MongoServerSelectionError: Server selection timed out after 2000 ms

commit: 3c5ef041a4d510d74cf8bc4a7ee871d125ab99fe

Timed out in connecting to the MongoDB server:

$ bin/up
Initiating Mongo replica set...
[+] Running 1/1
 ✔ Container mongo  Started                                                                             0.3s 
MongoServerSelectionError: Server selection timed out after 2000 ms
Waiting for Mongo...
MongoServerSelectionError: Server selection timed out after 2000 ms
Waiting for Mongo...
^Cexit status 130

The container is unhealthy:

$ docker ps -a
CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS                     PORTS       NAMES
4e6f794868a0   mongo:8.0   "docker-entrypoint.s…"   8 minutes ago   Up 8 minutes (unhealthy)   27017/tcp   mongo

OS information:

$ uname -r
6.8.0-87-generic
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 24.04.3 LTS
Release:        24.04
Codename:       noble

Docker version:

$ docker version
Client: Docker Engine - Community
 Version:           28.5.1
 API version:       1.51
 Go version:        go1.24.8
 Git commit:        e180ab8
 Built:             Wed Oct  8 12:17:26 2025
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          28.5.1
  API version:      1.51 (minimum version 1.24)
  Go version:       go1.24.8
  Git commit:       f8215cc
  Built:            Wed Oct  8 12:17:26 2025
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v1.7.28
  GitCommit:        b98a3aace656320842a23f4a392a33f46af97866
 runc:
  Version:          1.3.0
  GitCommit:        v1.3.0-0-g4ca628d1
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

Has anyone encountered this problem? I don't know how to fix this.

Start by running bin/up and checking the Mongo container's health and startup output on the reported Ubuntu and Docker versions. Compare the timeout with the mongo container logs and the configuration used by bin/up. Done means the MongoDB container becomes healthy and bin/up completes without repeated server-selection timeouts.