Pipeline language for keeping things up-to-date
Module Current
type 'a or_error = ( 'a, [ `Msg of string ] ) result
module Level : sig ... end

Each operation has a level, giving an estimate of the cost or risk of the operation. When testing a pipeline, it can be useful to set a maximum level, or to require confirmation for more risky operations.

module Config : sig ... end
type job_id = string
class type actions = object ... end
module Metadata : sig ... end

Metadata associated with primitive terms.

module Primitive : sig ... end

An OCurrent pipeline is made up of primitive operations. A primitive is roughly the content of a single box in the diagram.

include Current_term.S.TERM with type metadata := Metadata.t and type 'a primitive := 'a Primitive.t
type 'a t

An 'a t is a term that produces a value of type 'a.

type description

Information about operations hidden behind a bind.

val active : -> 'a t

active x is a term indicating that the result is not determined yet.

val return : ?label:string -> 'a -> 'a t

return x is a term that immediately succeeds with x.

  • parameter label

    Label the constant in the diagrams.

val fail : string -> 'a t

fail m is a term that immediately fails with message m.

val state : ?hidden:bool -> 'a t -> ( 'a, [ `Active of | `Msg of string ] ) result t

state t always immediately returns a successful result giving the current state of t.

  • parameter hidden

    If true, don't show a separate node for this on the diagrams.

val catch : ?hidden:bool -> 'a t -> 'a Current_term.S.or_error t

catch t successfully returns Ok x if t evaluates successfully to x, or successfully returns Error e if t fails with error e. If t is active then catch t will be active too.

  • parameter hidden

    If true, don't show a separate node for this on the diagrams.

val ignore_value : 'a t -> unit t

ignore_value x is map ignore x.

val of_output : 'a Current_term.Output.t -> 'a t

of_output x is a returned, failed or active term.

Sequencing terms

Applicative operations

val map : ( 'a -> 'b ) -> 'a t -> 'b t

map f x is a term that runs x and then transforms the result using f.

val map_error : ( string -> string ) -> 'a t -> 'a t

map_error f x is a term that runs x and then transforms the error string (if any) using f.

val pair : 'a t -> 'b t -> ('a * 'b) t

pair a b is the pair containing the results of evaluating a and b (in parallel).

val list_map : (module Current_term.S.ORDERED with type t = 'a) -> ?collapse_key:string -> ?label:string -> ( 'a t -> 'b t ) -> 'a list t -> 'b list t

list_map (module T) f xs adds f to the end of each input term and collects all the results into a single list.

  • parameter T

    Used to display labels for each item, and to avoid recreating pipelines unnecessarily.

  • parameter collapse_key

    If given, each element is wrapped with collapse.

val list_iter : (module Current_term.S.ORDERED with type t = 'a) -> ?collapse_key:string -> ?label:string -> ( 'a t -> unit t ) -> 'a list t -> unit t

Like list_map but for the simpler case when the result is unit.

val list_seq : 'a t list -> 'a list t

list_seq x evaluates to a list containing the results of evaluating each element in x, once all elements of x have successfully completed.

val option_map : ?label:string -> ( 'a t -> 'b t ) -> 'a option t -> 'b option t

option_map f x is a term that evaluates to Some (f y) if x evaluates to Some y, or to None otherwise.

val option_seq : 'a t option -> 'a option t

option_seq None is Current.return None and option_seq (Some x) is some x. This is useful for handling optional arguments that are currents.

val all : unit t list -> unit t

all xs is a term that succeeds if every term in xs succeeds.

val all_labelled : (string * unit t) list -> unit t

all xs is a term that succeeds if every term in xs succeeds. The labels are used if some terms fail, to indicate which ones are failing.

val gate : on:unit t -> 'a t -> 'a t

gate ~on:ctrl x is the same as x, once ctrl succeeds.

Note: gate does not delay x; it only delays whatever you put after the gate. e.g.

let binary = build src in
let tests_ok = test binary in
binary |> gate ~on:tests_ok |> deploy

Diagram control

val collapse : key:string -> value:string -> input:_ t -> 'a t -> 'a t

collapse ~key ~value ~input t is a term that behaves just like t, but when shown in a diagram it can be expanded or collapsed. When collapsed, it is shown as "input -> +" and the user can expand it to show t instead. The idea is that input is a dependency of t and the "+" represents everything in t after that. key and value are used as the parameters (e.g. in a URL) to control whether this is expanded or not. For example collapse ~key:"repo" ~value:"mirage/mirage-www" ~input:repo (process repo) Note: list_map ~collapse_key provides an easy way to use this.

val with_context : _ t -> ( unit -> 'a t ) -> 'a t

with_context ctx f is the term f (), where f is evaluated in context ctx. This means that ctx will be treated as an input to all terms created by f in the diagrams.

Monadic operations

N.B. these operations create terms that cannot be statically analysed until after they are executed.

val bind : ?info:description -> ( 'a -> 'b t ) -> 'a t -> 'b t

bind f x is a term that first runs x to get y and then behaves as the term f y. Static analysis cannot look inside the f function until x is ready, so using bind makes static analysis less useful. You can use the info argument to provide some information here.


val primitive : info:description -> ( 'a -> 'b Primitive.t ) -> 'a t -> 'b t

primitive ~info f x is a term that evaluates f on each new value of x. This is used to provide the primitive operations, which can then be combined using the other combinators in this module. info is used to label the operation in the diagram.

val component : ( 'a, Format.formatter, unit, description ) format4 -> 'a

component name is used to annotate binds, so that the system can show a name for the operations hidden inside the bind's function. name is used as the label for the bind in the generated dot diagrams. For convenience, name can also be a format string.

module Syntax : sig ... end
module Monitor : sig ... end

A monitor is an input pipeline stage that can watch for external events.

type 'a term = 'a t

An alias of t to make it easy to refer to later in this file.

module Analysis : Current_term.S.ANALYSIS with type 'a term := 'a t and type metadata := Metadata.t

Diagram generation, introspection, and statistics.

module Var (T : Current_term.S.T) : sig ... end

Variable pipeline inputs.

val state_dir : string -> Fpath.t

state_dir name is a directory under which state (build results, logs) can be stored. name identifies the sub-component of OCurrent, each of which gets its own subdirectory.

module String : sig ... end
module Unit : sig ... end
module Switch : sig ... end

Like Lwt_switch, but the cleanup functions are called in sequence, not in parallel.

module Pool : sig ... end

Resource pools, to control how many jobs can use a resource at a time. To use a pool within a job, pass the pool to Job.start or call Job.use_pool.

module Job : sig ... end

Jobs with log files. This is mostly an internal interface - use Current_cache instead.

module Engine : sig ... end

The main event loop.

module Process : sig ... end

Helper functions for spawning sub-processes.

module Db : sig ... end

Access to the sqlite database.

module Log_matcher : sig ... end

Analysing job logs.