@Danp As soon as I read that, I thought "I think I've been down this road before." Sure enough. I gave it 2G of RAM and it wouldn't build. I gave it 4G of RAM and I watched using systat and that final step went to about 52% of RAM usage. It has completed. I routinely run Xen Orchestra on a 1G VM because it's rarely used and it runs fine that way. But building it clearly takes a lot more RAM. I'll update my internal notes. It might be worth it to update the building from source docs to mention having enough RAM.

Thanks for hitting the nail on the head with that advice!

@olivierlambert You expect a system administrator to read documentation!?

Anyways, that was it. Sorry I didn't look more carefully. I rebuilt using node8 and poof it was running. Thanks guys.

@julien-f Yeah, I have just found the useSudo option in the docs. I swear things change fast enough on xen orchestra that "upgrading" almost doesn't make sense. I rebuild it like every 3-6 months and so much changes that it's almost easier to start over. If I had started over and pretended I didn't know anything, I would have read the documentation and seen the useSudo option. That's not a complaint. Fast development and adding features is awesome.

@nikade Short answer is that the spikes seem to have smoothed out. I'm not really sure what happened. I don't have them at any resolution now. Perhaps some kind of heisenbug.

@olivierlambert Nothing dramatic. Just things "feeling slower than usual." That's qualititative. Just a gut hunch. So that's why I'm asking about ways to test or investigate.

@nikade You misunderstand. I am calling them "spikes", which most people use that word to mean things going dramatically up. Your graph shows spikes going up. Look closely at my graph, including the point I have highlighted. These "spikes" are 0. That is, it's humming along and then suddenly there's a spike down to 0. That's unlikely because the system is plenty active. So your graph shows spikes up, which is normal. Mine is showing occassional drops to 0, which is what I'm asking about.

In my throughput/IO graphs on Xen Orchestra, I'm seeing these spikes of 0 IOPS, 0 throughput, 0 latency, 0 IOWait. What I don't know is whether this is some kind of graphing artifact (i.e., it's not really happening, but the graph makes it look like it's happening), or whether I'm experiencing some kind of underlying hard disk throughput issue.

I'm in the middle of migrating a VM and it's estimating 12 hours to move 100G, which is long. I moved a couple 20G VMs this morning at 15-20 minutes each.

My question is, where could I look in XCP-ng logs to investigate? How could I get a sense of whether I'm really running into problems here? I've looked at these graphs many times over the years, and these spikes are new. This hasn't always looked like this.

Any thoughts?

The underlying storage is a LSI 9266-8i SAS RAID controller with 3 hard disks in a RAID5 array (hardware raid). I don't think I'm experiencing any other major issues, but maybe I am and don't know how to see it?

I'm running XCP-ng 8.2.1 and Xen Orchestra built from sources (well, from ronivay's Docker container) Xen Orchestra, commit e75cc Master, commit 70014.

@olivierlambert I appreciate the explanation. That suggests that there are no updates to 8.0.0? Or 8.1.0? 8.1.0 is 2 years old and EOL. I guess that's what EOL means: no more updates.

Not sure if this is expected behaviour or not. In the past, when I went to the Patches tab on my XCP-ng hosts, I would see patches listed here and I could choose to apply them. Now, I see none.

I have 2 hosts: one is running xcp-ng 8.0.0, the other is running 8.1.0. (They are single-host pools). In both cases, I see the green check mark and "host is up to date". There are no patches listed.

For the 8.0.0 host, I followed the upgrade from CLI instructions. The yum update command finished successfully and now it shows up in Xen Orchestra as running 8.2.1. But I was expecting Xen Orchestra to offer some amount of updating/patching/upgrading.

I haven't made any changes to the 8.1.0 host because I wanted to see if there was something I need to fix.

Do I misunderstand what I should see?

I'm running xo-server 5.89.0 and xo-web 5.94.0 from the sources via a Docker container.

Thanks,
Paco

@olivierlambert The proxy page has a pretty decent diagram for what things look like when there is no proxy. But it doesn't have a diagram for what things look like if there IS a proxy. I'm trying to understand it. Does this diagram capture the two situations?

If you're running 2 sites using a single instance of Xen Orchestra, is this what happens?

NodeJS is not my best language. But it looks _mount.js uses the execa library to wrap around standard child-process stuff.

I did a little bit of code reading and it looks like, ultimately, execa and child-process-promise end up invoking child_process.spawn(), and it seems like spawn() is just an asynchronous wrapper around child_process.exec(). This leads me to believe that the input ultimately ends up on a shell command line.

According to the docs I found:

child_process.exec(): spawns a shell and runs a command within that shell, passing the stdout and stderr to a callback function when complete

Now, both execa and the child-process-promise library do a lot of parsing of arguments. I can't tell to what extent that parsing and marshalling of command line arguments actually defeats injection attacks. I've done a lot of code review in my day, and sometimes I miss the line that does the work of defeating injection attacks because it is terse and effective. I might have looked right at it and misunderstood its importance.

Like I said, NodeJS and all the modules that are getting loaded in here to make this happen is difficult for me to follow. It's not my strong suit. Sorry if I'm wasting your time because I can't follow the code flow. It looks to me like it all boils down to exec(), and exec() by definition invokes the shell. But maybe we're protected by one of the argument marshalling functions in the call chain.

@julien-f Yeah, I have just found the useSudo option in the docs. I swear things change fast enough on xen orchestra that "upgrading" almost doesn't make sense. I rebuild it like every 3-6 months and so much changes that it's almost easier to start over. If I had started over and pretended I didn't know anything, I would have read the documentation and seen the useSudo option. That's not a complaint. Fast development and adding features is awesome.

I want to confirm a couple things about Xen Orchestra and NFS backups.

1. Running Mount from XOA

When I go to Settings -> Remotes and try to add an NFS remote, it looks like Xen Orchestra wants to run mount on the XOA VM to mount it. That implies that the web server is running as root or the web server has the ability to invoke commands as root, because only root can mount filesystems. That seems decidedly suboptimal from a security point of view. If I run xo-web as root and there's an input validation error, then I not only have command injection, but I have commands injected that are running as root.

Imagine someone types ver=3; echo blah | tee -a /etc/shadow; : or similar as their options on the NFS remote. That potentially executes as root and does something nasty (where blah is a correctly formatted /etc/shadow entry).

I could potentially create a rule in my /etc/sudoers file to allow the unprivileged www user to invoke /bin/mount as root with no password, but I'm still not sure how exposed I would be to command injection. The risk is limited to that one command, but it's still sorta there. We'd have to change the mount command that is executed to be sudo mount, instead of mount.

2. Dataflow

If I follow the flow, the hypervisor will transmit the VM's data for backup to my XOA VM, who in turn writes it out to the NFS volume. If my XOA instance is not on the same network or host, that's a bad idea, right? I mean: it would be better for the host to do the NFS mount from the hypervisor and write the data out to the NFS share directly, wouldn't it? Even if my XOA VM is on the same host, the data is transmitted into the VM and back out again. Do I understand this correctly?