WIP: Port to Eio

Most of the complexity in the previous version was about managing the
child worker processes. With OCaml 5 this all goes away, and we just
use multiple domains instead.

Notes:

- opam is not thread-safe, so we need a lock around all opam file
  parsing operations. See ocaml/opam#5591

- We now load opam files lazily, which makes testing much faster.
  This reduces the time for `stress/stress.exe` from 97.4s to 11.5s for
  me.

- Epoch_lock is gone. It was just for managing sub-processes, but a
  simple Eio.Mutex.t will do now. This should also be much faster when
  switching between opam-repository commits.

- The main executable is now in the `bin` directory. Simplifies the dune
  file.

- test_service.ml is gone. It was only testing parsing of the
  communications between parent and child processes, which no longer
  exist. This also removed the need to functorise over opam repository.

- Default to `recommended_domain_count - 1` workers.

- Removed uses of (non-threadsafe) Str module.

TODO:

- Bring back parent/child pipe mode.

- Integrate worker mode?

- Add full stress test (i.e. solving for many packages over many hours).

.gitmodules

@@ -9,4 +9,7 @@
 [submodule "ocaml-dockerfile"]
 	path = ocaml-dockerfile
 	url = https://github.com/ocurrent/ocaml-dockerfile.git
-	branch = master
+	branch = master
+[submodule "opam-0install-solver"]
+	path = opam-0install-solver
+	url = https://github.com/ocaml-opam/opam-0install-solver.git

bin/dune

@@ -0,0 +1,7 @@
+(executable
+ (name main)
+ (package solver-service)
+ (public_name solver-service)
+ (preprocess
+  (pps ppx_deriving.std ppx_deriving_yojson))
+ (libraries solver-service logs.cli capnp-rpc-unix eio_main dune-build-info logs.fmt logs.threaded fmt.cli fmt.tty))

service/main.ml → bin/main.ml

@@ -1,7 +1,5 @@
-open Solver_service
-open Lwt.Syntax
-module Service = Service.Make (Opam_repository)
-module Worker_process = Internal_worker.Worker_process
+open Eio.Std
+module Service = Solver_service
 
 let pp_timestamp f x =
   let open Unix in
@@ -37,6 +35,7 @@ let setup_log style_renderer level =
   ()
 
 let export service ~on:socket =
+  let open Lwt.Syntax in
   let restore =
     Capnp_rpc_net.Restorer.single
       (Capnp_rpc_net.Restorer.Id.public "solver")
@@ -60,38 +59,36 @@ let export service ~on:socket =
   in
   crashed
 
-let start_server address ~n_workers =
+let start_server ~sw ~process_mgr ~domain_mgr address ~n_workers =
+  let open Lwt.Syntax in
+  Lwt_eio.run_lwt @@ fun () ->
   let config =
     Capnp_rpc_unix.Vat_config.create ~secret_key:(`File "server.pem") address
   in
   let service_id =
     Capnp_rpc_unix.Vat_config.derived_id config "solver-service"
   in
-  let create_worker commits =
-    let cmd =
-      ("", [| Sys.argv.(0); "--worker"; Remote_commit.list_to_string commits |])
-    in
-    Worker_process.create cmd
-  in
-  let* service = Service.v ~n_workers ~create_worker in
+  let service = Service.create ~sw ~domain_mgr ~process_mgr ~n_workers in
+  let service = Service.capnp_service service in
   let restore = Capnp_rpc_net.Restorer.single service_id service in
   let+ vat = Capnp_rpc_unix.serve config ~restore in
   Capnp_rpc_unix.Vat.sturdy_uri vat service_id
 
-let main () hash address sockpath n_workers =
-  match hash with
-  | Some commits_str -> Solver.main (Remote_commit.list_of_string_or_fail commits_str)
+let main () address sockpath n_workers =
+  Eio_main.run @@ fun env ->
+  Switch.run @@ fun sw ->
+  let process_mgr = env#process_mgr in
+  Lwt_eio.with_event_loop ~clock:env#clock @@ fun () ->
+  match address with
+  | Some address ->
+    (* Run with a capnp address as the endpoint *)
+    let uri = start_server ~sw ~process_mgr ~domain_mgr:env#domain_mgr address ~n_workers in
+    Fmt.pr "Solver service running at: %a@." Uri.pp_hum uri;
+    Fiber.await_cancel ()
   | None ->
-    Eio_main.run @@ fun env ->
-    Lwt_eio.with_event_loop ~clock:env#clock @@ fun () ->
-    Lwt_eio.run_lwt @@ fun () ->
-    match address with
-    | Some address ->
-      (* Run with a capnp address as the endpoint *)
-      let* uri = start_server address ~n_workers in
-      Fmt.pr "Solver service running at: %a@." Uri.pp_hum uri;
-      fst @@ Lwt.wait ()
-    | None ->
+    ignore (sockpath, export);
+    assert false
+(*
       let socket =
         match sockpath with
         | Some path ->
@@ -112,6 +109,7 @@ let main () hash address sockpath n_workers =
       in
       let* service = Service.v ~n_workers ~create_worker in
       export service ~on:socket
+*)
 
 (* Command-line parsing *)
 
@@ -122,15 +120,9 @@ let setup_log =
   Term.(
     const setup_log $ Fmt_cli.style_renderer ~docs () $ Logs_cli.level ~docs ())
 
-let worker_commits =
-  Arg.value
-  @@ Arg.opt Arg.(some string) None
-  @@ Arg.info ~doc:"The hash commits of the worker." ~docv:"COMMITS"
-       [ "worker" ]
-
 let internal_workers =
   Arg.value
-  @@ Arg.opt Arg.int 20
+  @@ Arg.opt Arg.int (Domain.recommended_domain_count () - 1)
   @@ Arg.info ~doc:"The number of sub-process solving requests in parallel"
        ~docv:"N" [ "internal-workers" ]
 
@@ -164,7 +156,6 @@ let cmd =
     Term.(
       const main
       $ setup_log
-      $ worker_commits
       $ address
       $ sockpath
       $ internal_workers)

dune

@@ -1,3 +1,3 @@
 (dirs :standard \ var)
 
-(vendored_dirs ocluster ocurrent ocaml-dockerfile)
+(vendored_dirs ocluster ocurrent ocaml-dockerfile opam-0install-solver)

examples/dune

@@ -4,6 +4,7 @@
  (names main submit)
  (package solver-service)
  (libraries
+  eio_main
   current_git
   capnp-rpc-unix
   solver-service-api

examples/main.ml

@@ -36,10 +36,11 @@ let opam_template arch =
 |}
     arch
 
-let get_vars ~ocaml_package_name ~ocaml_version ?arch () =
-  let+ vars =
-    Solver_service.Process.pread
-      ("", [| "opam"; "config"; "expand"; opam_template arch |])
+let get_vars ~process_mgr ~ocaml_package_name ~ocaml_version ?arch () =
+  Lwt_eio.run_eio @@ fun () ->
+  let vars =
+    Eio.Process.parse_out process_mgr Eio.Buf_read.take_all
+      ["opam"; "config"; "expand"; opam_template arch]
   in
   let json =
     match Yojson.Safe.from_string vars with
@@ -55,15 +56,16 @@ let get_vars ~ocaml_package_name ~ocaml_version ?arch () =
   in
   Result.get_ok @@ Solver_service_api.Worker.Vars.of_yojson json
 
-let get_opam_file pv =
-  Solver_service.Process.pread ("", [| "opam"; "show"; "--raw"; pv |])
+let get_opam_file ~process_mgr pv =
+  Lwt_eio.run_eio @@ fun () ->
+  Eio.Process.parse_out process_mgr Eio.Buf_read.take_all ["opam"; "show"; "--raw"; pv]
 
-let run_client ~package ~version ~ocaml_version ~opam_commit service =
+let run_client ~process_mgr ~package ~version ~ocaml_version ~opam_commit service =
   let pv = package ^ "." ^ version in
   let* platform =
-    get_vars ~ocaml_package_name:"ocaml-base-compiler" ~ocaml_version ()
+    get_vars ~process_mgr ~ocaml_package_name:"ocaml-base-compiler" ~ocaml_version ()
   in
-  let* opam_file = get_opam_file pv in
+  let* opam_file = get_opam_file ~process_mgr pv in
   let request =
     Solver_service_api.Worker.Solve_request.
       {
@@ -88,11 +90,14 @@ let run_client ~package ~version ~ocaml_version ~opam_commit service =
   | Error `Cancelled -> Fmt.failwith "Job Cancelled"
 
 let connect package version ocaml_version opam_commit uri =
-  Lwt_main.run
-    (let client_vat = Capnp_rpc_unix.client_only_vat () in
-     let sr = Capnp_rpc_unix.Vat.import_exn client_vat uri in
-     Capnp_rpc_unix.with_cap_exn sr
-       (run_client ~package ~version ~ocaml_version ~opam_commit))
+  Eio_main.run @@ fun env ->
+  let process_mgr = env#process_mgr in
+  Lwt_eio.with_event_loop ~clock:env#clock @@ fun () ->
+  Lwt_eio.run_lwt @@ fun () ->
+  let client_vat = Capnp_rpc_unix.client_only_vat () in
+  let sr = Capnp_rpc_unix.Vat.import_exn client_vat uri in
+  Capnp_rpc_unix.with_cap_exn sr
+    (run_client ~process_mgr ~package ~version ~ocaml_version ~opam_commit)
 
 open Cmdliner
 

service/dune

@@ -1,36 +1,14 @@
 (library
  (name solver_service)
  (public_name solver-service)
- (preprocess
-  (pps ppx_deriving.std ppx_deriving_yojson))
  (libraries
-  eio_main
+  eio
   lwt_eio
   solver-service-api
   ppx_deriving_yojson.runtime
+  prometheus-app
   opam-0install
-  capnp-rpc-unix
+  capnp-rpc-net
   git-unix
   ocaml-version
-  dune-build-info
-  str
-  fmt.cli
-  fmt.tty)
- (modules
-  epoch_lock
-  git_context
-  opam_repository
-  opam_repository_intf
-  process
-  remote_commit
-  internal_worker
-  service
-  solver
-  solver_service))
-
-(executable
- (name main)
- (package solver-service)
- (public_name solver-service)
- (libraries solver-service logs.cli)
- (modules main))
+  ocluster-api))