# \`MethodError\` in Julia processes launched with \`--worker\` argument

**URL:** <https://discourse.julialang.org/t/methoderror-in-julia-processes-launched-with-worker-argument/19143>\
**Category:** General Usage\
**Created:** [December 31, 2018, 2:49am UTC](https://discourse.julialang.org/t/methoderror-in-julia-processes-launched-with-worker-argument/19143 "2018-12-31T02:49:45Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![affans](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/affans/32/11911_2.png) [@affans](https://discourse.julialang.org/u/affans)\
**Post date:** [December 31, 2018, 2:49am UTC](https://discourse.julialang.org/t/methoderror-in-julia-processes-launched-with-worker-argument/19143/1 "2018-12-31T02:49:45Z")

</div>

I wrote a [my cluster manager](https://github.com/affans/ArettoClusterABMLAB) to be used with our cluster running Slurm. Now running the code is as simple as

```julia
julia> a = ArettoManager(124)
ArettoManager(124)

julia> addprocs(a, partition="defq", N=16)

```

which correctly launches 124 Julia binaries with `--worker` argument successfully on 16 nodes. However, these worker processes exit immediately with a `MethodError`. Capturing `STDOUT`, I have

```julia
[affans@hpc ArettoTest]$ cat job0000.out
julia_worker:9070#172.16.1.26
MethodError(convert, (Tuple, :all_to_all), 0x0000000000005549)CapturedException(MethodError(convert, (Tuple, :all_to_all), 0x0000000000005549), Any[(setindex!(::Array{Tuple,1}, ::Symbol, ::Int64) at array.jl:583, 1), ((::Base.Distributed.##99#100{TCPSocket,TCPSocket,Bool})() at event.jl:73, 1)])
Process(1) - Unknown remote, closing connection.
Master process (id 1) could not connect within 60.0 seconds.
exiting.

```

As you can see, the worker binary correctly writes the port and host information on STDOUT.  
The exception from the master Julia process itself

```julia
ERROR: InterruptException:
Stacktrace:
 [1] #addprocs_locked#44(::Base.Iterators.Pairs{Symbol,Any,Tuple{Symbol,Symbol},NamedTuple{(:partition, :N),Tuple{String,Int64}}}, ::Function, ::ArettoManager) at ./task.jl:266
 [2] #addprocs_locked at ./none:0 [inlined]
 [3] #addprocs#43(::Base.Iterators.Pairs{Symbol,Any,Tuple{Symbol,Symbol},NamedTuple{(:partition, :N),Tuple{String,Int64}}}, ::Function, ::ArettoManager) at /builddir/build/BUILD/julia/build/usr/share/julia/stdlib/v1.0/Distributed/src/cluster.jl:369
 [4] (::getfield(Distributed, Symbol("#kw##addprocs")))(::NamedTuple{(:partition, :N),Tuple{String,Int64}}, ::typeof(addprocs), ::ArettoManager) at ./none:0
 [5] top-level scope at none:0

```

I don’t know where the `MethodError` is coming from. It dosn’t seem to be from my side but something internally, likely in `Distributed.jl`.

Edit: Slightly different error in STDOUT from the workers

```julia
[affans@hpc ArettoTest]$ cat job0001.out
julia_worker:9015#172.16.1.26
TypeError(:deserialize_module, "typeassert", Module, ===)CapturedException(TypeError(:deserialize_module, "typeassert", Module, ===), Any[((::Base.Distributed.##99#100{TCPSocket,TCPSocket,Bool})() at event.jl:73, 1)])
Process(1) - Unknown remote, closing connection.
Master process (id 1) could not connect within 60.0 seconds.
exiting.

```