I am currently working on MoanaML.
My recent challenge was to code a backend based on Mirage/Irmin.
Ok, first thing first, what is Moana:
Now, what is Irmin:
Just to recap, at the moment, MoanaML contains:
To code Irmin-based backed we need to implement two Moana signatures, namely STORE and GRAPH
I am a noobie when it comes to Irmin, I am still trying to figure out all of its functionalities so proceed with caution :)
I recommend reading this blog post to get a better understanding on Irmin, also I found this short paper very insightful. For better code understanding, make sure you familiarise yourself with the lwt library.
So to use Irmin, I chose to use blocks of type String, just because it is provided; to have different types of values you need to implement your own IrminContents signature. This, from my understanding, involves letting Irmin know how to merge your values.
Ultimately, I want to use Irmin to store Moana tuples, not strings, so I will have to implement the Contents signature. For now, I convert Moana tuples into JSON string and store them in Irmin.
Now to the code...
Following Irmin examples, I first implemented t_of_view and view_to_t functions to convert list of tuples to view and take list of tuples from the view, respectively. I later use these functions to store the views inside Irmin.
The cool thing about Irmin that all my data is stored in git.
Thanks to this:
You can also visualise it!
My recent challenge was to code a backend based on Mirage/Irmin.
Ok, first thing first, what is Moana:
Moana, an information-centric middleware for distributed services and applications. Moana offers a shared graph-based storage abstraction through which applications communicate with each other by appending and observing the shared graph.MoanaML is an implementation of the Moana primitives in OCaml.
Moana supports two basic operations of ADD and MAP; add allows an application to persistently extend the global graph, and map provides a dynamically maintained mapping of the global graph to an application specific, internal sub-graph.
Now, what is Irmin:
Irmin is a distributed database with built-in snapshot, branch and revert mechanisms. It is designed to use a large variety of backends, although it is optimized for append-only store.
Just to recap, at the moment, MoanaML contains:
- Moana mli signature for Moana graph and the backend
- Tuple list-based based tuple store
- one can add tuples and run simple graph-queries on it
To code Irmin-based backed we need to implement two Moana signatures, namely STORE and GRAPH
I am a noobie when it comes to Irmin, I am still trying to figure out all of its functionalities so proceed with caution :)
I recommend reading this blog post to get a better understanding on Irmin, also I found this short paper very insightful. For better code understanding, make sure you familiarise yourself with the lwt library.
So to use Irmin, I chose to use blocks of type String, just because it is provided; to have different types of values you need to implement your own IrminContents signature. This, from my understanding, involves letting Irmin know how to merge your values.
Ultimately, I want to use Irmin to store Moana tuples, not strings, so I will have to implement the Contents signature. For now, I convert Moana tuples into JSON string and store them in Irmin.
Now to the code...
Following Irmin examples, I first implemented t_of_view and view_to_t functions to convert list of tuples to view and take list of tuples from the view, respectively. I later use these functions to store the views inside Irmin.
The cool thing about Irmin that all my data is stored in git.
Thanks to this:
module Git =
IrminGit.FS(struct let root = Some "/tmp/irmin/moana"
let bare = true
end)
(* Values are Strings * *)
module Store = Git.Make(IrminKey.SHA1)(IrminContents.String)(IrminTag.String)
You can also visualise it!
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