Testing the configuration
Dispatcher provides reports that can be used to verify the configuration. You can see whether the back-end servers that make up the cluster are active and sending responses to the advisors. You can also see if the traffic is being balanced using the server monitor on the GUI.
Example 4-1 shows the output of the dscontrol manager report command. The first table lists the back-end servers being load balanced and their status. The second table lists the servers by port, weight, number of active and new connections, and load values.
The last table shows the advisors that were started, the port, and the timeout value attributed to it.
Example 4-1 The dscontrol manager report
#dscontrol manager report
5630-A36, (C) COPYRIGHT International Business Machines Corp., 2001, 2002
All Rights Reserved * Licensed Materials - Property of IBM
--------------------------------------------------------------------
| SERVER | IP ADDRESS | STATUS |
--------------------------------------------------------------------
| web2 | 10.20.10.104 | ACTIVE |
| web1 | 10.20.10.103 | ACTIVE |
--------------------------------------------------------------------
-----------------------------
| MANAGER REPORT LEGEND |
-----------------------------
| ACTV | Active Connections |
| NEWC | New Connections |
| SYS | System Metric |
| NOW | Current Weight |
| NEW | New Weight |
| WT | Weight |
| CONN | Connections |
-----------------------------
-------------------------------------------------------------------
| www.itso.ibm.com | | | | | |
| 10.20.10.100 | WEIGHT | ACTV | NEWC | PORT | SYS |
| PORT: 80 |NOW NEW| 49% | 50% | 1% | 0% |
-------------------------------------------------------------------
| web2 | 9 9 | 0 | 0 | 190 | 0 |
| web1 | 10 10 | 0 | 0 | 10 | 0 |
-------------------------------------------------------------------
---------------------------------------------------
| ADVISOR | CLUSTER:PORT | TIMEOUT |
---------------------------------------------------
| http | 80 | unlimited |
---------------------------------------------------
You can check whether packets are being forwarded to the cluster by issuing the dscontrol executor report command, which produces a report of the packet traffic on the Executor component of Dispatcher, as shown in Example 4-2.
Example 4-2 The dscontrol Executor report
#dscontrol executor report
5630-A36, (C) COPYRIGHT International Business Machines Corp., 2001, 2002
All Rights Reserved * Licensed Materials - Property of IBM
Executor Report:
----------------
Version level ................................. 05.00.00.00 - 20021111-014835
Total packets received since starting ......... 1,202,275
Packets sent to nonforwarding address ......... 0
Packets processed locally on this machine ..... 0
Packets sent to collocated server ............. 0
Packets forwarded to any cluster .............. 1,066,105
Packets not addressed to active cluster/port .. 133,129
KBytes transferred per second ................. 0
Connections per second ........................ 0
Packets discarded - headers too short ......... 0
Packets discarded - no port or servers ........ 0
Packets discarded - network adapter failure ... 0
Packets with forwarding errors................. 0
We can use the server monitor on the GUI to graphically view the load being distributed among the servers:
Figure 4-8 Server Monitor chart
The line chart represents the new connections value for each server on the cluster, in idle state.
To monitor the behavior of the cluster, you can try repeatedly selecting a clustered page using the browser, or you can use an HTTP benchmarking tool to send requests to the cluster. In our lab, we used ApacheBench, a benchmark tool shipped with IBM HTTP Server and Apache UNIX distributions, to issue a burst of requests to the home page of our cluster:
/usr/HTTPServer/bin/ab -n 5000 -c 4 http://www.itso.ibm.com/
This means we sent a burst of 5000 requests with concurrency of four multiple requests. The chart in Figure 4-9 shows the distribution of new requests among the servers.
Figure 4-9 Request distribution to Web servers
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