4 ms·

I thought so too for a long time. Until that time when I upgraded the RAID10 on our database servers from a 4 drive to a 8 drive configuration (which requires r

by pilif 11y ago

I thought so too for a long time. Until that time when I upgraded the RAID10 on our database servers from a 4 drive to a 8 drive configuration (which requires rebuilding the whole array if you want the performance benefits). Getting the intricate configuration of the two machines (postgres streaming replication works, but has a lot of moving parts to keep in mind) back without having to remember any details was absolutely priceless. Completely wiping and reinstalling the main database servers (one after another of course) during the day while the system was in active use and completing the process with zero user intervention, that felt amazing. Since then, whenever I had to reinstall a machine for one reason or another, I always appreciated the immense speed-up I gained by not having to ever manually re-do the configuration. Better yet: All the years of growing the configuration, all the small insights learned over time, all the small fixes to the configuration: All are preserved and readily available. Even better: By using git, I can even go back in time and learn why I did what and when. "Why am I using TCP for NFS? Oh right - that was back in december of 2012 when we were using UDP and we ran into that kernel deadlock" - that's next to impossible to do when you're configuring servers manually.

qznc 11y ago
I don't think devit challenges the "automate" part, only the "separate tool" part. In Ansible you specify a sequence of commands just like you do in a shell script.
- jjnoakes 11y ago
  Take the time to learn a tool like Ansible. It is not about replaying a simple sequence of commands (imperative). It is more about declaring what you want your system to look like, and letting the tool decide which pieces need to run based on the current state of the system. It's like make vs a shell script. If you use scripts to build your programs, you either have to write your own checks to test whether every step is necessary or not (cumbersome, error prone, and quite complex) or you just script it to build from scratch every time (inefficient). But for systems management, rebuilding from scratch can be worse than just inefficient. Imagine if your script reinstalled MySQL from scratch every time you ran it...
  - devit 11y ago
    Most shell commands are actually "declarative" in a sense. If you run "apt-get -y install foo" that means that you want "foo" to be installed. If it's already installed, it just does nothing. In Ansible, you'd use "apt: name=foo state=present" which does exactly the same thing as the apt-get command, but requires a web search to figure out how to write (assuming you know normal Linux system usage but haven't memorized Ansible). The only differences seem to be that Ansible tells you whether the command made a change or not, and that you can parse the Ansible configuration with an external tool (assuming there are no loops/variable/etc.), but both of these things don't really seem that useful in practice.
    - pilif 11y ago
      > "apt-get -y install foo" that means that you want "foo" to be installed. If it's already installed, it just does nothing. not really. If you do that it means that you want to update foo to the latest version the system knows about. And other commands fail if the thing they are supposed to to is already done. Like `adducer`. So you could still run it and assume a failure to mean "the user already exists" - but it could of course also mean: "the user didn't exist, but creating it failed". Then you start to have a look at the exit code which may be different between the two cases. But every command behaves differently, so you need to learn all of this. With Ansible (or puppet), the syntax is always the same and the actually needed operations are abstracted away.
      - jjnoakes 11y ago
        Again, my advice is to take some time and learn the tools before discussing their strengths and weaknesses. You missed more Ansible strengths, like detecting changes and restarting only affected services for example. Show me the idempotent shell script which does apt-get to install some dependency, updates some configuration file, and then starts or restarts a service depending on both the current state of the service (was it already running?) and whether the apt-get or config file change actuallly modified things. Then scale that up. A lot. There is even more. If you care to learn it before dismissing it.

by pilif 11y ago

qznc 11y ago

I don't think devit challenges the "automate" part, only the "separate tool" part. In Ansible you specify a sequence of commands just like you do in a shell script.

jjnoakes 11y ago
Take the time to learn a tool like Ansible. It is not about replaying a simple sequence of commands (imperative). It is more about declaring what you want your system to look like, and letting the tool decide which pieces need to run based on the current state of the system. It's like make vs a shell script. If you use scripts to build your programs, you either have to write your own checks to test whether every step is necessary or not (cumbersome, error prone, and quite complex) or you just script it to build from scratch every time (inefficient). But for systems management, rebuilding from scratch can be worse than just inefficient. Imagine if your script reinstalled MySQL from scratch every time you ran it...
- devit 11y ago
  Most shell commands are actually "declarative" in a sense. If you run "apt-get -y install foo" that means that you want "foo" to be installed. If it's already installed, it just does nothing. In Ansible, you'd use "apt: name=foo state=present" which does exactly the same thing as the apt-get command, but requires a web search to figure out how to write (assuming you know normal Linux system usage but haven't memorized Ansible). The only differences seem to be that Ansible tells you whether the command made a change or not, and that you can parse the Ansible configuration with an external tool (assuming there are no loops/variable/etc.), but both of these things don't really seem that useful in practice.
  - pilif 11y ago
    > "apt-get -y install foo" that means that you want "foo" to be installed. If it's already installed, it just does nothing. not really. If you do that it means that you want to update foo to the latest version the system knows about. And other commands fail if the thing they are supposed to to is already done. Like `adducer`. So you could still run it and assume a failure to mean "the user already exists" - but it could of course also mean: "the user didn't exist, but creating it failed". Then you start to have a look at the exit code which may be different between the two cases. But every command behaves differently, so you need to learn all of this. With Ansible (or puppet), the syntax is always the same and the actually needed operations are abstracted away.
    - jjnoakes 11y ago
      Again, my advice is to take some time and learn the tools before discussing their strengths and weaknesses. You missed more Ansible strengths, like detecting changes and restarting only affected services for example. Show me the idempotent shell script which does apt-get to install some dependency, updates some configuration file, and then starts or restarts a service depending on both the current state of the service (was it already running?) and whether the apt-get or config file change actuallly modified things. Then scale that up. A lot. There is even more. If you care to learn it before dismissing it.