allow default_addprocs_params to be specialized on ClusterManager (JuliaLang/julia#38570)

I made this change to allow the set to be expanded for my own package, but I noticed this also helps unify JuliaLang/julia#38353 and existing ssh-only options.

Author: simonbyrne

docs/src/index.md

@@ -65,4 +65,5 @@ Distributed.connect(::ClusterManager, ::Int, ::WorkerConfig)
 Distributed.init_worker
 Distributed.start_worker
 Distributed.process_messages
+Distributed.default_addprocs_params
 ```

src/cluster.jl

@@ -448,7 +448,7 @@ function addprocs(manager::ClusterManager; kwargs...)
 end
 
 function addprocs_locked(manager::ClusterManager; kwargs...)
-    params = merge(default_addprocs_params(), Dict{Symbol,Any}(kwargs))
+    params = merge(default_addprocs_params(manager), Dict{Symbol,Any}(kwargs))
     topology(Symbol(params[:topology]))
 
     if PGRP.topology !== :all_to_all
@@ -513,12 +513,16 @@ function set_valid_processes(plist::Array{Int})
     end
 end
 
+"""
+    default_addprocs_params(mgr::ClusterManager) -> Dict{Symbol, Any}
+
+Implemented by cluster managers. The default keyword parameters passed when calling
+`addprocs(mgr)`. The minimal set of options is available by calling
+`default_addprocs_params()`
+"""
+default_addprocs_params(::ClusterManager) = default_addprocs_params()
 default_addprocs_params() = Dict{Symbol,Any}(
     :topology => :all_to_all,
-    :ssh      => "ssh",
-    :shell    => :posix,
-    :cmdline_cookie => false,
-    :env      => [],
     :dir      => pwd(),
     :exename  => joinpath(Sys.BINDIR::String, julia_exename()),
     :exeflags => ``,

src/managers.jl

@@ -34,8 +34,8 @@ struct SSHManager <: ClusterManager
 end
 
 
-function check_addprocs_args(kwargs)
-    valid_kw_names = collect(keys(default_addprocs_params()))
+function check_addprocs_args(manager, kwargs)
+    valid_kw_names = keys(default_addprocs_params(manager))
     for keyname in keys(kwargs)
         !(keyname in valid_kw_names) && throw(ArgumentError("Invalid keyword argument $(keyname)"))
     end
@@ -137,11 +137,23 @@ This timeout can be controlled via environment variable `JULIA_WORKER_TIMEOUT`.
 The value of `JULIA_WORKER_TIMEOUT` on the master process specifies the number of seconds a
 newly launched worker waits for connection establishment.
 """
-function addprocs(machines::AbstractVector; tunnel=false, multiplex=false, sshflags=``, max_parallel=10, kwargs...)
-    check_addprocs_args(kwargs)
-    addprocs(SSHManager(machines); tunnel=tunnel, multiplex=multiplex, sshflags=sshflags, max_parallel=max_parallel, kwargs...)
+function addprocs(machines::AbstractVector; kwargs...)
+    manager = SSHManager(machines)
+    check_addprocs_args(manager, kwargs)
+    addprocs(manager; kwargs...)
 end
 
+default_addprocs_params(::SSHManager) =
+    merge(default_addprocs_params(),
+          Dict{Symbol,Any}(
+              :ssh            => "ssh",
+              :sshflags       => ``,
+              :shell          => :posix,
+              :cmdline_cookie => false,
+              :env            => [],
+              :tunnel         => false,
+              :multiplex      => false,
+              :max_parallel   => 10))
 
 function launch(manager::SSHManager, params::Dict, launched::Array, launch_ntfy::Condition)
     # Launch one worker on each unique host in parallel. Additional workers are launched later.
@@ -426,8 +438,9 @@ processes on the local machine. If `restrict` is `true`, binding is restricted t
 `enable_threaded_blas` have the same effect as documented for `addprocs(machines)`.
 """
 function addprocs(np::Integer; restrict=true, kwargs...)
-    check_addprocs_args(kwargs)
-    addprocs(LocalManager(np, restrict); kwargs...)
+    manager = LocalManager(np, restrict)
+    check_addprocs_args(manager, kwargs)
+    addprocs(manager; kwargs...)
 end
 
 Base.show(io::IO, manager::LocalManager) = print(io, "LocalManager()")