You should use server clusters and cluster members to monitor
and manage the workloads of application servers.
Before you begin
You should understand your options for configuring application
servers. To assist you in understanding how to configure and use clusters
for workload management, consider this scenario. Client requests
are distributed among the cluster members on a single machine. A client refers
to any servlet, Java™ application, or other program
or component that connects the end user and the application server
that is being accessed.
In more complex workload
management scenarios, you can distribute cluster members to remote
machines.
In more complex workload management
scenarios, you can distribute cluster members within the same sysplex.
About this task
Perform the following steps if you decide to use clusters
to balance your workload.
Procedure
- Decide which application server you want to cluster.
- Decide whether you want to replicate data. Replication
is a service that transfers data, objects, or events among application
servers.
You can create a replication domain when creating
a cluster.
- Deploy the application onto the application server.
- Create a cluster.
After configuring the application
server and the application components exactly as you want them to
be, create a cluster. The original server instance becomes a cluster
member that is administered through the cluster.
- Create one or more cluster members.
![[AIX Solaris HP-UX Linux Windows]](../images/dist.gif)
Configure a backup cluster.
避免困難: 如果您有在某環境中執行的用戶端:
- 含有 Java 小型用戶端的環境,
- 在多個 Cell 間遞送要求,或
- 在包含舊版產品之節點的單一 Cell 中遞送要求,
它們可能會突然遇到目標叢集之成員相關埠資訊已過期的狀況。
當所有叢集成員都有動態埠,而且在沒有傳送任何要求的期間重新啟動時,最常發生此狀況。在這個狀況下,用戶端程序最終會試圖遞送至節點代理程式,以接收叢集成員的新埠資料,然後利用新的埠資料,遞送回叢集成員。
如果發生導致用戶端無法與節點代理程式通訊,或新的埠資料無法在叢集成員與節點代理程式之間傳播的任何問題,則可能會發生用戶端要求失敗。
在某些情況下,這些失敗是暫時的。在其他情況下,您需要重新啟動一或多個處理程序才能解決失敗。
如果要避開這些情況下可能發生的用戶端遞送問題,您可以對叢集成員配置靜態埠。有了靜態埠,埠資料就不會因為用戶端程序取得叢集成員相關資訊而變更。即使重新啟動叢集成員,或是程序之間有通訊或資料傳送問題,用戶端的埠資料仍然有效。這項補救措施不一定可以解決基礎通訊或資料傳送問題,但可以移除非預期或不穩定用戶端遞送決策的症狀。
gotcha
A
backup cluster handles requests if the primary cluster fails.
- Start the cluster.
When you start the cluster,
all of the application servers that are members of that cluster start.
Workload management automatically begins after the cluster members
start.
- After the cluster is running, you can perform the following
tasks:
- Stop the cluster.
- Upgrade the applications that are installed on the cluster members.
- Detect and handle problems with server clusters and their workloads.
- Change how frequently the workload management state of the client
refreshes.
The default timeout value for the com.ibm.CORBA.RequestTimeout
JVM property is 0, which means wait forever. This
default value is not a good setting to have for failover situations.
Therefore, if your application is experiencing problems with timeouts,
or if you have configured your system for failover situations, use
the -CCD option on the LaunchClient command to set an appropriate
non-zero value for this property.
If the workload management
state of the client refreshes too soon or too late, change the interval
setting of the JVM custom property com.ibm.websphere.wlm.unusable.interval.
![[IBM i]](../images/iseries.gif)
![[AIX Solaris HP-UX Linux Windows]](../images/dist.gif)
What to do next
For stand-alone Java clients,
you must define a bootstrap host. Stand-alone Java clients are clients
that are located on a different machine from the application server
and have no administrative server. Add the following line to the Java
virtual machine (JVM) arguments for the client:
-Dcom.ibm.CORBA.BootstrapHost=machine_name
where
machine_name is the name of the machine on which
the administrative server is running.