grpc/client/pool.go

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/*
Taken from the https://github.com/micro/go-micro/client/grpc
*/
package client
import (
"sync"
"time"
"google.golang.org/grpc"
"google.golang.org/grpc/connectivity"
)
var (
// DefaultPoolSize sets the connection pool size
DefaultPoolSize = 100
// DefaultPoolTTL sets the connection pool ttl
DefaultPoolTTL = time.Minute
// DefaultPoolMaxStreams maximum streams on a connectioin
// (20)
DefaultPoolMaxStreams = 20
// DefaultPoolMaxIdle maximum idle conns of a pool
// (50)
DefaultPoolMaxIdle = 50
// DefaultMaxRecvMsgSize maximum message that client can receive
// (4 MB).
DefaultMaxRecvMsgSize = 1024 * 1024 * 4
// DefaultMaxSendMsgSize maximum message that client can send
// (4 MB).
DefaultMaxSendMsgSize = 1024 * 1024 * 4
)
type pool struct {
size int
ttl int64
// max streams on a *poolConn
maxStreams int
// max idle conns
maxIdle int
sync.Mutex
conns map[string]*streamsPool
}
type streamsPool struct {
// head of list
head *poolConn
// busy conns list
busy *poolConn
// the siza of list
count int
// idle conn
idle int
}
type poolConn struct {
// grpc conn
*grpc.ClientConn
err error
addr string
// pool and streams pool
pool *pool
sp *streamsPool
streams int
created int64
// list
pre *poolConn
next *poolConn
in bool
}
func newPool(size int, ttl time.Duration, idle int, ms int) *pool {
if ms <= 0 {
ms = 1
}
if idle < 0 {
idle = 0
}
return &pool{
size: size,
ttl: int64(ttl.Seconds()),
maxStreams: ms,
maxIdle: idle,
conns: make(map[string]*streamsPool),
}
}
func (p *pool) getConn(addr string, opts ...grpc.DialOption) (*poolConn, error) {
now := time.Now().Unix()
p.Lock()
sp, ok := p.conns[addr]
if !ok {
sp = &streamsPool{head: &poolConn{}, busy: &poolConn{}, count: 0, idle: 0}
p.conns[addr] = sp
}
// while we have conns check streams and then return one
// otherwise we'll create a new conn
conn := sp.head.next
for conn != nil {
// check conn state
// https://github.com/grpc/grpc/blob/master/doc/connectivity-semantics-and-api.md
switch conn.GetState() {
case connectivity.Connecting:
conn = conn.next
continue
case connectivity.Shutdown:
next := conn.next
if conn.streams == 0 {
removeConn(conn)
sp.idle--
}
conn = next
continue
case connectivity.TransientFailure:
next := conn.next
if conn.streams == 0 {
removeConn(conn)
conn.ClientConn.Close()
sp.idle--
}
conn = next
continue
case connectivity.Ready:
case connectivity.Idle:
}
// a old conn
if now-conn.created > p.ttl {
next := conn.next
if conn.streams == 0 {
removeConn(conn)
conn.ClientConn.Close()
sp.idle--
}
conn = next
continue
}
// a busy conn
if conn.streams >= p.maxStreams {
next := conn.next
removeConn(conn)
addConnAfter(conn, sp.busy)
conn = next
continue
}
// a idle conn
if conn.streams == 0 {
sp.idle--
}
// a good conn
conn.streams++
p.Unlock()
return conn, nil
}
p.Unlock()
// create new conn
cc, err := grpc.Dial(addr, opts...)
if err != nil {
return nil, err
}
conn = &poolConn{cc, nil, addr, p, sp, 1, time.Now().Unix(), nil, nil, false}
// add conn to streams pool
p.Lock()
if sp.count < p.size {
addConnAfter(conn, sp.head)
}
p.Unlock()
return conn, nil
}
func (p *pool) release(addr string, conn *poolConn, err error) {
p.Lock()
p, sp, created := conn.pool, conn.sp, conn.created
// try to add conn
if !conn.in && sp.count < p.size {
addConnAfter(conn, sp.head)
}
if !conn.in {
p.Unlock()
conn.ClientConn.Close()
return
}
// a busy conn
if conn.streams >= p.maxStreams {
removeConn(conn)
addConnAfter(conn, sp.head)
}
conn.streams--
// if streams == 0, we can do something
if conn.streams == 0 {
// 1. it has errored
// 2. too many idle conn or
// 3. conn is too old
now := time.Now().Unix()
if err != nil || sp.idle >= p.maxIdle || now-created > p.ttl {
removeConn(conn)
p.Unlock()
conn.ClientConn.Close()
return
}
sp.idle++
}
p.Unlock()
return
}
func (conn *poolConn) Close() {
conn.pool.release(conn.addr, conn, conn.err)
}
func removeConn(conn *poolConn) {
if conn.pre != nil {
conn.pre.next = conn.next
}
if conn.next != nil {
conn.next.pre = conn.pre
}
conn.pre = nil
conn.next = nil
conn.in = false
conn.sp.count--
return
}
func addConnAfter(conn *poolConn, after *poolConn) {
conn.next = after.next
conn.pre = after
if after.next != nil {
after.next.pre = conn
}
after.next = conn
conn.in = true
conn.sp.count++
return
}