Upgrading from MongoDB 3.6 to MongoDB 7

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I was faced with this challenge when a workload in my homelab was using a very dated MongoDB 3.6 database, and updating it the workload, its now possible to run MongoDB 7.

I was not able to easily find any resources online that described this kind of upgrade so I decided to write my own.

The upgrade path for MongoDB is complex, requiring the sequence:
3.6 → 4.0
4.0 → 4.2
4.2 → 4.4
4.4 → 5.0
5.0 → 6.0
6.0 → 7.0

Additionally the package installation on Debian, particularly for the EOL versions is complex – so I opted to use Docker images from MongoDB for each version. In my case I performed this on a Debian environment under WSL.

At the start and the end I transferred the MongoDB database to and from the folder ~/db

With this process there were some differences with version 6 and 7 – but it was fairly straightforward.

I first began the migration by retrieving the docker images

docker pull mongo:3.6
docker pull mongo:4.0
docker pull mongo:4.2
docker pull mongo:4.4
docker pull mongo:5.0
docker pull mongo:6.0
docker pull mongo:7.0

Version 3.6

I felt it important to validate setFeatureCompatibilityVersion was set to 3.6 and confirm the Docker image is able to read my database

I started the container:

docker run -d \
  --name mongo36 \
  -v ~/db:/data/db \
  -p 27017:27017 \
  mongo:3.6

I spawned a mongo shell:

docker exec -it mongo36 mongo

I validated setFeatureCompatibilityVersion:

use admin
db.adminCommand({ getParameter: 1, featureCompatibilityVersion: 1 })
// If needed, set it to 3.6
db.adminCommand({ setFeatureCompatibilityVersion: "3.6" })
// exit the Mongo shell
exit

I stopped the container:

docker stop mongo36
docker rm mongo36

Version 4.0

I started the container:

docker run -d \
  --name mongo40 \
  -v ~/db:/data/db \
  -p 27017:27017 \
  mongo:4.0

I spawned a mongo shell:

docker exec -it mongo40 mongo

I set the new setFeatureCompatibilityVersion:

use admin
// Confirm current FCV
db.adminCommand({ getParameter: 1, featureCompatibilityVersion: 1 })

// Now set to 4.0
db.adminCommand({ setFeatureCompatibilityVersion: "4.0" })
exit

I stopped the container:

docker stop mongo40
docker rm mongo40

Version 4.2

I started the container:

docker run -d \
  --name mongo42 \
  -v ~/db:/data/db \
  -p 27017:27017 \
  mongo:4.2

I spawned a mongo shell:

docker exec -it mongo42 mongo

I set the new setFeatureCompatibilityVersion:

use admin
// Confirm current FCV
db.adminCommand({ getParameter: 1, featureCompatibilityVersion: 1 })

// Now set to 4.2
db.adminCommand({ setFeatureCompatibilityVersion: "4.2" })
exit

I stopped the container:

docker stop mongo42
docker rm mongo42

Version 4.4

I started the container:

docker run -d \
  --name mongo44 \
  -v ~/db:/data/db \
  -p 27017:27017 \
  mongo:4.4

I spawned a mongo shell:

docker exec -it mongo44 mongo

I set the new setFeatureCompatibilityVersion:

use admin
// Confirm current FCV
db.adminCommand({ getParameter: 1, featureCompatibilityVersion: 1 })

// Now set to 4.4
db.adminCommand({ setFeatureCompatibilityVersion: "4.4" })
exit

I stopped the container:

docker stop mongo44
docker rm mongo44

Version 5.0

I started the container:

docker run -d \
  --name mongo50 \
  -v ~/db:/data/db \
  -p 27017:27017 \
  mongo:5.0

I spawned a mongo shell:

docker exec -it mongo50 mongo

I set the new setFeatureCompatibilityVersion:

use admin
// Confirm current FCV
db.adminCommand({ getParameter: 1, featureCompatibilityVersion: 1 })

// Now set to 5.0
db.adminCommand({ setFeatureCompatibilityVersion: "5.0" })
exit

I stopped the container:

docker stop mongo50
docker rm mongo50

Version 6.0

I started the container:

docker run -d \
  --name mongo60 \
  -v ~/db:/data/db \
  -p 27017:27017 \
  mongo:6.0

I spawned a mongo shell:

docker exec -it mongo60 mongosh

I set the new setFeatureCompatibilityVersion:

use admin
// Confirm current FCV
db.adminCommand({ getParameter: 1, featureCompatibilityVersion: 1 })

// Now set to 6.0
db.adminCommand({ setFeatureCompatibilityVersion: "6.0" })
exit

I stopped the container:

docker stop mongo60
docker rm mongo60

Version 7.0

I started the container:

docker run -d \
  --name mongo70 \
  -v ~/db:/data/db \
  -p 27017:27017 \
  mongo:7.0

I spawned a mongo shell:

docker exec -it mongo70 mongosh

I set the new setFeatureCompatibilityVersion:

use admin
// Confirm current FCV
db.adminCommand({ getParameter: 1, featureCompatibilityVersion: 1 })

// Now set to 7.0
db.adminCommand({ setFeatureCompatibilityVersion: "7.0", confirm: true })
exit

I stopped the container:

docker stop mongo70
docker rm mongo70

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