DB connection failed after months of working and without updating

Developer help Self-hosting
1

I run 4 ghost blogs in a docker-compose variation. All 3 of them at around 1000 local today stopped working. All 3 of them had the same error:

Invalid DB Host

Error ID:
500

I updated both the DB and the Ghost image and I get this error on two of them.

Invalid database host.
0=P 1=l 2=e 3=a 4=s 5=e 6=  7=d 8=o 9=u 10=b 11=l 12=e 13=  14=c 15=h 16=e 17=c 18=k 19=  20=y 21=o 22=u 23=r 24=  25=d 26=a 27=t 28=a 29=b 30=a 31=s 32=e 33=  34=c 35=o 36=n 37=f 38=i 39=g 40=. 
Error ID:
    500
Error Code: 
    EAI_AGAIN
----------------------------------------
Error: getaddrinfo EAI_AGAIN db
    at /var/lib/ghost/versions/5.120.2/node_modules/knex-migrator/lib/database.js:50:23
    at GetAddrInfoReqWrap.onlookup [as oncomplete] (node:dns:107:26)
[2025-05-24 18:32:23] WARN Ghost is shutting down
[2025-05-24 18:32:23] WARN Ghost has shut down
[2025-05-24 18:32:23] WARN Your site is now offline
[2025-05-24 18:32:23] WARN Ghost was running for a few seconds

On another I just updated the Ghost image and that one seems to work just fine now, however I am getting this occasionally

[2025-05-24 18:28:23] INFO Running milestone emails job on Tue May 27 2025 18:28:23 GMT+0000 (Coordinated Universal Time)
[2025-05-24 18:28:25] WARN {{#get}} helper took 215ms to complete
{{#get}} helper took 215ms to complete

All of them have the same compose file with different passwords and ports, but identical outside of that. I have no idea what happened. Host is MFA secured and logs show no logins except me attempting to figure it out. How can I stop this from happening again? How do I even see what happened?

I am not sure what information you’ll need so here is what I can give you.

Host: Ubuntu 20.04
Version: 5.120.2
Environment: production
Database: mysql8
Mail: SMTP

Thank you for your help.

2

EAI_AGAIN is a DNS lookup error, so it’s either something with your docker network, or your host DNS that’s preventing the database host from being translated in to an IP address

1 Like
3

How would I check that? Nothing changed in the network settings. That are on the same docker-compose file.

4

I can’t help too much with debugging Docker network issues, but I would start by trying to e.g. ping the DB host in your Ghost container image

5

I problem is that it keeps rebooting since it can’t connect to the DB

6

Any other ideas? The container just restarts if it can’t connect to the DB. This is my docker compose file

ghost:
    image: ghost:latest
    restart: always
    ports:
      - 2369:2368
    environment:
      # see https://ghost.org/docs/config/#configuration-options
      database__client: mysql
      database__connection__host: db
      database__connection__user: [REDACTED]
      database__connection__password: [REDACTED]
      database__connection__database: ghost
      url: [REDACTED]
      mail__transport: SMTP
      mail__from:[REDACTED]
      mail__options__service: Mailgun
      mail__options__host: smtp.mailgun.org
      mail__options__port: 587
      mail__options__secureConnection: false
      mail__options__auth__user: [REDACTED]
      mail__options__auth__pass: [REDACTED]
    volumes:
      - [REDACTED]
    links:
      - db

  db:
    image: mysql:8.0
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: [REDACTED]
      MYSQL_DATABASE: ghost
      MYSQL_USER: [REDACTED]
      MYSQL_PASSWORD: [REDACTED]
    volumes:
      - [REDACTED]
7

It’s been a while since I debugged Docker image issues, that’s all I’ve got for now :upside_down_face: