badarg when trying to read a csv file in erlang, with tsung - parsing

Question

I am using tsung to load test my websocket server. I am new to tsung and to erlang.
I have a list of users and keys exported to a .csv file. To get it running i reduced the csv file to:
1;2
with no empty line at the end of the file.
This is a snippet of my tsung config (otherwise working fine):
<options>
<option name="file_server" id="users" value="PATH_TO_MY_CSV/users.csv"/>
</options>
[...]
<setdynvars sourcetype="erlang" callback="loadusers:user">
<var name="connection_url" />
</setdynvars>
[...]
<request subst="true">
<websocket type="connect" path="/?%%_connection_url%%"/>
</request>
Here's my loadusers.erl, which makes use of a ts_file_server tsung module:
-module(loadusers).
-export([user/1]).
user({Pid,DynVar})->
{ok,Line} = ts_file_server:get_next_line(),
[Username, Passwd] = string:tokens(Line,";"),
"username=" ++ Username ++"&password=" ++ Passwd.
Here's the erlang error stack:
** State machine <0.90.0> terminating
** Last message in was {timeout,#Ref<0.0.0.414>,end_thinktime}
** When State == think
** Data == {state_rcv,none,
{{0,0,0,0},0},
undefined,0,10000,"192.168.59.103",443,ts_tcp,
{proto_opts,negociate,"/http-bind/","/chat","binary",10,
600000,infinity,32768,32768,undefined,undefined,[]},
true,1,undefined,true,undefined,
{1431,872144,388666},
6,6,false,undefined,0,[],<<>>,
{websocket_session,undefined,undefined},
0,2,524288,524288,
[{tsung_userid,2}],
ts_websocket,[],undefined,none}
** Reason for termination =
** {{badarg,[{dict,fetch,
[default,
{dict,1,16,16,8,80,48,
{[],[],[],[],[],[],[],[],[],[],[],[],[],[],[],[]},
{{[],[],[],
[[users|{file,{<<"1;2">>},1,-1}]],
[],[],[],[],[],[],[],[],[],[],[],[]}}}],
[{file,"dict.erl"},{line,130}]},
{ts_file_server,handle_call,3,
[{file,"src/tsung_controller/ts_file_server.erl"},
{line,159}]},
{gen_server,try_handle_call,4,
[{file,"gen_server.erl"},{line,607}]},
{gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,639}]},
{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,237}]}]},
{gen_server,call,[{global,ts_file_server},{get_next_line,default}]}}
I know dynvars can be directly pulled from a tsung config, but I need to do it in the script since later I will need to dynamically manipulate the data. IMPORTANT: reading the same csv file works fine, so it seems like the script is the problem.
Can someone explain to me what erlang is complaining about here?

Answer 1

The error message is saying that dict:fetch(default, SomeDict) was called and threw a badarg exception. Typically this would happen when the key (default in your case) doesn't exist.
The problem is that in the Tsung config you set id="users", which sets the file id to users. But ts_file_server:get_next_line/0 expects the file id to be default.
Either remove id="users" from the config or change the Erlang part to use ts_file_server:get_next_line/1, passing in the file id you used in the config file.