This is a follow-up from the blog post of Russel as seen here: https://etbe.coker.com.au/2020/10/13/first-try-gnocchi-statsd/. There’s a bunch of things he wrote which I unfortunately must say is inaccurate, and sometimes even completely wrong. It is my point of view that none of the reported bugs are helpful for anyone that understand Gnocchi and how to set it up. It’s however a terrible experience that Russell had, and I do understand why (and why it’s not his fault). I’m very much open on how to fix this on the packaging level, though some things aren’t IMO fixable. Here’s the details.
1/ The daemon startups
First of all, the most surprising thing is when Russell claimed that there’s no startup scripts for the Gnocchi daemons. In fact, they all come with both systemd and sysv-rc support:
# ls /lib/systemd/system/gnocchi-api.service
/lib/systemd/system/gnocchi-api.service
# /etc/init.d/gnocchi-api
/etc/init.d/gnocchi-api
Russell then tried to start gnocchi-api without the good options that are set in the Debian scripts, and not surprisingly, this failed. Russell attempted to do what was in the upstream doc, which isn’t adapted to what we have in Debian (the upstream doc is probably completely outdated, as Gnocchi is unfortunately not very well maintained upstream).
The bug #972087 is therefore, IMO not valid.
2/ The database setup
By default for all things OpenStack in Debian, there are some debconf helpers using dbconfig-common to help users setup database for their services. This is clearly for beginners, but that doesn’t prevent from attempting to understand what you’re doing. That is, more specifically for Gnocchi, there are 2 databases: one for Gnocchi itself, and one for the indexer, which not necessarily is using the same backend. The Debian package already setups one database, but one has to do it manually for the indexer one. I’m sorry this isn’t well enough documented.
Now, if some package are supporting sqlite as a backend (since most things in OpenStack are using SQLAlchemy), it looks like Gnocchi doesn’t right now. This is IMO a bug upstream, rather than a bug in the package. However, I don’t think the Debian packages are to be blame here, as they simply offer a unified interface, and it’s up to the users to know what they are doing. SQLite is anyway not a production ready backend. I’m not sure if I should close #971996 without any action, or just try to disable the SQLite backend option of this package because it may be confusing.
3/ The metrics UUID
Russell then thinks the UUID should be set by default. This is probably right in a single server setup, however, this wouldn’t work setting-up a cluster, which is probably what most Gnocchi users will do. In this type of environment, the metrics UUID must be the same on the 3 servers, and setting-up a random (and therefore different) UUID on the 3 servers wouldn’t work. So I’m also tempted to just close #972092 without any action on my side.
4/ The coordination URL
Since Gnocchi is supposed to be setup with more than one server, as in OpenStack, having an HA setup is very common, then a backend for the coordination (ie: sharing the workload) must be set. This is done by setting an URL that tooz understand. The best coordinator being Zookeeper, something like this should be set by hand:
coordination_url=zookeeper://192.168.101.2:2181/
Here again, I don’t think the Debian package is to be blamed for not providing the automation. I would however accept contributions to fix this and provide the choice using debconf, however, users would still need to understand what’s going on, and setup something like Zookeeper (or redis, memcache, or any other backend supported by tooz) to act as coordinator.
5/ The Debconf interface cannot replace a good documentation
… and there’s not so much I can do at my package maintainer level for this.
Russell, I’m really sorry for the bad user experience you had with Gnocchi. Now that you know a little big more about it, maybe you can have another go? Sure, the OpenStack telemetry system isn’t an easy to understand beast, but it’s IMO worth trying. And the recent versions can scale horizontally…