Archives: MongoDB

Backup Files from Ubuntu to Azure

Hey there, how are you doing? I have been busy setting up a VPS (not in Azure) with PostgreSQL and wanted to have a recovery mechanism set for it. Because the VPS is not in Azure, I have zero options that would allow me to take a snapshot or backup of the server. So, I decided to write a simple script allowing me to take backups of files and upload them to Azure Blob Storage using Azure CLI. If you want to use something other than Azure, feel free to do so. I use Azure on my account, and the charges are low. You can check the pricing here.

Alright then, let’s start taking a backup of the database using the pgdump command:

#$USERNAME is the admin username that you have set
#$DATABASE_NAME is the Database name
#$BACKUP_FILE is the path where the file will be dumped
pg_dump -U $USERNAME -d $DATABASE_NAME > $BACKUP_FILE

Now that we have a way to export a dump of the database, let’s go ahead and identify the Access Key for the Container where I want to store the files. This can be found in the Access keys within the Security + networking section of the Storage Account. If you want to learn more about Azure Blob Storage, please visit the documentation.

Here, either of the key1 or key2 values can be used.

Next, to use this, we need to install the Azure CLI. Let’s execute this command to install the Azure CLI:

curl -sL https://aka.ms/InstallAzureCLIDeb | sudo bash
az --version

A successful installation would result in az --version giving the version info.

Now that the dependencies are sorted out, we can look into the backup script. Note that this script can be modified to back up any files. Save this file as backup_script.sh in /home/vps_backup/scripts directory.

#!/bin/bash

# Set the password for PostgreSQL user
export PGPASSWORD='YOUR_PASSWORD'

# Replace these values with your actual Azure Blob Storage account details
AZURE_STORAGE_ACCOUNT="MYBACKUP"
AZURE_STORAGE_ACCESS_KEY="STORAGE_ACCESS_KEY"
CONTAINER_NAME="backups"

# Define variables for the backup
USERNAME=postgres
DATABASE_NAME=mydatabse
# Get the current date and time
today=$(date +"%Y-%m-%d_%H-%M-%S")
todayDate=$(date +"%Y-%m-%d")

# Set the filenames to todays date. 
BACKUP_FILE=/home/vps_backup/backups/backup_$today.sql
BACKUP_ZIPFILE=/home/vps_backup/backups/backup_$today.tar.gz

# Perform the backup using pg_dump
pg_dump -U $USERNAME -d $DATABASE_NAME > $BACKUP_FILE

# Unset the password to clear it from the environment
unset PGPASSWORD

# Generating a compressed file using tar
tar -czvf $BACKUP_ZIPFILE $BACKUP_FILE

# Upload the backup files to Azure Blob Storage using Azure CLI
# using -d for directory using the $todayDate variable to store the files based on dates
az storage blob directory upload --account-name $AZURE_STORAGE_ACCOUNT --account-key $AZURE_STORAGE_ACCESS_KEY --container $CONTAINER_NAME --source $BACKUP_ZIPFILE -d $todayDate

The final step is to set the cron so that our script gets executed every hour.

crontab -e
0 * * * * /home/vps_backup/scripts/backup_script.sh

Although I have used Azure CLI for Azure, you can use any medium to store your files, such as a database dump from PostgreSQL, MongoDB, SQL, MySQL, etc., or any other file.

Here is a snapshot of the Azure Storage Browser showing the Container with a specific date directory:

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Update Property in a Nested Array of entities in MongoDB

MongoDB

Many of us would have already used MongoDB for storing data as Documents. However, I come from a world of SQL where everything is stored in Tables following the Normalization process. Hence, anything that can be further broken down, should be considered storing in a separate table.

In the world of MongoDB or rather, No-SQL, we do not have anything like that. Here, the more connected the data is supposed to have, the more chances of storing them together makes sense. Let’s look at the below example:

{
    "_id":"d5ebb427",
    "name":"Anubhav Ranjan",
    "email":"[email protected]",
    "subscriptions":[
        {
            "subscriptionId":"1abc",
            "showId":"d060b8ca",
            "notificationEnabled":true
        },
        {
            "subscriptionId":"2abc",
            "showId":"d060b8cb",
            "notificationEnabled":true
        }
    ]
}

Let’s consider the code snippet above. I have an object User having Two Subscriptions. Now I want to make one of the Subscriptions as false. This should be done using C#.

Let’s see how this can be achieved using Mongo shell

db.users.find({ _id: "d5ebb427", "subscriptions.subscriptionId":"1abc"});

db.users.update({ _id: "d5ebb427", "subscriptions.subscriptionId":"1abc"}, { $set: {"subscriptions.$.notificationEnabled": false}});

Let’s go ahead and check out the C# implementation

// C# Mongo Schema
public class User
{
    [BsonId]
    public string Id { get; set; }
    [BsonElement("name")]
    public string Name { get; set; }
    [BsonElement("email")]
    public string Email { get; set; }
    [BsonElement("subscriptions")]
    public Subscription[] Subscriptions { get; set; }
}


public class Subscription
{
    [BsonElement("subscriptionId")]
    public string SubscriptionId{ get; set; }
    [BsonElement("showId")]
    public string ShowId { get; set; }
    [BsonElement("notificationEnabled")]
    public bool NotificationEnabled { get; set; }
}

In order to do this, we are using the positional $ operator.
As per the MongoDB docs, The positional $ operator identifies an element in an array to update without explicitly specifying the position of the element in the array.

var filter = Builders.Filter;
var userSubscriptionFilter = filter.And(
    filter.Eq(u => u.Id, id),
    filter.ElemMatch(u => u.Subscriptions, s => s.SubscriptionId == subId)
);
// Find User with Id and Subscription Id
var user = await usersCollection.Find(userSubscriptionFilter).SingleOrDefaultAsync();

// Update using the positional operator
var update = Builders.Update;
var subscriptinonSetter = update.Set("subscriptions.$.notificationEnabled", false);
var updateResult = await usersCollection.UpdateOneAsync(userSubscriptionFilter, subscriptinonSetter);

After further reading, I have even found that you can change the line from this:

var subscriptinonSetter = update.Set("subscriptions.$.notificationEnabled", false);

to this:

var subscriptinonSetter = update.Set(s =>  s.Subscriptions[-1].NotificationEnabled, false);

Happy Coding!

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