.. _webmachine_debug:

Webmachine调试
########################


基本用法
=================
* 修改 ``init/1`` 方法::

    init(Config) ->
       {{trace, "/tmp"}, Config}.  %% debugging code
       %%{ok, Config}.             %% regular code

* 重新编译并载入这个模块, 然后执行如下方法::

    wmtrace_resource:add_dispatch_rule("wmtrace", "/tmp").

* 在浏览器中输入 http://YOUR_HOST/wmtrace/ 你就会得到如下图所示:

.. figure:: images/basic-trace-labeled.png
   :width: 30%


具体看 http://wiki.basho.com/Webmachine-Debugging.html

配置文件细节
======================

生产配置跟踪日志
-----------------------
注意: 跟踪日志文件可以很大，所以不要在生产环境中使用

* 全路径::

    init(Config) ->
       {{trace, "/tmp/traces"}, Config}. %% absolute path /tmp/traces

* 相对路径::

    init(Config) ->
       {{trace, "traces"}, Config}. %% "traces" directory in application's root


跟踪日志察看器配置
--------------------------
* 察看器可以通过 ``dispatch list`` 进行配置, 也可以使用如下两个方法可以修改::

    wmtrace_resource:add_dispatch_rule/2 
    or
    wmtrace_resource:remove_dispatch_rules/0

* 方法 ``add_dispatch_rule/2`` 带有两个参数——the HTTP-exported path和the path to the trace files,如::

    wmtrace_resource:add_dispatch_rule("dev/wmtrace", "/tmp/traces").
    % 在地址http://YOUR_HOST/dev/wmtrace/显示查看器
    % 日志文件所在目录为 /tmp/traces

* 如果你想让你的日志查看器一直可用,可以在application's dispatch list中进行配置::

    {["dev", "wmtrace", '*'], wmtrace_resource, [{trace_dir, "/tmp/traces"}]}

* To disable all trace viewer resources at any point::

    wmtrace_resource:remove_dispatch_rules/0 

跟踪日志格式
=======================

如果你不想通过日志查看器进行查看，想直接读日志文件，它的格式如下::

  {decision, X}. 
   indicates that a decision point was reached

  {attempt, Module, Function, Args}. 
   indicates that a call to Module:Function(Args) was made.

  {result, Module, Function, Result}. 
   indicates that the call to Module:Function(Args) returned Result .

  {not_expored, Module, Function, Args}. 
   indicates that Module:Function(Args) would have been called, but it was not exported (or not defined) by the module


这种格式的代码可以通过方法 ``file:consult/1`` 得到一系列的erlang terms.