Ambry

Ambry is a distributed object store that supports storage of trillion of small immutable objects (50K -100K) as well as billions of large objects. It was specifically designed to store and serve media objects in web companies. However, it can be used as a general purpose storage system to store DB backups, search indexes or business reports. The system has the following characterisitics:

Highly available and horizontally scalable
Low latency and high throughput
Optimized for both small and large objects
Cost effective
Easy to use

Documentation

Detailed documentation is available at https://github.com/linkedin/ambry/wiki

Getting Started

Step 1: Download the code, build it and prepare for deployment.

To get the latest code and build it, do

$ git clone git@github.com:linkedin/ambry.git
$ cd ambry
$ ./gradlew allJar
$ cd target
$ mkdir logs

Ambry uses files that provide information about the cluster to route requests from the frontend to servers and for replication between servers. We will use a simple clustermap that contains a single server with one partition. The partition will use /tmp as the mount point.

Step 2: Deploy a server.

$ nohup java -Dlog4j.configuration=file:../config/log4j.properties -jar ambry.jar --serverPropsFilePath ../config/server.properties --hardwareLayoutFilePath ../config/HardwareLayout.json --partitionLayoutFilePath ../config/PartitionLayout.json > logs/server.log &

Through this command, we configure the log4j properties, provide the server with configuration options and cluster definitions and redirect output to a log. Note down the process ID returned (serverProcessID) because it will be needed for shutdown.
The log will be available at logs/server.log. Alternately, you can change the log4j properties to write the log messages to a file instead of standard output.

Step 3: Deploy a frontend.

$ nohup java -Dlog4j.configuration=file:../config/log4j.properties -cp "*" com.github.ambry.frontend.AmbryFrontendMain --serverPropsFilePath ../config/frontend.properties --hardwareLayoutFilePath ../config/HardwareLayout.json --partitionLayoutFilePath ../config/PartitionLayout.json > logs/frontend.log &

Note down the process ID returned (frontendProcessID) because it will be needed for shutdown. Make sure that the frontend is ready to receive requests.

$ curl http://localhost:1174/healthCheck
GOOD

The log will be available at logs/frontend.log. Alternately, you can change the log4j properties to write the log messages to a file instead of standard output.

Step 4: Interact with Ambry !

We are now ready to store and retrieve data from Ambry. Let us start by storing a simple image. For demonstration purposes, we will use an image demo.gif that has been copied into the target folder.

POST

$ curl -i -H "x-ambry-blob-size : `wc -c demo.gif | xargs | cut -d" " -f1`" -H "x-ambry-service-id : CUrlUpload"  -H "x-ambry-owner-id : `whoami`" -H "x-ambry-content-type : image/gif" -H "x-ambry-um-description : Demonstration Image" http://localhost:1174/ --data-binary @demo.gif
HTTP/1.1 201 Created
Location: AmbryID
Content-Length: 0

The CUrl command creates a POST request that contains the binary data in demo.gif. Along with the file data, we provide headers that act as blob properties. These include the size of the blob, the service ID, the owner ID and the content type.
In addition to these properties, Ambry also has a provision for arbitrary user defined metadata. We provide x-ambry-um-description as user metadata. Ambry does not interpret this data and it is purely for user annotation. The Location header in the response is the blob ID of the blob we just uploaded.

GET - Blob Info

Now that we stored a blob, let us verify some properties of the blob we uploaded.

$ curl -i http://localhost:1174/AmbryID/BlobInfo
HTTP/1.1 200 OK
x-ambry-blob-size: {Blob size}
x-ambry-service-id: CUrlUpload
x-ambry-creation-time: {Creation time}
x-ambry-private: false
x-ambry-content-type: image/gif
x-ambry-owner-id: {username}
x-ambry-um-desc: Demonstration Image
Content-Length: 0

GET - Blob

Now that we have verified that Ambry returns properties correctly, let us obtain the actual blob.

$ curl http://localhost:1174/AmbryID > demo-downloaded.gif
$ diff demo.gif demo-downloaded.gif 
$

This confirms that the data that was sent in the POST request matches what we received in the GET. If you would like to see the image, simply point your browser to http://localhost:1174/AmbryID and you should see the image that was uploaded !

DELETE

Ambry is an immutable store and blobs cannot be updated but they can be deleted in order to make them irretrievable. Let us go ahead and delete the blob we just created.

$ curl -i -X DELETE http://localhost:1174/AmbryID
HTTP/1.1 202 Accepted
Content-Length: 0

You will no longer be able to retrieve the blob properties or data.

$ curl -i http://localhost:1174/AmbryID/BlobInfo
HTTP/1.1 410 Gone
Content-Type: text/plain; charset=UTF-8
Content-Length: 17
Connection: close

Failure: 410 Gone

Step 5: Stop the frontend and server.

$ kill -15 frontendProcessID
$ kill -15 serverProcessID

You can confirm that the services have been shut down by looking at the logs.

Additional information:

In addition to the simple APIs demonstrated above, Ambry provides support for GET of only user metadata and HEAD. In addition to the POST of binary data that was demonstrated, Ambry also supports POST of multipart/form-data via CUrl or web forms. Other features of interest include:

Time To Live (TTL): During POST, a TTL in seconds can be provided through the addition of a header named x-ambry-ttl. This means that Ambry will stop serving the blob after the TTL has expired. On GET, expired blobs behave the same way as deleted blobs.
Private: During POST, providing a header named x-ambry-private with the value true will mark the blob as private. API behavior can be configured based on whether a blob is public or private.