kestrel认知
1）Kestrel是twitter开源的一个scala写的简单高效MQ,采用的协议是memcached的文本协议，但是并不完全支持所有memcached协议，也不是完全兼容现有协议。
2）标准的协议它仅支持GET、SET、FLUSH_ALL、STATS，
3）Kestrel是一个队列服务器
使用示例
package com.wujintao.kestrel;
import java.io.IOException;
import java.util.concurrent.TimeoutException;
import org.junit.BeforeClass;
import org.junit.Test;
import net.rubyeye.xmemcached.MemcachedClient;
import net.rubyeye.xmemcached.MemcachedClientBuilder;
import net.rubyeye.xmemcached.XMemcachedClientBuilder;
import net.rubyeye.xmemcached.command.KestrelCommandFactory;
import net.rubyeye.xmemcached.exception.MemcachedException;
import net.rubyeye.xmemcached.utils.AddrUtil;
public class TestCase {
private static MemcachedClient memcachedClient;
private String ketrelQueueName = "abc";
@BeforeClass
public static void init() {
MemcachedClientBuilder builder = new XMemcachedClientBuilder(
AddrUtil.getAddresses("localhost:22133"));
builder.setCommandFactory(new KestrelCommandFactory());
/**
* 设置连接池大小，即客户端个数
* In a high concurrent enviroment,you may want to pool memcached clients.
* But a xmemcached client has to start a reactor thread and some thread pools,
* if you create too many clients,the cost is very large.
* Xmemcached supports connection pool instreadof client pool.
* you can create more connections to one or more memcached servers,
* and these connections share the same reactor and thread pools,
* it will reduce the cost of system.
* 默认的pool size是1。设置这一数值不一定能提高性能，请依据你的项目的测试结果为准。初步的测试表明只有在大并发下才有提升。
* 设置连接池的一个不良后果就是，同一个memcached的连接之间的数据更新并非同步的
* 因此你的应用需要自己保证数据更新的原子性（采用CAS或者数据之间毫无关联）。
*/
builder.setConnectionPoolSize(10);
try {
memcachedClient = builder.build();
} catch (IOException e) {
e.printStackTrace();
}
memcachedClient.setOptimizeGet(false);
memcachedClient.setConnectTimeout(60000);
}
@Test
public void testPutValue() throws TimeoutException, InterruptedException, MemcachedException{
boolean flag = memcachedClient.set(ketrelQueueName, 0, "1:111");
System.out.println(flag);
}
@Test
public void testGetValue() throws TimeoutException, InterruptedException, MemcachedException{
Object str = memcachedClient.get(ketrelQueueName);
System.out.println(str);
}
}
另附kestrel官方介绍如下：
kestrel的项目主页 http://github.com/robey/kestrel
Kestrel的安装配置 http://robey.github.io/kestrel/readme.html
https://github.com/robey/kestrel/blob/master/docs/guide.md
http://dmouse.iteye.com/blog/1746171
kestrel的wiki页 http://wiki.github.com/robey/kestrel
memcache官网 http://www.memcached.org/
xmemcached项目主页 http://code.google.com/p/xmemcached/
--------------------有关kestrel定义，官方如下很多描述
Kestrel
Kestrel is a simple, distributed message queue written on the JVM, based on Blaine Cook's "starling".
Each server handles a set of reliable, ordered message queues, with no cross communication, resulting in a cluster of k-ordered ("loosely ordered") queues. Kestrel is fast, small, and reliable.
Kestrel is:
1)fast
It runs on the JVM so it can take advantage of the hard work people have put into java performance.
2)small
Currently about 2500 lines of scala, because it relies on Netty (a rough equivalent of Danger's ziggurat or Ruby's EventMachine) -- and because Scala is extremely expressive.
3)durable
Queues are stored in memory for speed, but logged into a journal on disk so that servers can be shutdown or moved without losing any data.
4)reliable
A client can ask to "tentatively" fetch an item from a queue, and if that client disconnects from kestrel before confirming ownership of the item, the item is handed to another client. In this way, crashing clients don't cause lost messages.
Kestrel is based on Blaine Cook's "starling" simple, distributed message queue, with added features and bulletproofing, as well as the scalability offered by actors and the JVM.
Each server handles a set of reliable, ordered message queues. When you put a cluster of these servers together, with no cross communication, and pick a server at random whenever you do a set or get, you end up with a reliable, loosely ordered message queue.
In many situations, loose ordering is sufficient. Dropping the requirement on cross communication makes it horizontally scale to infinity and beyond: no multicast, no clustering, no "elections", no coordination at all. No talking! Shhh!
Kestrel is a very simple message queue that runs on the JVM. It supports multiple protocols:
memcache: the memcache protocol, with some extensions
thrift: Apache Thrift-based RPC
text: a simple text-based protocol
Features
memcache protocol
thrift protocol
journaled (durable) queues
fanout queues (one writer, many readers)
item expiration
transactional reads
----------------------------有关kestrel定义，官方如上很多描述
telnet 202.108.1.121 22133
命令：
stats
Server stats
Global stats reported by kestrel are:
执行完stats命令，命令行上最上面的是返回值如下：
uptime - seconds the server has been online kestrel服务已经启动多少秒
time - current time in unix epoch 当前kestrel服务器的时间
version - version string, like "1.2" kestrel的版本号
curr_items - total of items waiting in all queues 所有队列的ITEM条目数的总和
total_itmes - total of items that have ever been added in this server's lifetime 曾经被添加到队列的所有条目的生存时间总和
bytes - total byte size of items waiting in all queues 被写入队列的所有条目的字节数总和
curr_connections - current open connections from clients 当前客户端打开有多少个连接
total_connections - total connections that have been opened in this server's lifetime 在服务器打开的这段时间类总共的连接数
cmd_get - total GET requests get请求的总次数
cmd_set - total SET requests set请求的总次数
cmd_peek - total GET/peek requests peek请求总次数
get_hits - total GET requests that received an item get请求命令次数
get_misses - total GET requests on an empty queue get请求无效的次数,也就是请求在了空的队列上
bytes_read - total bytes read from clients 客户端总共读取字节总数
bytes_written - total bytes written to clients 写往客户端的总字节数
queue_creates - total number of queues created 当前kestrel上已经创建的队列总数
queue_deletes - total number of queues deleted (includes expires) 已经删除的队列总数
queue_expires - total number of queues expires 已经过期的队列总数
------例如：
STAT uptime 26327844
STAT time 1375153623
STAT version 2.1.3
STAT curr_items 7727349
STAT total_items 460922839
STAT bytes 2552974113
STAT curr_connections 146
STAT total_connections 25500291
STAT cmd_get 10776718344
STAT cmd_set 460922839
STAT cmd_peek 0
STAT get_hits 383861308
STAT get_misses 10392857037
STAT bytes_read 1957725152259
STAT bytes_written 1777370590356
------
紧接着上面那几条返回值，是许多类似下面的条目：
For each queue, the following stats are also reported:
items - items waiting in this queue 队列中当前存在的条目数
bytes - total byte size of items waiting in this queue 队列中当前条目的总字节数
total_items - total items that have been added to this queue in this server's lifetime 总共向队列中添加的条目总个数
logsize - byte size of the queue's journal file 当前队列日志的大小
expired_items - total items that have been expired from this queue in this server's lifetime 当前队列失效的条目总数
mem_items - items in this queue that are currently in memory 当前队列中存在于内存中的条目数
mem_bytes - total byte size of items in this queue that are currently in memory (will always be less than or equal to max_memory_size config for the queue)
age - time, in milliseconds, that the last item to be fetched from this queue had been waiting; that is, the time between SET and GET; if the queue is empty, this will always be zero
discarded - number of items discarded because the queue was too full
waiters - number of clients waiting for an item from this queue (using GET/t)
open_transactions - items read with /open but not yet confirmed
transactions - number of transactional get requests (irrespective of whether an item was read or not)
canceled_transactions - number of transactional get requests canceled (for any reason)
total_flushes - total number of times this queue has been flushed
age_msec - age of the last item read from the queue
create_time - the time that the queue was created (in milliseconds since epoch)
-----例如：
STAT queue_hems_ds_news_items 0
STAT queue_hems_ds_news_bytes 0
STAT queue_hems_ds_news_total_items 27231842
STAT queue_hems_ds_news_logsize 15425969
STAT queue_hems_ds_news_expired_items 0
STAT queue_hems_ds_news_mem_items 0
STAT queue_hems_ds_news_mem_bytes 0
STAT queue_hems_ds_news_age 0
STAT queue_hems_ds_news_discarded 0
STAT queue_hems_ds_news_waiters 0
STAT queue_hems_ds_news_open_transactions 0
DUMP_STATS 命令会以队列分组的格式显示出来
===========================
关于三种协议：
Protocols
Kestrel supports three protocols: memcache, thrift and text.
The Finagle project can be used to connect clients to a Kestrel server via the memcache or thrift protocols.
Finagle项目可以通过thrift协议或者memcache协议使客户端连接到kestrel服务器
Thrift
The thrift protocol is documented in the thrift IDL: kestrel.thrift
Reliable reads via the thrift protocol are specified by indicating how long the server should wait before aborting the unacknowledged read.
Memcache
kestrel遵守memcache官方标准协议，如下这个文件有描述：
The official memcache protocol is described here: protocol.txt
https://github.com/memcached/memcached/blob/master/doc/protocol.txt
Text protocol
kestrel支持受限制的，只是文本的协议。不过还是推荐你用memcache协议替代文本协议。因为文本协议不支持可靠的读操作。
Kestrel supports a limited, text-only protocol. You are encouraged to use the memcache protocol instead.
The text protocol does not support reliable reads.
kestrel实现memcache协议的命令如下：
The kestrel implementation of the memcache protocol commands is described below.
SET <queue-name> <flags (ignored)> <expiration> <# bytes>
Add an item to a queue. It may fail if the queue has a size or item limit and it's full.
GET <queue-name>[options]
Remove an item from a queue. It will return an empty response immediately if the queue is empty. The queue name may be followed by options separated by /:
/t=<milliseconds>
Wait up to a given time limit for a new item to arrive. If an item arrives on the queue within this timeout, it's returned as normal. Otherwise, after that timeout, an empty response is returned.
/open
Tentatively remove an item from the queue. The item is returned as usual but is also set aside in case the client disappears before sending a "close" request. (See "Reliable Reads" below.)
/close
Close any existing open read. (See "Reliable Reads" below.)
/abort
Cancel any existing open read, returing that item to the head of the queue. It will be the next item fetched. (See "Reliable Reads" below.)
/peek
Return the first available item from the queue, if there is one, but don't remove it. You can't combine this with any of the reliable read options.
For example, to open a new read, waiting up to 500msec for an item:
GET work/t=500/open
Or to close an existing read and open a new one:
GET work/close/open
DELETE <queue-name> 删除某个队列同时删除所有条目,也会删除有关联的日志文件
Drop a queue, discarding any items in it, and deleting any associated journal files.
FLUSH <queue-name> 删除某个队列中的所有条目
Discard all items remaining in this queue. The queue remains live and new items can be added. The time it takes to flush will be linear to the current queue size, and any other activity on this queue will block while it's being flushed.
FLUSH_ALL 删除所有队列中的所有条目，就好像是每个队列都接受到了FLUSH命令一样
Discard all items remaining in all queues. The queues are flushed one at a time, as if kestrel received a FLUSH command for each queue.
VERSION 查询KESTREL的版本号
Display the kestrel version in a way compatible with memcache.
SHUTDOWN 关闭KESTREL服务器然后退出
Cleanly shutdown the server and exit.
RELOAD 重新加载配置文件
Reload the config file and reconfigure all queues. This should have no noticable effect on the server's responsiveness.
STATS 跟MEMCACHE显示的格式一样显示
Display server stats in memcache style. They're described below.
DUMP_STATS 按照队列名分组来显示
Display server stats in a more readable style, grouped by queue. They're described below.
MONITOR <queue-name> <seconds> [max-items]
Monitor a queue for a time, fetching any new items that arrive, up to an optional maximum number of items. Clients are queued in a fair fashion, per-item, so many clients may monitor a queue at once. After the given timeout, a separate END response will signal the end of the monitor period. Any fetched items are open transactions (see "Reliable Reads" below), and should be closed with CONFIRM.
CONFIRM <queue-name> <count>
Confirm receipt of count items from a queue. Usually this is the response to a MONITOR command, to confirm the items that arrived during the monitor period.
STATUS
Displays the kestrel server's current status (see section on Server Status, below).
STATUS <new-status>
Switches the kestrel server's current status to the given status (see section on Server Status, below).
------------------
另附其他参考：http://www.blogjava.net/killme2008/archive/2009/09/15/295119.html