Use Storm TickTuples to execute tasks at fixed intervals.

Configure TickTuple interval like so

Config conf = new Config();
conf.put(Config.TOPOLOGY_TICK_TUPLE_FREQ_SECS, 1);

Here's how you tell if it's a tick tuple

if(input.getSourceStreamId().equals("__tick")) {
    System.out.println("Got a tick tuple here!");
}