package hack_parallel
Parallel and shared memory library
Install
Dune Dependency
Authors
Maintainers
Sources
1.0.1.tar.gz
md5=ba7c72bc207e326b72e294fc76f6ad2c
sha512=5020d47f97bea2f88e2a40411894d03232a7f2282606926c93c7d4c96d72e94a966be852897a9b16f7e0893ba376512045abb9d93020a7c03c3def4f3d918f8e
doc/src/hack_parallel.procs/worker.ml.html
Source file worker.ml
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(** * Copyright (c) 2015, Facebook, Inc. * All rights reserved. * * This source code is licensed under the BSD-style license found in the * LICENSE file in the "hack" directory of this source tree. An additional grant * of patent rights can be found in the PATENTS file in the same directory. * *) open Hack_core (***************************************************************************** * Module building workers * * A worker is a subprocess executing an arbitrary function * * You should first create a fixed amount of workers and then use those * because the amount of workers is limited and to make the load-balancing * of tasks better (cf multiWorker.ml) * * On Unix, we "spawn" workers when initializing Hack. Then, this * worker, "fork" a slave for each incoming request. The forked "slave" * will die after processing a single request. * * On Windows, we do not "prespawn" when initializing Hack, but we just * allocate all the required information into a record. Then, we * spawn a slave for each incoming request. It will also die after * one request. * * A worker never handle more than one request at a time. * *****************************************************************************) exception Worker_exited_abnormally of int * Unix.process_status exception Worker_oomed exception Worker_busy exception Worker_killed type send_job_failure = | Worker_already_exited of Unix.process_status | Other_send_job_failure of exn exception Worker_failed_to_send_job of send_job_failure (* Should we 'prespawn' the worker ? *) let use_prespawned = not Sys.win32 (* The maximum amount of workers *) let max_workers = 1000 (***************************************************************************** * The job executed by the worker. * * The 'serializer' is the job continuation: it is a function that must * be called at the end of the request ir order to send back the result * to the master (this is "internal business", this is not visible outside * this module). The slave will provide the expected function. * cf 'send_result' in 'slave_main'. * *****************************************************************************) type request = Request of (serializer -> unit) and serializer = { send: 'a. 'a -> unit } and void (* an empty type *) type call_wrapper = { wrap: 'x 'b. ('x -> 'b) -> 'x -> 'b } (***************************************************************************** * Everything we need to know about a worker. * *****************************************************************************) type t = { id: int; (* Simple id for the worker. This is not the worker pid: on Windows, we spawn a new worker for each job. *) (* The call wrapper will wrap any workload sent to the worker (via "call" * below) before invoking the workload. * * That is, when calling the worker with workload `f x`, it will be wrapped * as `wrap (f x)`. * * This allows universal handling of workload at the time we create the actual * workers. For example, this can be useful to handle exceptions uniformly * across workers regardless what workload is called on them. *) call_wrapper: call_wrapper; (* Sanity check: is the worker still available ? *) mutable killed: bool; (* Sanity check: is the worker currently busy ? *) mutable busy: bool; (* On Unix, a reference to the 'prespawned' worker. *) prespawned: (void, request) Daemon.handle option; (* On Windows, a function to spawn a slave. *) spawn: unit -> (void, request) Daemon.handle; } (***************************************************************************** * The handle is what we get back when we start a job. It's a "future" * (sometimes called a "promise"). The scheduler uses the handle to retrieve * the result of the job when the task is done (cf multiWorker.ml). * *****************************************************************************) type 'a handle = 'a delayed ref and 'a delayed = | Processing of 'a slave | Cached of 'a | Failed of exn and 'a slave = { worker: t; (* The associated worker *) slave_pid: int; (* The actual slave pid *) (* The file descriptor we might pass to select in order to wait for the slave to finish its job. *) infd: Unix.file_descr; (* A blocking function that returns the job result. *) result: unit -> 'a; } (***************************************************************************** * Entry point for spawned worker. * *****************************************************************************) let slave_main ic oc = let start_user_time = ref 0.0 in let start_system_time = ref 0.0 in let send_result data = let tm = Unix.times () in let end_user_time = tm.Unix.tms_utime +. tm.Unix.tms_cutime in let end_system_time = tm.Unix.tms_stime +. tm.Unix.tms_cstime in Measure.sample "worker_user_time" (end_user_time -. !start_user_time); Measure.sample "worker_system_time" (end_system_time -. !start_system_time); let stats = Measure.serialize (Measure.pop_global ()) in let s = Marshal.to_string (data,stats) [Marshal.Closures] in let len = String.length s in if len > 10 * 1024 * 1024 (* 10 MB *) then begin Hh_logger.log "WARNING: you are sending quite a lot of data (%d bytes), \ which may have an adverse performance impact. If you are sending \ closures, double-check to ensure that they have not captured large \ values in their environment." len; Printf.eprintf "%s" (Printexc.raw_backtrace_to_string (Printexc.get_callstack 100)); end; Daemon.output_string oc s; Daemon.flush oc in try Measure.push_global (); let Request do_process = Daemon.from_channel ic in let tm = Unix.times () in start_user_time := tm.Unix.tms_utime +. tm.Unix.tms_cutime; start_system_time := tm.Unix.tms_stime +. tm.Unix.tms_cstime; do_process { send = send_result }; exit 0 with | End_of_file -> exit 1 | SharedMem.Out_of_shared_memory -> Exit_status.(exit Out_of_shared_memory) | SharedMem.Hash_table_full -> Exit_status.(exit Hash_table_full) | SharedMem.Heap_full -> Exit_status.(exit Heap_full) | SharedMem.Sql_assertion_failure err_num -> let exit_code = match err_num with | 11 -> Exit_status.Sql_corrupt | 14 -> Exit_status.Sql_cantopen | 21 -> Exit_status.Sql_misuse | _ -> Exit_status.Sql_assertion_failure in Exit_status.exit exit_code | e -> let error_backtrace = Printexc.get_backtrace () in let error_str = Printexc.to_string e in Printf.printf "Exception: %s\n" error_str; EventLogger.log_if_initialized (fun () -> EventLogger.worker_exception error_str ); Printf.printf "Potential backtrace:\n%s" error_backtrace; exit 2 let win32_worker_main restore state (ic, oc) = restore state; slave_main ic oc let unix_worker_main restore state (ic, oc) = restore state; let in_fd = Daemon.descr_of_in_channel ic in if !Utils.profile then Utils.log := prerr_endline; try while true do (* Wait for an incoming job : is there something to read? But we don't read it yet. It will be read by the forked slave. *) let readyl, _, _ = Unix.select [in_fd] [] [] (-1.0) in if readyl = [] then exit 0; (* We fork a slave for every incoming request. And let it die after one request. This is the quickest GC. *) match Fork.fork() with | 0 -> slave_main ic oc | pid -> (* Wait for the slave termination... *) match snd (Unix.waitpid [] pid) with | Unix.WEXITED 0 -> () | Unix.WEXITED 1 -> raise End_of_file | Unix.WEXITED code -> Printf.printf "Worker exited (code: %d)\n" code; flush stdout; Pervasives.exit code | Unix.WSIGNALED x -> let sig_str = PrintSignal.string_of_signal x in Printf.printf "Worker interrupted with signal: %s\n" sig_str; exit 2 | Unix.WSTOPPED x -> Printf.printf "Worker stopped with signal: %d\n" x; exit 3 done; assert false with End_of_file -> exit 0 type 'a entry_state = 'a * Gc.control * SharedMem.handle type 'a entry = ('a entry_state, request, void) Daemon.entry let entry_counter = ref 0 let register_entry_point ~restore = incr entry_counter; let restore (st, gc_control, heap_handle) = restore st; SharedMem.connect heap_handle; Gc.set gc_control in let name = Printf.sprintf "slave_%d" !entry_counter in Daemon.register_entry_point name (if Sys.win32 then win32_worker_main restore else unix_worker_main restore) (************************************************************************** * Creates a pool of workers. * **************************************************************************) let workers = ref [] let current_worker_id = ref 0 (* Build one worker. *) let make_one spawn id = if id >= max_workers then failwith "Too many workers"; let prespawned = if not use_prespawned then None else Some (spawn ()) in let wrap f input = current_worker_id := id; f input in let worker = { call_wrapper = { wrap }; id; busy = false; killed = false; prespawned; spawn } in workers := worker :: !workers; worker (** Make a few workers. When workload is given to a worker (via "call" below), * the workload is wrapped in the call_wrapper. *) let make ~saved_state ~entry ~nbr_procs ~gc_control ~heap_handle = let spawn _log_fd = Unix.clear_close_on_exec heap_handle.SharedMem.h_fd; let handle = Daemon.spawn (Daemon.null_fd (), Unix.stdout, Unix.stderr) entry (saved_state, gc_control, heap_handle) in Unix.set_close_on_exec heap_handle.SharedMem.h_fd; handle in let made_workers = ref [] in for n = 1 to nbr_procs do made_workers := make_one spawn n :: !made_workers done; !made_workers let current_worker_id () = !current_worker_id (************************************************************************** * Send a job to a worker * **************************************************************************) let call w (type a) (type b) (f : a -> b) (x : a) : b handle = if w.killed then raise Worker_killed; if w.busy then raise Worker_busy; (* Spawn the slave, if not prespawned. *) let { Daemon.pid = slave_pid; channels = (inc, outc) } as h = match w.prespawned with | None -> w.spawn () | Some handle -> handle in (* Prepare ourself to read answer from the slave. *) let result () : b = match Unix.waitpid [Unix.WNOHANG] slave_pid with | 0, _ | _, Unix.WEXITED 0 -> let res : b * Measure.record_data = Daemon.input_value inc in if w.prespawned = None then Daemon.close h; Measure.merge ~from:(Measure.deserialize (snd res)) (); fst res | _, Unix.WEXITED i when i = Exit_status.(exit_code Out_of_shared_memory) -> raise SharedMem.Out_of_shared_memory | _, exit_status -> raise (Worker_exited_abnormally (slave_pid, exit_status)) in (* Mark the worker as busy. *) let infd = Daemon.descr_of_in_channel inc in let slave = { result; slave_pid; infd; worker = w; } in w.busy <- true; let request = let { wrap } = w.call_wrapper in Request (fun { send } -> send (wrap f x)) in (* Send the job to the slave. *) let () = try Daemon.to_channel outc ~flush:true ~flags:[Marshal.Closures] request with | e -> begin match Unix.waitpid [Unix.WNOHANG] slave_pid with | 0, _ -> raise (Worker_failed_to_send_job (Other_send_job_failure e)) | _, status -> raise (Worker_failed_to_send_job (Worker_already_exited status)) end in (* And returned the 'handle'. *) ref (Processing slave) (************************************************************************** * Read results from a handle. * This might block if the worker hasn't finished yet. * **************************************************************************) let is_oom_failure msg = (String_utils.string_starts_with msg "Subprocess") && (String_utils.is_substring "signaled -7" msg) let get_result d = match !d with | Cached x -> x | Failed exn -> raise exn | Processing s -> try let res = s.result () in s.worker.busy <- false; d := Cached res; res with | Failure (msg) when is_oom_failure msg -> raise Worker_oomed | exn -> s.worker.busy <- false; d := Failed exn; raise exn (***************************************************************************** * Our polling primitive on workers * Given a list of handle, returns the ones that are ready. * *****************************************************************************) type 'a selected = { readys: 'a handle list; waiters: 'a handle list; } let get_processing ds = List.rev_filter_map ds ~f:(fun d -> match !d with Processing p -> Some p | _ -> None) let select ds = let processing = get_processing ds in let fds = List.map ~f:(fun {infd; _} -> infd) processing in let ready_fds, _, _ = if fds = [] || List.length processing <> List.length ds then [], [], [] else Unix.select fds [] [] ~-.1. in List.fold_right ~f:(fun d { readys ; waiters } -> match !d with | Cached _ | Failed _ -> { readys = d :: readys ; waiters } | Processing s when List.mem ready_fds s.infd -> { readys = d :: readys ; waiters } | Processing _ -> { readys ; waiters = d :: waiters}) ~init:{ readys = [] ; waiters = [] } ds let get_worker h = match !h with | Processing {worker; _} -> worker | Cached _ | Failed _ -> invalid_arg "Worker.get_worker" (************************************************************************** * Worker termination **************************************************************************) let kill w = if not w.killed then begin w.killed <- true; match w.prespawned with | None -> () | Some handle -> Daemon.kill handle end let killall () = List.iter ~f:kill !workers
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