Add a cli arg to support redirect log (#230)

* add cli arg to support redirect log

simulations/src/bin/app/log.rs

@@ -1,7 +1,14 @@
-use std::str::FromStr;
+use std::{
+    fs::File,
+    io::{stderr, stdout},
+    path::PathBuf,
+    str::FromStr,
+};
+use tracing_subscriber::fmt::{format::Format, FormatEvent, FormatFields, SubscriberBuilder};
 
-#[derive(Copy, Clone)]
+#[derive(Default, Copy, Clone)]
 pub enum LogFormat {
+    #[default]
     Plain,
     Json,
 }
@@ -18,30 +25,62 @@ impl FromStr for LogFormat {
     }
 }
 
-pub fn config_tracing(fmt: Option<LogFormat>) {
+#[derive(Default, Clone)]
+pub enum LogOutput {
+    #[default]
+    StdOut,
+    StdErr,
+    File(PathBuf),
+}
+
+impl FromStr for LogOutput {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.trim().to_ascii_lowercase().as_str() {
+            "stdout" => Ok(Self::StdOut),
+            "stderr" => Ok(Self::StdErr),
+            path => Ok(Self::File(PathBuf::from(path))),
+        }
+    }
+}
+
+pub fn config_tracing(fmt: LogFormat, file: &LogOutput) {
     let filter = std::env::var("SIMULATION_LOG").unwrap_or_else(|_| "info".to_owned());
-    if let Some(LogFormat::Json) = fmt {
+
     let subscriber = tracing_subscriber::fmt::fmt()
         .without_time()
         .with_line_number(true)
         .with_env_filter(filter)
         .with_file(false)
-            .with_target(true)
+        .with_target(true);
-            .with_ansi(true)
+
-            .json()
+    if let LogFormat::Json = fmt {
-            .finish();
+        set_global(subscriber.json(), file);
-        tracing::subscriber::set_global_default(subscriber)
-            .expect("config_tracing is only called once");
     } else {
-        let subscriber = tracing_subscriber::fmt::fmt()
+        set_global(subscriber, file);
-            .without_time()
-            .with_line_number(true)
-            .with_env_filter(filter)
-            .with_file(false)
-            .with_target(true)
-            .with_ansi(true)
-            .finish();
-        tracing::subscriber::set_global_default(subscriber)
-            .expect("config_tracing is only called once");
     }
 }
+
+fn set_global<N, L, T>(
+    subscriber: SubscriberBuilder<N, Format<L, T>, tracing_subscriber::EnvFilter>,
+    output: &LogOutput,
+) where
+    N: for<'writer> FormatFields<'writer> + 'static + Send + Sync,
+    Format<L, T>: FormatEvent<tracing_subscriber::Registry, N>,
+    L: Send + Sync + 'static,
+    T: Send + Sync + 'static,
+{
+    use tracing::subscriber::set_global_default;
+    match output {
+        LogOutput::StdOut => set_global_default(subscriber.with_writer(stdout).finish()),
+        LogOutput::StdErr => set_global_default(subscriber.with_writer(stderr).finish()),
+        LogOutput::File(path) => set_global_default(
+            subscriber
+                .with_ansi(false)
+                .with_writer(File::create(path).expect("Unable to create log file"))
+                .finish(),
+        ),
+    }
+    .expect("Unable to set global default subscriber")
+}

simulations/src/bin/app/main.rs

@@ -39,8 +39,10 @@ pub struct SimulationApp {
     input_settings: PathBuf,
     #[clap(long)]
     stream_type: Option<StreamType>,
-    #[clap(long)]
+    #[clap(long, default_value = "plain")]
-    log_format: Option<log::LogFormat>,
+    log_format: log::LogFormat,
+    #[clap(long, default_value = "stdout")]
+    log_to: log::LogOutput,
 }
 
 impl SimulationApp {
@@ -49,6 +51,7 @@ impl SimulationApp {
             input_settings,
             stream_type,
             log_format: _,
+            log_to: _,
         } = self;
         let simulation_settings: SimulationSettings = load_json_from_file(&input_settings)?;
 
@@ -174,7 +177,7 @@ fn load_json_from_file<T: DeserializeOwned>(path: &Path) -> anyhow::Result<T> {
 
 fn main() -> anyhow::Result<()> {
     let app: SimulationApp = SimulationApp::parse();
-    log::config_tracing(app.log_format);
+    log::config_tracing(app.log_format, &app.log_to);
 
     if let Err(e) = app.run() {
         tracing::error!("error: {}", e);