JniPing vs. JnaPing

As described in the previous article we have build an OpenNMS Horizon Core component from source. If you don’t do anything else, it will uses an ICMP implementation using Java Native Access (JNA). The big benefit here, it’s all Java and supports IPv4 and IPv6. You also don’t need additional permissions on your Linux system such as net.ipv4.ping_group_range and SELinux. It makes it perfect for local development and also if you want to run OpenNMS on exotic architectures where you can’t easily compile or build the JNI equivalent written in C from the source code. The downside it comes with some overhead for each ICMP service test. You can see the effect on the latency measurements, especially on very fast responding IP addresses, such as the local loopack interface.

OpenNMS - Auf die harte Tour

I asked many questions in 2004 on IRC when I tried to get my first OpenNMS instance up and running. People in the community held my hand when I was struggling. They helped me to get to my personal “Aha!” moments. If you have time and patience, this is great, because this is a great learning opportunity. In the world of User Experience Design, this is called “friction”. How can you determine friction? My background is that of someone who cut his hands on sharp metal changing network equipment and operating IT gear for others – I have empathy for people running OpenNMS. I like to run user empathy sessions with someone in your target group and figure out where and how they struggle. If you have no one, the next best option is to put yourself in the shoes and get your hands dirty.

Kickstart your homelab with netboot.xyz

I use a home lab for daily work and for testing purposes, I need to hop between Linux distros often. I’ve replaced my homegrown PXE boot environment with netboot.xyz. I built it for a few operating systems and all was good. I ran into netboot.xyz, and it was quickly pretty clear, this is what you want in a homelab when you have to hop between operating systems using virtual machines. Reducing the need for building bootable thumb drives or shuffling ISOs around is great. It has batteries included with boot menu configs, and it works out of the box. It allows also a lot of customization if needed. As a reminder to my future self and for others here is my config to get it working quickly.

UDP tuning and performance testing

Problem statement

• Ingesting UDP traffic is complicated to measure
• Packet drops, connectionless and unreliable
• Measuring on ingest on the network interface card
• How can you make sure you measure reasonably?
• You want a method to create some confidence how many UDP packets your system drops

Create a lab environment to reproduce the problem

• Make the problem visible using with overloading a small device Raspberry Pi 3
• Use sysctl default settings
• Use something like hping3 or iperf to create a overload situation

You can’t improve what you don’t measure

• Show tools like dropwatch or ss -lump or SNMP udp metrics to visualize packet drops
• Compare packets received with tcpdump vs. iperf
• Theory should show who be tcpdump should have more but not all then the sender

Increase buffers size?

• What happens if you increase the buffer size?

Use PF_RING

• How does the behavior change when you use PF_RING with TCPDUMP

Conclusion

Stop using PowerPoint as a working document

I’m spending more time working with people with management titles, and I find a few things disturbing. I have attended working sessions where the collaborative document was a PowerPoint slide deck. That was super confusing to me because a slide deck is something I have used when I had to attend a conference to give a talk about a specific topic. A PowerPoint slide deck as a work deliverable blew my mind.

Mirroring a container registry

I was working on an article How to run an air gap installation of OpenNMS Horizon on Rocky Linux. I ran into a similar use case and it was not about RPMs or DEB packages, it was all about container images and registries. My question was, how can I get “all” container images into a private registry from DockerHub? Getting your hands dirty with a private registry is something I’ve described in Running a private container registry for testing. Here is a short how-to on how I did it for my future self or anyone else with a similar question.

Make your network traffic visible using flows

Getting metrics about the utilization of network interfaces isn’t very complicated these days. Most of the time your network gear is instrumented with an SNMP agent which you can use to measure it or if you get modern, they have telemetry streaming, and they send you measurements with protocols like gNMI. I’m not explaining fancy new tech here, everything mentioned here is old, but your devices might have these capabilities but aren’t exploited :)