Memcached 是一个高性能的分布式内存对象缓存系统，用于动态Web应用以减轻数据库负载。同时也可以用作不同系统之间的数据共享。应用比较广泛。下面介绍一下环境的memcached环境的搭建及简单实用
- 1. 下载 libevent。官网下载 libevent
- 2. 下载 memcached。官网下载 memcached
- 3. 安装libevent，解压压缩包
1: ./configure –prefix=/usr/local/libevent2: make3: make install 4.安装memcached。
1: ./configure-prefix=/usr/local/memcached-with-libevent –with-libevent=/usr/local/libevent2: make3: make install- 5. 运行
1: ./memcached -u root- 不出意外的话，服务器端的安装完毕了。
- 简单的Java客户端Demo。使用的是spymemcached客户端
- 最近上生产环境因为使用memcached差点导致宕机。由于spymemcached在发不通主机是会不断的请求连接。同时代码的写法有问题，每一次请求都新建了一个客户端。所以需要注意的是，SpyMemcachedManager 应该全局使用一个对象。减少开销。
- /*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package memcached;import java.io.IOException;
import java.io.OutputStream;
import java.net.SocketAddress;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import net.spy.memcached.AddrUtil;
import net.spy.memcached.ConnectionObserver;
import net.spy.memcached.MemcachedClient;
import net.spy.memcached.transcoders.Transcoder;/**
*
* @author yingzi.zhu
*/
public class SpyMemcachedManager {private List<String> servers; // 192.168.159.129:11211
private MemcachedClient memClient;
public static int DEFAULT_TIMEOUT = 5;
public static TimeUnit DEFAULT_TIMEUNIT = TimeUnit.SECONDS;
public SpyMemcachedManager(List<String> servers) {
this.servers = servers;
}
public void connect() throws IOException {
if (memClient != null) {
return;
}
StringBuffer buf = new StringBuffer();
for (int i = 0; i < servers.size(); i++) {
String server = servers.get(i);
buf.append(server).append(” “);
}
memClient = new MemcachedClient(AddrUtil.getAddresses(buf.toString()));
}
public void disConnect() {
if (memClient == null) {
return;
}
memClient.shutdown();
}
public void addObserver(ConnectionObserver obs) {
memClient.addObserver(obs);
}
public void removeObserver(ConnectionObserver obs) {
memClient.removeObserver(obs);
}
public boolean set(String key, Object value, int expire) {
Future<Boolean> f = memClient.set(key, expire, value);
return getBooleanValue(f);
}
public Object get(String key) {
return memClient.get(key);
}
public Object asyncGet(String key) {
Object obj = null;
Future<Object> f = memClient.asyncGet(key);
try {
obj = f.get(SpyMemcachedManager.DEFAULT_TIMEOUT,
SpyMemcachedManager.DEFAULT_TIMEUNIT);
} catch (Exception e) {
f.cancel(false);
}
return obj;
}
public boolean add(String key, Object value, int expire) {
Future<Boolean> f = memClient.add(key, expire, value);
return getBooleanValue(f);
}
public boolean replace(String key, Object value, int expire) {
Future<Boolean> f = memClient.replace(key, expire, value);
return getBooleanValue(f);
}
public boolean delete(String key) {
Future<Boolean> f = memClient.delete(key);
return getBooleanValue(f);
}
public boolean flush() {
Future<Boolean> f = memClient.flush();
return getBooleanValue(f);
}
public Map<String, Object> getMulti(Collection<String> keys) {
return memClient.getBulk(keys);
}
public Map<String, Object> getMulti(String[] keys) {
return memClient.getBulk(keys);
}
public Map<String, Object> asyncGetMulti(Collection<String> keys) {
Map map = null;
Future<Map<String, Object>> f = memClient.asyncGetBulk(keys);
try {
map = f.get(SpyMemcachedManager.DEFAULT_TIMEOUT,
SpyMemcachedManager.DEFAULT_TIMEUNIT);
} catch (Exception e) {
f.cancel(false);
}
return map;
}
public Map<String, Object> asyncGetMulti(String keys[]) {
Map map = null;
Future<Map<String, Object>> f = memClient.asyncGetBulk(keys);
try {
map = f.get(SpyMemcachedManager.DEFAULT_TIMEOUT,
SpyMemcachedManager.DEFAULT_TIMEUNIT);
} catch (Exception e) {
f.cancel(false);
}
return map;
}public long increment(String key, int by, long defaultValue, int expire) {
return memClient.incr(key, by, defaultValue, expire);
}
public long increment(String key, int by) {
return memClient.incr(key, by);
}
public long decrement(String key, int by, long defaultValue, int expire) {
return memClient.decr(key, by, defaultValue, expire);
}
public long decrement(String key, int by) {
return memClient.decr(key, by);
}
public long asyncIncrement(String key, int by) {
Future<Long> f = memClient.asyncIncr(key, by);
return getLongValue(f);
}
public long asyncDecrement(String key, int by) {
Future<Long> f = memClient.asyncDecr(key, by);
return getLongValue(f);
}
public void printStats() throws IOException {
printStats(null);
}
public void printStats(OutputStream stream) throws IOException {
Map<SocketAddress, Map<String, String>> statMap =
memClient.getStats();
if (stream == null) {
stream = System.out;
}
StringBuffer buf = new StringBuffer();
Set<SocketAddress> addrSet = statMap.keySet();
Iterator<SocketAddress> iter = addrSet.iterator();
while (iter.hasNext()) {
SocketAddress addr = iter.next();
buf.append(addr.toString() + “/n”);
Map<String, String> stat = statMap.get(addr);
Set<String> keys = stat.keySet();
Iterator<String> keyIter = keys.iterator();
while (keyIter.hasNext()) {
String key = keyIter.next();
String value = stat.get(key);
buf.append(” key=” + key + “;value=” + value + “/n”);
}
buf.append(“/n”);
}
stream.write(buf.toString().getBytes());
stream.flush();
}
public Transcoder getTranscoder() {
return memClient.getTranscoder();
}
private long getLongValue(Future<Long> f) {
try {
Long l = f.get(SpyMemcachedManager.DEFAULT_TIMEOUT,
SpyMemcachedManager.DEFAULT_TIMEUNIT);
return l.longValue();
} catch (Exception e) {
f.cancel(false);
}
return -1;
}
private boolean getBooleanValue(Future<Boolean> f) {
try {
Boolean bool = f.get(SpyMemcachedManager.DEFAULT_TIMEOUT,
SpyMemcachedManager.DEFAULT_TIMEUNIT);
return bool.booleanValue();
} catch (Exception e) {
f.cancel(false);
return false;
}
}
}
