database. I have process with boundary timer event.
Does Flowable guaranteed this event at specified time will be executed only by one node of cluster. So, it will not happens two nodes of cluster with process same event at same time?
The same statement is valid for the entire engine execution. This also includes timers. You can read more about how timers are executed in the Advanced Async Executor section of the documentation