Daniel Doubrovkine bio photo

Daniel Doubrovkine

aka dB., @awscloud, former CTO @artsy, +@vestris, NYC

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I’ve been running a pet project using Dokku on DigitalOcean for a number of years with MongoDB, backing up data into Dropbox. See Running Slack Bots on DigitalOcean with Dokku and Backing up MongoDB Databases in Dokku Containers to Dropbox.

Today I had to selectively export data from a backup, and restore this data into a MongoDB running inside a Dokku container. This was a bit tedious.

Exporting a Subset of Data

I am dealing with slack-gamebot data, which contains a teams collection with a row per team and related data in other collections, including users and matches. I wrote a bash script to export this data.

Construct a query string, eg. {"team_id":"ID"} and fetch the _id value for querying relationships.

TEAM_QUERY='{"team_id":"'"$TEAM_ID"'"}'
ID=`mongo $DB --quiet --eval "db.teams.findOne($TEAM_QUERY)._id.valueOf()"`

Export team data.

mongoexport --db $DB -c teams --out $OUT/teams.dump --query=$TEAM_QUERY

Construct a query string with the MongoDB Object ID, an $oid.

ID_QUERY='{"team_id":{"$oid":"'"$ID"'"}}'

Export all related collections.

for coll in challenges matches seasons users
do
  mongoexport --db $DB -c $coll --out $OUT/$coll.dump --query=$ID_QUERY
done

We now have files such as teams.dump, users.dump, etc.

Expose Containerized MongoDB

Expose the MongoDB in a container on the Dokku host so we can connect to it.

dokku mongo:expose app

This will randomly assign ports. You can run dokku mongo:info app to see the exposed ports.

# dokku mongo:info app
=====> Container Information
       ...
       Exposed ports:       27017->13450 27018->25362 27019->18545 28017->29405
       Dsn:                 mongodb://username:password@dokku-mongo-app:27017/app
       Status:              running
       Version:             mongo:3.2.1

Note the mapping for 27017, mine is 13450 and the username and password.

Try connecting to the database directly with mongo. Make sure the client version matches the version of MongoDB inside the container - I was getting confusing errors until I ran apt-get mongodb-org-shell and apt-get mongodb-org-tools to get a MongoDB 3.x client.

Restore Data

mongoimport --host=... --port=13450 --username=username --password=password --db app -c teams teams.dump

Unexpose MongoDB

dokku mongo:unexpose app