Last time I ended my work getting etcd-compute running at the point where I needed to configure the virtual networking. I’ve been busy the past few days with meetings and other work-related stuff, so it’s taken me a while to continue on this experiment. But I have some time now; let’s jump back in!
The reason I thought that I needed to set up virtual networking was that when I ran ip a on my controller node, all I had was the loopback and main ethernet interfaces. The directions for etcd-compute talked about setting up the metadata server by adding the IP address it uses to a virtual bridge: sudo ip addr add 169.254.169.254 dev virbr0. As I didn’t have such a bridge on my VM, I figured I had to add it. I tried sever guides on adding a bridge to an Ubuntu server, but each one ended up messing up the networking, making the VM unreachable. I ended up re-creating my etcd1 so many times that I gave up and figured I try without the metadata server. I started the placement and etcd servers by running docker.sh, and then just on a lark I re-ran ip a. This time it showed:
ed@etcd1:~$ ip a
1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens3: mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether fa:16:3e:90:6d:d0 brd ff:ff:ff:ff:ff:ff
inet 9.114.111.201/24 brd 9.114.111.255 scope global ens3
valid_lft forever preferred_lft forever
inet6 fe80::f816:3eff:fe90:6dd0/64 scope link
valid_lft forever preferred_lft forever
3: virbr0: mtu 1500 qdisc noqueue state DOWN group default qlen 1000
link/ether 52:54:00:35:c1:0d brd ff:ff:ff:ff:ff:ff
inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
valid_lft forever preferred_lft forever
4: virbr0-nic: mtu 1500 qdisc fq_codel master virbr0 state DOWN group default qlen 1000
link/ether 52:54:00:35:c1:0d brd ff:ff:ff:ff:ff:ff
I’m not sure how those entries for ‘virbr0’ and ‘virbr0-nic’ got added (maybe docker added them?), but I wasn’t going to worry about that! So I ran the following commands, and they worked without a problem:
sudo ip addr add 169.254.169.254 dev virbr sudo python md_server/mdserver/server.py mdserver.conf &
So now that the metadata server is running, time to try running ecompute on all the nodes. I use iTerm2, which has some sweet tools for splitting the terminal screen and running the same command in the different panes. I recorded a script of what happened:
I ran the command ecompute & on all the nodes to start the compute service in the background.
It’s interesting to see that because I had run this a few times earlier, etcd-compute recognized the UUID of the node, and noted that there was already an entry for that resource provider, with a generation of 7. If I were to stop that ecompute service and then re-start it, I would see the same as above, except this time the generation would be 8. That’s because when the service is killed, it changes the ‘reserved’ amount of its VCPU inventrory to the total amount, effectively preventing that node from being provisioned. That change increments the resource provider’s generation.
At about the 30-second mark, I tried to create a VM by running the command eschedule 'resources=VCPU:1,DISK_GB:1,MEMORY_MB:256' on the etcd3 node. That worked, and almost immediately you can see that it was scheduled to the etcd1 node, and the build process starts. However, there were many errors output, with the main one being error: failed to get domain ‘ff77fe58-e96a-498b-a3f5-a59030987238’. This is repeated several times, along with a bunch of network errors. So at this point I stopped the experiment.
There’s a lot I learned by going through all this, and I see many places where the etcd-compute project could be improved, starting with the documentation. I’d also like to get some less ethereal debugging output, so that when there are problems like I had spinning up a VM, they are recorded for later analysis. I’d also like to learn a lot more about the details of the networking required so that I can make sense of some of the networking errors.
The author of etcd-compute, Chris Dent, and I are hoping to have a mini-sprint on this project next week at the Open Infrastructure Summit in Denver, Colorado. If you will be there and want to join in the fun, drop me an email and I’ll let you know when we settle on a time and place.
I’ve been interested in the etcd-compute project by Chris Dent. It’s sort of a lightweight virtual machine manager like OpenStack Nova, but without the complexity and cruft Nova has accumulated over the past 9 years. It takes advantage of technologies that simply didn’t exist in 2010 when Nova was created, using etcd‘s built-in notifications instead of passing large, complex objects over a message bus to make Remote Procedure Calls (RPC).
Keep in mind that Nova does a lot of things that etcd-compute can’t, so this isn’t a potential 1:1 replacement for Nova. But it does have potential as a much lighter replacement for those applications where the full power of Nova isn’t needed.
This post is designed to be obsolete within a week or so. What I’m aiming for is to record what worked for me following Chris’s instructions. Where I run into problems shows one of three things: our systems start out differently, or Chris assumed something that wasn’t in the README.md file, or my brain is not firing on all cylinders. It is my hope that this may help improve the installation instructions, and guide others who may wish to explore etcd-compute.
I don’t have a lot of hardware—ok, any hardware—at my disposal to experiment with, so I started by creating 3 Ubuntu 18.04 VMs in the internal OpenStack cloud for my team here at IBM. Yes, you can run virtualization on top of virtualization, and it’s turtles all the way down. But it does work! I named the instances etcd1, etcd2, and etcd3, with etcd1 being the controller and the others used as standard compute nodes.
There are some requirements—docker.io, virtinst, libvirt-daemon, libvirt-clients, and libguestfs-tools—that need to be installed on all the nodes, so I updated the distro packages and installed the requirements. Unfortunately, libvirtd wouldn’t start, and well, that’s kind of an important piece. So I cleaned house and tried again:
It’s also a pain to always have to use sudo to run docker commands, so add your user to the docker group. The command for this is sudo usermod -a -G docker ed, which adds user ‘ed’ to the group ‘docker’. You have to log out and log back in for it to take effect, but once you do, you can run commands like docker ps -a without sudo.
Also, in my experience I’ve run into various odd problems using the distro version of Python, so I prefer to install from source to get the latest Python (3.7.3 right now).
Being a creature of habit, I like having the project code I’m working with to be under a ~/projects directory. So for each of these instances, I ran the following:
As the etcd-compute code has its own dependencies, those need to be installed by running sudo python setup.py develop. When I ran that the first time, I got an error when it was trying to install libvirt-python. I tried installing some other libvirt-related libraries and binaries, but I kept getting the same error. After a while I was trying anything I could think of, even running under Python 2! (didn’t work). Maybe it was something about Python 3.7 that was problematic, so I created a venv for Python 3.6, and ran pip install libvirt-python. It installed without a problem. Hmmm. So I fired up a Python 3.7 venv, and it also installed into that. It seems that the installation using setup.py was doing something different than a straight pip install. To test that, I got rid of the venvs, and ran sudo pip install libvirt-python, and it worked just fine. I was then able to install the rest of the dependencies by running sudo python setup.py develop.
Now that the dependencies are installed, we need to create the database for placement, and then modify the dockerenv file so that the OS_PLACEMENT_DATABASE__CONNECTION setting points to that. My database is on a MariaDB server, so I needed to change the value to:
mysql+pymysql://user:secret@my_host/placement
That means, of course, that I need to install pymysql using sudo pip install pymysql before I can make a connection. Once that’s done, I started the docker containers by running ./docker.sh from the primary VM. In my case, that’s etcd1.
That brings up another edit that’s needed on all your “machines”: changing the location of the host in compute.yaml and schedule.yaml. These assume that the host is named ‘ds1’, which isn’t true in this case. I changed ‘ds1’ to ‘etcd1’, and then added an entry in each node’s /etc/hosts file with the IP address of the etcd1 VM.
We also want to create a value for the uuid in compute.yaml. One simple way is to run python -c "import uuid; print(uuid.uuid4())", and copy the output to paste into compute.yaml. Do that on every compute node you are running.
That’s enough for one day. Tomorrow we start with configuring networking!
While many of the VMs I create are meant to be short-lived, some are created as working environments for me. For me, it is infinitely easier to have them all have the username ‘ed‘ so that my brain doesn’t have to do too much context-switching, and so I can use muscle memory.
When creating a new VM with an Ubuntu image, though, the default user is ‘ubuntu‘. It’s rather simple to change that to ‘ed’, but to do it correctly requires a series of steps. Note that these steps are for the current 18.04 LTS release; other releases may need some small changes, but the general steps should be the same. And as I found out those steps by searching the web and finding blogs of people who had done similar things, I thought I’d write down the steps so that in the future others can find this posting and find it useful. And it’ll also be easier for me to find all of it in one place!
So start by creating a VM, using whatever tool you prefer. I use OpenStack (surprise!), which gives me the ability to upload my public key and have it available in the VM so that passwords aren’t needed. The one I’m working on today is for deploying my IRCbot using kubernetes, so I named the instance ‘kubeirc‘. I add a line to my /etc/hosts file to point that name to the IP address of the instance. Once the VM is running I can connect using:
ssh ubuntu@kubeirc
Some people feel that using a password-less sudo reduces security, but if someone has access to your user in your VM, you are probably already pretty hosed. So I change sudo to not require passwords. To do this, run sudo visudo, and change the line beginning with ‘%sudo’ to read:
%sudo ALL=NOPASSWD: ALL
One of the problems to overcome is that you cannot rename the user you used to SSH into the instance. So I create another user, and give them sudo powers:
sudo adduser temp sudo usermod -a -G sudo temp
My cloud doesn’t allow SSH with passwords, so the next thing to do is copy the public key from the ubuntu user to the temp user:
Once that’s done, I disconnect the SSH session, and the re-connect as the temp user:
ssh temp@kubeirc
If that doesn’t connect you, go back in as the ubuntu user and re-check the permissions on the /home/temp/.ssh directory and its contents – that’s usually the problem. Once I’m connected as temp, I can then get to work on switching the ubuntu user.
# Change the ubuntu username to 'ed', and change the home directory sudo usermod -l ed -d /home/ed -m ubuntu # Rename the 'ubuntu' group sudo groupmod -n ed ubuntu
That’s it! Now to verify, disconnect the current SSH session, and re-connect with the new name. Since my username on my home system is ‘ed’ (I told you I like muscle memory), I can just run:
ssh kubeirc
…and I’m in! The only thing left is to remove the ‘temp’ user. It’s not critical that you do so, but I like to clean up after myself. To do that, run the following:
sudo deluser temp
That will delete the user and group named ‘temp’, as well as the ‘/home/temp’ directory.
Now I can continue using that VM with the same username as my other development environments. And while this isn’t a large amount of work to do each time, I’d rather not do such repetitive work if I don’t have to. So I add my standard stuff, such as git and vim configuration files, and then take a snapshot of the instance at this point. In the future, whenever I need an Ubuntu 18.04 instance, I can create it from this snapshot, and I’m ready to go.
This is a quick demonstration of how to create a virtual environment in Python3. I’m starting with an empty directory in ~/projects/demo. I then run the command to create a virtual environment:
ed@imac:~/projects/demo$ ll ed@imac:~/projects/demo$ python3 -m venv my_env ed@imac:~/projects/demo$ ll total 0 drwxr-xr-x 6 ed staff 192B Jan 24 18:14 my_env
Note that the command created a directory with the name I gave it: ‘my_env’. Next we have to activate it. ‘Activate’ changes Python’s internal references to look for things such as which Python version to run, and where installed modules are placed.
I have a bash script that changes the prompt to show the current Python environment; notice that after activating the prompt now starts with ‘(myenv)’.
Installed modules are located in the ‘site-packages’ subdirectory that’s a few levels deep. Let’s see what’s in this fresh virtual env’s site-packages:
(my_env)ed@imac:~/projects/demo$ ll my_env/lib/python3.6/site-packages/ total 8 drwxr-xr-x 3 ed staff 96B Jan 24 18:14 pycache -rw-r--r-- 1 ed staff 126B Jan 24 18:14 easy_install.py drwxr-xr-x 23 ed staff 736B Jan 24 18:14 pip drwxr-xr-x 10 ed staff 320B Jan 24 18:14 pip-9.0.1.dist-info drwxr-xr-x 6 ed staff 192B Jan 24 18:14 pkg_resources drwxr-xr-x 34 ed staff 1.1K Jan 24 18:14 setuptools drwxr-xr-x 12 ed staff 384B Jan 24 18:14 setuptools-28.8.0.dist-info
One of my favorite development tools for Python is the pudb debugger. To show that we can install a package, let’s try importing it first (and failing):
(my_env)ed@family-imac:~/projects/demo$ python Python 3.6.4 (v3.6.4:d48ecebad5, Dec 18 2017, 21:07:28) [GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import pudb Traceback (most recent call last): File "", line 1, in ModuleNotFoundError: No module named 'pudb' >>> ^D (my_env)ed@family-imac:~/projects/demo$
Let’s look at the site-packages directory after installing pudb:
(my_env)ed@family-imac:~/projects/demo$ ll my_env/lib/python3.6/site-packages/ total 8 drwxr-xr-x 10 ed staff 320B Jan 24 18:38 Pygments-2.3.1.dist-info drwxr-xr-x 3 ed staff 96B Jan 24 18:14 pycache -rw-r--r-- 1 ed staff 126B Jan 24 18:14 easy_install.py drwxr-xr-x 7 ed staff 224B Jan 24 18:35 pip drwxr-xr-x 9 ed staff 288B Jan 24 18:35 pip-19.0.1.dist-info drwxr-xr-x 6 ed staff 192B Jan 24 18:14 pkg_resources drwxr-xr-x 18 ed staff 576B Jan 24 18:38 pudb drwxr-xr-x 9 ed staff 288B Jan 24 18:38 pudb-2018.1.dist-info drwxr-xr-x 22 ed staff 704B Jan 24 18:38 pygments drwxr-xr-x 34 ed staff 1.1K Jan 24 18:14 setuptools drwxr-xr-x 12 ed staff 384B Jan 24 18:14 setuptools-28.8.0.dist-info drwxr-xr-x 33 ed staff 1.0K Jan 24 18:38 urwid drwxr-xr-x 7 ed staff 224B Jan 24 18:38 urwid-2.0.1.dist-info (my_env)ed@family-imac:~/projects/demo$ python
Note that there are now entries for both pudb and its dependency, pygments. And to verify that it has been successfully installed:
(my_env)ed@family-imac:~/projects/demo$ python Python 3.6.4 (v3.6.4:d48ecebad5, Dec 18 2017, 21:07:28) [GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import pudb >>> pudb.version '2018.1' >>> ^D (my_env)ed@family-imac:~/projects/demo$
There’s a ton more to using virtual environments, but that should give you a start.
The OpenStack PTG for the Stein cycle was held in Denver this past week from September 10—14. And yes, it was at the same hotel as last year for the Queens PTG, complete with loud commuter train whistles. There was one clear theme that was expressed in different sessions across different teams:
“Not Enough Cycles”
It seemed that everyone has been stretched pretty thin by the demands of the upstream OpenStack work as well as the internal demands of their employers. As the New Car Smell™ has worn off of OpenStack, employers aren’t as willing to have their employees spend as much time on OpenStack projects, and several projects that were either in the planning stages or the early development cycle have had to be pushed aside for lack of time to work on them.
The API-SIG had its sessions on Monday, and one of the main topics slated for discussion was a perfect example of this: the effort to provide common healthcheck middleware across OpenStack projects. This would provide the benefit of allowing deployments to monitor all their cloud processes, and be able to detect when one of them is not running so they can automatically re-launch it. It’s a great idea, but it has stalled in the last few months due to the people who were working on it being re-tasked at their jobs on non-OpenStack projects. Since this effort may be of interest to the members of the Self-healing SIG, we will approach them to see if they may have people who can work on it. If anyone else feels strongly about this effort and does have available time, please reply on that review to let the original authors know, as they would be happy to help new people get up to speed with this.
We also discussed the GraphQL experiment, but unfortunately no one who is involved in this attended the PTG, so there wasn’t a lot of discussion. Oh, except to note that those involved have said that the effort has been slow because (you guessed it!) they don’t have enough cycles to focus on this.
We discussed design approaches that reduce the number of exceptions raised as a way to reduce complexity in code. For example, what should the behavior be when calling DELETE on a resource that doesn’t exist? The answer is that it depends on how you define what DELETE does. One possibility is that you locate a resource and then delete it; if the resource doesn’t exist, raise a 404 Not Found. The other is to define DELETE as “make sure that this resource doesn’t exist”. Under this approach, if the resource isn’t found, then Mission Accomplished! Not only does this make DELETE idempotent, it eliminates the need of everyone who calls the API to have to bracket each call in code like:
try:
delete(my_resource)
except NotFound:
pass
We agreed that in general, we should emphasize designs that minimize the complexity of code that calls an API. Most of the time when DELETE is called on a resource, the caller simply wants that resource gone. In the rare event that they need to ensure that the resource exists ahead of deleting it, they can do a HEAD or GET first. But in the vast majority of cases, there is no need to return a 404 if the resource doesn’t exist.
The last thing we addressed was the state of Monty Taylor’s patch for consuming version discovery. Once again, these have languished because Monty has been doing like a zillion other things. We agreed that, while not complete, there is a large amount of useful information there, so we will merge them so that they are available, and add some wording to indicate that they are still a work in progress. As they say, perfect is the enemy of the good.
There was one other event on Monday, and that was an impromptu meeting of the principle people involved in the process of extracting the Placement service into its own project. When Placement was created it was supposed to be separate from Nova, but people argued that for $REASONS it would be easier to start as part of Nova, and then later on be separated into its own project. Every cycle since then, the separation has been put off, because there were too many other things to get done, and because the effort required to separate Placement kept increasing as Placement grew. Six months ago at the PTG in Dublin, we agreed that we would finally do this as part of the Stein release. During the Rocky time frame, a lot of work was done by Chris Dent, and to a lesser degree myself, to determine just what the extraction process would require. So as soon as Rocky was released, we started the process of extracting the Placement code from Nova, and began talking about the project split. That’s when we ran into a wall: the current leaders of the Nova team accepted the code split, but were adamant that now was not the time for a governance split. This was confusing, as we had already agreed that the core team for the new Placement project would start off as the current Nova core team, so any code development would not be affected, but it seemed as though there was a fundamental mistrust that was not being expressed that was in the way.
So we had this meeting that was mediated by Mohammed Naser to figure out just what needed to be done before the Nova team would agree to allow the creation of the Placement project. We agreed (some of us reluctantly) on a set of technical milestones that needed to be achieved before Placement would be separated into its own project. The reluctance was the result of two things: the unlikelihood that some of the milestones would be completed any time soon, but also because the underlying cause of the mistrust was never acknowledged or discussed. So I’m happy that there is finally a path forward, but disappointed that the discussions couldn’t be more honest and forthcoming.
Tuesday was a cross-project day, with discussions between Nova/Placement and the Blazar, Cinder, and Ops teams. The Blazar discussions were interesting, as they are basically “consuming” resources by reserving them, and then parceling out those resources to individual reservations. It is too bad that discussions like this did not happen when the Placement design discussions happened over the past few years, as it would have been nice to consider this use case. As it is now, there really isn’t a clean way to handle that in Placement.
Wednesday was the start of the three days of Nova discussions. If you want to see the details of what topics were discussed, and various input people had, you can read the etherpad tracking the schedule. We started off with the standard retrospective discussion, which covered many of the same things we normally cover, and produced the typical “let’s do better” resolutions. There was no “how can we be a better team” sort of discussions, because frankly we’ve tried to have them before, and they quickly turn into defensive posturing instead of positive discussion, so no one was interested in going through that again.
The Placement discussions were next, and covered many topics, but we still only got part-way through the list. Much of the early discussion covered the state of extraction and what else needs to happen to have a fully independent repo. We also covered the desire by some on the Nova team to put more Nova-centric information into Placement, so that Nova could do things like quota counting and the like. Personally, I would strongly prefer that Nova-specific information be stored in Nova, but for now it seems like that distinction isn’t very important to others. I didn’t argue these points very much in person, as these in-person discussions tend to devolve quickly since everyone has a slightly different understanding of what is being proposed, and we tend to talk past each other. I hope to persuade more once actual specs with concrete proposals are available for review.
Wednesday afternoon was mostly discussions of Cells v2. Frankly, I didn’t pay close attention to most of it, as I have little interest in this topic. It always seemed odd to design a distributed system like cells and not use a distributed database. So instead I started writing this blog post, and reviewed some Placement patches in gerrit. Fortunately, the cells discussions ended early, and there was time to have more Placement discussions. One thing that involved more disagreement than I expected was how to handle a potential new library to handle standard resource classes. There is already the os-traits library for enumerating standard traits, so creating an os-resource-classes lib seemed like it would be uncontroversial. However, there was an objection to now having two separate things when both were pretty lightweight. OK, then let’s combine them into a new os-placement library, right? No, not so simple. There was concern that packagers would have to edit their packaging scripts, so it was proposed that the resource classes be added to the os-traits library. In other words, to work with traits, you’d use os-traits. To work with resource classes, you’d use os-traits. Wait, what?? This, in my opinion, is a great example of short-term thinking: making life a little easier for a few people now, in return for confusing the hell out of everyone who will have to use it for years in the future by having a misleading name.
Thursday morning was the Nova – Cinder discussions. Once again, this isn’t an area I’m active in, so I listened with one ear while reviewing Placement code. The discussions surrounding the transfer of ownership of an in-use volume, though, caught my attention. It is something that cloud operators seem to really want, but there are a bunch of technical hurdles, as Cinder doesn’t allow transfer of either in-use or encrypted volumes. Operators are doing it using a variety of hacks, so it was agreed that we need to provide them a way to get this done.
There were some good Nova – Cyborg discussions, both on Monday morning and again on Thursday before lunch. These concerned themselves with issues such as which service “owns” the accelerator devices, and how to configure that. I won’t go into details here, but you can read the etherpad if you want more information.
Thursday afternoon had two more joint sessions: Nova – Neutron, and Nova – Ironic. The etherpad (starting around line 563) contains the topics and the resolutions from those meetings; again, as I’m not working on those areas, I only half-paid attention. Friday was set aside for a variety of miscellaneous topics; too many to list here. It seemed like, as in past PTGs, people were burnt out after days of intense discussions. The Nova room was half-empty, and the common areas seemed relatively empty. I suppose many people left for home by then.
This was the last “pure” PTG. Starting next spring, the PTG will take place alongside the OpenStack Summit; the exact days haven’t been announced, but the general assumption is that there will be 3 days for the summit, and 3 or 4 days for the PTG, and these days may or may not overlap. The thinking is that it will reduce the number of times that people have to fly, since many attend both events. I’ll have to say that, while I understand the financial realities, this will be a step backwards. Having the PTG at the start of the cycle helps with focus for a project, and not having the distractions of the Summit is a big plus. But the reality is that companies aren’t approving travel for events that don’t involve customer interaction, and many saw the PTG as not important for that reason. That kind of short-sightedness is disappointing, as OpenStack as a whole will suffer as a result.
