Using the JASMIN Object Store

This article describes how to use the JASMIN high-performance object storage.

What is object storage?  

An object store  is a data storage system that manages data as objects referenced by a globally unique identifier, with attached metadata. This is a fundamental change from traditional file systems that you may be used to, as there is no directory hierarchy - the objects exist in a single flat domain. These semantics allow the object store to scale out much more easily than a traditional shared file system.

The other fundamental change is that the data is no longer accessed by mounting a file system onto a host and referencing a file path (where authentication is “can I log in to the host”). Instead, the data is accessed over HTTP, with authentication using HTTP headers. This has many benefits, the biggest of which is that we can make the object store available outside of the JASMIN firewall, for example to the JASMIN External Cloud. Data can be read and written in the same way, using the same tools, from inside and outside JASMIN. Contrast this with Group Workspaces, where you must be logged in to a JASMIN host in order to write data using the file system, and data is only accessible externally in a readonly way using HTTP or OPeNDAP or via data transfer methods.

Object stores are seen as the most efficient (and cheapest!) way to store and access data from the cloud, and all the major cloud providers support some variant of object store. The JASMIN object store is S3 compatible  - S3 is the object store for Amazon Web Services (AWS), and has become a de- facto standard interface for object stores. This means that all the same tools that work with AWS S3 will also work with the JASMIN object store.

Accessing the object store  

The JASMIN object store is organised into tenancies. These are shared areas of the object store, similar in concept to Group Workspaces, and are requested by users, usually Group Workspace Managers. Several users can have access to a tenancy, and so they can be used collaboratively.

To join an existing object store tenancy, navigate to the “Services” section in the JASMIN Accounts Portal and select the “Object store” category. Select a tenancy and submit a request to join. This request will then be considered by the manager of the tenancy and either accepted or rejected.

For details on how to request and manage an object store tenancy, please see the help article “JASMIN Object Store for Managers” (forthcoming).

Default access policies  

As of Jan 2024, we have changed the default access policy for newly created tenancies to provide a more sensible and flexible set of access policies.

The old policy allowed any members of the tenancy access to any bucket created in the tenancy by default. The new policy allow Users (USER only in the JASMIN Accounts Portal) of the tenancy only access to buckets they own by default. This can be effectively changed to the old policy by setting the policy of the bucket to the LDAP group for the tenancy members (-members, e.g. cedadev-o-members) - this can be done using the JASMIN Object Store portal (below) or the Swarm portal. Specific JASMIN users or groups can also be given permission to buckets (group access is controlled by LDAP groups, and only existing LDAP group will work - you may need to ask for one to be created).

The new policy also gives admin access for tenancy MANAGER and DEPUTY roles, who have access to all the buckets in the tenancy.

Creating an access key and secret  

Authentication with the object store uses an access key and secret that are separate to your JASMIN username and password. You can generate keys and manage bucket permissions through the JASMIN Object Store Portal. 

You can log in with your JASMIN username and password. You can then click on the “Object Stores” button on the right. This will present you with the list of object store tenancies that you have access to. If you don’t see an object store tenancy that you expect to, please check you have access in the JASMIN Accounts Portal  . If you have access in the Accounts Portal, but not in the Object Store Portal then please email the helpdesk.

The URL for the object store tenancy is also presented here for convenience. You can click on the “Manage Object Store” button to manage you keys and buckets. This will ask you to confirm your JASMIN password.

You will then be presented with the following page.

From this page you can view your existing keys, and delete them if you require. You can also use the “Create Key” tab on the left.

You need to name the key and enter an expiry date for it. This will then present you with a pop-up with details on your access key and secret key. This is the only time your secret key will visible, so save it immediately in a secure password manager.

Managing bucket permissions  

You can also manage the permissions on buckets using the “Buckets” tab from this page. This allows you to manage the access policies for your buckets without using the S3 API or the Swarm portal.

Click on the “Manage permissions” button for a bucket to add or change access policies for that bucket.

By default this lets you grant access to specific JASMIN Users and/or groups (these are LDAP groups and you might need to request that one is created for you if you require a subgroup for your tenancy). The advanced tab gives you the same options as available through the Swarm portal - including making buckets publicly accessible. Once done, hit the save to add the policy to the bucket. You can edit or delete permissions from that bucket through the “View Bucket Policies” tab.

Legacy method for key creation  

This is the old way of creating keys which still works, but the new way above is accessible outside JASMIN on the public internet.

You can generate an access key and secret using the Caringo portal.

Authentication with the object store uses an access key and secret that are separate to your JASMIN username and password. You can generate an access key and secret using the Caringo portal. This portal is not currently available outside of JASMIN - you will need to use a graphical session on JASMIN to access a Firefox browser running on a JASMIN system.

The recommended way to do this is using the NX Graphical Desktop service. You can start Firefox from the “Activities” menu once you have logged in to your graphical desktop on one of the nx-login* servers (so no need to make an onward connection to a sci server).

An alternative option is to using X11 Forwarding on your SSH connection. You need to do this on one of the nx* servers (not the sci servers as previously) because this is where firefox is now installed:

ssh -X <user>@nx1.jasmin.ac.uk firefox

(try -Y if -X does not work for you).

Once you have Firefox open, navigate to

http://my-os-tenancy-o.s3.jc.rl.ac.uk:81/_admin/portal

but replace my-os-tenancy-o with your tenancy name.

You will see a login screen where you should enter your JASMIN username and password:

If you receive a “HTTP ERROR 500 java…” error, it is likely that you haven’t added the port (81) to the address.

Upon successfully entering the username and password of a user who belongs to the tenancy, you will see a dashboard. To create an access key and secret, click on the cog icon and select “Tokens”:

On the tokens page, click “Add”:

In the dialogue that pops up, enter a description for the token and set an expiration date. Make sure to click “S3 Secret Key” - this will expose an additional field containing the secret key. Make sure you copy this and store it somewhere safe - you will not be able to see it again! This value will be used whenever the “S3 secret key” is required.

Once the token is created, it will appear in the list. The “Token” should be used whenever the “S3 access key” is required:

Accessing data in the object store  

URLs for internal and external access  

Although the data is exactly the same in both cases, a slightly different URL must be used depending on whether you are accessing the object store from the JASMIN managed cloud servers or from the JASMIN External Cloud.

From inside JASMIN, including LOTUS and the Scientific Analysis servers, my-os-tenancy-o.s3.jc.rl.ac.uk should be used, with the `http://`` prefix.

From the JASMIN External Cloud, and from locations external to JASMIN, my-os-tenancy-o.s3-ext.jc.rl.ac.uk should be used - note the https:// prefix and additional -ext.

(Where my-os-tenancy-o needs to be replaced with your tenancy name)

Using s3cmd  

s3cmd is a command line tool provided by Amazon to work with S3 compatible Object Storage. It is installed on JASMIN, both on the sci-machines and on LOTUS. It is a little more complicated to use than the MinIO client, but is more powerful and flexible. For full details on s3cmd, see the s3tools.org website  .

To configure s3cmd to use the JASMIN object store, you need to create and edit a ~/.s3cfg file. To access the my-os-tenancy-o tenancy (where “my-os- tenancy-o” needs to be replaced with your tenancy name), the following should be in the ~/.s3cfg file:

access_key = <access key generated above>
host_base = my-os-tenancy-o.s3.jc.rl.ac.uk
host_bucket = my-os-tenancy-o.s3.jc.rl.ac.uk
secret_key = <secret key generated above>
use_https = False
signature_v2 = False

or, from an external tenancy or locations outside of JASMIN:

access_key = <access key generated above>
host_base = my-os-tenancy-o.s3-ext.jc.rl.ac.uk
host_bucket = my-os-tenancy-o.s3-ext.jc.rl.ac.uk
secret_key = <secret key generated above>
use_https = True
signature_v2 = False

To see which commands can be used with s3cmd, type:

s3cmd -h

To list a tenancy’s buckets:

s3cmd ls

To list the contents of a bucket:

s3cmd ls s3://<bucket_name>

Make a new bucket:

s3cmd mb s3://<bucket_name>

s3cmd uses PUT and GET nomenclature for copying files to and from the object store.
To copy a file to a bucket in the object store:

s3cmd put <file name> s3://<bucket_name>

To copy a file from a bucket in the object store to the file system:

s3cmd get s3://<bucket_name>/<object_name> <file_name>

For more commands and ways of using s3cmd, see the s3tools website  .

Using the MinIO client  

The MinIO Client is a command line tool to connect to object stores (among other types of file storage) and interface with it as you would with a UNIX filesystem. As such, many of the UNIX file management commands found in standard installations of the OS are found within this client ( ls, cat, cp, rm for example).

There are a number of ways to install this client as shown in the quickstart guide  . Methods include: docker, Homebrew for macOS, wget for Linux and instructions for Windows. Follow these steps to get the client installed on the relevant system.

MinIO Client is not installed on JASMIN, but users can download and install it to their own user space, following the instructions for “64-bit Intel” (linux- amd64) in the MinIO quickstart guide. Below is an example to install it into the bin directory in your user space

mkdir ~/bin
wget https://dl.min.io/client/mc/release/linux-amd64/mc ~/bin
chmod u+x ~/bin/mc

You can then add the ~/bin directory to the PATH environment variable in your ~/.bashrc file to allow mc to be accessed from anywhere on JASMIN.

# User specific aliases and functions
PATH=$PATH:$HOME/bin

To configure the client with the JASMIN object store, create an access key and secret as documented above and insert them into the command:

mc config host add [ALIAS] [S3-ENDPOINT] [TOKEN] [S3 SECRET KEY]

The ALIAS is the name you’ll reference the object store when using the client. To demonstrate, if the alias was set to “jasmin-store”, displaying a specific bucket in the object store would be done in the following way:

mc ls jasmin-store/my-bucket

The commands available in the client are documented in the quickstart guide (linked above). Copying an object from one place to another is very similar to a UNIX filesystem:

mc cp jasmin-store/my-bucket/object-1 jasmin-store/different-bucket/

From Python  

One method of accessing the object store from Python is using s3fs  . This library builds on botocore  but abstracts a lot of the complexities away. There are three main types of object in this library: S3FileSystem  , S3File  and S3Map  . The filesystem object is used to configure a connection to the object store. Note: it’s strongly recommended to store the endpoint, token and secret outside of the Python file, either using environment variables or an external file. This object can be used for lots of the operations which can be done MinIO:

with open('jasmin_object_store_credentials.json') as f:
    jasmin_store_credentials = json.load(f)

    jasmin_s3 = s3fs.S3FileSystem(
        anon=False, secret=jasmin_store_credentials['secret'],
        key=jasmin_store_credentials['token'],
        client_kwargs={'endpoint_url': jasmin_store_credentials['endpoint_url']}
    )

    my_object_size = jasmin_s3.du('my-bucket/object-1')

Please note in the example above, the jasmin_object_store_credentials.json file would look along the lines of:

{
    "token": "<access key generated above>",
    "secret": "<secret key generated above>",
    "endpoint_url": "http://my-os-tenancy-o.s3.jc.rl.ac.uk"
}

or, from an external tenancy or locations outside of JASMIN:

{
    "token": "<access key generated above>",
    "secret": "<secret key generated above>",
    "endpoint_url": "https://my-os-tenancy-o.s3-ext.jc.rl.ac.uk"
}

S3File is used for dealing with individual files on the object store within Python. These objects can read and written to and from the store:

file_object = s3fs.S3File(jasmin_s3, 'my-bucket/object-1', mode='rb')
# refresh can be set to True to disable metadata caching
file_metadata = file_object.metadata(refresh=False)

# Writing data to variable in Python
file_object.write(data)
# Data will only be written to the object store if flush() is used. This can be executed in S3FS source code if the buffer >= the blocksize
file_object.flush()

S3Map is very useful when using xarray  to open a number of data files (netCDF4 for example), and turn them into the zarr format ready to be stored as objects on the store. The function for this can store a .zarr file in a POSIX filesystem, or can be streamed directly to an object store. These datasets can then be opened back into Python:

xarray.open_mfdataset(filepath_list, engine=netcdf4)
s3_store = s3fs.S3Map('my-bucket/zarr-data', s3=jasmin_s3)
dataset.to_zarr(store=s3_store, mode='w')

# Reopening the dataset from object store using xarray
xarray.open_zarr(s3_store, consolidated=True)