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remove lock #13

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remove lock #13

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40 changes: 21 additions & 19 deletions main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ import (
"sync/atomic"
"syscall"
"time"
"unsafe"

_ "net/http/pprof"

Expand All @@ -45,7 +46,7 @@ var (

var (
_BackendAddrCacheMutex sync.Mutex
_BackendAddrCache atomic.Value
_BackendAddrCache unsafe.Pointer
)

var (
Expand All @@ -60,7 +61,7 @@ func main() {
runtime.GOMAXPROCS(runtime.NumCPU())
os.Setenv("GOTRACEBACK", "crash")

_BackendAddrCache.Store(make(backendAddrMap))
_BackendAddrCache = unsafe.Pointer(&map[uint]uint{})

var lim syscall.Rlimit
syscall.Getrlimit(syscall.RLIMIT_NOFILE, &lim)
Expand Down Expand Up @@ -339,7 +340,7 @@ func dialTimeout(network, address string, timeout time.Duration) (conn net.Conn,

func backendAddrDecrypt(key []byte) ([]byte, error) {
// Try to check cache
m1 := _BackendAddrCache.Load().(backendAddrMap)
m1 := *(*backendAddrMap)(atomic.LoadPointer(&_BackendAddrCache))
k1 := string(key)
addr, ok := m1[k1]
if ok {
Expand All @@ -357,25 +358,26 @@ func backendAddrDecrypt(key []byte) ([]byte, error) {
}

func backendAddrList(key string, val []byte) {
_BackendAddrCacheMutex.Lock()
defer _BackendAddrCacheMutex.Unlock()

m1 := _BackendAddrCache.Load().(backendAddrMap)
// double check
if _, ok := m1[key]; ok {
return
}
done := false
for !done {
mptr := (atomic.LoadPointer(&_BackendAddrCache))
m1 := *(*backendAddrMap)(mptr)
// double check
if _, ok := m1[key]; ok {
return
}

m2 := make(backendAddrMap)
// flush cache if there is way too many
if len(m1) < _MaxBackendAddrCacheCount {
// copy-on-write
for k, v := range m1 {
m2[k] = v // copy all data from the current object to the new one
m2 := make(backendAddrMap)
// flush cache if there is way too many
if len(m1) < _MaxBackendAddrCacheCount {
// copy-on-write
for k, v := range m1 {
m2[k] = v // copy all data from the current object to the new one
}
}
m2[key] = val
done = atomic.CompareAndSwapPointer(&_BackendAddrCache, mptr, unsafe.Pointer(&m2))
}
m2[key] = val
_BackendAddrCache.Store(m2) // atomically replace the current object with the new one
}

// Request.RemoteAddress contains port, which we want to remove i.e.:
Expand Down