Sven Anderson <[email protected]> schrieb am Fr., 24. Nov. 2017 um 20:12 Uhr:
> TL;DR: Irmin_http.KV(Cohttp_mirage.Client)(Irmin.Contents.String) doesn’t
> work, because the default context uses an empty conduit without TCP
> support. How to do it right?
>
> I’m trying to play with the Irmin_http module (as it seems to be the
> closest option with MirageOS to what would otherwise be solved with simple
> remote queries to a SQL database from concurrent application instances).
>
> When I - instead of
> Irmin_mem.KV(Cohttp_mirage.Client)(Irmin.Contents.String), which works fine
> - use Irmin_http.KV(Cohttp_mirage.Client)(Irmin.Contents.String), the
> database queries fail with „TCP not supported“ errors. Looking at the code,
> I saw that the default context is with an empty conduit. Since Irmin_http
> doesn’t set a context when calling the Cohttp functions, it uses this
> default context I assume. So, how can I set the context from „outside“ in
> Cohttp before instantiating the Irmin_http with it?
>
In the meantime I managed to get Irmin_http work together
with Cohttp_mirage.Client. However, I wonder if it is the right way to do
it, and would like to hear comments about it. Since I figured that I need
runtime values for the Cohttp_mirage.Client, because the conduit and dns
resolver come in as arguments of the start function, I saw no other way
than to instantiate the modules in the code path, and I'm not sure if this
is an anti-pattern. Also, because I saw no way to replace the default
context of the conduit, I "monkey-patched" the module, by defining a new
module that includes Cohttp_mirage.Client and overwrites the call function
(which is the only one that Irmin_http seems to use) that brings its own
context. It looks now something like this:
let start _clock data certs http res_dns con =
let module Client =
struct
include Cohttp_mirage.Client
let call ?ctx:_ctx = call ~ctx:(ctx res_dns con)
end
in
let module Storage = Irmin_http.KV(Client)(Irmin.Contents.String) in
[...]
Is this acceptable code? Is it possible to solve it with globally defined
modules? Is there a nicer way to set the client context, if the http
functions are called in 3rd party code (Irmin_http) without setting a
context?
I also found a weird problem, that I will address in another email.
Cheers,
Sven
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