mirror of
https://github.com/etcd-io/etcd.git
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115 lines
3.3 KiB
Go
115 lines
3.3 KiB
Go
// Copyright 2016 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package etcdserver
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import (
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pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
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"github.com/coreos/etcd/mvcc/backend"
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)
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// Quota represents an arbitrary quota against arbitrary requests. Each request
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// costs some charge; if there is not enough remaining charge, then there are
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// too few resources available within the quota to apply the request.
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type Quota interface {
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// Available judges whether the given request fits within the quota.
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Available(req interface{}) bool
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// Cost computes the charge against the quota for a given request.
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Cost(req interface{}) int
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// Remaining is the amount of charge left for the quota.
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Remaining() int64
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}
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type passthroughQuota struct{}
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func (*passthroughQuota) Available(interface{}) bool { return true }
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func (*passthroughQuota) Cost(interface{}) int { return 0 }
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func (*passthroughQuota) Remaining() int64 { return 1 }
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type backendQuota struct {
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s *EtcdServer
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maxBackendBytes int64
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}
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const (
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// leaseOverhead is an estimate for the cost of storing a lease
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leaseOverhead = 64
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// kvOverhead is an estimate for the cost of storing a key's metadata
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kvOverhead = 256
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)
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func NewBackendQuota(s *EtcdServer) Quota {
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if s.Cfg.QuotaBackendBytes < 0 {
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// disable quotas if negative
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plog.Warningf("disabling backend quota")
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return &passthroughQuota{}
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}
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if s.Cfg.QuotaBackendBytes == 0 {
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// use default size if no quota size given
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return &backendQuota{s, backend.DefaultQuotaBytes}
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}
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if s.Cfg.QuotaBackendBytes > backend.MaxQuotaBytes {
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plog.Warningf("backend quota %v exceeds maximum quota %v; using maximum", s.Cfg.QuotaBackendBytes, backend.MaxQuotaBytes)
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return &backendQuota{s, backend.MaxQuotaBytes}
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}
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return &backendQuota{s, s.Cfg.QuotaBackendBytes}
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}
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func (b *backendQuota) Available(v interface{}) bool {
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// TODO: maybe optimize backend.Size()
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return b.s.Backend().Size()+int64(b.Cost(v)) < b.maxBackendBytes
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}
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func (b *backendQuota) Cost(v interface{}) int {
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switch r := v.(type) {
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case *pb.PutRequest:
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return costPut(r)
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case *pb.TxnRequest:
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return costTxn(r)
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case *pb.LeaseGrantRequest:
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return leaseOverhead
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default:
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panic("unexpected cost")
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}
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}
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func costPut(r *pb.PutRequest) int { return kvOverhead + len(r.Key) + len(r.Value) }
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func costTxnReq(u *pb.RequestOp) int {
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r := u.GetRequestPut()
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if r == nil {
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return 0
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}
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return costPut(r)
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}
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func costTxn(r *pb.TxnRequest) int {
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sizeSuccess := 0
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for _, u := range r.Success {
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sizeSuccess += costTxnReq(u)
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}
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sizeFailure := 0
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for _, u := range r.Failure {
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sizeFailure += costTxnReq(u)
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}
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if sizeFailure > sizeSuccess {
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return sizeFailure
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}
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return sizeSuccess
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}
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func (b *backendQuota) Remaining() int64 {
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return b.maxBackendBytes - b.s.Backend().Size()
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}
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