UniFi - Repairing Database Issues on the UniFi Network Application

32-bit MongoDB collections are limited to a total size of 2GB. While running the MMAPv1 storage engine this can cause issues when trying to shrink the aggregate collection sizes. When running a compact command on the MongoDB, the database is rewritten and defragmented without error correction. This process does not return usable disk space to the UniFi Console when the storage engine is MMAPv1.

Getting back that valuable disk space on a 32-bit MongoDB instance will require a repair of the database. This repair may be needed for those who are suspecting invalid entries, corruption, or collection scaling issues. To be able to run a database repair, the CloudKey will have to have enough free disk space equal to the size of the current data set plus 2 gigabytes. If the dataset has already grown too large to proceed with the db.repairDatabase() command there are instructions below to work around that.

Note: The Legacy CloudKey (UC CK) utilizes the following:

• 32-Bit architecture
• MMAPv1
• MongoDB Version 2.4.10

1. Establish an SSH connection with the CloudKey.
2. Download the mongo pruning script. As written, the script will only keep entries from the past 7 days. It will not remove entries that are required for UniFi administration. Do so by running the following command:
   

   cd /tmp/
       wget https://help.ui.com/hc/en-us/article_attachments/360008640574/CK_repair.js

3. Stop the UniFi service:
   

   service unifi stop

4. The UniFi service will shut down the mongo process. Make sure that the UniFi service has been completely shut down. Repair the database to compact the data entries and free unused disk space field that is included in the query criteria.
   

   mongod --dbpath /usr/lib/unifi/data/db --logpath /usr/lib/unifi/logs/server.log --repair

   1. NOTE: Steps 5-8 are optional if you need to prune back the database to conserve disk space.
5. Restart mongo using:
   

   mongod --dbpath /usr/lib/unifi/data/db --logpath /usr/lib/unifi/logs/server.log --journal --bind_ip 127.0.0.1 --fork

   1. NOTE: Journaling may not be have been enabled in your mongo database. If so, then remove the --journal option in the above command.
6. Execute the script to prune the stat collections that are causing the problem:
   

   mongo < /tmp/CK_repair.js

7. Shut down the mongo server with this command:
   

   mongod --dbpath /usr/lib/unifi/data/db --logpath /usr/lib/unifi/logs/server.log --shutdown

   1. Note: The last command in the CK_repair.js script is "db.repairDatabase()". It may result in an error if the stats collections have already grown too large to be repaired while the mongo server is running. If you see such an error running the script then you will need to repair the database from the command line once again by running the command in step 3.
8. Finally, restart the UniFi service:
   

   service unifi start

The CloudKey should now be able to run the Network application. If you still have database issues, please upgrade to the latest CloudKey Gen2 Plus which does not experience this problem.

Attention: This section does not apply to 32-bit architecture consoles including the UC-CK G1.

After UniFi Network is functional again, a user may wish to migrate it to the WiredTiger storage engine.

To verify how much space is used, run the following command:

du -shc /usr/lib/unifi/data/db/ace* /usr/lib/unifi/data/db/journal/* /usr/lib/unifi/data/db/local* | grep total

To verify which MongoDB version is being used, run the following:

mongod --version | grep "db version"

To verify what storage engine version is being used, run the following two commands:

mongo localhost:27117
    db.serverStatus().storageEngine.name

How to Migrate to WiredTiger

1. Create a backup under Settings > Maintenance > Backup with the desired retention settings.
2. Uninstall UniFi from Windows or macOS. Purge UniFi from Debian-based Linux with the command:
   

   sudo dpkg -P unifi

3. Reinstall UniFi on Windows or macOS. Reinstall UniFi on Debian-based Linux with the commands:
   

   cd /tmp/
   wget <https link to download>
   sudo dpkg -i unifi_sysvinit_all.deb

4. In the UniFi Setup Wizard restore the backup from step 1.