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https://github.com/skx/sos

Simple Object Storage (I wish I could call it Steve's Simple Storage, or S3 ;)
https://github.com/skx/sos

blob-servers daemon golang replication storage

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Simple Object Storage (I wish I could call it Steve's Simple Storage, or S3 ;)

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README 

        
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# Simple Object Storage



This Simple Object Storage (SOS) project is a HTTP-based object-storage system which allows files to be uploaded, and later retrieved via HTTP.



Files can be replicated across a number of hosts to ensure redundancy, and increased availability in the event of hardware failure.



* [The design of the system](DESIGN.md).

* [Scaling to large numbers of objects](SCALING.md).

* [How replication works](REPLICATION.md).

* [The APIs we present, both internal and private](API.md).



## Installation



There are two ways to install this project from source, which depend on the version of the [go](https://golang.org/) version you're using.



If you just need the binaries you can find them upon the [project release page](https://github.com/skx/sos/releases).



### Source Installation go <=  1.11



If you're using `go` before 1.11 then the following command should fetch/update the project and install it upon your system:



     $ go get -u github.com/skx/sos



### Source installation go  >= 1.12



If you're using a more recent version of `go` (which is _highly_ recommended), you need to clone to a directory which is not present upon your `GOPATH`:



    git clone https://github.com/skx/sos

    cd sos

    go install



## Overview



You can read the [design overview](DESIGN.md) for more details, but the

core idea behind the implmentation  relies upon the notion of a

"blob server" - which is a very simple service which provides only the

following simple primitives:



* Store a particular chunk of binary data with a specific name.

* Given a name retrieve the chunk of binary data associated with it.

* Return a list of all known names.



The public API is built upon the top of that primitive, and both are

launched via the same command `sos`, by specifying the sub-command

to use:



     $ ./sos blob-server ...

     $ ./sos api-server ...



Here the first command launches a blob-server, which is the back-end for

storage, and the second command launches the public API server - which is

what your code/users should operate against.



If you launch `sos` with no arguments you'll see brief details of the

available subcommands.



## Quick Start



In an ideal deployment at least two hosts would be used:



* One host would run the public-server.

   * This allows uploads to be made, and later retrieved.

* Each of the two hosts would also run a blob-server.

   * The blob-servers provide the actual storage of the uploaded-objects.

   * The contents of these are replicated out of band.



We can simulate a deployment upon a single host for the purposes of testing.  You'll just need to make sure you have four terminals open to run the appropriate daemons.



First of all you'll want to launch a pair of blob-servers:



    $ sos blob-server -store data1 -port 4001

    $ sos blob-server -store data2 -port 4002



> **NOTE**: The storage-paths (`./data1` and `./data2` in the example above) is where the uploaded-content will be stored.  These directories will be created if missing.



In production usage you'd generally record the names of the blob-servers in a configuration file, either `/etc/sos.conf`, or `~/.sos.conf`, however they may also be specified upon the command line.



We'll then start the public/API-server ensuring that it knows about the blob-servers to store content in:



    $ sos api-server -blob-server http://localhost:4001,http://localhost:4002

    Launching API-server

    ..



Now you, or your code, can connect to the server and start uploading/downloading objects.  By default the following ports will be used by the `sos-server`:



|service           | port |

|----------------- | ---- |

| upload service   | 9991 |

| download service | 9992 |



Providing you've started all three daemons you can now perform a test upload with `curl`:



    $ curl -X POST --data-binary @/etc/passwd http://localhost:9991/upload

    {"id":"cd5bd649c4dc46b0bbdf8c94ee53c1198780e430","size":2306,"status":"OK"}



If all goes well you'll receive a JSON-response as shown, and you can use the ID which is returned to retrieve your object:



    $ curl http://localhost:9992/fetch/cd5bd649c4dc46b0bbdf8c94ee53c1198780e430

    ..

    $



> **NOTE**: The download service runs on a different port.  This is so that you can make policy decisions about uploads/downloads via your local firewall.



At the point you run the upload the contents will only be present on one of the blob-servers, chosen at random.  To ensure your data is replicated you need to (regularly) launch the replication utility:



    $ sos replicate -blob-server http://localhost:4001,http://localhost:4002 --verbose

	group - server

	   default - http://localhost:4001

	   default - http://localhost:4002

    Syncing group: default

       Group member: http://localhost:4001

       Group member: http://localhost:4002

       Object cd5bd649c4dc46b0bbdf8c94ee53c1198780e430 is missing on http://localhost:4001

         Mirroring cd5bd649c4dc46b0bbdf8c94ee53c1198780e430 from http://localhost:4002 to http://localhost:4001

            Fetching :http://localhost:4002/blob/cd5bd649c4dc46b0bbdf8c94ee53c1198780e430

            Uploading :http://localhost:4001/blob/cd5bd649c4dc46b0bbdf8c94ee53c1198780e430



## Meta-Data



When uploading objects it is often useful to store meta-data, such as the original name of the uploaded object, the owner, or some similar data.  For that reason any header you add to your upload with an `X-`prefix will be stored and returned on download.



As a special case the header `X-Mime-Type` can be used to set the returned `Content-Type` header too.



For example uploading an image might look like this:



    $ curl -X POST -H "X-Orig-Filename: steve.jpg" \

                   -H "X-MIME-Type: image/jpeg" \

                   --data-binary @/home/skx/Images/tmp/steve.jpg \

            http://localhost:9991/upload

    {"id":"20b30df22469e6d7617c7da6a457d4e384945a06","status":"OK","size":17599}



Downloading will result in the headers being set:



    $ curl -v http://localhost:9992/fetch/20b30df22469e6d7617c7da6a457d4e384945a06 >/dev/null

    ..

    < HTTP/1.1 200 OK

    < X-Orig-Filename: steve.jpg

    < Date: Fri, 27 May 2016 06:17:39 GMT

    < Content-Type: image/jpeg

    < Transfer-Encoding: chunked

    <

    { [data not shown]



## Production Usage



* The API service must be visible to clients, to allow downloads to be made.

    * Because the download service runs on port `9992` it is assumed that corporate firewalls would deny access.

    * We assume you'll configure an Apache/nginx/similar reverse-proxy to access the files via a host like `http://objects.example.com/`.



* It is assumed you might wish to restrict uploads to particular clients, rather than allow the world to make uploads.  The simplest way of doing this is to use your firewall to filter access to port `9991`.



* The blob-servers must be reachable by the host(s) running the API-service, but they should not be publicly visible.

    * If your blob-servers are exposed to the internet remote users could [use the API](API.md) to spider and download all your content.



* None of the servers need to be launched as root, because they don't bind to privileged ports, or require special access.

    * **NOTE**: [issue #6](https://github.com/skx/sos/issues/6) improved the security of the `blob-server` by invoking `chroot()`.  However `chroot()` will fail if the server is not launched as root, which is harmless.



* You can also read about scaling when your data is too large to fit upon a single `blob-server`:

   * [Read about scaling SoS](SCALING.md)



## Future Changes?



It would be possible to switch to using _chunked_ storage, for example breaking up each file that is uploaded into 128Mb sections and treating them as distinct.  The reason that is not done at the moment is because it relies upon state:



* The public server needs to be able to know that the file with a given ID is comprised of the following chunks of data:

    * `a5d606958533634fed7e6d5a79d6a5617252021f`

    * `038deb6940db2d0e7b9ee9bba70f3501a0667989`

    * `a7914eb6ff984f97c5f6f365d3d93961be2e8617`

    * `...`

* That data must be always kept up to date and accessible.



At the moment the API-server is stateless, so tracking that data is not possible.  It possible to imagine using [redis](http://redis.io/), or some other external database to record the data, but that increases the complexity of deployment.



## Github Setup



This repository is configured to run tests upon every commit, and when

pull-requests are created/updated.  The testing is carried out via

[.github/run-tests.sh](.github/run-tests.sh) which is used by the

[github-action-tester](https://github.com/skx/github-action-tester) action.



Releases are automated in a similar fashion via [.github/build](.github/build),

and the [github-action-publish-binaries](https://github.com/skx/github-action-publish-binaries) action.



## Questions?



Questions/Changes are most welcome; just report an issue.



Steve

 --