/
usage.go
65 lines (56 loc) · 1.48 KB
/
usage.go
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package randomsanity
import (
"appengine"
"appengine/datastore"
"encoding/json"
"log"
"math/rand" // don't need cryptographically secure randomness here
"net/http"
)
// Keep track of usage stats
// If frequency of database writes becomes a problem, increase SAMPLING_FACTOR
// to only write about every SAMPLING_FACTOR usages.
const SAMPLING_FACTOR = 1
type UsageRecord struct {
K string
N int64 `datastore:",noindex"`
}
func RecordUsage(ctx appengine.Context, k string, n int64) {
if rand.Intn(SAMPLING_FACTOR) != 0 {
return
}
key := datastore.NewKey(ctx, "UsageRecord", k, 0, nil)
err := datastore.RunInTransaction(ctx, func(ctx appengine.Context) error {
r := UsageRecord{K: k, N: 0}
err := datastore.Get(ctx, key, &r)
if err != nil && err != datastore.ErrNoSuchEntity {
return err
}
r.N += n * SAMPLING_FACTOR
_, err = datastore.Put(ctx, key, &r)
return err
}, nil)
if err != nil {
log.Printf("Datastore error: %s", err.Error())
}
}
func GetUsage(ctx appengine.Context) []UsageRecord {
var results []UsageRecord
q := datastore.NewQuery("UsageRecord")
_, err := q.GetAll(ctx, &results)
if err != nil {
log.Printf("Datastore error: %s", err.Error())
}
return results
}
func usageHandler(w http.ResponseWriter, r *http.Request) {
w.Header().Add("Content-Type", "application/json")
ctx := appengine.NewContext(r)
usage := GetUsage(ctx)
m := make(map[string]int64)
for _, rr := range usage {
m[rr.K] = rr.N
}
enc := json.NewEncoder(w)
enc.Encode(m)
}