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:

../../../_images/basic-trace-labeled.png

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.