Deployment
https://github.com/memcached/memcached
See the file BUILD to learn how to build.
The default configuration file /etc/memcached.conf is used by scripts/start-memcached when using this script to start service.
Protocol
Protocol is described in doc/protocol.txt.
server:
$ memcached -vv -m 3 -M
<17 server listening (auto-negotiate)
<18 server listening (auto-negotiate)
<19 new auto-negotiating client connection
19: Client using the ascii protocol
<19 get foo
>19 END
<19 set foo 0 0 3
>19 STORED
<19 get foo
>19 sending key foo
>19 END
client:
$ nc -c localhost 11211
get foo
END
set foo 0 0 3
bar
STORED
get foo
VALUE foo 0 3
bar
END
Evication
server:
$ memcached -vv -m 3 -M
<19 new auto-negotiating client connection
19: Client using the ascii protocol
<19 set 0 0 0 10240
>19 STORED
<19 set 1 0 0 10240
>19 STORED
<19 set 2 0 0 10240
>19 STORED
<19 set 3 0 0 10240
>19 STORED
<19 set 4 0 0 10240
>19 STORED
<19 set 5 0 0 10240
>19 STORED
<19 set 6 0 0 10240
>19 STORED
......
<19 set 280 0 0 10240
>19 STORED
<19 set 281 0 0 10240
>19 STORED
<19 set 282 0 0 10240
>19 SERVER_ERROR out of memory storing object
<19 connection closed.
client:
# coding: utf-8
from pymemcache.client import base
def main():
client = base.Client((‘localhost‘, 11211), default_noreply=False)
sz = 0
pos = 0
while True:
key = str(pos)
value = ‘x‘ * 10240
try:
res = client.set(key, value)
if res:
sz += len(key) + len(value)
pos += 1
else:
break
except Exception as e:
print(‘exception: %s, sz: %s‘ % (e, sz))
break
if __name__ == "__main__":
main()
$ python3 main.py
exception: b‘out of memory storing object‘, sz: 2888416
package main
import (
"bytes"
"os"
"github.com/bradfitz/gomemcache/memcache"
logger "github.com/sirupsen/logrus"
"github.com/x-cray/logrus-prefixed-formatter"
)
func init() {
logger.SetFormatter(&prefixed.TextFormatter{
TimestampFormat: "2006-01-02 15:04:05",
FullTimestamp: true,
ForceFormatting: true,
DisableColors: true,
})
logger.SetOutput(os.Stdout)
logger.SetLevel(logger.DebugLevel)
}
func main() {
mc := memcache.New("localhost:11211")
buf := bytes.NewBuffer(nil)
for i := 0; i < 10240; i++ {
buf.WriteRune(‘x‘)
}
if err := mc.Set(&memcache.Item{
Key: "foo",
Value: buf.Bytes(),
}); err != nil {
logger.Errorf("set error: %v", err)
}
if it, err := mc.Get("32"); err != nil {
logger.Errorf("get error: %v, is miss: %v", err, err == memcache.ErrCacheMiss)
} else {
logger.Infof("key: %v, value: %v", it.Key, string(it.Value))
}
if it, err := mc.Get("non"); err != nil {
logger.Errorf("get error: %v, is miss: %v", err, err == memcache.ErrCacheMiss)
} else {
logger.Infof("key: %v, value: %v", it.Key, string(it.Value))
}
}
[2020-05-19 18:21:20] ERROR set error: memcache: unexpected response line from "set": "SERVER_ERROR out of memory storing object\r\n"
[2020-05-19 18:21:20] INFO key: 32, value: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
[2020-05-19 18:21:20] ERROR get error: memcache: cache miss, is miss: true