func (self *Coordinator) getShardsAndProcessor(querySpec *parser.QuerySpec, writer engine.Processor) ([]*cluster.ShardData, engine.Processor, error) {
shards, err := self.clusterConfiguration.GetShardsForQuery(querySpec)
if err != nil {
return nil, nil, err
}
shouldAggregateLocally := shards.ShouldAggregateLocally(querySpec)
q := querySpec.SelectQuery()
if q == nil {
return shards, writer, nil
}
if !shouldAggregateLocally {
// if we should aggregate in the coordinator (i.e. aggregation
// isn't happening locally at the shard level), create an engine
shardIds := make([]uint32, len(shards))
for i, s := range shards {
shardIds[i] = s.Id()
}
writer, err = engine.NewQueryEngine(writer, q, shardIds)
if err != nil {
log.Error(err)
log.Debug("Coordinator processor chain: %s", engine.ProcessorChain(writer))
}
return shards, writer, err
}
// if we have a query with limit, then create an engine, or we can
// make the passthrough limit aware
writer = engine.NewPassthroughEngineWithLimit(writer, 100, q.Limit)
return shards, writer, nil
}
func (self *ShardData) Query(querySpec *parser.QuerySpec, response chan<- *p.Response) {
log.Debug("QUERY: shard %d, query '%s'", self.Id(), querySpec.GetQueryStringWithTimeCondition())
defer common.RecoverFunc(querySpec.Database(), querySpec.GetQueryStringWithTimeCondition(), func(err interface{}) {
response <- &p.Response{
Type: p.Response_ERROR.Enum(),
ErrorMessage: p.String(fmt.Sprintf("%s", err)),
}
})
// This is only for queries that are deletes or drops. They need to be sent everywhere as opposed to just the local or one of the remote shards.
// But this boolean should only be set to true on the server that receives the initial query.
if querySpec.RunAgainstAllServersInShard {
if querySpec.IsDeleteFromSeriesQuery() {
self.logAndHandleDeleteQuery(querySpec, response)
} else if querySpec.IsDropSeriesQuery() {
self.logAndHandleDropSeriesQuery(querySpec, response)
}
}
if self.IsLocal {
var processor engine.Processor = NewResponseChannelProcessor(NewResponseChannelWrapper(response))
var err error
processor = NewShardIdInserterProcessor(self.Id(), processor)
processor, err = self.getProcessor(querySpec, processor)
if err != nil {
response <- &p.Response{
Type: p.Response_ERROR.Enum(),
ErrorMessage: p.String(err.Error()),
}
log.Error("Error while creating engine: %s", err)
return
}
shard, err := self.store.GetOrCreateShard(self.id)
if err != nil {
response <- &p.Response{
Type: p.Response_ERROR.Enum(),
ErrorMessage: p.String(err.Error()),
}
log.Error("Error while getting shards: %s", err)
return
}
defer self.store.ReturnShard(self.id)
log.Debug("Processor chain: %s\n", engine.ProcessorChain(processor))
err = shard.Query(querySpec, processor)
// if we call Close() in case of an error it will mask the error
if err != nil {
response <- &p.Response{
Type: p.Response_ERROR.Enum(),
ErrorMessage: p.String(err.Error()),
}
return
}
processor.Close()
response <- &p.Response{Type: p.Response_END_STREAM.Enum()}
return
}
if server := self.randomHealthyServer(); server != nil {
log.Debug("Querying server %d for shard %d", server.GetId(), self.Id())
request := self.createRequest(querySpec)
server.MakeRequest(request, response)
return
}
message := fmt.Sprintf("No servers up to query shard %d", self.id)
response <- &p.Response{
Type: p.Response_ERROR.Enum(),
ErrorMessage: &message,
}
log.Error(message)
}