Merge pull request #31036 from tanmaykm/tan/fix31035

start_worker option to close stdin redirect stdout

Author: tanmaykm

stdlib/Distributed/src/cluster.jl

@@ -207,26 +207,27 @@ worker_timeout() = parse(Float64, get(ENV, "JULIA_WORKER_TIMEOUT", "60.0"))
 
 ## worker creation and setup ##
 """
-    start_worker([out::IO=stdout], cookie::AbstractString=readline(stdin))
+    start_worker([out::IO=stdout], cookie::AbstractString=readline(stdin); close_stdin::Bool=true, stderr_to_stdout::Bool=true)
 
 `start_worker` is an internal function which is the default entry point for
 worker processes connecting via TCP/IP. It sets up the process as a Julia cluster
 worker.
 
 host:port information is written to stream `out` (defaults to stdout).
 
-The function closes stdin (after reading the cookie if required), redirects stderr to stdout,
-listens on a free port (or if specified, the port in the `--bind-to` command
-line option) and schedules tasks to process incoming TCP connections and requests.
+The function reads the cookie from stdin if required, and  listens on a free port
+(or if specified, the port in the `--bind-to` command line option) and schedules
+tasks to process incoming TCP connections and requests. It also (optionally)
+closes stdin and redirects stderr to stdout.
 
 It does not return.
 """
-start_worker(cookie::AbstractString=readline(stdin)) = start_worker(stdout, cookie)
-function start_worker(out::IO, cookie::AbstractString=readline(stdin))
+start_worker(cookie::AbstractString=readline(stdin); kwargs...) = start_worker(stdout, cookie; kwargs...)
+function start_worker(out::IO, cookie::AbstractString=readline(stdin); close_stdin::Bool=true, stderr_to_stdout::Bool=true)
     init_multi()
 
-    close(stdin) # workers will not use it
-    redirect_stderr(stdout)
+    close_stdin && close(stdin) # workers will not use it
+    stderr_to_stdout && redirect_stderr(stdout)
 
     init_worker(cookie)
     interface = IPv4(LPROC.bind_addr)

stdlib/Distributed/test/distributed_exec.jl

@@ -1497,6 +1497,42 @@ cluster_cookie("foobar") # custom cookie
 npids = addprocs_with_testenv(WorkerArgTester(`--worker=foobar`, false))
 @test remotecall_fetch(myid, npids[1]) == npids[1]
 
+# tests for start_worker options to retain stdio (issue #31035)
+struct RetainStdioTester <: ClusterManager
+    close_stdin::Bool
+    stderr_to_stdout::Bool
+end
+
+function launch(manager::RetainStdioTester, params::Dict, launched::Array, c::Condition)
+    dir = params[:dir]
+    exename = params[:exename]
+    exeflags = params[:exeflags]
+
+    jlcmd = "using Distributed; start_worker(\"\"; close_stdin=$(manager.close_stdin), stderr_to_stdout=$(manager.stderr_to_stdout));"
+    cmd = detach(setenv(`$exename $exeflags --bind-to $(Distributed.LPROC.bind_addr) -e $jlcmd`, dir=dir))
+    proc = open(cmd, "r+")
+
+    wconfig = WorkerConfig()
+    wconfig.process = proc
+    wconfig.io = proc.out
+    push!(launched, wconfig)
+
+    notify(c)
+end
+manage(::RetainStdioTester, ::Integer, ::WorkerConfig, ::Symbol) = nothing
+
+
+nprocs()>1 && rmprocs(workers())
+cluster_cookie("")
+
+for close_stdin in (true, false), stderr_to_stdout in (true, false)
+    npids = addprocs_with_testenv(RetainStdioTester(close_stdin,stderr_to_stdout))
+    @test remotecall_fetch(myid, npids[1]) == npids[1]
+    @test close_stdin != remotecall_fetch(()->isopen(stdin), npids[1])
+    @test stderr_to_stdout == remotecall_fetch(()->(stderr === stdout), npids[1])
+    rmprocs(npids)
+end
+
 # Issue # 22865
 # Must be run on a new cluster, i.e., all workers must be in the same state.
 rmprocs(workers())