func (self *CoordinatorImpl) runQuerySpec(querySpec *parser.QuerySpec, seriesWriter SeriesWriter) error {
shards, processor, seriesClosed, err := self.getShardsAndProcessor(querySpec, seriesWriter)
if err != nil {
return err
}
if len(shards) == 0 {
return fmt.Errorf("Couldn't look up columns")
}
defer func() {
if processor != nil {
processor.Close()
<-seriesClosed
} else {
seriesWriter.Close()
}
}()
shardConcurrentLimit := self.config.ConcurrentShardQueryLimit
if self.shouldQuerySequentially(shards, querySpec) {
log.Debug("Querying shards sequentially")
shardConcurrentLimit = 1
}
log.Debug("Shard concurrent limit: %d", shardConcurrentLimit)
errors := make(chan error, shardConcurrentLimit)
for i := 0; i < shardConcurrentLimit; i++ {
errors <- nil
}
responseChannels := make(chan (<-chan *protocol.Response), shardConcurrentLimit)
go self.readFromResponseChannels(processor, seriesWriter, querySpec.IsExplainQuery(), errors, responseChannels)
err = self.queryShards(querySpec, shards, errors, responseChannels)
// make sure we read the rest of the errors and responses
for _err := range errors {
if err == nil {
err = _err
}
}
for responsechan := range responseChannels {
for response := range responsechan {
if response.GetType() != endStreamResponse {
continue
}
if response.ErrorMessage != nil && err == nil {
err = common.NewQueryError(common.InvalidArgument, *response.ErrorMessage)
}
break
}
}
return err
}
func (self *CoordinatorImpl) getShardsAndProcessor(querySpec *parser.QuerySpec, writer SeriesWriter) ([]*cluster.ShardData, cluster.QueryProcessor, chan bool, error) {
shards := self.clusterConfiguration.GetShardsForQuery(querySpec)
shouldAggregateLocally := self.shouldAggregateLocally(shards, querySpec)
var err error
var processor cluster.QueryProcessor
responseChan := make(chan *protocol.Response)
seriesClosed := make(chan bool)
selectQuery := querySpec.SelectQuery()
if selectQuery != nil {
if !shouldAggregateLocally {
// if we should aggregate in the coordinator (i.e. aggregation
// isn't happening locally at the shard level), create an engine
processor, err = engine.NewQueryEngine(querySpec.SelectQuery(), responseChan)
} else {
// if we have a query with limit, then create an engine, or we can
// make the passthrough limit aware
processor = engine.NewPassthroughEngineWithLimit(responseChan, 100, selectQuery.Limit)
}
} else if !shouldAggregateLocally {
processor = engine.NewPassthroughEngine(responseChan, 100)
}
if err != nil {
return nil, nil, nil, err
}
if processor == nil {
return shards, nil, nil, nil
}
go func() {
for {
response := <-responseChan
if *response.Type == endStreamResponse || *response.Type == accessDeniedResponse {
writer.Close()
seriesClosed <- true
return
}
if !(*response.Type == queryResponse && querySpec.IsExplainQuery()) {
if response.Series != nil && len(response.Series.Points) > 0 {
writer.Write(response.Series)
}
}
}
}()
return shards, processor, seriesClosed, nil
}