fix(logger): add structured api (#450)

* doc(logger): add structured api

* fix(logger): wrong api usage example

common/logger/README.md

@@ -60,8 +60,25 @@ This signature of the function is showed below. The `JsonValue` is a `enum` from
 pub fn metrics(name: &str, mut content: JsonValue)
 ```
 
+## Structured Event Log With TraceId Included
+
+Structured event log api provide a convenient way to log structured json data. It's signature is provided as below:
+
+```rust
+pub fn log(level: Level, module: &str, event: &str, ctx: &Context, mut msg: JsonValue)
+```
+
+`module` should be your component name, `event` is just event name, better begin with 4 chars with 4 digits
+to identify this event. `Context` is used to extract trace id. `msg` is `JsonValue` which is same as `metrics`.
+
+Useage example:
+
+```rust
+common_logger::log(Level::Info, "network", "netw0001", &ctx, common_logger::object!{"music": "beautiful world"});
+```
+
 ## Yaml File
 
 The `log.yml` in this crate is the yaml style config of log4rs with default logger config.
 
-If you need more customized configurations, you can copy the file to some config path, edit the file, and replace the `init` function with `log4rs::init_file("/path/to/log.yml", Default::default()).unwrap();`.
+If you need more customized configurations, you can copy the file to some config path, edit the file, and replace the `init` function with `log4rs::init_file("/path/to/log.yml", Default::default()).unwrap();`.

common/logger/src/lib.rs

@@ -128,8 +128,8 @@ pub fn metrics(name: &str, mut content: JsonValue) {
 }
 
 // Usage:
-// log(Level::Info, "network", "netw0001", &ctx, json!{"music": "beautiful
-// world"})
+// log(Level::Info, "network", "netw0001", &ctx, common_logger::object!{"music"
+// : "beautiful world"})
 pub fn log(level: Level, module: &str, event: &str, ctx: &Context, mut msg: JsonValue) {
     if let Some(trace_ctx) = trace_context(ctx) {
         msg["trace_id"] = trace_ctx.trace_id.to_string().into();