thomas-leister.de

Switching Mastodon from Scaleway S3 to self-hosted Minio S3 media storage

Since the user flood of November 2022 I’ve been using Scaleway’s S3 storage for media file caching and storage of my metalhead.club Mastodon instance. It was easy to set up and has been working reliably for me. Back then the media cache size increased so much that my server’s internal storage could not keep up with the increasing demand. I didn’t want to shrink down the cache duration too much and therefore left it at 14 days.

acme.sh fails with error 404 - ACME challenge not found (Nginx)

Recently I can into an issue with acme.sh / Let’s Encrypt and a failing ACME validation

Error 404 when running acme.sh --renew -d mydomain.tld

[Wed May  3 15:31:45 UTC 2023] Pending, The CA is processing your order, please just wait. (1/30)
[Wed May  3 15:31:49 UTC 2023] mydomain.tld:Verify error:<ipaddress> Invalid response from https://mydomain.tld/.well-known/acme-challenge/5GmSwd0P0ukTtX302yHHhAuZMCEDJx7MmAaBBoPIKtk: 404
[Wed May  3 15:31:49 UTC 2023] Please add '--debug' or '--log' to check more details.
[Wed May  3 15:31:49 UTC 2023] See: https://github.com/acmesh-official/acme.sh/wiki/How-to-debug-acme.sh

Mastodon: Adding S3 based cloud storage to your instance

My Mastodon instance metalhead.club exists since summer 2016 and seen several waves of new users - but never as many new users as in early November 2022. This has not only led to heavy CPU work on the servers (see my post about scaling up Mastodon’s Sidekiq Workers), but also to greater load on storage space. Mastodon uses a media cache that not only stores copies of preview images for posts containing links - but also copies of all media files that the server knows of. Before the user wave of late 2020 metalhead.club’s media cache was about 350 GB in size with a cache retention time of 60 days. Quickly the numbers escalated and after a few days we were already at 400 GB - and after about 3 weeks we had more than 550 GB of cached media files. Not with 60 days retention time - but with 30 only.

Despite I added hundreds of GB of new storage space, the cache showed no signs of shrinking in the near future, so decided to offload the storage to an S3 storage provider. The local disks would have been full a few days later.

Scaling up your Mastodon Sidekiq workers for better performance

Mastodon has recently gained popularity amongst tech-savvy users after Elon Musk has bought Twitter. With November’s wave of new Mastodon users, many servers experienced mayor problems with their performance - so did metalhead.club, the Mastodon instance that I’m hosting myself. Here’s how I tackled performance issues on metalhead.club.

Network settings for second Wireguard-based default gateway

Situation: One of my servers is located at my home. It’s connected to the internet via two different interfaces at the same time:

Physical Interface: Connected to Deutsche Telekom ISP via DSL / landline.
Virtual Wireguard VPN interface: Connected to one of my data center servers, has a public IPv6 address.

The “data center server” acts as a gateway for my home server and routes a static IPv6 address to it. This setup lets me reach my home server via a static and public IP address, although my DSL provider does not assign a static IPv6 subnet to my landline. (But that is subject to another story … ;-) ).

After finishing the setup, I ran into the problem of asymmetric routing: Packets addresses to my static IPv6 address (and thus routed via the Wireguard VPN) did arrive at my home server, but the response packets were not send back the same way: They were routed via my Deutsche Telekom landline and therefore originated from another source IP address, which the original requester did not expect.