A tty based interface to the Erlang debugger and tracer.
Useful if you, for example, work from home but still want to debug your code at your work desktop, or if you simply don't like the standard debugger GUI.
Note that lots of the debugger functionality is already supported by the
standard OTP int.erl module. What the edbg debugger brings is basically the
tty based attached mode and the possibility to make use of interactively
defined conditional break points.
The edbg tracing functionality is (hopefully) a somewhat more novel approach and actually is what I myself is using all the time. In fact it is so good that I now have moved the Trace Example chapter just below the Installation ditto. It is all you need... ;-)
Run: make
Add: code:add_path("YOUR-PATH-HERE/edbg/_build/default/lib/edbg/ebin").
Add: code:add_path("YOUR-PATH-HERE/edbg/_build/default/lib/pp_record/ebin").
to your ~/.erlang file.
NOTE: The coloring code makes use of 'maps', so in case of an older Erlang system where 'maps' isn't supported, you must compile the code as:
env USE_COLORS=false make
NOTE: If you don't like rebar (like me) and favour plain Make + Erlc then:
Run: make old
Add: code:add_path("YOUR-PATH-HERE/edbg/ebin").
Add: code:add_path("YOUR-PATH-HERE/edbg/deps/pp_record/ebin").
to your ~/.erlang file.
# TRACE THE SPECIFIED MODULES BELOW.
# THE TRACE OUTPUT WILL BE STORED ON FILE.
1> edbg:fstart([yaws_server,yaws,yaws_config],[{max_msgs,10000}]).
ok
# NOW RUN A CALL TOWARD YAWS !!
2> edbg:fstop().
ok
# WE RELY ON USING THE DEFAULT FILENAME, HENCE NO NEED TO
# SPECIFY IT HERE WHEN LOADING THE TRACE INFO.
3> edbg:file().
(h)elp (a)t [<N>] (d)own (u)p (t)op (b)ottom
(s)how <N> [<ArgN>] (r)etval <N> ra(w) <N>
(pr)etty print record <N> <ArgN>
(f)ind <M>:<Fx> [<ArgN> <ArgVal>] | <RetVal>
(p)agesize <N> (q)uit
0: <0.255.0> yaws_server:gserv_loop/4
1: <0.258.0> yaws_server:gserv_loop/4
2: <0.233.0> yaws:month/1
4: <0.259.0> yaws_server:peername/2
6: <0.258.0> yaws_server:close_accepted_if_max/2
8: <0.258.0> yaws_server:acceptor/1
10: <0.258.0> yaws_server:gserv_loop/4
11: <0.281.0> yaws_server:acceptor0/2
12: <0.281.0> yaws_server:do_accept/1
13: <0.259.0> yaws_server:aloop/4
14: <0.259.0> yaws_server:init_db/0
16: <0.259.0> yaws:http_get_headers/2
17: <0.259.0> yaws:do_http_get_headers/2
18: <0.259.0> yaws:http_recv_request/2
19: <0.259.0> yaws:setopts/3
# TO INSPECT A PARTICULAR CALL (without drowning in output),
# WE USE THE (s)how COMMAND WHICH WILL DISPLAY THE FUNCTION
# CLAUSE HEADS IN ORDER TO HELP US DECIDE WHICH ARGUMENT TO INSPECT.
tlist> s 4
Call: yaws_server:peername/2
-----------------------------------
peername(CliSock, ssl) ->
peername(CliSock, nossl) ->
-----------------------------------
# SHOW WHAT THE SECOND ARGUMENT CONTAINED
tlist> s 4 2
Call: yaws_server:peername/2 , argument 2:
-----------------------------------
nossl
# WHAT DID THE FUNCTION CALL RETURN?
tlist> r 4
Call: yaws_server:peername/2 , return value:
-----------------------------------
{{127,0,0,1},35871}
# IF WE KNOW THE ARGUMENT TO BE A RECORD, WE CAN PRETTY PRINT IT
tlist> s 177
Call: yaws_server:handle_request/3
-----------------------------------
handle_request(CliSock, ARG, _N)
when is_record(ARG#arg.state, rewrite_response) ->
handle_request(CliSock, ARG, N) ->
-----------------------------------
tlist> s 177 2
Call: yaws_server:handle_request/3 , argument 2:
-----------------------------------
{arg,#Port<0.6886>,
{{127,0,0,1},35871},
{headers,undefined,"*/*","localhost:8008",undefined,undefined,undefined,
undefined,undefined,undefined,undefined,"curl/7.35.0",undefined,
[],undefined,undefined,undefined,undefined,undefined,
{"admin","admin","Basic YWRtaW46YWRtaW4="},
undefined,undefined,[]},
....
tlist> pr 177 2
Call: yaws_server:handle_request/3 , argument 2:
-----------------------------------
#arg{clisock = #Port<0.6886>,
client_ip_port = {{127,0,0,1},35871},
headers = #headers{connection = undefined,accept = "*/*",
host = "localhost:8008",if_modified_since = undefined,
if_match = undefined,if_none_match = undefined,
if_range = undefined,if_unmodified_since = undefined,
range = undefined,referer = undefined,
user_agent = "curl/7.35.0",accept_ranges = undefined,
cookie = [],keep_alive = undefined,location = undefined,
content_length = undefined,content_type = undefined,
content_encoding = undefined,
authorization = {"admin","admin","Basic YWRtaW46YWRtaW4="},
transfer_encoding = undefined,x_forwarded_for = undefined,
other = []},
req = #http_request{method = 'GET',
path = {abs_path,"/restconf/data"},
....
# HERE IS AN EXAMPLE OF HOW WE CAN SEARCH FOR PARTICULAR
# FUNCTION CALL THAT WE ARE INTERESTED IN.
# NOTE THAT IT IS ENOUGH TO JUST SPECIFY A PREFIX OF THE FUNCTION NAME
tlist> f yaws:decode_b
32: <0.537.0> yaws:decode_base64/1
33: <0.537.0> yaws:decode_base64/2
34: <0.537.0> yaws:d/1
...
# WE CAN ALSO SEARCH IN A PARTICULAR ARGUMENT
# (the 2:nd argument should contain 'packet_size')
tlist> f yaws:setopts 2 packet_size
22: <0.537.0> yaws:setopts/3
24: <0.537.0> yaws:do_recv/3
26: <0.537.0> yaws:http_collect_headers/5
...
tlist> s 22 2
Call: yaws:setopts/3 , argument 2:
-----------------------------------
[{packet,httph},{packet_size,16384}]
# WE CAN ALSO SEARCH AMONG THE RETURN VALUES:
tlist> f GET
184: <0.537.0> yaws:make_allow_header/1
187: <0.537.0> yaws_server:deliver_accumulated/1
188: <0.537.0> yaws:outh_get_content_encoding/0
190: <0.537.0> yaws:outh_set_content_encoding/1
...
tlist> r 184
Call: yaws:make_allow_header/1 , return value:
-----------------------------------
["Allow: GET, POST, OPTIONS, HEAD\r\n"]By using the option 'monotonic_ts', we will also see the elapsed monotonic time, in nano seconds, from the first received trace message.
# BY ADDING THE OPTION 'monotonic_ts' WHEN STARTING
# THE TRACE; WE WILL SEE THE ELAPSED NANO SECONDS FOR
# EACH CALL, COUNTED FROM THE FIRST TRACED CALL.
(confd@hedlund)1> edbg:fstart([yaws_server],[{max_msgs,10000},
monotonic_ts]).
ok
(confd@hedlund)2> edbg:fstop().
ok
(confd@hedlund)3> edbg:file().
(h)elp (a)t [<N>] (d)own (u)p (t)op (b)ottom
(s)how <N> [<ArgN>] (r)etval <N> ra(w) <N>
(pr)etty print record <N> <ArgN>
(f)ind <M>:<Fx> [<ArgN> <ArgVal>] | <RetVal>
(p)agesize <N> (q)uit
0: <0.297.0> yaws_server:peername/2 - 0
2: <0.296.0> yaws_server:close_accepted_if_max/2 - 37276
4: <0.296.0> yaws_server:acceptor/1 - 46436
6: <0.296.0> yaws_server:gserv_loop/4 - 72287
7: <0.315.0> yaws_server:acceptor0/2 - 104797
8: <0.315.0> yaws_server:do_accept/1 - 110475
9: <0.297.0> yaws_server:aloop/4 - 142479
10: <0.297.0> yaws_server:init_db/0 - 164453
12: <0.297.0> yaws_server:fix_abs_uri/2 - 216505
14: <0.297.0> yaws_server:pick_sconf/4 - 220942
15: <0.297.0> yaws_server:pick_sconf/3 - 225815
16: <0.297.0> yaws_server:pick_host/4 - 230099
17: <0.297.0> yaws_server:comp_sname/2 - 235914
18: <0.297.0> yaws_server:comp_sname/2 - 238042
19: <0.297.0> yaws_server:comp_sname/2 - 239546
20: <0.297.0> yaws_server:comp_sname/2 - 240632
tlist>By using the option 'send_receive', we will also see sent and received messages by any 'known' pid.
# BY ADDING THE OPTION 'send_receive' WHEN STARTING
# THE TRACE; WE CAN NOW SEE AND INSPECT MESSAGES
# SENT AND RECEIVED BY ANY KNOWN PID.
(confd@hedlund)1> edbg:fstart([yaws_server],[{max_msgs,10000},
send_receive]).
ok
(confd@hedlund)2> edbg:fstop().
ok
(confd@hedlund)3> edbg:file().
(h)elp (a)t [<N>] (d)own (u)p (t)op (b)ottom
(s)how <N> [<ArgN>] (r)etval <N> ra(w) <N>
(pr)etty print record <N> <ArgN>
(f)ind <M>:<Fx> [<ArgN> <ArgVal>] | <RetVal>
(on)/(off) send_receive
(p)agesize <N> (q)uit
0: <0.651.0> yaws_server:gserv_loop/4
1: <<< Receive(<0.651.0>) timeout...
2: <0.651.0> yaws_server:gserv_loop/4
3: <<< Receive(<0.651.0>) {<0.652.0>,next,{ok,...
4: <0.652.0> yaws_server:peername/2
6: >>> Send(<0.652.0>) -> To(<0.626.0>) {'$gen_call',{<0.652...
7: <<< Receive(<0.652.0>) {#Ref<0.733272738.27...
8: <0.652.0> yaws_server:aloop/4
9: <0.651.0> yaws_server:close_accepted_if_max/2
11: <0.651.0> yaws_server:acceptor/1
13: <0.651.0> yaws_server:gserv_loop/4
14: <0.799.0> yaws_server:acceptor0/2
15: >>> Send(<0.799.0>) -> To(yaws_trace) {'$gen_cast',{open,<...
16: <0.799.0> yaws_server:do_accept/1
17: <0.652.0> yaws_server:init_db/0
19: <<< Receive(<0.652.0>) {inet_async,#Port<0....
20: <<< Receive(<0.652.0>) {inet_async,#Port<0....
tlist> s 6
Message sent by: <0.652.0> to: <0.626.0>
{'$gen_call',{<0.652.0>,#Ref<0.733272738.2716598273.214730>},get_filter}
tlist> s 7
Message received by: <0.652.0>
{#Ref<0.733272738.2716598273.214730>,undefined}
# NOTE THAT WE CAN TOGGLE ON/OFF THE DISPLAY OF THE
# SENT AND RECEIVED MESSAGES
tlist> off send_receive
turning off display of send/receive messages
tlist> a
0: <0.651.0> yaws_server:gserv_loop/4
2: <0.651.0> yaws_server:gserv_loop/4
4: <0.652.0> yaws_server:peername/2
8: <0.652.0> yaws_server:aloop/4
9: <0.651.0> yaws_server:close_accepted_if_max/2
11: <0.651.0> yaws_server:acceptor/1
13: <0.651.0> yaws_server:gserv_loop/4
14: <0.799.0> yaws_server:acceptor0/2
16: <0.799.0> yaws_server:do_accept/1
17: <0.652.0> yaws_server:init_db/0
tlist>By using the option 'memory', we will also track the memory usage.
# BY ADDING THE OPTION 'memory' WHEN STARTING
# THE TRACE; WE CAN NOW TRACK THE MEMORY USAGE OF THE
# TRACED PROCESSES
(confd@hedlund)1> edbg:fstart([yaws_server],[{max_msgs,1000},memory]).
ok
(confd@hedlund)2> edbg:fstop().
ok
(confd@hedlund)3> edbg:file().
(h)elp (a)t [<N>] (d)own (u)p (t)op (b)ottom
(s)how <N> [<ArgN>] (r)etval <N> ra(w) <N>
(pr)etty print record <N> <ArgN>
(f)ind <M>:<Fx> [<ArgN> <ArgVal>] | <RetVal>
(on)/(off) send_receive | memory
(p)agesize <N> (q)uit
0: <0.297.0>(14016) yaws_server:peername/2
2: <0.296.0>(21848) yaws_server:close_accepted_if_max/2
4: <0.296.0>(21848) yaws_server:acceptor/1
6: <0.297.0>(42624) yaws_server:aloop/4
7: <0.296.0>(21848) yaws_server:gserv_loop/4
8: <0.314.0>(8944) yaws_server:acceptor0/2
9: <0.314.0>(8944) yaws_server:do_accept/1
10: <0.297.0>(42624) yaws_server:init_db/0
12: <0.297.0>(42624) yaws_server:fix_abs_uri/2
14: <0.297.0>(42624) yaws_server:pick_sconf/4
15: <0.297.0>(42624) yaws_server:pick_sconf/3
16: <0.297.0>(42624) yaws_server:pick_host/4
17: <0.297.0>(42624) yaws_server:comp_sname/2
18: <0.297.0>(42624) yaws_server:comp_sname/2
19: <0.297.0>(42624) yaws_server:comp_sname/2
20: <0.297.0>(42624) yaws_server:comp_sname/2
tlist> off memory
turning off display of memory usage
tlist> at
0: <0.297.0> yaws_server:peername/2
2: <0.296.0> yaws_server:close_accepted_if_max/2
4: <0.296.0> yaws_server:acceptor/1
6: <0.297.0> yaws_server:aloop/4
7: <0.296.0> yaws_server:gserv_loop/4
8: <0.314.0> yaws_server:acceptor0/2
9: <0.314.0> yaws_server:do_accept/1
10: <0.297.0> yaws_server:init_db/0
12: <0.297.0> yaws_server:fix_abs_uri/2
14: <0.297.0> yaws_server:pick_sconf/4
15: <0.297.0> yaws_server:pick_sconf/3
16: <0.297.0> yaws_server:pick_host/4
17: <0.297.0> yaws_server:comp_sname/2
18: <0.297.0> yaws_server:comp_sname/2
19: <0.297.0> yaws_server:comp_sname/2
20: <0.297.0> yaws_server:comp_sname/2Custom colors may be set using the environment variable EDBG_COLOR.
It should contain a SPACE separated string with ITEM=COLOR entries.
Valid ITEMs are:
att - attention color (default: whiteb)
warn - warning color (default: yellow)
err - error color (default: red)
cur - current line color (default: green)
Valid COLORs are:
black, blackb
red, redb
green, greenb
yellow, yellowb
blue, blueb
magenta, magentab
cyan, cyanb
white, whiteb
Colors ending in 'b' are the bright variants.
Example:
export EDBG_COLOR="att=yellowb warn=magenta"
Colors not specified in EDBG_COLOR will keep their defaults.
Start interpret module Mod and set a break point at line Line.
With only one argument, you don't set an explicit break point,
but you will be able to step into the module while debugging.
Set a break point in Mod at line Line.
Start interpret module Mod and set a conditional break point
in Mod at line Line.
The Fun/1 as an anonymous function of arity 1 that gets executed
each time the break point is passed. When the Fun/1 returns
true the break point will trigger and the execution will stop,
else the execution will continue.
The Fun/1 takes an argument which will be a list of current Variable
bindings; typically it makes use of the function
int:get_binding(Var, Bindings) (where Var is an atom denoting a
particular variable) to decide if the break point should trigger
or not. See the example further below for how to use it.
Note that only one interactive trigger function can be used at a time.
Works at edbg:it/3 but assumes that the module alread is being
interpreted.
The t/2 function will reuse an already existing trigger function.
Show all interpreted processes and what state there are in.
In particular this is useful to see if a process is has stopped
in a break point. The process identifier (Pid) displayed in the
leftmost column can be used with the edbg:attach/1 function.
Attach to an interpreted process in order to manually control the further execution, inspect variables, etc. When called, you will enter a sort of mini-shell where you can issue a number of commands; see the examples below.
The a/0 function is a shortcut to attach to the first process found
that has stopped at a break point.
The a/3 and attach/3 functions are shorthands for supplying a pid as a
sequence of integers.
edbg:mlist(Mod) | edbg:mlist(Pid) | edbg:mlist(Mod, Line) | edbg:mlist(Mod, Line, Context) | edbg:mlist(P0, P1, P2)
List the source code of a Module, either centered around a triggered
break point, or around a given Line. The amount of lines being display
around the line is controled by the Context value, which per default
is set to 5 (i.e display 5 lines above and below the line).
Note that the listing will display the line numbers at the left border
of the output where breakpoints are high lighted by a * character
and the given line as >. However, if no line is given, the >
character will be used to denote where we currently are stopped.
The mlist/3 can take a sequence of integers for supplying a pid.
Display all break points.
Display the break points in module Mod.
Step the execution of a stopped process.
Next the execution of a stopped process.
Continue the execution of a stopped process.
Show all interpreted modules.
Delete/Disable/Enable a break point.
Whenever a break point is set or modified, information is
stored on disk in the file breakpoints.edbg. This function
will load and set those breakpoints found in this file.
The fstart functions is a newer interface which is using the
Erlang trace BIFs directly (i.e not using the dbg.erl module).
They also store the trace output on file so that it survives
the initial session where the tracing took place (which can
be good if called from within a Common-Test test case or similar).
Start tracing to file. ModFunList is a list of module names (atoms)
or tuples {ModuleName, FunctionName}. This makes it possible to trace
on all functions within a Module, or just a few functions within a Module.
Opts is a list of option tuples:
- {log_file, FileName} : file where to store trace output; default:
edbg.trace_result - {max_msgs, MaxNumOfMsgs} : max number of trace messages; default = 1000
- {trace_time, Seconds} : max time to trace; default = 10 seconds
- {trace_spec, Spec} : see the erlang:trace/3 docs; default = all
- dump_output_eager : trace output goes to file often
- dump_output_lazy : trace output goes to file not so often (default)
- monotonic_ts : show the elapsed monotonic nano seconds
- send_receive : trace send/receive messages from 'known' pids
- memory : track the memory usage of the 'known' pids
Tracing in an Erlang node is setup by the erlang:trace/3 and
erlang:trace_pattern/3 BIFs`. The generated trace output in
a production system can quickly produce a staggering amount of
data, which easily can swamp the whole system, so that it becomes
unusable.
It is therefore important to restrict what to trace, the amount of
generated trace messages and the maximum time we allow tracing to go on.
edbg helps you with this but you can still brake
your system if you are careless setting the trace parameters.
With the max_msgs and trace_time parameters you can
restrict the amount of generated trace messages and running time
before stopping the tracing.
The trace_spec is also a way of restricting what to trace on.
Default is all, but for later OTP versions (> 18.3): processes
is available and would be more specific.
For more info about this, see the erlang:trace/3 documentation.
With the dump_output_lazy switch set, trace output goes to file not
until the tracer is stopped (e.g by calling the file/1 function), or
that a limiting filter such as max_msg or trace_time is reached.
This is the default.
With the dump_output_eager switch set, trace output goes to file often
which may be necessary if you run edbg tracing and the system goes down.
With the monotonic_ts switch set, each trace message will have a
monotonic timestamp, in nanoseconds, attached to it. This will be displayed
in the call graph as the elapsed time counted from the first received
trace message.
With the send_receive switch set, we will also trace messages sent and
received by 'known' pids. By 'known' pids we mean processes that we have
seen earlier in a traced call. The reason for this is to avoid beig swamped
by all the messages that the trace BIF is sending us. Note that we still
may get a lots of messages that will cause the resulting trace file to be
large and make the handling of it slower. The display of sent and received
messages can be toggled on/off from the trace command prompt, see also the
trace examples.
With the memory switch set, we will also track the memory usage of
the processes that we get trace messages for. The memory size shown
is the size in bytes of the process. This includes call stack, heap,
and internal structures, as what we get from the process_info(Pid, memory)
BIF. NOTE: we run the process_info/2 BIF when we receive the
trace message from the BEAM engine so the memory size we present does
not exactly represent the state of the process at the creation of the
trace message.
% Example, trace calls to the foo module, no more than 1000 trace msgs
edbg:fstart([foo], [{max_msgs, 1000}]). % Example, trace all modules in a particular process,
% dump the traced output to file often,
% no more than 1000 trace msgs.
edbg:fstart([], [{trace_spec,Pid}, dump_output_eager, {max_msgs, 1000}]).As edbg:fstart/2 but using no Options.
Resuse the last setup from edbg:fstart/[1,2].
Load the trace output from the file LogFileName and
enter the trace list mode.
As edbg:file/1 but use the default trace output filename.
Stop tracing and dump the trace output to file.
This is an older and obsoleted interface for starting the tracing.
Start tracing the first time Mod (an atom) is called, in any process,
and in any spawned process from such a process.
Do also trace any call to the modules Mods (list of atoms).
Opts is a list of any of the following options:
{setup_mod, Mod}: the module that will setup the tracing; default isedbg_trace_filter.{trace_max}: max number of trace messages; default is 10000.
The trace-start setup will automatically be stored on file for easy reload.
Enter trace list mode, where the trace output can be inspected.
Stop and quit the edbg tracer.
Load the latest trace-start setup from file.
# LOAD THE yaws_server MODULE INTO THE DEBUGGER AND SET A BREAK POINT
1> edbg:i(yaws_server, 1189).
ok
# NOW RUN THE TEST...
# LIST DEBUGGED PROCESSES
2> edbg:plist().
<0.536.0> yaws_server:gserv_loop/4 waiting
<0.648.0> yaws_server:acceptor0/2 break yaws_server:1189
<0.537.0> yaws_server:POST/4 exit Reason: shutdown
<0.516.0> yaws_server:safe_decode_p idle
<0.663.0> yaws_server:acceptor0/2 running
ok
# ATTATCH TO A DEBUGGED PROCESS
# NOTE THE LINE WHERE WE HAVE STOPPED ON THE BREAK POINT: '1189>'
3> edbg:attach(0,648,0).
(h)elp (a)t <Ctx> (n)ext (s)tep (f)inish (c)ontinue s(k)ip
(m)essages (t)oggle trace (q)uit (br)eakpoints (p)rocesses
(de)lete/(di)sable/(en)able/(te)st/(b)reak <Line | Mod Line>
(v)ar <variable> (e)val <expr> (i)nterpret <Mod> conte(x)t <Ctx>
(u)p (d)own (l)ist module <Mod Line <Ctx>>
MODULE: yaws_server.erl
1184: _ ->
1185: ok
1186: end,
1187:
1188: process_flag(trap_exit, false),
1189> init_db(),
1190: SSL = GS#gs.ssl,
1191: Head = yaws:http_get_headers(CliSock, SSL),
1192: process_flag(trap_exit, true),
1193: ?Debug("Head = ~p~n", [Head]),
1194: case Head of
# NOW WE CAN SINGLE STEP AS USUAL
# NOTE THE LINE INDICATION FOR A BREAK POINT: '1189*'
(<0.648.0>)> n
MODULE: yaws_server.erl
1185: ok
1186: end,
1187:
1188: process_flag(trap_exit, false),
1189* init_db(),
1190> SSL = GS#gs.ssl,
1191: Head = yaws:http_get_headers(CliSock, SSL),
1192: process_flag(trap_exit, true),
1193: ?Debug("Head = ~p~n", [Head]),
1194: case Head of
1195: {error, {too_many_headers, ReqTooMany}} ->
# WE STEP ONE MORE LINE AND CHECK THE CONTENT OF A VARIABLE
# NOTE THAT WE ONLY NEED TO SPECIFY A PREFIX OF THE VARIABLE NAME
(<0.648.0>)> n
MODULE: yaws_server.erl
1186: end,
1187:
1188: process_flag(trap_exit, false),
1189* init_db(),
1190: SSL = GS#gs.ssl,
1191> Head = yaws:http_get_headers(CliSock, SSL),
1192: process_flag(trap_exit, true),
1193: ?Debug("Head = ~p~n", [Head]),
1194: case Head of
1195: {error, {too_many_headers, ReqTooMany}} ->
1196: %% RFC 6585 status code 431
(<0.648.0>)> v SS
'SSL' = nossl
# SUPPLYING AN EMPTY PROMPT REPEATS LAST COMMAND
(<0.648.0>)>
'SSL' = nossl
# IF WE KNOW THE VARIABLE CONTAINS A RECORD, WE CAN PRETTY PRINT IT
(<0.660.0>)> pr GS
'GS' =
#gs{gconf =
#gconf{
yaws_dir = undefined,trace = false,flags = 64,
logdir = "./logs",ebin_dir = [],src_dir = [],runmods = [],
....
# AFTER SOME MORE 'next' OPERATIONS, WE ARE HERE:
(<0.648.0>)> n
MODULE: yaws_server.erl
1198: SC = pick_sconf(GS#gs.gconf, #headers{}, GS#gs.group),
1199: put(sc, SC),
1200: put(outh, #outh{}),
1201: deliver_431(CliSock, ReqTooMany);
1202: {Req0, H0} when Req0#http_request.method /= bad_request ->
1203> {Req, H} = fix_abs_uri(Req0, H0),
1204: ?Debug("{Req, H} = ~p~n", [{Req, H}]),
1205: SC = pick_sconf(GS#gs.gconf, H, GS#gs.group),
1206: put(outh, #outh{}),
1207: put(sc, SC),
1208: DispatchResult = case SC#sconf.dispatch_mod of
# WE CAN NOW STEP INTO A FUNCTION AS USUAL
(<0.648.0>)> s
MODULE: yaws_server.erl
91420: deepforeach(F, X) ->
1421: F(X).
1422:
1423:
1424: fix_abs_uri(Req, H) ->
1425> case Req#http_request.path of
1426: {absoluteURI, _Scheme, Host0, Port, RawPath} ->
1427: Host = case Port of
1428: P when is_integer(P) ->
1429: Host0 ++ [$: | integer_to_list(P)];
1430: % Is this ok?
# WE CAN GO UP IN THE CALL CHAIN...
(<0.648.0>)> u
MODULE: yaws_server.erl
1198: SC = pick_sconf(GS#gs.gconf, #headers{}, GS#gs.group),
1199: put(sc, SC),
1200: put(outh, #outh{}),
1201: deliver_431(CliSock, ReqTooMany);
1202: {Req0, H0} when Req0#http_request.method /= bad_request ->
1203> {Req, H} = fix_abs_uri(Req0, H0),
1204: ?Debug("{Req, H} = ~p~n", [{Req, H}]),
1205: SC = pick_sconf(GS#gs.gconf, H, GS#gs.group),
1206: put(outh, #outh{}),
1207: put(sc, SC),
1208: DispatchResult = case SC#sconf.dispatch_mod of
# ...AND DOWN AGAIN
(<0.648.0>)> d
MODULE: yaws_server.erl
1420: deepforeach(F, X) ->
1421: F(X).
1422:
1423:
1424: fix_abs_uri(Req, H) ->
1425> case Req#http_request.path of
1426: {absoluteURI, _Scheme, Host0, Port, RawPath} ->
1427: Host = case Port of
1428: P when is_integer(P) ->
1429: Host0 ++ [$: | integer_to_list(P)];
1430: % Is this ok?
# WE CAN FINISH THIS FUNCTION
(<0.648.0>)> f
MODULE: yaws_server.erl
1199: put(sc, SC),
1200: put(outh, #outh{}),
1201: deliver_431(CliSock, ReqTooMany);
1202: {Req0, H0} when Req0#http_request.method /= bad_request ->
1203: {Req, H} = fix_abs_uri(Req0, H0),
1204> ?Debug("{Req, H} = ~p~n", [{Req, H}]),
1205: SC = pick_sconf(GS#gs.gconf, H, GS#gs.group),
1206: put(outh, #outh{}),
1207: put(sc, SC),
1208: DispatchResult = case SC#sconf.dispatch_mod of
1209: undefined ->
# AT THIS POINT WE REALIZE THAT WE WOULD LIKE TO ENTER A NEW MODULE...
(<0.648.0>)> n
MODULE: yaws_server.erl
1232: ?TC([{record, SC, sconf}]),
1233: ?Debug("Headers = ~s~n", [?format_record(H, headers)]),
1234: ?Debug("Request = ~s~n",
1235: [?format_record(Req, http_request)]),
1236: run_trace_filter(GS, IP, Req, H),
1237> yaws_stats:hit(),
1238: check_keepalive_maxuses(GS, Num),
1239: Call = case yaws_shaper:check(SC, IP) of
1240: allow ->
1241: call_method(Req#http_request.method,CliSock,
1242: IPPort,Req,H);
# ...SO WE LOAD THE 'yaws_stats' MODULE INTO THE DEBUGGER...
(<0.648.0>)> i yaws_stats
Interpreted modules: [yaws_server,yaws_stats]
# ...WE CAN NOW ENTER THAT MODULE
(<0.648.0>)> s
MODULE: yaws_stats.erl
41: stop(Pid) ->
42: gen_server:cast(Pid, {stop}).
43:
44:
45: hit() ->
46> case get_stats() of
47: undefined ->
48: ok;
49: Pid ->
50: gen_server:cast(Pid, {hit})
51: end.
# WE CAN EVALUATE EXPRESSIONS
(<0.648.0>)> e io:format("Test of eval: ~p~n",[[X*2 || X <- [1,2,3]]]).
Test of eval: [2,4,6]
EVALUATED VALUE:
ok
# WE CAN LIST BREAK POINTS
(<0.648.0>)> br
BREAKPOINTS
yaws_server:1189 Status=active Trigger=enable Cond=null
# WE CAN LIST DEBUGGED PROCESSES
(<0.648.0>)> p
<0.536.0> yaws_server:gserv_loop/4 waiting
<0.648.0> yaws_server:acceptor0/2 break yaws_server:1238
<0.537.0> yaws_server:POST/4 exit Reason: shutdown
<0.516.0> yaws_server:safe_decode_p idle
<0.663.0> yaws_server:acceptor0/2 running
# WE CAN LIST ANY MODULE (not just debugged ones)
(<0.648.0>)> l yaws_api 343
MODULE: yaws_api.erl
338: parse_arg_value(Line, Key, [C|Value], Quote, true).
339:
340:
341: %%
342:
343> make_parse_line_reply(Key, Value, Rest) ->
344: {{yaws:funreverse(Key, fun yaws:to_lowerchar/1),
345: lists:reverse(Value)}, Rest}.
346:
347:
348: -record(mp_parse_state, {
# TO SEE WHERE WE ARE AT THE MOMENT:
(<0.648.0>)> a
MODULE: yaws_server.erl
1233: ?Debug("Headers = ~s~n", [?format_record(H, headers)]),
1234: ?Debug("Request = ~s~n",
1235: [?format_record(Req, http_request)]),
1236: run_trace_filter(GS, IP, Req, H),
1237: yaws_stats:hit(),
1238> check_keepalive_maxuses(GS, Num),
1239: Call = case yaws_shaper:check(SC, IP) of
1240: allow ->
1241: call_method(Req#http_request.method,CliSock,
1242: IPPort,Req,H);
1243: {deny, Status, Msg} ->
# WE CAN CHANGE THE AMOUNT OF CONTEXT TO BE SHOWN
(<0.648.0>)> x 15
(<0.648.0>)> a
MODULE: yaws_server.erl
1223: true -> {ok, Num+1};
1224: false -> aloop(CliSock, IPPort, GS, Num+1)
1225: end;
1226: closed ->
1227: %% Dispatcher closed the socket
1228: erase_transients(),
1229: {ok, Num+1};
1230: continue ->
1231: ?Debug("SC: ~s", [?format_record(SC, sconf)]),
1232: ?TC([{record, SC, sconf}]),
1233: ?Debug("Headers = ~s~n", [?format_record(H, headers)]),
1234: ?Debug("Request = ~s~n",
1235: [?format_record(Req, http_request)]),
1236: run_trace_filter(GS, IP, Req, H),
1237: yaws_stats:hit(),
1238> check_keepalive_maxuses(GS, Num),
1239: Call = case yaws_shaper:check(SC, IP) of
1240: allow ->
1241: call_method(Req#http_request.method,CliSock,
1242: IPPort,Req,H);
1243: {deny, Status, Msg} ->
1244: deliver_xxx(CliSock, Req, Status, Msg)
1245: end,
1246: Call2 = fix_keepalive_maxuses(Call),
1247: handle_method_result(Call2, CliSock, IPPort,
1248: GS, Req, H, Num)
1249: end;
1250: closed ->
1251: case yaws_trace:get_type(GS#gs.gconf) of
1252: undefined -> ok;
1253: _ -> yaws_trace:write(from_client, "closed\n")Here is an example of an interactively defined conditional break point (not possible from the standard GUI debugger):
# FIRST WE DEFINE THE TRIGGER FUNCTION.
# IT WILL GET THE CURRENT VARIABLE BINDINGS AS THE ARGUMENT
# AND MUST RETURN EITHER 'true' OR 'false'
1> F = fun(Bindings) -> case int:get_binding('SSL', Bindings) of
{value,nossl} -> true;
_ -> false
end
end.
#Fun<erl_eval.6.50752066>
# NOW WE SET OUR INTERCTIVELY DEFINED BREAK POINT
2> edbg:it(yaws_server, 1191, F).
ok
# WE RUN OUR TEST...
# LIST THE DEBUGGED PROCESSES
3> edbg:plist().
<0.537.0> yaws_server:gserv_loop/4 waiting
<0.538.0> yaws_server:POST/4 exit Reason: shutdown
<0.517.0> yaws_server:safe_decode_p idle
<0.666.0> yaws_server:acceptor0/2 break yaws_server:1191
<0.519.0> yaws_server:handle_call/3 idle
<0.718.0> yaws_server:acceptor0/2 running
ok
# ATTACH OURSELVES TO THE FIRST PROCESS STOPPED AT A BREAK POINT
4> edbg:a().
(h)elp (a)t <Ctx> (n)ext (s)tep (f)inish (c)ontinue s(k)ip
(m)essages (t)oggle trace (q)uit (br)eakpoints (p)rocesses
(de)lete/(di)sable/(en)able/(te)st/(b)reak <Line | Mod Line>
(v)ar <variable> (e)val <expr> (i)nterpret <Mod> conte(x)t <Ctx>
(u)p (d)own (l)ist module <Mod Line <Ctx>>
MODULE: yaws_server.erl
1186: end,
1187:
1188: process_flag(trap_exit, false),
1189: init_db(),
1190: SSL = GS#gs.ssl,
1191> Head = yaws:http_get_headers(CliSock, SSL),
1192: process_flag(trap_exit, true),
1193: ?Debug("Head = ~p~n", [Head]),
1194: case Head of
1195: {error, {too_many_headers, ReqTooMany}} ->
1196: %% RFC 6585 status code 431
(<0.666.0>)> v SSL
'SSL' = nossl