User Guide

This package has been developed taking in account the usage easily.


  • The server is the responsible of running all julia scripts.
  julia -t auto -e 'using DaemonMode; serve()'

The -t auto allow clients to use several threads if they want it.

  • A client, that send to the server the file to run, and return the output obtained.
  julia -e 'using DaemonMode; runargs()' program.jl <arguments>

you can use an alias

  alias juliaclient='julia -e "using DaemonMode; runargs()"'

then, instead of julia program.jl you can do juliaclient program.jl. The output should be the same, but with a lot less time.

Running specific code

Although the function runargs() is the simpler way to run the client, it is not the only function.

Running several clients at the same time

In previous versions, the server run one task for each client. However, since v0.1.5 DaemonMode is able to run each client in parallel. However, you can run the server function with the parameter async=false to have the previous behaviour. In all following examples, I use -t auto to allow julia to use different CPUs.

$  julia -e 'using DaemonMode; serve(async=false)'

In that way, the juliaserver only work in a only CPU, and only each client is running at the same time.

The recommended way of running is always using -t auto.

$  julia -t auto -e 'using DaemonMode; serve(async=false)'

In that way, each client could use different CPUs, but only each client is running at the same time. However, the current client can run different threads.

With the optional parameter async=true to server, the server run each client in a new task, but only using a CPU.

$  julia -t auto -e 'using DaemonMode; serve(async=true)'

That command will allow to run different clients in parallel. It is using several threads in parallel by default. If you want to run different clients in parallel but always at the same CPU (pure async mode), you can do:

$  julia -t auto -e 'using DaemonMode; serve(async=true, threaded=false)'

Auto allows DaemonMode to use all processors of the computer, but you can put -t 1, -t 2, ... It is the default mode.

The parallel option have several advantages:

  • You can run any new client without waiting the previous close.

  • If one process ask for close the Daemon, it will wait until all clients have been finished.

  • With several threads (threaded instead of async), you can run several clients in different CPUs, without increasing the time for each client. If there is only one process, the processing time will be divided between the different clients.

The main drawback is that the @show and logs in console can be send to the last task.

Typical errors

Error, cannot connect with server. Is it running?

It could not be connected with the server, you should check it is running, and that the port used in both is the same one.

ERROR: could not open file '<file>'

the file cannot be found by the server. Remember that the file is going to be searched using as current directory the directory in which the julia client is run.

Changing the port

By default the DaemonMode work in the port 3000, but in many contexts that port can be unavailable, or been busy for another application.

it is simple to change the port, but it must be done both in the server and the client.

  • In the server:
   using DaemonMode: serve

  • In the client:
   using DaemonMode: runargs

  • or using the alias:
  alias juliaclient='julia -e "using DaemonMode; runargs(port=9000)"'

That port keyword can be add to any other parameter.

Different contexts

In order to avoid conflict of different versions of the same library, sometimes it is needed to run programs using different contexts or environments.

This can be achieve with DaemonMode run different servers, each one using a different port.

# server1.jl
using Pkg
using DaemonMode: serve
# server2.jl
using Pkg
using DaemonMode: serve

First, we run the two servers:

> julia server1.jl &
> julia server2.jl &

Then, to run file1.jl in the first context and run file2.jl in second environment.

julia -e 'using DaemonMode; runargs(3001)' file1.jl
julia -e 'using DaemonMode; runargs(3002)' file1.jl

Shared code and Conflict of names

By default each file/expression is run in a new Module to avoid any conflict of names. This implies that each run is completely independently.

It is possible to run the different files/expressions in the same Module, using the parameter shared to true in the function serve(). This implies that the variables are shared between the different clients. It could be useful to avoid repeating evaluations, but it could produce conflict of names.

julia -e 'using DaemonMode; runargs(3001)' file1.jl

Debugging a script

Sometimes the script is not lack of errors, in this case, it is only show the first line of error.

By example:

function fun2(a)

function fun1()


and the server:

julia --project -e 'using DaemonMode; serve(3000)'

The output usually should be:

# julia --project=. -e "using DaemonMode; runargs()" test/bad.jl 
LoadError: syntax: incomplete: premature end of input
in expression starting at string:1

This is usually not wanted.

In order to fix it, and to receive more informative messages, it is recommended the parameter print_stack:

julia --project -e 'using DaemonMode; serve(3000, print_stack=true)'

When it is run the code now more informative messages:

# julia --project=. -e "using DaemonMode; runargs()" test/bad2.jl 
LoadError: UndefVarError: b not defined
 [1] fun2(::Int64) at ./string:2
 [2] fun1() at ./string:6
 [3] top-level scope at string:9
 [4] include_string(::Function, ::Module, ::String, ::String) at ./loading.jl:1088
 [5] include_string at ./loading.jl:1096 [inlined] (repeats 2 times)
 [6] #7 at /mnt/home/daniel/working/DaemonMode/src/DaemonMode.jl:140 [inlined]
 [7] (::DaemonMode.var"#3#5"{DaemonMode.var"#7#9"{String},Sockets.TCPSocket,Bool,Bool})() at /mnt/home/daniel/working/DaemonMode/src/DaemonMode.jl:97
 [8] redirect_stderr(::DaemonMode.var"#3#5"{DaemonMode.var"#7#9"{String},Sockets.TCPSocket,Bool,Bool}, ::Sockets.TCPSocket) at ./stream.jl:1150
 [9] #2 at /mnt/home/daniel/working/DaemonMode/src/DaemonMode.jl:88 [inlined]
 [10] redirect_stdout(::DaemonMode.var"#2#4"{DaemonMode.var"#7#9"{String},Sockets.TCPSocket,Bool,Bool}, ::Sockets.TCPSocket) at ./stream.jl:1150
 [11] serverRun at /mnt/home/daniel/working/DaemonMode/src/DaemonMode.jl:87 [inlined]
 [12] #6 at /mnt/home/daniel/working/DaemonMode/src/DaemonMode.jl:139 [inlined]
 [13] cd(::DaemonMode.var"#6#8"{Sockets.TCPSocket,Bool,Bool,String}, ::String) at ./file.jl:104
 [14] serverRunFile(::Sockets.TCPSocket, ::Bool, ::Bool) at /mnt/home/daniel/working/DaemonMode/src/DaemonMode.jl:137
 [15] serve(::Int64, ::Missing; print_stack::Bool) at /mnt/home/daniel/working/DaemonMode/src/DaemonMode.jl:40
 [16] top-level scope at none:1
 [17] eval(::Module, ::Any) at ./boot.jl:331
 [18] exec_options(::Base.JLOptions) at ./client.jl:272
 [19] _start() at ./client.jl:506
in expression starting at string:9

Obviously, the majority of the complete stack mention the DaemonMode functions, but at least the error can be identified more easily.

Including a file

In first versions of the package, you cannot use the "include" function to include the code of an external file (for a better organization of the code). This has been solved, so now you can use include function as normal.


In file include_test.jl:



and in to_include.jl:

function f_aux(a,b)
    return a*b
# julia --project=. -e "using DaemonMode; runargs()" include_test.jl 

Remember that the current directory is the directory in which julia command is run, so it is recommended to run in the same directory that the script with the include.

Automatically reload the modified packages

DaemonMode would execute the codes that are directly passed to the server, so each time the codes are updated, you would get the up-to-date results. However, sometimes you may also be developing some packages in the same time, and want they got reloaded when modified. You can use Revise together with DaemonMode for this purpose. You only need to add using Revise, before starting the DaemonMode server:

julia --startup-file=no -e 'using Revise; using DaemonMode; serve()'