Multi Line TTY printing weirdness from the non-main thread

General Usage
,
1

There’s some TTY-weirdness going on when I try to print a multi-line strings to stdout or stderr from a spawned task.

Sometimes when printing a string with multiple line-breaks in it (although not always), the printed string is truncated prematurely at a line break character and the rest of the string is not printed.

I’m guessing this is some interaction between task yielding in Julia and printing out to a TTY stream, but I’m hoping someone with more information here can figure out what’s going on.

On Julia 1.9.1 running on Debian 11, with JULIA_NUM_THREADS=4, for example, when running

julia> channel = Channel(; spawn=true) do ch
   while isopen(ch)
        println(take!(ch)::String)
   end
end

and repeatedly evaluating (via Up + Enter in the REPL)

julia> put!(channel, join(string.(1:10), '\n'));

will most often yield the following output

julia> put!(channel, join(string.(1:10), '\n'));
1
2
3
4
5
6
7
8
9
10

but occasionally (but not always) will display

julia> put!(channel, join(string.(1:10), '\n'));

1
2
3
4
5
6
7
8
9

This happens when printing to stderr as well as stdout. This problem doesn’t seem occur when not spawning a task on a separate thread, via

julia> channel = Channel() do ch
   while isopen(ch)
        println(take!(ch)::String)
   end
end

or when setting JULIA_NUM_THREADS=1.

I’ve tried and failed to recreate this behaviour when running Julia 1.9.1 on MacOS 13.1, so this seems to be a linux issue perhaps.

Does anyone have any idea what’s going on here? Thanks in advance.

1 Like
2

Do you ever encounter this issue when setting the thread to :interactive?