/**
* For each segment-set in the instanceToSegmentMap, we select one (or more speculative) servers
*
* @param requestContext
*/
private void selectServicesPerPartitionGroup(ScatterGatherRequestContext requestContext) {
Map<ServerInstance, SegmentIdSet> selectedServers = new HashMap<ServerInstance, SegmentIdSet>();
ScatterGatherRequest request = requestContext.getRequest();
Map<List<ServerInstance>, SegmentIdSet> instanceToSegmentMap = requestContext.getInvertedMap();
// int numDuplicateRequests = request.getNumSpeculativeRequests();
ReplicaSelection selection = request.getReplicaSelection();
for (Entry<List<ServerInstance>, SegmentIdSet> e : instanceToSegmentMap.entrySet()) {
ServerInstance s =
selection.selectServer(e.getValue().getOneSegment(), e.getKey(), request.getHashKey());
mergePartitionGroup(selectedServers, s, e.getValue());
/**
* TODO: We can easily add speculative execution here. The below code will pick a distinct
* server for the segmentId, This entry needs to be maintained in a separate container in
* ScatterGatherRequestContext Then in sndRequest, we need to construct SelectingFuture for
* the pairs of Future corresponding to original and speculative(duplicate) request.
*
* <p>int numServers = e.getKey().size();
*
* <p>// Pick Unique servers for speculative request int numIterations = Math.min(numServers -
* 1, numDuplicateRequests); for (int i = 0, c = 0; i < numIterations; i++, c++) {
* ServerInstance s1 = e.getKey().get(c); if ( s.equals(s1)) { c++; s1 = e.getKey().get(c); }
* mergePartitionGroup(selectedServers, s1, e.getValue()); //TODO: speculative servers need to
* be maintained in a separate entry in ScatterGatherRequestContext }
*/
}
requestContext.setSelectedServers(selectedServers);
}
/**
* For each segmentId in the instanceToSegmentMap, we select one (or more speculative) servers
*
* @param requestContext
*/
private void selectServicesPerPartition(ScatterGatherRequestContext requestContext) {
Map<ServerInstance, SegmentIdSet> selectedServers = new HashMap<ServerInstance, SegmentIdSet>();
ScatterGatherRequest request = requestContext.getRequest();
Map<List<ServerInstance>, SegmentIdSet> instanceToSegmentMap = requestContext.getInvertedMap();
ReplicaSelection selection = request.getReplicaSelection();
for (Entry<List<ServerInstance>, SegmentIdSet> e : instanceToSegmentMap.entrySet()) {
SegmentId firstPartition = null;
for (SegmentId p : e.getValue().getSegments()) {
/**
* For selecting the server, we always use first segmentId in the group. This will provide
* more chance for fanning out the query
*/
if (null == firstPartition) {
firstPartition = p;
}
ServerInstance s = selection.selectServer(firstPartition, e.getKey(), request.getHashKey());
mergePartitionGroup(selectedServers, s, p);
}
}
requestContext.setSelectedServers(selectedServers);
}