A MongoDB replica set, priced like three VMs

Deploy

Initiate rs0 from one bootstrap script

Save one bootstrap, create three members from it, and initiate the set from the first.

~/infra

$ for n in 1 2 3; do

edge compute create --name mongo-$n \

--size s-4vcpu-8gb --image ubuntu-24 \

--region london --script mongodb-8

done

✓ mongo-1, mongo-2, mongo-3 running

$ mongosh --eval 'rs.initiate(cfg)'

$ mongosh --eval 'rs.status().members' \

--quiet | grep stateStr

✓ PRIMARY, SECONDARY, SECONDARY

Inter-node transfer$0

rs0 in LondonHealthy

Primarymongo-1, 10.185.0.5

Secondariesmongo-2, mongo-3

1. 01

   Save a MongoDB bootstrap

   Installs MongoDB 8.0 from MongoDB's own apt repository for Ubuntu 24.04.

   mongodb.shCopy

   #!/bin/bash
   set -e
   export DEBIAN_FRONTEND=noninteractive
   curl -fsSL https://www.mongodb.org/static/pgp/server-8.0.asc | \
     gpg --dearmor -o /usr/share/keyrings/mongodb-8.0.gpg
   echo "deb [signed-by=/usr/share/keyrings/mongodb-8.0.gpg] \
   https://repo.mongodb.org/apt/ubuntu noble/mongodb-org/8.0 multiverse" \
     > /etc/apt/sources.list.d/mongodb-org-8.0.list
   apt-get update && apt-get install -y mongodb-org
   systemctl enable --now mongod

2. 02

   Create three members

   Attach all three to one private network, allow 27017 from that range only, and add each member's private IP to /etc/hosts.

   shellCopy

   $ edge compute scripts create --name mongodb-8 --file mongodb.sh
   
   $ for n in 1 2 3; do
       edge compute create --name mongo-$n --size s-4vcpu-8gb \
         --image ubuntu-24 --region london --script mongodb-8
     done

3. 03

   Configure the replica set

   Same file on every member, each with its own private IP and a shared keyfile. The keyfile also switches on authentication.

   /etc/mongod.confCopy

   net:
     port: 27017
     bindIp: 127.0.0.1,10.185.0.5
   replication:
     replSetName: rs0
   security:
     keyFile: /etc/mongo-keyfile

4. 04

   Initiate the set and schedule backups

   Run rs.initiate on mongo-1 itself, then create your admin user. Dump nightly from a secondary so the primary keeps its cache.

   shellCopy

   # on mongo-1
   $ mongosh --eval 'rs.initiate({ _id: "rs0", members: [
       { _id: 0, host: "mongo-1:27017" },
       { _id: 1, host: "mongo-2:27017" },
       { _id: 2, host: "mongo-3:27017" } ] })'
   
   $ mongodump --uri "$MONGO_URI" --readPreference=secondary \
       --oplog --archive --gzip | \
     aws s3 cp - s3://mongo-backups/$(date +%F).gz \
       --endpoint-url https://storage.edge.network

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