func walkOnce(
dst farm.Selecter,
wait waiter,
src <-chan []string,
maxSize int,
instr instrumentation.WalkInstrumentation,
) {
for batch := range src {
log.Printf("walk: received batch of %d, requesting tokens", len(batch))
wait.Wait(int64(len(batch)))
log.Printf("walk: received tokens, performing Select")
dst.Select(batch, 0, maxSize)
instr.WalkKeys(len(batch))
log.Printf("walk: performed Select, waiting for next batch")
}
}
func handleSelect(selecter farm.Selecter) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
began := time.Now()
if err := r.ParseForm(); err != nil {
respondError(w, r.Method, r.URL.String(), http.StatusInternalServerError, err)
return
}
offset := parseInt(r.Form, "offset", 0)
limit := parseInt(r.Form, "limit", 10)
coalesce := parseBool(r.Form, "coalesce", false)
var keys [][]byte
defer r.Body.Close()
if err := json.NewDecoder(r.Body).Decode(&keys); err != nil {
respondError(w, r.Method, r.URL.String(), http.StatusBadRequest, err)
return
}
keyStrings := make([]string, len(keys))
for i := range keys {
keyStrings[i] = string(keys[i])
}
var records interface{}
if coalesce {
// We need to Select from 0 to offset+limit, flatten the map to a
// single ordered slice, and then cut off the last limit elements.
m, err := selecter.Select(keyStrings, 0, offset+limit)
if err != nil {
respondError(w, r.Method, r.URL.String(), http.StatusInternalServerError, err)
return
}
records = flatten(m, offset, limit)
} else {
// We can directly Select using the given offset and limit.
m, err := selecter.Select(keyStrings, offset, limit)
if err != nil {
respondError(w, r.Method, r.URL.String(), http.StatusInternalServerError, err)
return
}
records = m
}
respondSelected(w, keys, offset, limit, records, time.Since(began))
}
}