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I dabbled with an idea similar to Fly.io's Heroku supercharging functionality (Turboku?). One issue I encountered is that the app in question does not benefit

I dabbled with an idea similar to Fly.io's Heroku supercharging functionality (Turboku?). One issue I encountered is that the app in question does not benefit from full-page caching. Even if we deployed our app through Fly.io, we'd still have our databases hosted somewhere else. How does Fly.io solve this, or how could we solve this? When I dabbled with this idea, I thought about deploying DB read-only replicas around the world. There would be some replication lag, but for the app in question, that would not be problematic. Writes would still be affected by the added latency, but this would not be that problematic as the fast majority of the queries are reads.

mrkurt 7y ago
You've pretty much nailed the problem. The ?good? news though is that Heroku is really slow, so just running Firecracker VMs on real hardware, doing edge TLS, and adding http2 + brotli is a huge win. When people use https://fly.io/heroku https://fly.io/heroku, we launch VMs in the same region their Heroku app is in so there's no latency hit to the DB. Weirdly, latency between a Fly app a DB on AWS in the same region is sometimes even better than AWS cross-zone latency. We _also_ give apps a special global Redis cache (https://fly.io/docs/redis https://fly.io/docs/redis). This is sometimes enough to make a full stack app multi-regional, usually people cut way down on DB queries when they use their framework's caching abilities, which can make it pretty nice to run a Rails app + cache in, say, San Jose while the DB is in Virginia. I know of a couple of devs running Elixir apps on Fly that leave a data service in the region where their DB is and basically rpc to it from other regions, which seems to work well. Read replicas are a good idea, we'd actually like to try that out at some point. It seems pretty doable to put something like pgbounce/pgpool in front of a read replica and let it handle routing write transactions properly.
- photonios 7y ago
  > The ?good? news though is that Heroku is really slow Did you do any measurements and if so, on which dyno types? We found that using Performance-M dynos' gives us a rather large performance boost. Performance-m dyno's are also more stable because they run on dedicatd hardware. They're expensive, but we don't run any apps in production without it. One thing that worked really well for us is to just put Cloudflare or Cloudfront in front of our app. As I mentioned, we don't do any full-page caching. We cache pretty much everything else, but pages themselves have zero caching (business requirement). I believe Cloudflare and Cloudfront also do edge TLS. > Read replicas are a good idea, we'd actually like to try that out at some point. It seems pretty doable to put something like pgbounce/pgpool in front of a read replica and let it handle routing write transactions properly. This is going to be tricky. We weren't able to set up replication from Heroku Postgres databases to hosts outside of Heroku. Another thing to keep in mind that is it might be better to let the app decide what is a read query and what is a write query. We have some parts of the app that we need reading directly from the master, so we let the app handle it. The app receives two database URI's, both pointing to pgbouncer.
  - sudhirj 7y ago
    I tried adding Cloudfront in front of an app hosted on Heroku with page caching off (Vary by Cookie) and it increased latency to 3X, never could figure out why. Would like to do it but seems like way too much of a trade off.
    - mrkurt 7y ago
      Shameless plug, https://fly.io/heroku https://fly.io/heroku gives you a lot of the benefit of Cloudfront without adding a layer. It's like running Heroku with a modern router. --edit-- I confused Cloudfront and CloudFlare yet again. :)
      - sudhirj 7y ago
        Yeah, I’m gonna try this out. I’m writing a book authoring platform and I want to let people give access to their books on their own domains. Is there an API to add custom domains with LE certs to my app? And is there a limit on how many domains I can add?
        mrkurt 7y ago
        There is indeed a certificate API! We’re putting up a guide for it this week, I can send you the draft if you’d like. The CLI commands for managing certs are here: https://fly.io/docs/flyctl/certs/ https://fly.io/docs/flyctl/certs/ There’s no limit to domains.
  - mrkurt 7y ago
    > Did you do any measurements and if so, on which dyno types? We found that using Performance-M dynos' gives us a rather large performance boost. Performance-m dyno's are also more stable because they run on dedicatd hardware. They're expensive, but we don't run any apps in production without it. We did some measurements, but mostly focusing on the network bits (which you largely solved with CloudFlare): https://fly.io/blog/turboku/ https://fly.io/blog/turboku/ I was surprised at how much faster things seemed on our VMs vs Heroku's Dynos, to be honest. We only compared Standard dynos, but we should be even better price vs performance compared to the performance dynos since we run our own physical servers. A performance-m dyno on Heroku costs about the same as 8 cpus on fly. It's totally self serving, but if you feel like playing around with the Fly stuff I'd love to know how it compares. > This is going to be tricky. We weren't able to set up replication from Heroku Postgres databases to hosts outside of Heroku. Another thing to keep in mind that is it might be better to let the app decide what is a read query and what is a write query. We have some parts of the app that we need reading directly from the master, so we let the app handle it. The app receives two database URI's, both pointing to pgbouncer. This is why I think the in memory caching is such a good option. Usually if I'm building an app, I'll add a caching layer before a DB replica. Write through caching seems to fit my mental processes better. :D

mrkurt 7y ago

You've pretty much nailed the problem. The ?good? news though is that Heroku is really slow, so just running Firecracker VMs on real hardware, doing edge TLS, and adding http2 + brotli is a huge win. When people use https://fly.io/heroku https://fly.io/heroku, we launch VMs in the same region their Heroku app is in so there's no latency hit to the DB. Weirdly, latency between a Fly app a DB on AWS in the same region is sometimes even better than AWS cross-zone latency. We _also_ give apps a special global Redis cache (https://fly.io/docs/redis https://fly.io/docs/redis). This is sometimes enough to make a full stack app multi-regional, usually people cut way down on DB queries when they use their framework's caching abilities, which can make it pretty nice to run a Rails app + cache in, say, San Jose while the DB is in Virginia. I know of a couple of devs running Elixir apps on Fly that leave a data service in the region where their DB is and basically rpc to it from other regions, which seems to work well. Read replicas are a good idea, we'd actually like to try that out at some point. It seems pretty doable to put something like pgbounce/pgpool in front of a read replica and let it handle routing write transactions properly.

photonios 7y ago
> The ?good? news though is that Heroku is really slow Did you do any measurements and if so, on which dyno types? We found that using Performance-M dynos' gives us a rather large performance boost. Performance-m dyno's are also more stable because they run on dedicatd hardware. They're expensive, but we don't run any apps in production without it. One thing that worked really well for us is to just put Cloudflare or Cloudfront in front of our app. As I mentioned, we don't do any full-page caching. We cache pretty much everything else, but pages themselves have zero caching (business requirement). I believe Cloudflare and Cloudfront also do edge TLS. > Read replicas are a good idea, we'd actually like to try that out at some point. It seems pretty doable to put something like pgbounce/pgpool in front of a read replica and let it handle routing write transactions properly. This is going to be tricky. We weren't able to set up replication from Heroku Postgres databases to hosts outside of Heroku. Another thing to keep in mind that is it might be better to let the app decide what is a read query and what is a write query. We have some parts of the app that we need reading directly from the master, so we let the app handle it. The app receives two database URI's, both pointing to pgbouncer.
- sudhirj 7y ago
  I tried adding Cloudfront in front of an app hosted on Heroku with page caching off (Vary by Cookie) and it increased latency to 3X, never could figure out why. Would like to do it but seems like way too much of a trade off.
  - mrkurt 7y ago
    Shameless plug, https://fly.io/heroku https://fly.io/heroku gives you a lot of the benefit of Cloudfront without adding a layer. It's like running Heroku with a modern router. --edit-- I confused Cloudfront and CloudFlare yet again. :)
    - sudhirj 7y ago
      Yeah, I’m gonna try this out. I’m writing a book authoring platform and I want to let people give access to their books on their own domains. Is there an API to add custom domains with LE certs to my app? And is there a limit on how many domains I can add?
      - mrkurt 7y ago
        There is indeed a certificate API! We’re putting up a guide for it this week, I can send you the draft if you’d like. The CLI commands for managing certs are here: https://fly.io/docs/flyctl/certs/ https://fly.io/docs/flyctl/certs/ There’s no limit to domains.
- mrkurt 7y ago
  > Did you do any measurements and if so, on which dyno types? We found that using Performance-M dynos' gives us a rather large performance boost. Performance-m dyno's are also more stable because they run on dedicatd hardware. They're expensive, but we don't run any apps in production without it. We did some measurements, but mostly focusing on the network bits (which you largely solved with CloudFlare): https://fly.io/blog/turboku/ https://fly.io/blog/turboku/ I was surprised at how much faster things seemed on our VMs vs Heroku's Dynos, to be honest. We only compared Standard dynos, but we should be even better price vs performance compared to the performance dynos since we run our own physical servers. A performance-m dyno on Heroku costs about the same as 8 cpus on fly. It's totally self serving, but if you feel like playing around with the Fly stuff I'd love to know how it compares. > This is going to be tricky. We weren't able to set up replication from Heroku Postgres databases to hosts outside of Heroku. Another thing to keep in mind that is it might be better to let the app decide what is a read query and what is a write query. We have some parts of the app that we need reading directly from the master, so we let the app handle it. The app receives two database URI's, both pointing to pgbouncer. This is why I think the in memory caching is such a good option. Usually if I'm building an app, I'll add a caching layer before a DB replica. Write through caching seems to fit my mental processes better. :D