6.4. Throughput issue troubleshooting methods

Use a packet analyzer, such as ping or tcpdump to analyze traffic between a pod and its node.

For example, run the tcpdump tool on each pod while reproducing the behavior that led to the issue. Review the captures on both sides to compare send and receive timestamps to analyze the latency of traffic to and from a pod. Latency can occur in Red Hat build of MicroShift if a node interface is overloaded with traffic from other pods, storage devices, or the data plane.

$ tcpdump -s 0 -i any -w /tmp/dump.pcap host <podip 1> && host <podip 2> 

The tcpdump command generates a file at /tmp/dump.pcap containing all traffic between these two pods. You can run the analyzer shortly before the issue is reproduced and stop the analyzer shortly after the issue is finished reproducing to minimize the size of the file. You can also run a packet analyzer between the nodes (eliminating the SDN from the equation) with:

$ tcpdump -s 0 -i any -w /tmp/dump.pcap port 4789