Inventor's Paradox

Background Open VSwitch or ovs is the software that openshift used to ensure pods in the openshift cluster could talk to each other using cluster-internal IP addresses. In default settings, hosts outside the cluster are not be able to connect directly to pods; and haproxy (running in  'openshift router' pods) sofware listening on host port is doing the work of distributing http request into each and every application's pods.  In order to follow this blog post you will need root-level OS access on the hosts / openshift nodes, so it is geared towards system administrator of the openshift platform, not the casual application developer. Examining OVS bridge [root@node3 ~]# ovs-vsctl list-br br0 So we know the OVS bridge is named br0. [root@node1 ~]# ovs-ofctl -O OpenFlow13 dump-ports-desc br0 OFPST_PORT_DESC reply (OF1.3) (xid=0x2):  1(vxlan0): addr:62:b2:af:23:90:ea      config:     0      state:      0      speed: 0 Mbps now, 0 Mbps max  2(tun0): addr:b2:23:c3:0f:e4:56      c

Background When deploying openshift/kubernetes cluster in production, usually we used more than 3 machine/hosts, and in my company's deployment we used more than 10 VMs. Monitoring resource usage in multiple VM is nothing new but using kubernetes we have an option to use kubectl / oc adm top nodes to do this. Using kubectl/ oc adm top nodes will show overall CPU and memory usage for each node The old ways (pre-kubernetes) Before using kubernetes/openshift, we used RHEL/CentOS VMs and to get resource usage we use the sar utility. Of course we need to install sar first (sudo  yum install sysstat) , and then sar is quite unique that it store historical data based on the date of the month.   To get cpu usage for current date : sar To get memory usage for current date : sar -r To get memory usage for the date 30 : sar -r -f /var/log/sa/sa30 To get cpu usage for the date 30 : sar -f /var/log/sa/sa30 There are other interesting resource usage such as per core cpu usage (sar -P ALL), block

When running an application in the server, sometimes things doesn't goes the way it supposed to be, and we need to debug the application. For desktop application based on Java or .NET technology, it is just a matter of setting the breakpoint in IDE and then running the application with debug enabled. For web application based on ASP.NET, similar thing could be done by using Visual Studio and running the web application in debug mode using IIS Express. But what about web services that being served by SAP Netweaver AS ? This post shows how. Option 1. Execute - Debugging in SE37 This is the most standard way to debug ABAP remote function module. Just open up transaction SE37, type function module name, and click on the caliper icon  (For those who are not so into STEM stuffs, you could see this wiki page to know about calipers). Then fill in the input parameters before clicking on the Execute - Debugging icon. Now you are inside the ABAP debugger, and