peridot/vendor/google.golang.org/grpc/balancer/grpclb/grpclb_util.go

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/*
*
* Copyright 2016 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 grpclb
import (
"fmt"
"sync"
"time"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/resolver"
)
const subConnCacheTime = time.Second * 10
// lbCacheClientConn is a wrapper balancer.ClientConn with a SubConn cache.
// SubConns will be kept in cache for subConnCacheTime before being shut down.
//
// Its NewSubconn and SubConn.Shutdown methods are updated to do cache first.
type lbCacheClientConn struct {
balancer.ClientConn
timeout time.Duration
mu sync.Mutex
// subConnCache only keeps subConns that are being deleted.
subConnCache map[resolver.Address]*subConnCacheEntry
subConnToAddr map[balancer.SubConn]resolver.Address
}
type subConnCacheEntry struct {
sc balancer.SubConn
cancel func()
abortDeleting bool
}
func newLBCacheClientConn(cc balancer.ClientConn) *lbCacheClientConn {
return &lbCacheClientConn{
ClientConn: cc,
timeout: subConnCacheTime,
subConnCache: make(map[resolver.Address]*subConnCacheEntry),
subConnToAddr: make(map[balancer.SubConn]resolver.Address),
}
}
func (ccc *lbCacheClientConn) NewSubConn(addrs []resolver.Address, opts balancer.NewSubConnOptions) (balancer.SubConn, error) {
if len(addrs) != 1 {
return nil, fmt.Errorf("grpclb calling NewSubConn with addrs of length %v", len(addrs))
}
addrWithoutAttrs := addrs[0]
addrWithoutAttrs.Attributes = nil
ccc.mu.Lock()
defer ccc.mu.Unlock()
if entry, ok := ccc.subConnCache[addrWithoutAttrs]; ok {
// If entry is in subConnCache, the SubConn was being deleted.
// cancel function will never be nil.
entry.cancel()
delete(ccc.subConnCache, addrWithoutAttrs)
return entry.sc, nil
}
scNew, err := ccc.ClientConn.NewSubConn(addrs, opts)
if err != nil {
return nil, err
}
scNew = &lbCacheSubConn{SubConn: scNew, ccc: ccc}
ccc.subConnToAddr[scNew] = addrWithoutAttrs
return scNew, nil
}
func (ccc *lbCacheClientConn) RemoveSubConn(sc balancer.SubConn) {
logger.Errorf("RemoveSubConn(%v) called unexpectedly", sc)
}
type lbCacheSubConn struct {
balancer.SubConn
ccc *lbCacheClientConn
}
func (sc *lbCacheSubConn) Shutdown() {
ccc := sc.ccc
ccc.mu.Lock()
defer ccc.mu.Unlock()
addr, ok := ccc.subConnToAddr[sc]
if !ok {
return
}
if entry, ok := ccc.subConnCache[addr]; ok {
if entry.sc != sc {
// This could happen if NewSubConn was called multiple times for
// the same address, and those SubConns are all shut down. We
// remove sc immediately here.
delete(ccc.subConnToAddr, sc)
sc.SubConn.Shutdown()
}
return
}
entry := &subConnCacheEntry{
sc: sc,
}
ccc.subConnCache[addr] = entry
timer := time.AfterFunc(ccc.timeout, func() {
ccc.mu.Lock()
defer ccc.mu.Unlock()
if entry.abortDeleting {
return
}
sc.SubConn.Shutdown()
delete(ccc.subConnToAddr, sc)
delete(ccc.subConnCache, addr)
})
entry.cancel = func() {
if !timer.Stop() {
// If stop was not successful, the timer has fired (this can only
// happen in a race). But the deleting function is blocked on ccc.mu
// because the mutex was held by the caller of this function.
//
// Set abortDeleting to true to abort the deleting function. When
// the lock is released, the deleting function will acquire the
// lock, check the value of abortDeleting and return.
entry.abortDeleting = true
}
}
}
func (ccc *lbCacheClientConn) UpdateState(s balancer.State) {
s.Picker = &lbCachePicker{Picker: s.Picker}
ccc.ClientConn.UpdateState(s)
}
func (ccc *lbCacheClientConn) close() {
ccc.mu.Lock()
defer ccc.mu.Unlock()
// Only cancel all existing timers. There's no need to shut down SubConns.
for _, entry := range ccc.subConnCache {
entry.cancel()
}
}
type lbCachePicker struct {
balancer.Picker
}
func (cp *lbCachePicker) Pick(i balancer.PickInfo) (balancer.PickResult, error) {
res, err := cp.Picker.Pick(i)
if err != nil {
return res, err
}
res.SubConn = res.SubConn.(*lbCacheSubConn).SubConn
return res, nil
}