How To Set Up Scheduled MongoDB Backups to DigitalOcean Spaces

By Hanif Jetha on 2 May 2018

Introduction

Regular database backups are a crucial step in guarding against unintended data loss events. In general, there are two broad categories of backups: filesystem-level (“physical”) backups and logical backups.

Filesystem-level backups involve snapshotting the underlying data files at a point in time, and allowing the database to cleanly recover using the state captured in the snapshotted files. They are instrumental in backing up large databases quickly, especially when used in tandem with filesystem snapshots, such as LVM snapshots, or block storage volume snapshots, such as DigitalOcean Block Storage Snapshots.

Logical backups involve using a tool (e.g. mongodump or pg_dump) to export data from the database into backup files, which are then restored using a corresponding restore tool (e.g. mongorestore or pg_restore). They offer granular control over what data to back up and restore and backups are often portable across database versions and installations. As logical backup tools read all data being backed up through memory, they can be slow and cause non-trivial additional load for particularly large databases.

Designing an effective backup and recovery strategy often involves trading off performance impact, implementation costs, and data storage costs with recovery speed, data integrity, and backup coverage. The optimal solution will depend on your recovery point and time objectives and database scale and architecture.

In this guide, we’ll demonstrate how to back up a MongoDB database using mongodump, a built-in logical backup tool. We’ll then show how to compress and upload the resulting serialized data backup files to DigitalOcean Spaces, a highly redundant object store. We’ll also show how to regularly schedule the backup and upload operation using Bash and cron, and finally conclude with a sample data recovery scenario.

By the end of this tutorial, you’ll have implemented the framework for an extensible automated backup strategy that will allow you to quickly recover should your application suffer from data loss. For smaller to medium-sized databases, logical backups using mongodump give you fine-grained control over what data to back up and recover. Storage of these compressed backup archives in DigitalOcean Spaces ensures that they are readily available in a durable object store, so that your application data is protected and quickly recoverable should a data loss event occur.

Note: There may be some performance impact when using the mongodump tool, especially on highly loaded databases. You should test this procedure first using a non-production database with simulated load to verify that this method will work in your production deployment.

Prerequisites

Before you get started with this guide, make sure you have the following prerequisites available to you:

Once you’ve logged in to your Droplet, have MongoDB up and running, and have created your Space, you’re ready to get started.

Step 1 — Insert Test Data

If you’re starting from a clean MongoDB installation and haven’t stored any data yet, you should first insert some sample data into a dummy restaurants collection for test purposes. If you already have some collections and documents stored in your database, feel free to skip this step and continue on to Step 2.

First, connect to the running database using the MongoDB shell:

mongo

You’ll see the following Mongo shell prompt:

MongoDB shell version: 3.2.19
connecting to: test
Welcome to the MongoDB shell.
For interactive help, type "help".
For more comprehensive documentation, see
	http://docs.mongodb.org/
Questions? Try the support group
	http://groups.google.com/group/mongodb-user
Server has startup warnings:
2018-04-11T20:30:57.320+0000 I CONTROL  [initandlisten]
2018-04-11T20:30:57.320+0000 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2018-04-11T20:30:57.320+0000 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2018-04-11T20:30:57.320+0000 I CONTROL  [initandlisten]
>

By default, the shell connects to the test database.

Let’s list the collections present in the test database:

show collections

Since we haven’t inserted anything into the database yet, there are no collections, and we’re brought back to the prompt with no output.

Let’s insert a document into a dummy restaurants collection, which will automatically be created (as it doesn’t yet exist):

db.restaurants.insert({'name': 'Pizzeria Sammy'})

You’ll see the following output:

Output
WriteResult({ "nInserted" : 1 })

This indicates that the insert operation was successful.

Let’s list collections once again:

show collections

We now see our newly created restaurants collection:

Output
restaurants

To exit the MongoDB shell, press CTRL + D.

Now that we’ve stored some sample data in the database, we’re ready to back it up.

Step 2 — Use mongodump to Back Up MongoDB Data

We’ll now use the built-in mongodump utility to back up (or “dump”) an entire MongoDB database to a compressed archive file.

First, let’s create a temporary directory called backup to store the archive created by mongodump:

mkdir backup

Now, let’s back up the test database in this MongoDB instance to a compressed archive file called test_dump.gz. If your instance contains other databases, you can substitute another database name for test after the --db flag. You also may omit the --db flag to back up all databases in your MongoDB instance.

Note: The following command should be run from the terminal and not the Mongo shell.

mongodump --db test --archive=./backup/test_dump.gz --gzip

Here, we use the --archive flag to specify that we’d like to save all the data to a single archive file (whose location is specified by the archive parameter) , and the --gzip flag to specify that we’d like to compress this file. In addition, you optionally may use the --collection or --query flags to select a given collection or query to archive. To learn more about these flags, consult the mongodump documentation.

After running the dump command, you will see the following output:

Output
2018-04-13T16:29:32.191+0000	writing test.restaurants to archive './backup/test_dump.gz'
2018-04-13T16:29:32.192+0000	done dumping test.restaurants (1 document)

This indicates that our test data has successfully been dumped.

In the next step, we’ll upload this backup archive to object storage.

Step 3 — Upload the Backup Archive to DigitalOcean Spaces

To upload this archive to our DigitalOcean Space, we’ll need to use the s3cmd tool, which we installed and configured in the Prerequisites.

We’ll first test our s3cmd configuration and attempt to access our backups Space. In this tutorial, we’ll use mongo-backup-demo as our Space name, but you should fill in the actual name of your Space:

s3cmd info s3://mongo-backup-demo/

You’ll see the following output:

Output
s3://mongo-backup-demo/ (bucket):
   Location:  nyc3
   Payer:     BucketOwner
   Expiration Rule: none
   Policy:    none
   CORS:      none
   ACL:       3587522: FULL_CONTROL

Which indicates the connection was successful and s3cmd can transfer objects to the Space.

Let’s transfer the archive we created in Step 2 to our Space using the put command:

s3cmd put ./backup/test_dump.gz s3://mongo-backup-demo/

You’ll see some file transfer output:

Output
upload: './backup/test_dump.gz' -> 's3://mongo-backup-demo/test_dump.gz'  [1 of 1]
 297 of 297   100% in    0s    25.28 kB/s  done

Once the transfer completes, we’ll verify that the file was successfully transferred to our Space by listing the Space contents:

s3cmd ls s3://mongo-backup-demo/

You should see the backup archive file:

Output
2018-04-13 20:39       297   s3://mongo-backup-demo/test_dump.gz

At this point you’ve successfully backed up the test MongoDB database and transferred the backup archive to your DigitalOcean Space.

In the next section we’ll cover how to script the above procedure using Bash so that we can schedule it using cron.

Step 4 — Create and Test Backup Script

Now that we’ve backed up our MongoDB database to a compressed archive file and transferred this file to our Space, we can combine these manual steps into a single Bash script.

Create Backup Script

We’ll first write a script combining the mongodump and s3cmd put commands, and add a few extra bells and whistles, like some logging (using echos).

Open a blank file in your preferred text editor (here we’ll use nano):

nano backup_mongo.sh

Paste in the following code snippets, being sure to update the relevant values to refer to your own Space, database, and file names. We’ll call the file backup_mongo.sh, but you may name this file however you’d like. You can also find the full script at the end of this section.

Let’s go through this script piece by piece:

backup_mongo.sh

#!/bin/bash

set -e
...

Here, #!/bin/bash tells the shell to interpret the script as Bash code. set -e tells the interpreter to exit immediately if any of the script commands fail.

backup_mongo.sh

...

SPACE_NAME=mongo-backup-demo
BACKUP_NAME=$(date +%y%m%d_%H%M%S).gz
DB=test

...

In this section, we’re setting three variables that we’ll use later on:

  • SPACE_NAME: The name of the DigitalOcean space to which we’re uploading our backup file
  • BACKUP_NAME: The backup archive’s name. Here, we set it to a basic date-time string.
  • DB: Specifies which MongoDB database the script will back up. If you’re backing up the entire MongoDB instance (all databases), this variable won’t be used.

backup_mongo.sh

...

date
echo "Backing up MongoDB database to DigitalOcean Space: $SPACE_NAME"

echo "Dumping MongoDB $DB database to compressed archive"
mongodump --db $DB --archive=$HOME/backup/tmp_dump.gz --gzip

echo "Copying compressed archive to DigitalOcean Space: $SPACE_NAME"
s3cmd put $HOME/backup/tmp_dump.gz s3://$SPACE_NAME/$BACKUP_NAME

...

We then print the date and time (for logging purposes), and begin the backup by running the mongodump command we tested above. We once again save the backup archive to ~/backup/.

We next use s3cmd to copy this archive to the location specified by those two SPACE_NAME and BACKUP_NAME variables. For example, if our Space name is mongo-backup-demo and the current date and time is 2018/04/12 12:42:21, the backup will be named 180412_124221.gz and it’ll be saved to the mongo-backup-demo Space.

backup_mongo.sh

...

echo "Cleaning up compressed archive"
rm $HOME/backup/tmp_dump.gz

echo 'Backup complete!'

Here we remove the backup archive from the ~/backup directory as we’ve successfully copied it to our Space, with final output indicating that the backup is complete.

After combining all these code snippets, the full script should look like this:

backup_mongo.sh

#!/bin/bash

set -e

SPACE_NAME=mongo-backup-demo
BACKUP_NAME=$(date +%y%m%d_%H%M%S).gz
DB=test

date
echo "Backing up MongoDB database to DigitalOcean Space: $SPACE_NAME"

echo "Dumping MongoDB $DB database to compressed archive"
mongodump --db $DB --archive=$HOME/backup/tmp_dump.gz --gzip

echo "Copying compressed archive to DigitalOcean Space: $SPACE_NAME"
s3cmd put $HOME/backup/tmp_dump.gz s3://$SPACE_NAME/$BACKUP_NAME

echo "Cleaning up compressed archive"
rm $HOME/backup/tmp_dump.gz

echo 'Backup complete!'

Be sure to save this file when you’re done.

Next, we’ll test this script to validate that all the subcommands work.

Test Backup Script

Let’s quickly run the backup_mongo.sh script.

First, make the script executable:

chmod +x backup_mongo.sh

Now, run the script:

./backup_mongo.sh

You will see the following output:

Output
Mon Apr 16 22:20:26 UTC 2018
Backing up MongoDB database to DigitalOcean Space: mongo-backup-demo
Dumping MongoDB test database to compressed archive
2018-04-16T22:20:26.664+0000	writing test.restaurants to archive '/home/sammy/backup/tmp_dump.gz'
2018-04-16T22:20:26.671+0000	done dumping test.restaurants (1 document)
Copying compressed archive to DigitalOcean Space: mongo-backup-demo
upload: '/home/sammy/backup/tmp_dump.gz' -> 's3://mongo-backup-demo/180416_222026.gz'  [1 of 1]
 297 of 297   100% in    0s     3.47 kB/s  done
Cleaning up compressed archive
Backup complete!

We’ve successfully created a backup shell script and can now move on to scheduling it using cron.

Step 5 — Schedule Daily Backups Using Cron

To schedule a nightly run of the backup script, we’ll use cron, a job scheduling utility built-in to Unix-like operating systems.

First, we’ll create a directory to store the logs for our backup script. Next, we’ll add the backup script to the crontab (cron’s configuration file) so cron schedules it to run nightly. Because cron supports any regular frequency, you can optionally schedule weekly or monthly backups.

Create Logging Directory

Let’s create a directory to store our backup script’s log files. These logs will allow us to periodically check up on the backup script to ensure that all is well, and debug should some command fail.

Create a mongo_backup subdirectory in /var/log (by convention used for logging):

sudo mkdir /var/log/mongo_backup

Now, make that directory writeable to our Unix user. In this case, our user’s name is sammy, but you should use the relevant non-root username with sudo privileges for your server.

sudo chown sammy:sammy /var/log/mongo_backup

Our Unix user sammy can now write to /var/log/mongo_backup. Since the cronjob will run as sammy, it can now write its log files to this directory.

Let’s create the scheduled cronjob.

Create Cronjob

To create the cronjob, we’ll edit the file containing the list of scheduled jobs, called the “crontab.” Note that there are multiple crontabs, one per user, and a system-wide crontab at /etc/crontab. In this tutorial, we’ll run the backup script as our user sammy; depending on your use case, you may elect to run it from the system-wide crontab.

Open up the crontab for editing:

crontab -e

You’ll see the following menu allowing you to choose your preferred text editor:

Output
no crontab for sammy - using an empty one

Select an editor.  To change later, run 'select-editor'.
  1. /bin/ed
  2. /bin/nano        <---- easiest
  3. /usr/bin/vim.basic
  4. /usr/bin/vim.tiny

Choose 1-4 [2]: no crontab for sammy - using an empty one

Select your preferred editor; to choose nano enter 2. Now, append the following line to the file, following the commented-out section:

crontab -e

# For more information see the manual pages of crontab(5) and cron(8)
#
# m h  dom mon dow   command

0 2 * * * /home/sammy/backup_mongo.sh >>/var/log/mongo_backup/mongo_backup.log 2>&1

Be sure to include a trailing newline at the end of the crontab. Save and close the file.

You’ll see the following output:

Output
no crontab for sammy - using an empty one
crontab: installing new crontab

The backup script will now run at 2:00 AM every morning. Both stdout and stderr (the output and error streams) will be piped and appended to a log file called mongo_backup.log in the log directory we created earlier.

You may change 0 2 * * * (execute nightly at 2:00 AM in cron syntax) to your desired backup frequency and time. To learn more about cron and its syntax, consult our tutorial on How To Use Cron To Automate Tasks On A VPS.

We’ll conclude this tutorial with a quick recovery exercise to ensure that our backups are functional.

Step 6 — Perform a Test Recovery

Any backup strategy should contain a recovery procedure that is routinely tested. Here, we’ll quickly test a restore from the compressed backup file we uploaded to DigitalOcean spaces.

First, we’ll download test_dump.gz from our Space to the home directory in our MongoDB Droplet:

s3cmd get s3://mongo-backup-demo/test_dump.gz

You will see the following output:

Output
download: 's3://mongo-backup-demo/test_dump.gz' -> './test_dump.gz'  [1 of 1]
 297 of 297   100% in    0s  1305.79 B/s  done

If you began this tutorial with a fresh MongoDB instance, you’ll recall that it only contained the test database, which in turn was the only database we backed up.

For demonstration purposes, we’ll now drop this test database so that we can perform a clean restore. If we don’t perform this first step, the restore procedure will encounter the original documents, which it’ll skip. In your particular use case restoring only new documents may be acceptable, but for the purposes of this tutorial we’d like to explicitly test a full restore into an empty database.

Connect to your MongoDB instance using the mongo shell:

mongo

Now, use the test database, and drop it from the MongoDB instance:

use test
db.dropDatabase()

You’ll see the following output confirming the test drop:

Output
{ "dropped" : "test", "ok" : 1 }

Now, exit the mongo shell and execute the mongorestore command:

mongorestore --gzip --archive=test_dump.gz --db test

Here, we specify that the source backup file is compressed and in “archive file” form (recall that we used the --archive and --gzip flags when calling mongodump), and that we’d like to restore to the test database.

You will see the following output:

Output
2018-04-16T23:10:07.317+0000	creating intents for archive
2018-04-16T23:10:07.453+0000	reading metadata for test.restaurants from archive 'test_dump.gz'
2018-04-16T23:10:07.497+0000	restoring test.restaurants from archive 'test_dump.gz'
2018-04-16T23:10:07.541+0000	restoring indexes for collection test.restaurants from metadata
2018-04-16T23:10:07.541+0000	finished restoring test.restaurants (1 document)
2018-04-16T23:10:07.541+0000	done

This indicates that the test restore succeeded.

To conclude, let’s confirm that our initial restaurants data has successfully been restored.

Open up the MongoDB shell and query the restaurants collection:

db.restaurants.find()

You should see the object we saved in the first step of this tutorial:

Output
{ "_id" : ObjectId("5ace7614dbdf8137afe60025"), "name" : "Pizzeria Sammy" }

You’ve now successfully implemented and tested this MongoDB backup strategy.

Conclusion

In this tutorial, we’ve learned how to implement and test a strategy for nightly logical MongoDB backups.

This guide can be extended or modified in many ways. Here are some quick suggestions:

  • Depending on your recovery point objectives (RPOs), you may want to increase or decrease the suggested backup frequency to match your data recovery window.
  • Another helpful addition would be an alert function, triggered if a backup script subcommand fails (e.g. this function could send an email to a regularly monitored alert inbox).
  • This script does not handle Spaces object deletion. You may want to clean out backups older than, say, 6 months or so.
  • You may want to implement a more complex backup rotation scheme, depending on your production use case.

As the mongodump procedure involves quickly reading through all the dumped data, this backup method is most suitable for small- to medium-sized databases, particularly for partial backups such as a specific collection or result set. Filesystem-level backups are recommended for larger deployments. To learn more about filesystem-level MongoDB backups, consult this tutorial on How To Back Up MongoDB Using Droplet Snapshots. To learn more about various methods of backing up a MongoDB database, you can consult the MongoDB manual.

The solution presented in this tutorial leverages mongodump for granular control over backup data coverage and DigitalOcean Spaces for cost-effective and durable long-term data storage. To learn more about the mongodump backup utility, consult its reference page in the MongoDB manual. To learn more about DigitalOcean Spaces, you can read An Introduction To DigitalOcean Spaces.

This tutorial was originally published on the DigitalOcean Community website.
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