So this is a bit of a puzzling issue.
Since upgrading MAAS to 2.5.0, i’ve noticed that often machines will take forever to download both the initial kernel/initrd images when PXE booting as well as the root.tmp.img later in boot. This takes so long that the MAAS often times out the operation and marks the machine as failed.
The only fixes i’ve been able to determine for this are to either reboot the machine or… run tcpdump. As soon as I fire up a tcpdump session the image starts transferring at full speed! The fact that running tcpdump fixes the issue makes it rather tricky to work out what’s going on - i’ve not yet been able to mirror the port to another machine and capture MAAS’s traffic that way.
My MAAS machine itself is an ESXi VM running Ubuntu 18.04, it is a single machine running both the region and rack controller. Nothing of relevance seems to pop up in MAAS’s logs, journalctl or dmesg.
Any idea what might be going on here? I can also reproduce the slow speeds by pointing a browser at the download URL from my desktop. (e.g. http://184.108.40.206:5248/images/ubuntu/amd64/generic/bionic/daily/boot-initrd )