[MirageOS-devel] rfc: irmin + mirageos talk submission

[Mindy <mindy@xxxxxxxxxxxxxxxxxxx>]

Hi folks,

Some of us have put together a talk submission for the OCaml Workshop in 
September (alongside ICFP).  In the ~20 minutes remaining before the 
submission deadline, I'd be happy to hear anyone's feedback on the 
proposal.
General thoughts on the subject would also be welcome, as we have lots 
of time to explore this space and think about what to address in more 
depth if the talk is accepted :)
Proposal below:

It is traditionally challenging to build and debug reliable distributed 
applications due to the difficulty of reasoning about the ordering and 
failure modes of remote communications.  In this talk, we will describe 
an alternative to network simulators and emulators by using several 
OCaml libraries to build a persistent, interactive network stack from 
off-the-shelf OCaml libraries that are present in OPAM.
Irmin (the database that never forgets) presents users with an API 
allowing DVCS-like access to ordinary program data [1].  Using Irmin, we 
can construct data structures that are commonly found in network 
protocols (such as distributed hash tables), and manipulate them across 
nodes via DVCS pull/push/merge operations.
MirageOS [2] is a library operating system written in OCaml where all 
structures are ordinary program data, even ones that normally live deep 
within the kernel in traditional architectures.  Mirage provides a 
network stack that provides a complete TCP/IP implementation, including 
Ethernet, ARP, ICMP, IP, UDP, TCP, and DHCP.
We combine both Irmin and the existing MirageOS stack to build a 
persistent network stack. With Irmin, we can manage updates for 
structures like the ARP cache, which is mutated by both incoming network 
traffic and the passage of time, with clear semantics, history, and 
conflict resolution.  It also becomes possible, through Irmin's sync 
interface or Git filesystem backend, to make this data persistent in a 
consistent and convenient way.
Using Irmin's Git filesystem backend, it's also possible to interact 
with this data with Git tools.  One can, for example, examine the 
history of the cache with `gitk` and observe whether an expiration 
thread is correctly removing old entries on its branch.  It's even 
possible to make edits to the serialized cache data and commit them from 
the command line, resulting in live changes to the cache!
From an implemented example of an ARP cache, we'll motivate further 
possibilities in more complicated protocols and their related data 
stores, including TCP and its associated state.  We will also discuss 
potential future uses in the context of many MirageOS unikernels running 
in a hypervisor, including coordination that traditionally uses 
broadcast traffic across a local area network.
A fuller blog post series on this work is available online [3].

[1] http://irmin.io
[2] https://mirage.io
[3] 
http://somerandomidiot.com/blog/2015/04/24/what-a-distributed-version-controlled-ARP-cache-gets-you/
Thanks,
Mindy

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