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/*
*
* Copyright 2020 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package clusterimpl
import (
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/internal/wrr"
"google.golang.org/grpc/status"
"google.golang.org/grpc/xds/internal/xdsclient"
"google.golang.org/grpc/xds/internal/xdsclient/load"
v3orcapb "github.com/cncf/xds/go/xds/data/orca/v3"
)
// NewRandomWRR is used when calculating drops. It's exported so that tests can
// override it.
var NewRandomWRR = wrr.NewRandom
const million = 1000000
type dropper struct {
category string
w wrr.WRR
}
// greatest common divisor (GCD) via Euclidean algorithm
func gcd(a, b uint32) uint32 {
for b != 0 {
t := b
b = a % b
a = t
}
return a
}
func newDropper(c DropConfig) *dropper {
w := NewRandomWRR()
gcdv := gcd(c.RequestsPerMillion, million)
// Return true for RequestPerMillion, false for the rest.
w.Add(true, int64(c.RequestsPerMillion/gcdv))
w.Add(false, int64((million-c.RequestsPerMillion)/gcdv))
return &dropper{
category: c.Category,
w: w,
}
}
func (d *dropper) drop() (ret bool) {
return d.w.Next().(bool)
}
const (
serverLoadCPUName = "cpu_utilization"
serverLoadMemoryName = "mem_utilization"
)
// loadReporter wraps the methods from the loadStore that are used here.
type loadReporter interface {
CallStarted(locality string)
CallFinished(locality string, err error)
CallServerLoad(locality, name string, val float64)
CallDropped(locality string)
}
// Picker implements RPC drop, circuit breaking drop and load reporting.
type picker struct {
drops []*dropper
s balancer.State
loadStore loadReporter
counter *xdsclient.ClusterRequestsCounter
countMax uint32
}
func newPicker(s balancer.State, config *dropConfigs, loadStore load.PerClusterReporter) *picker {
return &picker{
drops: config.drops,
s: s,
loadStore: loadStore,
counter: config.requestCounter,
countMax: config.requestCountMax,
}
}
func (d *picker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
// Don't drop unless the inner picker is READY. Similar to
// https://github.com/grpc/grpc-go/issues/2622.
if d.s.ConnectivityState == connectivity.Ready {
// Check if this RPC should be dropped by category.
for _, dp := range d.drops {
if dp.drop() {
if d.loadStore != nil {
d.loadStore.CallDropped(dp.category)
}
return balancer.PickResult{}, status.Errorf(codes.Unavailable, "RPC is dropped")
}
}
}
// Check if this RPC should be dropped by circuit breaking.
if d.counter != nil {
if err := d.counter.StartRequest(d.countMax); err != nil {
// Drops by circuit breaking are reported with empty category. They
// will be reported only in total drops, but not in per category.
if d.loadStore != nil {
d.loadStore.CallDropped("")
}
return balancer.PickResult{}, status.Errorf(codes.Unavailable, err.Error())
}
}
var lIDStr string
pr, err := d.s.Picker.Pick(info)
if scw, ok := pr.SubConn.(*scWrapper); ok {
// This OK check also covers the case err!=nil, because SubConn will be
// nil.
pr.SubConn = scw.SubConn
var e error
// If locality ID isn't found in the wrapper, an empty locality ID will
// be used.
lIDStr, e = scw.localityID().ToString()
if e != nil {
logger.Infof("failed to marshal LocalityID: %#v, loads won't be reported", scw.localityID())
}
}
if err != nil {
if d.counter != nil {
// Release one request count if this pick fails.
d.counter.EndRequest()
}
return pr, err
}
if d.loadStore != nil {
d.loadStore.CallStarted(lIDStr)
oldDone := pr.Done
pr.Done = func(info balancer.DoneInfo) {
if oldDone != nil {
oldDone(info)
}
d.loadStore.CallFinished(lIDStr, info.Err)
load, ok := info.ServerLoad.(*v3orcapb.OrcaLoadReport)
if !ok || load == nil {
return
}
d.loadStore.CallServerLoad(lIDStr, serverLoadCPUName, load.CpuUtilization)
d.loadStore.CallServerLoad(lIDStr, serverLoadMemoryName, load.MemUtilization)
for n, c := range load.RequestCost {
d.loadStore.CallServerLoad(lIDStr, n, c)
}
for n, c := range load.Utilization {
d.loadStore.CallServerLoad(lIDStr, n, c)
}
}
}
if d.counter != nil {
// Update Done() so that when the RPC finishes, the request count will
// be released.
oldDone := pr.Done
pr.Done = func(doneInfo balancer.DoneInfo) {
d.counter.EndRequest()
if oldDone != nil {
oldDone(doneInfo)
}
}
}
return pr, err
}
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