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[2477.22 --> 2479.50] That's something worth emphasizing again and again.
[2480.16 --> 2480.26] Yeah.
[2480.52 --> 2491.94] I think in certain contexts, it's much easier to maybe use feature flags or something similar in that you're shipping the feature, but you're not enabling the feature.
[2492.08 --> 2494.38] And this is a very important distinction to make.
[2494.88 --> 2497.42] In some cases, you can ship it, but not enable it.
[2497.42 --> 2498.42] And that's okay.
[2498.58 --> 2503.56] And then test it or, you know, trickle it down through users, beta testers and whatnot.
[2503.82 --> 2508.24] And when you have all your feedback, then if you can ship an update, then you do that.
[2508.34 --> 2509.76] And everything is good.
[2509.80 --> 2514.20] And everybody has the best latest version, right?
[2514.30 --> 2519.06] Or the closest it can get because it can always be improved and there will always be bugs.
[2519.48 --> 2522.08] After all, we are all human and we will make mistakes.
[2522.40 --> 2523.10] And that's okay.
[2523.18 --> 2523.88] That's not the problem.
[2524.40 --> 2526.28] Don't try not to make mistakes.
[2526.28 --> 2533.26] Try to limit the impact of those mistakes and fix them before anyone notices because then it looks like you've never made the mistake.
[2533.44 --> 2535.20] Well, everybody knows the truth, right?
[2535.70 --> 2538.20] So, yeah, countless times this has happened and it will happen.
[2538.38 --> 2540.06] So, better be honest about it.
[2540.54 --> 2546.14] That's why it's important to communicate well to contributors and users.
[2546.78 --> 2549.10] That's the responsibility of that release engineering.
[2549.40 --> 2552.78] You know that it might not be perfect in the end, what you ship.
[2552.78 --> 2562.50] But at least you try to make sure that people are aware of what is fine and what might not be fine.
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[2612.52 --> 2616.08] Again, linode.com slash changelog.
[2623.24 --> 2626.94] So, JSP, what did you work on before RapidMQ?
[2626.94 --> 2631.14] So, I worked as an airline developer for a small French company.
[2631.82 --> 2643.90] The company was providing a website aggregating ad so that people could look for jobs, apartments, various objects they would like to buy.
[2644.18 --> 2646.62] Craigslist or country for the listeners.
[2646.62 --> 2647.44] Yeah, something like that.
[2647.44 --> 2656.46] And we wanted to provide some kind of social media features on top of that so that people could easily interact between them.
[2656.94 --> 2660.18] In that company, so I was an airline developer.
[2660.66 --> 2666.12] We were two airline developers working on the server side of that service.
[2666.50 --> 2672.08] We chose to take Yoz, which is an airline-based web server.
[2672.08 --> 2680.00] So, we chose that because it was easy for us to extend right directly in the AirLong VM.
[2680.26 --> 2685.44] In fact, add our own AirLong modules and application in addition to Yoz.
[2686.12 --> 2690.48] The website itself was developed in PHP and JavaScript.
[2690.98 --> 2692.92] So, that part, we were not working on it.
[2692.92 --> 2695.56] Other developers were responsible for it.
[2695.56 --> 2703.56] But, yeah, those PHP files and static files were served by an AirLong VM.
[2704.52 --> 2714.68] And what I liked about what we did is that we put some effort to make sure that the website was always running,
[2714.68 --> 2719.36] even when we were working on it and upgrading it.
[2720.14 --> 2726.28] So, if we had to upgrade the operating system, and especially the kernel, which was Debian,
[2726.76 --> 2729.14] obviously, we would have to reboot the computer.
[2730.42 --> 2734.58] But otherwise, we wanted to leave the service running.
[2734.58 --> 2741.32] And what was great is that we could, in the end, benefit from the hot code reloading feature of AirLong,
[2741.44 --> 2743.70] which is really an awesome feature.
[2744.12 --> 2750.90] We were very happy because we could build Debian packages for our service.
[2751.02 --> 2757.96] So, it packaged the Yoz server, all our AirLong code base, and the website itself.
[2758.08 --> 2763.86] So, the PHP scripts, static resources, so JavaScript and CSS and images, and so on.
[2764.58 --> 2768.00] So, we packaged everything as Debian packages.
[2769.36 --> 2775.78] And when we would apt-gate update, apt-gate dist-upgrade the machine, the servers,
[2776.40 --> 2781.22] then the new copy of the AirLong code was deployed,
[2781.66 --> 2786.92] and we were using the AirLong features to reload that code live,
[2787.02 --> 2792.20] while the server, the HTTP server, was still running and serving requests.
[2792.20 --> 2795.90] And, yeah, we were very happy with that.
[2796.32 --> 2797.96] It's a really great feature from AirLong.
[2797.96 --> 2801.84] So, to me, that sounds like you're using AirLong the way it was meant to be used.
[2802.06 --> 2805.80] And what you're telling me is that it works really well when you use it the way it was built.
[2806.20 --> 2806.48] Okay.
[2806.66 --> 2807.98] Well, that is a great compliment.
[2808.48 --> 2811.38] And working as expected in this case, it's great, right?
[2811.76 --> 2813.20] And sometimes even rare.
[2814.02 --> 2816.40] And obviously, not all software works as expected.
[2816.48 --> 2817.32] That's why I mentioned this.
[2817.40 --> 2820.22] And when it does, like, oh, yes, everything works the way it should.
[2820.26 --> 2820.82] It's great.
[2820.82 --> 2821.56] And it feels great.
[2821.56 --> 2825.58] So, you were on the beaten track as designed, and everything was good.
[2825.98 --> 2830.42] I know the answer to this, but I know that many listeners will be wondering,
[2830.82 --> 2833.64] first of all, is RabbitMQ using hot code reloading?
[2834.04 --> 2834.68] No, it's not.
[2834.88 --> 2836.24] And the follow-up, why not?
[2836.62 --> 2839.74] So, it's quite difficult to manage.
[2839.74 --> 2849.42] The first part is that all developers and all contributions to the RabbitMQ code might lead to changes,
[2849.74 --> 2858.16] which don't look as breaking changes when you think of a single instance of your AirLong VM, for instance.
[2858.28 --> 2859.34] You stop the service.
[2860.14 --> 2860.28] Okay.
[2860.36 --> 2862.80] So, you load the code from the disk.
[2863.12 --> 2864.16] It runs as expected.
[2865.42 --> 2866.96] You stop the VM.
[2867.38 --> 2868.72] And, okay, all is fine.
[2869.74 --> 2879.74] But problem starts to show when, for instance, the state of a process changes between one copy of the module and the next one.
[2880.22 --> 2886.04] So, you need to handle that migration from state V1 to state V2.
[2886.92 --> 2890.48] There are tools to do that in AirLong, but this is not magic.
[2890.80 --> 2896.38] You have to use them and implement that migration from V1 to V2.
[2896.38 --> 2904.38] And it gets even more complicated when you're having a cluster of AirLong VMs.
[2905.00 --> 2920.94] So, you have to take care of the fact that, for instance, an AirLong process, while the code is reloaded, will modify its own state and will start to use inter-process messages with a newer structure.
[2920.94 --> 2932.96] So, when I say message in this context, it's messages exchanged between AirLong processes, not messages that RabbitMQ would handle from other applications.
[2932.96 --> 2936.70] So, you have to handle all those changes live.
[2937.02 --> 2945.66] So, that new process, which was reloaded, might receive new messages using the new format from process on that same node.
[2945.94 --> 2950.62] But it might receive old messages from a node which was not yet upgraded.
[2951.70 --> 2952.18] And so on.
[2952.18 --> 2955.86] So, that part is quite difficult to handle.
[2956.16 --> 2960.08] And if you have mistakes, then it will crash, obviously.
[2960.60 --> 2967.74] So, that feature is great, but it puts a lot of load and responsibilities on developers and contributors' shoulders.