From 71fc75974e9a5745922e32ec1c5a5a781614a04a Mon Sep 17 00:00:00 2001
From: sunface <cto@188.com>
Date: Mon, 4 Apr 2022 22:13:35 +0800
Subject: [PATCH] =?UTF-8?q?=E6=96=B0=E5=A2=9E=E7=AB=A0=20[Cookbook=20-=20?=
 =?UTF-8?q?=E9=85=8D=E7=BD=AE=E6=97=A5=E5=BF=97]?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 book.toml                           |   2 +-
 src/cookbook/devtools/config-log.md | 139 ++++++++++++++++++++++++++++
 2 files changed, 140 insertions(+), 1 deletion(-)

diff --git a/book.toml b/book.toml
index 5e439c80..22f16de7 100644
--- a/book.toml
+++ b/book.toml
@@ -13,7 +13,7 @@ edit-url-template = "https://github.com/sunface/rust-course/edit/main/{path}"
 [output.html.playground]
 editable = true
 copy-js = true
-line-numbers = true
+# line-numbers = true
 
 [output.html.fold]
 enable = true
diff --git a/src/cookbook/devtools/config-log.md b/src/cookbook/devtools/config-log.md
index e0099ddb..1121571f 100644
--- a/src/cookbook/devtools/config-log.md
+++ b/src/cookbook/devtools/config-log.md
@@ -1 +1,140 @@
 # 配置日志
+
+### 为每个模块开启独立的日志级别
+下面代码创建了模块 `foo` 和嵌套模块 `foo::bar`，并通过 [RUST_LOG](https://docs.rs/env_logger/*/env_logger/#enabling-logging) 环境变量对各自的日志级别进行了控制。
+
+```rust,editable
+mod foo {
+    mod bar {
+        pub fn run() {
+            log::warn!("[bar] warn");
+            log::info!("[bar] info");
+            log::debug!("[bar] debug");
+        }
+    }
+
+    pub fn run() {
+        log::warn!("[foo] warn");
+        log::info!("[foo] info");
+        log::debug!("[foo] debug");
+        bar::run();
+    }
+}
+
+fn main() {
+    env_logger::init();
+    log::warn!("[root] warn");
+    log::info!("[root] info");
+    log::debug!("[root] debug");
+    foo::run();
+}
+```
+
+要让环境变量生效，首先需要通过 `env_logger::init()` 开启相关的支持。然后通过以下命令来运行程序:
+```shell
+RUST_LOG="warn,test::foo=info,test::foo::bar=debug" ./test
+```
+
+此时的默认日志级别被设置为 `warn`，但我们还将 `foo` 模块级别设置为 `info`, `foo::bar` 模块日志级别设置为 `debug`。
+
+```bash
+WARN:test: [root] warn
+WARN:test::foo: [foo] warn
+INFO:test::foo: [foo] info
+WARN:test::foo::bar: [bar] warn
+INFO:test::foo::bar: [bar] info
+DEBUG:test::foo::bar: [bar] debug
+```
+
+### 使用自定义环境变量来设置日志
+
+[Builder](https://docs.rs/env_logger/*/env_logger/struct.Builder.html) 将对日志进行配置，以下代码使用 `MY_APP_LOG` 来替代 `RUST_LOG` 环境变量:
+
+```rust,editable
+use std::env;
+use env_logger::Builder;
+
+fn main() {
+    Builder::new()
+        .parse(&env::var("MY_APP_LOG").unwrap_or_default())
+        .init();
+
+    log::info!("informational message");
+    log::warn!("warning message");
+    log::error!("this is an error {}", "message");
+}
+```
+
+### 在日志中包含时间戳
+
+```rust,editable
+use std::io::Write;
+use chrono::Local;
+use env_logger::Builder;
+use log::LevelFilter;
+
+fn main() {
+    Builder::new()
+        .format(|buf, record| {
+            writeln!(buf,
+                "{} [{}] - {}",
+                Local::now().format("%Y-%m-%dT%H:%M:%S"),
+                record.level(),
+                record.args()
+            )
+        })
+        .filter(None, LevelFilter::Info)
+        .init();
+
+    log::warn!("warn");
+    log::info!("info");
+    log::debug!("debug");
+}
+```
+
+以下是 `stderr` 的输出:
+```shell
+2022-03-22T21:57:06 [WARN] - warn
+2022-03-22T21:57:06 [INFO] - info
+```
+
+### 将日志输出到指定文件
+[log4rs](https://docs.rs/log4rs/) 可以帮我们将日志输出指定的位置，它可以使用外部 YAML 文件或 `builder` 的方式进行配置。
+
+```rust,editable
+# use error_chain::error_chain;
+
+use log::LevelFilter;
+use log4rs::append::file::FileAppender;
+use log4rs::encode::pattern::PatternEncoder;
+use log4rs::config::{Appender, Config, Root};
+
+#error_chain! {
+#    foreign_links {
+#        Io(std::io::Error);
+#        LogConfig(log4rs::config::Errors);
+#        SetLogger(log::SetLoggerError);
+#    }
+#}
+
+fn main() -> Result<()> {
+    // 创建日志配置，并指定输出的位置
+    let logfile = FileAppender::builder()
+        // 编码模式的详情参见: https://docs.rs/log4rs/1.0.0/log4rs/encode/pattern/index.html
+        .encoder(Box::new(PatternEncoder::new("{l} - {m}\n")))
+        .build("log/output.log")?;
+
+    let config = Config::builder()
+        .appender(Appender::builder().build("logfile", Box::new(logfile)))
+        .build(Root::builder()
+                   .appender("logfile")
+                   .build(LevelFilter::Info))?;
+
+    log4rs::init_config(config)?;
+
+    log::info!("Hello, world!");
+
+    Ok(())
+}
+
+```
\ No newline at end of file