# Azure Blob Store

This guide describes how to configure Alluxio with [Azure Blob Store](https://azure.microsoft.com/en-in/services/storage/blobs/) as the under storage system.

## Prerequisites

The Alluxio binaries must be on your machine.

In preparation for using Azure Blob Store with Alluxio, create a new container in your Azure storage account or use an existing container. You should also note that the directory you want to use in that container, either by creating a new directory in the container, or using an existing one. For the purposes of this guide, the Azure storage account name is called `<AZURE_ACCOUNT>`, the container in that storage account is called `<AZURE_CONTAINER>` and the directory in that container is called `<AZURE_DIRECTORY>`. For more information about Azure storage account, Please see [here](https://docs.microsoft.com/en-us/azure/storage/storage-create-storage-account).

## Basic Setup

### Root Mount

To use Azure blob store as the UFS of Alluxio root mount point, you need to configure Alluxio to use under storage systems by modifying `conf/alluxio-site.properties`. If it does not exist, create the configuration file from the template.

```console
$ cp conf/alluxio-site.properties.template conf/alluxio-site.properties
```

Specify the underfs address by modifying `conf/alluxio-site.properties` to include:

```
alluxio.master.mount.table.root.ufs=wasbs://<AZURE_CONTAINER>@<AZURE_ACCOUNT>.blob.core.windows.net/<AZURE_DIRECTORY>/
```

Specify credentials for the Azure account of the root mount point by adding the following properties in `conf/alluxio-site.properties`:

```
alluxio.master.mount.table.root.option.fs.azure.account.key.<AZURE_ACCOUNT>.blob.core.windows.net=<YOUR ACCESS KEY>
```

### Nested Mount

An Azure blob store location can be mounted at a nested directory in the Alluxio namespace to have unified access to multiple under storage systems. Alluxio's [Command Line Interface](https://documentation.alluxio.io/ee-da-en/da-2.10/operations/user-cli) can be used for this purpose.

```console
$ ./bin/alluxio fs mount \
  --option fs.azure.account.key.<AZURE_ACCOUNT>.blob.core.windows.net=<AZURE_ACCESS_KEY> \
  /mnt/azure wasb://<AZURE_CONTAINER>@<AZURE_ACCOUNT>.blob.core.windows.net/<AZURE_DIRECTORY>/
```

After these changes, Alluxio should be configured to work with Azure Blob Store as its under storage system, and you can run Alluxio locally with it.

## Running Alluxio Locally with Azure Blob Store

Start up Alluxio locally to see that everything works.

```
./bin/alluxio format
./bin/alluxio-start.sh local
```

This should start an Alluxio master and an Alluxio worker. You can see the master UI at <http://localhost:19999>.

Run a simple example program:

```
./bin/alluxio runTests
```

Visit your container `<AZURE_CONTAINER>` to verify the files and directories created by Alluxio exist. For this test, you should see files named like:

```
<AZURE_CONTAINER>/<AZURE_DIRECTORY>/default_tests_files/BASIC_CACHE_PROMOTE_CACHE_THROUGH
```

To stop Alluxio, you can run:

```
./bin/alluxio-stop.sh local
```

## FAQ

### What should I do if I get http not support error?

If you mount the Blob and configure the Blob path start with `wasb://`, you may see the error as follows:

```
alluxio.exception.AlluxioException: com.microsoft.azure.storage.StorageException: The account being accessed does not support http.
```

You can change the Blob path start with `wasbs://`.