module Nfs:sig
..end
There are a few caveats compared to local file locks:
val create : ?message:string -> string -> unit Core_kernel.Std.Or_error.t
create ?message path
tries to create and lock the file at path
by creating a hard
link to path
.nfs_lock. The contents of path
will be replaced with a sexp
containing the caller's hostname and pid, and the optional message
.
Efforts will be made to release this lock when the calling program exits. But there
is no guarantee that this will occur under some types of program crash. If the
program crashes without removing the lock file an attempt will be made to clean up
on restart by checking the hostname and pid stored in the lockfile.
val create_exn : ?message:string -> string -> unit
create_exn ?message path
like create, but throws an exception when it fails to
obtain the lockval blocking_create : ?timeout:Time.Span.t -> ?message:string -> string -> unit
blocking_create ?message path
like create, but sleeps for 1 second between lock
attempts and does not return until it succeeds or timeout expires. Timeout defaults
to wait indefinitelyval critical_section : ?message:string -> string -> timeout:Time.Span.t -> f:(unit -> 'a) -> 'a
critical_section ?message ~timeout path ~f
wrap function f
(including exceptions
escaping it) by first locking (using Lock_file.Nfs.blocking_create
) and then unlocking the
given lock file.val get_hostname_and_pid : string -> (string * Core_kernel.Std.Pid.t) option
get_hostname_and_pid path
reads the lock file at path
and returns the hostname
and path in the file. Returns None
if the file cannot be read.val get_message : string -> string option
get_message path
reads the lock file at path
and returns the message in the
file. Returns None
if the file cannot be read.val unlock_exn : string -> unit
unlock_exn path
unlocks path
if path
was locked from the same host and the pid
in the file is either the current pid or not the pid of a running process. It will
raise if for some reason the lock at the given path cannot be unlocked, for example
if the lock is taken by somebody else that is still alive on the same box, or taken
by a process on a different host, or unix permissions issues, etc. This function
should be used only by programs that need to release their lock before exiting. If
releasing the lock can or should wait till the end of the running process, do not
call this function -- this library already takes care of releasing at exit all the
locks taken.val unlock : string -> unit Core_kernel.Std.Or_error.t