public static Execution onServers(RegionService regionService, String... groups) {
    return getInternalFunctionExecutionService().onServers(regionService, groups);
  }
Returns an {@link Execution} object that can be used to execute a data independent function on
all the servers that the given cache is connected to. If the optional groups parameter is
provided, function is executed on all servers that belong to the provided groups.
<p>
If one of the servers goes down while dispatching or executing the function on the server, an
Exception will be thrown.

@param regionService obtained from {@link ClientCacheFactory#create} or
       {@link ClientCache#createAuthenticatedView(java.util.Properties)}.
@param groups optional list of GemFire configuration property "groups" (see
       <a href="../../distributed/DistributedSystem.html#groups"> <code>groups</code></a>) on
       which to execute the function. Function will be executed on all servers of each group
@since GemFire 7.0
geode-core/src/main/java/org/apache/geode/internal/cache/execute/InternalFunctionService.java