Module `Async_durable`Source

Durable is designed to help recover from simple errors when using mutable data types that silently fail and can be easily rebuilt or created anew. A clear candidate is Rpc.Connection.t.

Durable and Persistent_connection have overlapping functionality when Durable is used for an Rpc.Connection.t. Consider using Durable if you want out-of-the-box support for Durable Pipe and State RPC connections, or if you prefer the with_ based interface, which returns connection level errors to the calling code and avoids the complexities that can arise from Deferreds that never become determined.

Sourcetype 'a t

Source

val create : 
  to_create:(unit -> 'a Async_kernel.Deferred.Or_error.t) ->
  is_broken:('a -> bool) ->
  ?to_rebuild:('a -> 'a Async_kernel.Deferred.Or_error.t) ->
  unit ->
  'a t

to_create tells the Durable how to build a fresh 'a value. If to_create raises, the exception is treated as if an Error was returned. If to_create needs to fail permanently when exceptions occur, then consider using Scheduler.within' ~monitor:Monitor.main inside of to_create, so that the exceptions go to a monitor that will abend the app.

is_broken tests whether the current 'a value can be used. It should return true when you want the Durable to attempt to rebuild or recreate the 'a.

to_rebuild Is called on the broken 'a. It should return a "fixed" 'a.

When the function with_ below is called, it uses is_broken to test if the current Durable value is broken. If so, it calls either to_create or to_rebuild. If to_rebuild is None (as in the default case), the Durable will try to create a fresh value with to_create.

create does not create the Durable value. The first call to to_create will be made on the first use of with_.

Source

val create_or_fail : 
  to_create:(unit -> 'a Async_kernel.Deferred.Or_error.t) ->
  is_broken:('a -> bool) ->
  ?to_rebuild:('a -> 'a Async_kernel.Deferred.Or_error.t) ->
  unit ->
  'a t Core.Or_error.t Async_kernel.Deferred.t

create_or_fail immediately calls to_create, returning an error if that first attempt fails. This function will also return an error if the initial durable value is broken.

Source

val with_ : 
  'a t ->
  f:('a -> 'b Async_kernel.Deferred.Or_error.t) ->
  'b Async_kernel.Deferred.Or_error.t

with_ applies the given function to the Durable value if is_broken returns false. If is_broken return true, it first calls to_create or to_rebuild. This function will return an error if either to_create or to_rebuild returns an error, or if the rebuilt or recreated durable value is broken. is_broken is checked immediately before calling f.

We will only make one attempt to rebuild a broken value. If a call to to_rebuild returns Error _, we will drop the previously built value. The next call to with_ will call to_create.

with_ will raise if f raises.

Sourceval is_intact_bus : 'a t -> (bool -> unit) Bus.Read_only.t

is_intact exposes whether the Durable value is in a valid state (i.e. it has been built and it is not currently broken).

Sourcemodule Subscription : sig ... end

Sourcemodule Pipe_rpc : sig ... end

This module is designed to help processess maintain update subscriptions that will automatically recover from lost connections. It exposes to the client when the subscription has been lost or recovered, so the client can choose how to handle a lost connection.

Sourcemodule State_rpc : sig ... end

This module is designed to help processess maintain state RPCs that will automatically recover from lost connections. It exposes to the client when the subscription has been lost or recovered, so the client can choose how to handle a lost connection.

package async_durable

Module Async_durableSource

Module `Async_durable`Source