Julia RemoteChanel example gives UndefVarError - julia

Question

I tried to run the example from https://docs.julialang.org/en/v1/manual/parallel-computing/#Channels-and-RemoteChannels-1
Just copy-pasted commands to my julia console. I am using version 1.0.0
_ _ _(_)_ | Documentation: https://docs.julialang.org
(_) | (_) (_) |
_ _ _| |_ __ _ | Type "?" for help, "]?" for Pkg help.
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 1.0.0 (2018-08-08)
_/ |\__'_|_|_|\__'_| | Official https://julialang.org/ release
|__/ |
julia> nprocs()
5
julia> const results = RemoteChannel(()->Channel{Tuple}(32));
julia> const jobs = RemoteChannel(()->Channel{Int}(32));
julia> #everywhere function do_work(jobs, results) # define work function everywhere
while true
job_id = take!(jobs)
exec_time = rand()
sleep(exec_time) # simulates elapsed time doing actual work
put!(results, (job_id, exec_time, myid()))
end
end
julia> function make_jobs(n)
for i in 1:n
put!(jobs, i)
end
end;
julia> n = 12
12
julia> #async make_jobs(n);
julia> for p in workers() # start tasks on the workers to process requests in parallel
remote_do(do_work, p, jobs, results)
end
julia> #elapsed while n > 0 # print out results
job_id, exec_time, where = take!(results)
println("$job_id finished in $(round(exec_time; digits=2)) seconds on worker $where")
n = n - 1
end
It gave the following error:
4 finished in 0.46 seconds on worker 4
ERROR: UndefVarError: n not defined
Stacktrace:
[1] macro expansion at ./REPL[9]:4 [inlined]
[2] top-level scope at ./util.jl:213 [inlined]
[3] top-level scope at ./none:0
Why it crashed on worker 4? I assumed the while loop should run only on master.

Answer 1

The problem is that line:
n = n - 1
should be
global n = n - 1
This is unrelated to workers but new scope rules in Julia 1.0 (see https://docs.julialang.org/en/latest/manual/variables-and-scoping/#Local-Scope-1).
The example in the manual should be fixed.
Edit: the example is fixed on master https://docs.julialang.org/en/v1.1-dev/manual/parallel-computing/, but was not backported.