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/*
** Zabbix
** Copyright (C) 2001-2022 Zabbix SIA
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
**/
package memcached
import (
"context"
"sync"
"time"
"zabbix.com/pkg/uri"
"zabbix.com/pkg/zbxerr"
"github.com/memcachier/mc/v3"
"zabbix.com/pkg/log"
)
const poolSize = 1
type MCClient interface {
Stats(key string) (mc.McStats, error)
NoOp() error
}
type MCConn struct {
client mc.Client
lastTimeAccess time.Time
}
// stubConn for testing
type stubConn struct {
NoOpFunc func() error
StatsFunc func(key string) (mc.McStats, error)
}
func (c *stubConn) Stats(key string) (mc.McStats, error) {
return c.StatsFunc(key)
}
func (c *stubConn) NoOp() error {
return c.NoOpFunc()
}
// Stats wraps the mc.Client.StatsWithKey function.
func (conn *MCConn) Stats(key string) (stats mc.McStats, err error) {
res, err := conn.client.StatsWithKey(key)
if err != nil {
return nil, err
}
if len(res) == 0 {
return nil, zbxerr.ErrorEmptyResult
}
if len(res) > 1 {
panic("unexpected result")
}
// get the only entry of stats
for _, stats = range res {
break
}
return stats, err
}
// NoOp wraps the mc.Client.NoOp function.
func (conn *MCConn) NoOp() error {
return conn.client.NoOp()
}
// updateAccessTime updates the last time a connection was accessed.
func (conn *MCConn) updateAccessTime() {
conn.lastTimeAccess = time.Now()
}
// ConnManager is thread-safe structure for manage connections.
type ConnManager struct {
sync.Mutex
connMutex sync.Mutex
connections map[uri.URI]*MCConn
keepAlive time.Duration
timeout time.Duration
Destroy context.CancelFunc
}
// NewConnManager initializes connManager structure and runs Go Routine that watches for unused connections.
func NewConnManager(keepAlive, timeout, hkInterval time.Duration) *ConnManager {
ctx, cancel := context.WithCancel(context.Background())
connMgr := &ConnManager{
connections: make(map[uri.URI]*MCConn),
keepAlive: keepAlive,
timeout: timeout,
Destroy: cancel, // Destroy stops originated goroutines and close connections.
}
go connMgr.housekeeper(ctx, hkInterval)
return connMgr
}
// closeUnused closes each connection that has not been accessed at least within the keepalive interval.
func (c *ConnManager) closeUnused() {
c.connMutex.Lock()
defer c.connMutex.Unlock()
for uri, conn := range c.connections {
if time.Since(conn.lastTimeAccess) > c.keepAlive {
conn.client.Quit()
delete(c.connections, uri)
log.Debugf("[%s] Closed unused connection: %s", pluginName, uri.Addr())
}
}
}
// closeAll closes all existed connections.
func (c *ConnManager) closeAll() {
c.connMutex.Lock()
for uri, conn := range c.connections {
conn.client.Quit()
delete(c.connections, uri)
}
c.connMutex.Unlock()
}
// housekeeper repeatedly checks for unused connections and close them.
func (c *ConnManager) housekeeper(ctx context.Context, interval time.Duration) {
ticker := time.NewTicker(interval)
for {
select {
case <-ctx.Done():
ticker.Stop()
c.closeAll()
return
case <-ticker.C:
c.closeUnused()
}
}
}
// create creates a new connection with given credentials.
func (c *ConnManager) create(uri uri.URI) *MCConn {
c.connMutex.Lock()
defer c.connMutex.Unlock()
if _, ok := c.connections[uri]; ok {
// Should never happen.
panic("connection already exists")
}
client := mc.NewMCwithConfig(
uri.String(),
uri.User(),
uri.Password(),
&mc.Config{
Hasher: mc.NewModuloHasher(),
Retries: 2,
RetryDelay: 200 * time.Millisecond,
Failover: true,
ConnectionTimeout: c.timeout,
DownRetryDelay: 60 * time.Second,
PoolSize: poolSize,
TcpKeepAlive: true,
TcpKeepAlivePeriod: c.keepAlive,
TcpNoDelay: true,
},
)
c.connections[uri] = &MCConn{
client: *client,
lastTimeAccess: time.Now(),
}
log.Debugf("[%s] Created new connection: %s", pluginName, uri.Addr())
return c.connections[uri]
}
// get returns a connection with given uri if it exists and also updates lastTimeAccess, otherwise returns nil.
func (c *ConnManager) get(uri uri.URI) *MCConn {
c.connMutex.Lock()
defer c.connMutex.Unlock()
if conn, ok := c.connections[uri]; ok {
conn.updateAccessTime()
return conn
}
return nil
}
// GetConnection returns an existing connection or creates a new one.
func (c *ConnManager) GetConnection(uri uri.URI) (conn *MCConn) {
c.Lock()
defer c.Unlock()
conn = c.get(uri)
if conn == nil {
conn = c.create(uri)
}
return
}
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