func walkOnce(
dst farm.Selecter,
wait waiter,
src <-chan []string,
maxSize int,
instr instrumentation.WalkInstrumentation,
) {
defer func(t time.Time) { log.Printf("single walk complete, %s", time.Since(t)) }(time.Now())
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.SelectOffset(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
}
var keys [][]byte
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 (
offset, offsetGiven = parseInt(r.Form, "offset", 0)
startStr, startGiven = parseStr(r.Form, "start", "")
stopStr, stopGiven = parseStr(r.Form, "stop", "")
limit, _ = parseInt(r.Form, "limit", 10)
coalesce, _ = parseBool(r.Form, "coalesce", false)
)
switch {
case !offsetGiven && (startGiven || stopGiven):
// SelectRange. `coalesce` has no impact on the request, only the
// handling of the response.
var (
start = common.Cursor{Score: math.MaxFloat64}
stop = common.Cursor{Score: 0}
)
if startGiven {
if err := start.Parse(startStr); err != nil {
respondError(w, r.Method, r.URL.String(), http.StatusBadRequest, err)
return
}
}
if stopGiven {
if err := stop.Parse(stopStr); err != nil {
respondError(w, r.Method, r.URL.String(), http.StatusBadRequest, err)
return
}
}
results, err := selecter.SelectRange(keyStrings, start, stop, limit)
if err != nil {
respondError(w, r.Method, r.URL.String(), http.StatusInternalServerError, err)
return
}
//cursorResults := addCursor(results)
if coalesce {
respondSelected(w, flatten(results, 0, limit), time.Since(began))
return
}
respondSelected(w, results, time.Since(began))
return
case !startGiven && !stopGiven:
// SelectOffset. The offset/limit may be altered by `coalesce`.
var (
selectOffset = offset
selectLimit = limit
)
if coalesce {
selectOffset = 0
selectLimit = offset + limit
}
results, err := selecter.SelectOffset(keyStrings, selectOffset, selectLimit)
if err != nil {
respondError(w, r.Method, r.URL.String(), http.StatusInternalServerError, err)
return
}
//cursorResults := addCursor(results)
if coalesce {
respondSelected(w, flatten(results, offset, limit), time.Since(began))
return
}
respondSelected(w, results, time.Since(began))
return
case offsetGiven && (startGiven || stopGiven):
respondError(w, r.Method, r.URL.String(), http.StatusBadRequest, fmt.Errorf("cannot specify both offset and start/stop"))
return
default:
panic("unreachable")
}
}
}