Apache Tomcat 5.5 Servlet/JSP 容器 怎样配制集群/Session复制
源文：http://www.jaxmao.org/tomcat-docs/cluster-howto.htmlApache Tomcat 5.5 Servlet/JSP 容器
怎
样配制集群/Session复制
快速入门
要在Tomcat 5.5容器里进行session复制，必须完成下列步骤：
[*]你的所有会话属性值必须实现java.io.Serializable
[*]把server.xml文件里的群集(Cluster
)元素的注释取消(Uncomment)
[*]把server.xml文件里的Valve(ReplicationValve)
元素注释取消(Uncomment)
[*]如果有多个Tomcat实例在一台机器上运行，确保每个实例的tcpListenPort
属性值是不冲突的。
[*]确定 web.xml
中含有 <distributable/>
元素，
或者设置 <Context distributable="true" />
[*]确定设置好Engine元素的 jvmRoute 的属性值： <Engine name="Catalina"
jvmRoute="node01" >
[*]确定所有节点拥有相同的时间， 并且通过网络时间服务(NTP)同步操作系统的时间！
[*]确定负载均衡器已经配置为黏性会话模式.
负载均衡可以有很多种方式实现，请参考负载均衡
章节。
注意：记住你的会话状态是被一个cookie跟踪的，所以你的URL从外面看必须是相同的，否则一个新的session就会被产生。
注意：集群支持目前需要JDK 1.4或其后版本。
概要
要在Tomcat里实现会话session复制，下面三种方法都可以实现相同效果：
[*]使用session 持久化, 并将 session 保存到一个共享的文件系统(持久管理器 +
文件存储)(PersistenceManager + FileStore)
[*]使用session 持久化, 并将 session 保存到一个共享的 数据库 (持久管理器 + JDBC存储)
(PersistenceManager + JDBCStore)
[*]使用in-memory-replication，使用和Tomcat
5自带的SimpleTcpCluster(server/lib/catalina-cluster.jar)
In this release of session replication, Tomcat performs an all-to-all
replication of session state.
This is an algorithm that is only efficient when the clusters are
small. For large clusters, the next
release will support a primary-secondary session replication where
the session will only be stored at one
or maybe two backup servers.
Currently you can use the domain worker attribute (mod_jk > 1.2.8)
to build cluster partitions
with the potential of very scaleable cluster solution.
In order to keep the network traffic down in an all-to-all
environment, you can split your cluster
into smaller groups. This can be easily achieved by using different
multicast addresses for the different groups.
A very simple setup would look like this:
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DNS 轮询
|
负载均衡器
/ \
集群1集群2
/ \ / \
Tomcat1 Tomcat2 Tomcat3 Tomcat4
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What is important to mention here, is that session replication is
only the beginning of clustering.
Another popular concept used to implement clusters is farming, ie,
you deploy your apps only to one
server, and the cluster will distribute the deployments across the
entire cluster.
This is all capabilities that can go into with the FarmWarDeployer
(s. cluster example at server.xml
)
下一章将深入讨论session复制是怎样实现的，以及怎样配置它。
它
是怎样工作的
为了便于理解集群是怎样工作的,我们将用一系列的场景来描述.
在这个场景中，我们只计划使用两个tomcat 实例 TomcatA
和 TomcatB
.
我们将覆盖下面连续的事件:
[*]
TomcatA
启动
[*]
TomcatB
启动 (等待TomcatA 启动完成)
[*]
TomcatA
接受一个请求，session S1
被产生。
[*]
TomcatA
崩溃停止
[*]
TomcatB
接受一个session S1
的请求
[*]
TomcatA
启动
[*]
TomcatA
接受一个请求，session ( S1
)失效。
[*]
TomcatB
接受一个新的session ( S2
)的请求。
[*]
TomcatA
因为没有活动session S2
过期失效。
好了, 现在我们有了一个很好的顺序,我们将告诉你在session复制代码里发生的所有事情
[*]
TomcatA
启动
Tomcat 标准方式启动. 当 Host 对象被创建之后, 一个 cluster 对象与它关联.
当上下文被解析完, 如果 web.xml中有distributable元素，
Tomcat 通过 Cluster class (in this case SimpleTcpCluster
)
为支持复制的上下文创建一个管理器.
因此通过设置web.xml中的distributable来启用集群。
Tomcat 将为上下文创建 DeltaManager
莱取代 StandardManager
.
cluster class 将启动 a membership service (multicast) 和 a
replication service (tcp unicast).
More on the architecture further down in this document.
[*]
TomcatB
启动 当TomcatB启动时，除了一个例外以外，它按照TomcatA一样的顺
序启动。群集被启用，并将建立一组会员(TomcatA,TomcatB)。TomcatB现在将要request已经存在于群集里的服务器的会话状态，
在这里这个服务器是TomcatA。TomcatA回应TomcatB的请求，并且在TomcatB开始为HTTP
requests监听之前，这个状态已经由TomcatA传递给TomcatB了。在TomcatA不回应的情况下，TomcatB在60秒后中断，并发
出一个日志记录。对于每个已经分布在web.xml里的web应用程序，会话状态会被转移。注意：要有效地使用会话复制，你的所有tomcat实例要配置
成一样的。
[*]
TomcatA
接受一个请求，session S1
被产生。 TomcatA对待传递来的请求与对待没有会话复制一样。当请求完成以后，活动就开始了，ReplicationValve
在
回应被返回到用户那里之前会截断这个请求。在这时，它发现会话被修改过，它就用TCP把这个会话复制给TomcatB。一旦这个分段的数据被递交给操作系
统TCP logic，请求就通过valve pipeline返回给用户。对于每个请求，整个会话都被复制，这允许在不调用setAttribute 或
removeAttribute情况下，在会话中修改属性的代码被复制。配置参数useDirtyFlag可以被用来优化会话复制的次数。
[*]
TomcatA
崩溃停止 当TomcatA崩溃时，TomcatB会收到通知说TomcatA已经退出群集。TomcatB把TomcatA从它的会员列单中删除
掉，TomcatB里有任何更改也不会再通知TomcatA。装载均衡器会把对TomcatA的请求引向TomcatB以及所有当前活动会话。
[*]
TomcatB
接受一个session S1
的请求 TomcatB
像处理其他任何请求一样处理这个请求。
[*]
TomcatA
启动 TomcatA启动时，在它接受新的请求以及让它自己可被使用之前，它要按照上面 1)
2)中所描述的顺序进行启动。它会加入群集，与TomcatB联系，了解所有会话的当前状态。一旦它接受到会话状态，它就完成装载并打开它的
HTTP/mod_jk ports。所以在TomcatA接受到来自TomcatB的会话状态之前，不会对它发出请求。
[*]
TomcatA
接受一个请求，session ( S1
)失效。 失效的呼叫被拦截，这个会话就加入到失效的会话行列。在这个请求完成以后，它向TomcatB发出一个"expire"信息，TomcatB也把这
个会话变为失效。
[*]
TomcatB
接受一个新的session ( S2
)的请求。 与步骤3)情形一样。
[*]
TomcatA
因为没有活动session S2
过期失效。 就如一个会话由用户让
它无效一样，invalidate呼叫被拦截到，这个会话就加入失效的会话行列。这一点上，除非另一个请求通过系统来检查失效行列，会话失效不会在其他地
方重复。
Phuuuhh! :)
Membership
Clustering membership可以通过使用非常简单的multicast
pings被建立。每个Tomcat实例定期会发出multicast ping，在ping message里，这个实例会散布它的IP 及 TCP
监听端口以用于复制。如果一个实例在所给的时间范围内还没有收到这样的ping，这个会员就被认为是不存在了。很简单，也很有效。当然，你需要在你的系统
上让multicasting可被使用。
TCP Replication
，在收到一个multicast
ping以后，会员就被添加到群集里。在下一个复制请求时，发出请求的实例将使用host和port信息来建立一个TCP
socket。通过使用这个socket，它把分段的数据发送过去。我选择TCP sockets
的原因是它具备有流量控制，并确保发送到位。因此，我知道，当我发送数据时，这个数据就会被送到。
Distributed locking and pages using frames
： Tomcat
并没有让会话实例在群集之间保持一致。这个逻辑的实现需要太大空间，也会带来很多问题。如果你的客户使用多个请求同时访问同一个会话，那么最后一个请求会
覆盖群集里的其它会话。
Cluster Architecture
组件层次：
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Server
|
Service
|
Engine
|\
|--- Cluster --*
|
Host
|
------
/ \
Cluster Context(1-N)
| \
| -- Manager
| \
| -- DeltaManager
|
-----------------------------
| | | \
Receiver Sender Membership\
\ -- Valve
-- SocketReplicationListener | \
-- ReplicationListener | -- ReplicationValve
| -- JvmRouteBinderValve
|
-- LifecycleListener
|
-- ClusterListener
| \
| -- ClusterSessionListener
| -- JvmRouteSessionIDBinderListener
|
-- Deployer
\
-- FarmWarDeployer
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Sender
\
-- ReplicationTransmitter
|
---------
\
IDataSender
\
|
--- (sync)
|\
| -- PooledSocketSender (pooled)
| -- SockerSender (synchronous)
|
--- (async)
\
-- AsyncSocketSender (asynchronous)
-- FastAsyncSocketSender (fastasyncqueue)
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Cluster Configuration
群集配置在样品server.xml 文件里有描述。需要指出的是以mcastXXX开头的是关于会员成分multicast
ping的属性，以tcpXXX开头的是关于TCP replication的属性。
会员成分是通过在相同的multicast IP 和 port上的所有tomcat实例建立的。TCP listen
port是从其他会员那里来的会话复制在这它里被接收到的端口。
复制阀被用来发现请求什么时候被完成，并启动复制。
One of the most important performance considerations is the
synchronous (pooled or not pooled) versus asynchronous replication
mode. In a synchronous replication mode the request doesn't return
until the replicated session has been
sent over the wire and reinstantiated on all the other cluster
nodes.
There are two settings for synchronous replication. Pooled or not
pooled.
Not pooled (ie replicationMode="fastasnycqueue" or "synchronous")
means that all the replication request are sent over a single
socket.
Using synchronous mode can potentially becomes a bottleneck when a
lot of messages generated,
You can overcome this bottleneck by setting replicationMode="pooled"
but then you worker threads blocks with replication .
What is recommended here is to increase the number of threads that
handle
incoming replication request. This is the tcpThreadCount property in
the cluster
section of server.xml. The pooled setting means that we are using
multiple sockets, hence increases the performance.
Asynchronous replication, should be used if you have sticky sessions
until fail over, then
your replicated data is not time crucial, but the request time is,
at this time leave the tcpThreadCount to
be number-of-nodes-1.
During async replication, the request is returned before the data
has been replicated. async replication yields shorter
request times, and synchronous replication guarantees the session to
be replicated before the request returns.
The parameter "replicationMode" has four different settings:
"pooled", "synchronous", "asynchronous" and "fastasyncqueue"
Simple Cluster
Configuration
Simple one line configuration
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<Server port="8011"
shutdown="SHUTDOWN" >
<GlobalNamingResources>
<Resource name="UserDatabase" auth="Container"
type="org.apache.catalina.UserDatabase"
description="User database that can be updated and saved"
factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
pathname="conf/tomcat-users.xml" />
</GlobalNamingResources>
<Service name="Catalina">
<Connector port="9012"
protocol="AJP/1.3"
<Connector port="9013"
maxThreads="100"
minSpareThreads="4"
maxSpareThreads="4"
/>
<Engine name="Catalina"
defaultHost="localhost"
jvmRoute="node01">
<Realm className="org.apache.catalina.realm.UserDatabaseRealm"
resourceName="UserDatabase" />
<Host name="localhost"
appBase="webapps">
<Cluster className="org.apache.catalina.cluster.tcp.SimpleTcpCluster"/>
</Host>
</Engine>
</Service>
</Server>
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The default mode configuration setup a fastasyncqueue
mode
cluster configuration with following
parameters:
[*]Open Membership receiver at 228.0.0.4
and send to
multicast udp port 8012
[*]Send membership every 1 sec and drop member after 30sec.
[*]Open message receiver at default ip interface at first free port
between 8015
and 8019
.
[*]Receiver message with SocketReplicationListener
[*]Configure a ReplicationTransmitter
with fastasyncqueue
sender mode.
[*]Add ClusterSessionListener
and ReplicationValve
.
NOTE
: Use this configuration when you need very quick a test
cluster with
at your developer machine. You can change the default attributes from
cluster sub elements.
Use following cluster attribute prefixes sender.
,
receiver.
, service.
, manager.
, valve.
and listener.
.
Example
configure cluster at windows laptop with network
connection and
change receiver port range
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<Cluster className="org.apache.catalina.cluster.tcp.SimpleTcpCluster"
service.mcastBindAddress="127.0.0.1"
receiver.tcpListenPort="9070"
receiver.tcpListenMaxPort="9075" />
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WARNING
: When you add you sub elements, there overwrite the
defaults complete.
Example
configure cluster with cluster failover jsessionid
support. In this
case you need also the defaultmode Cluster listener ClusterSessionListener
and ReplicationValve
.
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<Cluster className="org.apache.catalina.cluster.tcp.SimpleTcpCluster"
service.mcastBindAddress="127.0.0.1"
receiver.tcpListenPort="9070"
receiver.tcpListenMaxPort="9075" >
<ClusterListenerclassName="org.apache.catalina.cluster.session.ClusterSessionListener" />
<ClusterListenerclassName="org.apache.catalina.cluster.session.JvmRouteSessionIDBinderListener" />
<Valve className="org.apache.catalina.cluster.tcp.ReplicationValve"
filter=".*\.gif;.*\.js;.*\.css;.*\.png;.*\.jpeg;.*\.jpg;.*\.htm;.*\.html;.*\.txt;"
primaryIndicator="true" />
<Valve className="org.apache.catalina.cluster.session.JvmRouteBinderValve"
enabled="true"/>
<Cluster/>
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Simple
Engine Cluster Configuration for all hosts
Simple one line engine configuration
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<Server port="8011"
shutdown="SHUTDOWN" >
<GlobalNamingResources>
<Resource name="UserDatabase" auth="Container"
type="org.apache.catalina.UserDatabase"
description="User database that can be updated and saved"
factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
pathname="conf/tomcat-users.xml" />
</GlobalNamingResources>
<Service name="Catalina">
<Connector port="9012"
protocol="AJP/1.3"
<Connector port="9013"
maxThreads="100"
minSpareThreads="4"
maxSpareThreads="4"
/>
<Engine name="Catalina"
defaultHost="localhost"
jvmRoute="node01">
<Realm className="org.apache.catalina.realm.UserDatabaseRealm"
resourceName="UserDatabase" />
<Cluster className="org.apache.catalina.cluster.tcp.SimpleTcpCluster"/>
<Host name="localhost"
appBase="webapps"/>
</Engine>
</Service>
</Server>
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See default mode configuration description as simple host cluster
example before.
Complex Cluster
Configuration
Example
Configure cluster with complete sub elements.
Activate this node
as master farm delopyer. Message receiver is NIO based ReplicationListener
with six parallel
worker threads.
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<Server port="8011"
shutdown="SHUTDOWN" >
<GlobalNamingResources>
<Resource name="UserDatabase" auth="Container"
type="org.apache.catalina.UserDatabase"
description="User database that can be updated and saved"
factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
pathname="conf/tomcat-users.xml" />
</GlobalNamingResources>
<Service name="Catalina">
<Connector port="9012"
protocol="AJP/1.3"
<Connector port="9013"
maxThreads="100"
minSpareThreads="4"
maxSpareThreads="4"
/>
<Engine name="Catalina"
defaultHost="localhost"
jvmRoute="node01">
<Realm className="org.apache.catalina.realm.UserDatabaseRealm"
resourceName="UserDatabase" />
<Host name="localhost"
appBase="webapps">
<Cluster className="org.apache.catalina.cluster.tcp.SimpleTcpCluster"
doClusterLog="true"
clusterLogName="clusterlog"
manager.className="org.apache.catalina.cluster.session.DeltaManager"
manager.expireSessionsOnShutdown="false"
manager.notifyListenersOnReplication="false"
manager.notifySessionListenersOnReplication="false"
manager.sendAllSessions="false"
manager.sendAllSessionsSize="500"
manager.sendAllSessionsWaitTime="20">
<Membership
className="org.apache.catalina.cluster.mcast.McastService"
mcastAddr="228.0.0.4"
mcastBindAddress="127.0.0.1"
mcastClusterDomain="d10"
mcastPort="45564"
mcastFrequency="1000"
mcastDropTime="30000"/>
<Receiver
className="org.apache.catalina.cluster.tcp.ReplicationListener"
tcpListenAddress="auto"
tcpListenPort="9015"
tcpSelectorTimeout="100"
tcpThreadCount="6"
<Sender
className="org.apache.catalina.cluster.tcp.ReplicationTransmitter"
replicationMode="fastasyncqueue"
recoverTimeout="5000"
recoverCounter="6"
doTransmitterProcessingStats="true"
doProcessingStats="true"
doWaitAckStats="true"
queueTimeWait="true"
queueDoStats="true"
queueCheckLock="true"
ackTimeout="15000"
waitForAck="true"
keepAliveTimeout="80000"
keepAliveMaxRequestCount="-1"/>
<Valve className="org.apache.catalina.cluster.tcp.ReplicationValve"
filter=".*\.gif;.*\.js;.*\.css;.*\.png;.*\.jpeg;.*\.jpg;.*\.htm;.*\.html;.*\.txt;"
primaryIndicator="true" />
<Valve className="org.apache.catalina.cluster.session.JvmRouteBinderValve"
enabled="true" />
<ClusterListener className="org.apache.catalina.cluster.session.ClusterSessionListener" />
<ClusterListener className="org.apache.catalina.cluster.session.JvmRouteSessionIDBinderListener" />
<Deployer className="org.apache.catalina.cluster.deploy.FarmWarDeployer"
tempDir="${catalina.base}/war-temp"
deployDir="${catalina.base}/war-deploy/"
watchDir="${catalina.base}/war-listen/"
watchEnabled="true"/>
</Cluster>
</Host>
</Engine>
</Service>
</Server>
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Cluster
Configuration for ReplicationTransmitter
List of Attributes
属性
描述
Default value
replicationMode
replication mode (synchronous
, pooled
, asynchronous
or fastasyncqueue
)
pooled
processSenderFrequency
Control the sender keepalive status and drop sender socket
connection after timeout is reached.
Check every processSenderFrequency value engine background ticks.
2
compress
compress bytes before sending (consume memory, but reduce
network traffic - GZIP)
false
ackTimeout
acknowledge timeout and only usefull it waitForAck is true
15000 msec
waitForAck
Wait for ack after data send
false
autoConnect
is sender disabled, fork a new socket
false
doTransmitterProcessingStats
create processing time stats
false
Example to get statistic information, wait for ack at every message send
and transfer at compressed mode
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<Sender
className="org.apache.catalina.cluster.tcp.ReplicationTransmitter"
replicationMode="fastasyncqueue"
compress="true"
doTransmitterProcessingStats="true"
ackTimeout="15000"
waitForAck="true"
autoConnect="false"/>
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Cluster Configuration for ReplicationTransmitter
(fastayncqueue - mode)
List of Attributes
属性
描述
Default value
keepAliveTimeout
active socket keep alive timeout
60000 msec
keepAliveMaxRequestCount
max request over this socket
-1
doProcessingStats
create Processing time stats
false
doWaitAckStats
create waitAck time stats
false
resend
resend message after failure, can overwrite at message
false
recoverTimeout
recover Timeout after push message failure
5000 msec
recoverCounter
number of recover tries
0
queueDoStats
activated queue stats
false
queueCheckLock
check to lost locks
false
queueAddWaitTimeout
queue add wait time (tomcat connector thread waits)
10000 msec
queueRemoveWaitTimeout
queue remove wait time (queue thread waits)
30000 msec
maxQueueLength
max queue length (default without limit)
-1
threadPriority
change queue thread priority (1-10 ; 5 is normal)
5
Example to get a lot of statistic information, wait for ACK and
recover after connection failure (wait 5 secs and 6 trails (==30 secs
Mcast Timeout)
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<Sender
className="org.apache.catalina.cluster.tcp.ReplicationTransmitter"
replicationMode="fastasyncqueue"
recoverTimeout="5000"
recoverCounter="6"
doTransmitterProcessingStats="true"
doProcessingStats="true"
queueTimeWait="true"
queueDoStats="true"
queueCheckLock="true"
waitForAck="true"
autoConnect="false"
keepAliveTimeout="320000"
keepAliveMaxRequestCount="-1"/>
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Cluster Configuration for ReplicationTransmitter (
asynchronous - mode)
List of Attributes
属性
描述
Default value
keepAliveTimeout
active socket keep alive timeout
60000 msec
keepAliveMaxRequestCount
max request over this socket
-1
doProcessingStats
create Processing time stats
false
doWaitAckStats
create waitAck time stats
false
resend
resend message after failure, can overwrite at message
false
Example to get a processing statistic information, resend after failure
and wait for ACK
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<Sender
className="org.apache.catalina.cluster.tcp.ReplicationTransmitter"
replicationMode="asynchronous"
doProcessingStats="true"
doWaitAckStats="true"
waitForAck="true"
ackTimeout="30000"
resend="true"
keepAliveTimeout="320000"
keepAliveMaxRequestCount="-1"/>
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Cluster Configuration for ReplicationTransmitter (
synchronous - mode)
List of Attributes
属性
描述
Default value
keepAliveTimeout
active socket keep alive timeout
60000 msec
keepAliveMaxRequestCount
max request over this socket
-1
doProcessingStats
create Processing time stats
false
doWaitAckStats
create waitAck time stats
true
resend
resend message after failure, can overwrite at message
false
Example to get a no processing statistic information, no wait for ACK,
after 10000 request renew socket and autoconnect before first request is
send.
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<Sender
className="org.apache.catalina.cluster.tcp.ReplicationTransmitter"
replicationMode="synchronous"
autoConnect="true"
keepAliveTimeout="-1"
keepAliveMaxRequestCount="100000"/>
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Cluster Configuration for ReplicationTransmitter ( pooled
- mode)
List of Attributes
属性
描述
Default value
keepAliveTimeout
active socket keep alive timeout
60000 msec
keepAliveMaxRequestCount
max request over this socket
-1
maxPoolSocketLimit
max pooled sockets (Sender Sockets)
25
resend
resend message after failure, can overwrite at message
false
Example to get a no processing statistic information, wait for ACK,
after 10000 request renew socket, only 10 SockerSender available and
autoconnect before first request is send.
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<Sender
className="org.apache.catalina.cluster.tcp.ReplicationTransmitter"
replicationMode="pooled"
autoConnect="true"
maxPoolSocketLimit="10"
keepAliveTimeout="-1"
keepAliveMaxRequestCount="10000"
waitForAck="true" />
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Cluster Configuration for ReplicationTransmitter (
DeltaManager Attribute)
List of Attributes
属性
描述
Default value
expireSessionsOnShutdown
When server stopped, expire all sessions also at backup nodes
(only for testing)
false
maxActiveSessions
Number of active sessions. (Default is no limit)
-1
notifyListenersOnReplication
Notify application session listener to session creation
and expiring events at backup nodes
true
notifySessionListenersOnReplication
Notify application session listener to attribute changes at
backup nodes
true
stateTransferTimeout
Timeout that session state transfer is complete. Is attribute stateTransferTimeout
== -1
then application wait that other node send the complete session
state
60 sec
sendAllSessions
Flag to send sessions as splited blocks
true
sendAllSessionsSize
Number of serialize sessions inside a send block session
message. Only useful when sendAllSessions==false
1000
sendAllSessionsWaitTime
wait time between two session send blocks.
2000 msec
sendClusterDomainOnly
Send all session messages only to member inside same cluster
domain
(value od Membership attribute mcastClusterDomain). Also don't
handle
session messages from other domains.
true
stateTimestampDrop
DeltaManager queued Sessions messages when send GET_ALL_SESSION
to other node.
with stateTimestampDrop all messages before state transfer message
creation date (find session) are dropped.
Only other GET_ALL_SESSION events are handle with date before state
transfer message.
true
Example send all sessions at separate blocks. Serialize and send 100
session inside one block.
Wait maximale two minutes before the complete backup sessions are loaded
inside tomcat boot process.
Between send blocks wait 5 secs to transfers the session block to other
node. This save memory
when you use the async modes with queues.
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<Cluster className="org.apache.catalina.tcp.SimpleTcpCluster"
managerClassName="org.apache.catalina.cluster.session.DeltaManager"
manager.stateTransferTimeout="120"
manager.sendAllSessions="false"
manager.sendAllSessionsSize="100"
manager.sendAllSessionsWaitTime="5000"
"/>
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注意
As Cluster.defaultMode=true
you can configure the manager
attributes with prefix manager.
.
注意
With Cluster.setProperty(<String>,<String>)
you can
modify
attributes for all register managers. The method exists as MBeans
operation.
Bind session
after crash to failover node
As you configure more then two nodes at same cluster for backup, most
loadbalancer
send don't all your requests after failover to the same node.
The JvmRouteBinderValve handle tomcat jvmRoute takeover using mod_jk
module after node
failure. After a node crashed the next request going to other cluster
node. The JvmRouteBinderValve
now detect the takeover and rewrite the jsessionid
information to the backup cluster node. After the next response all
client
request goes direct to the backup node. The change sessionid send also
to all
other cluster nodes. Well, now the session stickyness work directly to
the
backup node, but traffic don't go back too restarted cluster nodes!
As jsessionid was created by cookie, the change JSESSIONID cookie resend
with next response.
You must add JvmRouteBinderValve and the corresponding cluster message
listener JvmRouteSessionIDBinderListener.
As you add the new listener you must also add the default
ClusterSessionListener that receiver the normal cluster messages.
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<Cluster className="org.apache.catalina.tcp.SimpleTcpCluster" >
...
<Valve className="org.apache.catalina.cluster.session.JvmRouteBinderValve"
enabled="true" sessionIdAttribute="takeoverSessionid"/>
<ClusterListener className="org.apache.catalina.cluster.session.JvmRouteSessionIDBinderListener" />
<ClusterListener className="org.apache.catalina.cluster.session.ClusterSessionListener" />
...
<Cluster>
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Hint:
With attribute sessionIdAttribute
you can change the request
attribute name that included the old session id.
Default attribuite name is org.apache.catalina.cluster.session.JvmRouteOrignalSessionID
.
Trick:
You can enable this mod_jk turnover mode via JMX before you drop a node
to all backup nodes!
Set enable true on all JvmRouteBinderValve backups, disable worker at
mod_jk
and then drop node and restart it! Then enable mod_jk Worker and disable
JvmRouteBinderValves again.
This use case means that only requested session are migrated.
通
过 JMX 监控集群
Monitoring is a very important question when you use a cluster. Some
of the cluster objects are JMX MBeans
Add the following parameter to your startup script with Java 5:
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set CATALINA_OPTS=\
-Dcom.sun.management.jmxremote \
-Dcom.sun.management.jmxremote.port=%my.jmx.port% \
-Dcom.sun.management.jmxremote.ssl=false \
-Dcom.sun.management.jmxremote.authenticate=false
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