func writeFromPointers(queryid string, f io.Writer, pointers []resultPointer) error {
var capnbuf bytes.Buffer
firstPathRank := state[queryid].FirstPathRank
state[queryid].tempFilesMu.Lock()
defer state[queryid].tempFilesMu.Unlock()
if _, err := f.Write([]byte("[")); err != nil {
return err
}
for idx, pointer := range pointers {
src := state[queryid].perBackend[pointer.backendidx].tempFile
if _, err := src.Seek(pointer.offset, os.SEEK_SET); err != nil {
return err
}
if idx > 0 {
if _, err := f.Write([]byte(",")); err != nil {
return err
}
}
seg, err := capn.ReadFromPackedStream(src, &capnbuf)
if err != nil {
return err
}
z := proto.ReadRootZ(seg)
if z.Which() != proto.Z_MATCH {
return fmt.Errorf("Expected to find a proto.Z_MATCH, instead got %d", z.Which())
}
result := z.Match()
// We need to fix the ranking here because we persist raw results from
// the dcs-source-backend in queryBackend(), but then modify the
// ranking in storeResult().
result.SetRanking(result.Pathrank() + ((firstPathRank * 0.1) * result.Ranking()))
if err := result.WriteJSON(f); err != nil {
return err
}
}
if _, err := f.Write([]byte("]\n")); err != nil {
return err
}
return nil
}
func queryBackend(queryid string, backend string, backendidx int, sourceQuery []byte) {
// When exiting this function, check that all results were processed. If
// not, the backend query must have failed for some reason. Send a progress
// update to prevent the query from running forever.
defer func() {
filesTotal := state[queryid].filesTotal[backendidx]
if state[queryid].filesProcessed[backendidx] == filesTotal {
return
}
if filesTotal == -1 {
filesTotal = 0
}
seg := capn.NewBuffer(nil)
p := proto.NewProgressUpdate(seg)
p.SetFilesprocessed(uint64(filesTotal))
p.SetFilestotal(uint64(filesTotal))
storeProgress(queryid, backendidx, p)
addEventMarshal(queryid, &Error{
Type: "error",
ErrorType: "backendunavailable",
})
}()
// TODO: switch in the config
log.Printf("[%s] [src:%s] connecting...\n", queryid, backend)
conn, err := net.DialTimeout("tcp", strings.Replace(backend, "28082", "26082", -1), 5*time.Second)
if err != nil {
log.Printf("[%s] [src:%s] Connection failed: %v\n", queryid, backend, err)
return
}
defer conn.Close()
if _, err := conn.Write(sourceQuery); err != nil {
log.Printf("[%s] [src:%s] could not send query: %v\n", queryid, backend, err)
return
}
bufferedReader := bufio.NewReaderSize(conn, 65536)
bstate := state[queryid].perBackend[backendidx]
tempFileWriter := bstate.tempFileWriter
var capnbuf bytes.Buffer
var written countingWriter
for !state[queryid].done {
conn.SetReadDeadline(time.Now().Add(10 * time.Second))
written = 0
tee := io.TeeReader(bufferedReader, io.MultiWriter(
tempFileWriter, &written))
seg, err := capn.ReadFromPackedStream(tee, &capnbuf)
if err != nil {
if err == io.EOF {
log.Printf("[%s] [src:%s] EOF\n", queryid, backend)
return
} else {
log.Printf("[%s] [src:%s] Error decoding result stream: %v\n", queryid, backend, err)
return
}
}
z := proto.ReadRootZ(seg)
if z.Which() == proto.Z_PROGRESSUPDATE {
storeProgress(queryid, backendidx, z.Progressupdate())
} else {
storeResult(queryid, backendidx, z.Match())
}
bstate.tempFileOffset += int64(written)
}
log.Printf("[%s] [src:%s] query done, disconnecting\n", queryid, backend)
}