Add log-format option to CLI (#744)

* Add log-format CLI option

* Cargo fmt

* Add log format logic for file logging. Add doc

* Review comment

* Fix compilation errors

* Remove Mutex from logger

lcli/src/main.rs

@@ -249,7 +249,7 @@ fn run<T: EthSpec>(env_builder: EnvironmentBuilder<T>, matches: &ArgMatches) {
     let env = env_builder
         .multi_threaded_tokio_runtime()
         .expect("should start tokio runtime")
-        .async_logger("trace")
+        .async_logger("trace", None)
         .expect("should start null logger")
         .build()
         .expect("should build env");

lighthouse/environment/src/lib.rs

@@ -15,7 +15,6 @@ use std::cell::RefCell;
 use std::ffi::OsStr;
 use std::fs::{rename as FsRename, OpenOptions};
 use std::path::PathBuf;
-use std::sync::Mutex;
 use std::time::{SystemTime, UNIX_EPOCH};
 use tokio::runtime::{Builder as RuntimeBuilder, Runtime, TaskExecutor};
 use types::{EthSpec, InteropEthSpec, MainnetEthSpec, MinimalEthSpec};
@@ -99,12 +98,27 @@ impl<E: EthSpec> EnvironmentBuilder<E> {
     /// The logger is "async" because it has a dedicated thread that accepts logs and then
     /// asynchronously flushes them to stdout/files/etc. This means the thread that raised the log
     /// does not have to wait for the logs to be flushed.
-    pub fn async_logger(mut self, debug_level: &str) -> Result<Self, String> {
-        // Build the initial logger.
-        let decorator = slog_term::TermDecorator::new().build();
-        let decorator = logging::AlignedTermDecorator::new(decorator, logging::MAX_MESSAGE_WIDTH);
-        let drain = slog_term::FullFormat::new(decorator).build().fuse();
-        let drain = slog_async::Async::new(drain).build();
+    pub fn async_logger(
+        mut self,
+        debug_level: &str,
+        log_format: Option<&str>,
+    ) -> Result<Self, String> {
+        // Setting up the initial logger format and building it.
+        let drain = if let Some(format) = log_format {
+            match format.to_uppercase().as_str() {
+                "JSON" => {
+                    let drain = slog_json::Json::default(std::io::stdout()).fuse();
+                    slog_async::Async::new(drain).build()
+                }
+                _ => return Err("Logging format provided is not supported".to_string()),
+            }
+        } else {
+            let decorator = slog_term::TermDecorator::new().build();
+            let decorator =
+                logging::AlignedTermDecorator::new(decorator, logging::MAX_MESSAGE_WIDTH);
+            let drain = slog_term::FullFormat::new(decorator).build().fuse();
+            slog_async::Async::new(drain).build()
+        };
 
         let drain = match debug_level {
             "info" => drain.filter_level(Level::Info),
@@ -230,7 +244,12 @@ impl<E: EthSpec> Environment<E> {
     }
 
     /// Sets the logger (and all child loggers) to log to a file.
-    pub fn log_to_json_file(&mut self, path: PathBuf, debug_level: &str) -> Result<(), String> {
+    pub fn log_to_json_file(
+        &mut self,
+        path: PathBuf,
+        debug_level: &str,
+        log_format: Option<&str>,
+    ) -> Result<(), String> {
         // Creating a backup if the logfile already exists.
         if path.exists() {
             let start = SystemTime::now();
@@ -256,8 +275,14 @@ impl<E: EthSpec> Environment<E> {
             .open(&path)
             .map_err(|e| format!("Unable to open logfile: {:?}", e))?;
 
-        let drain = Mutex::new(slog_json::Json::default(file)).fuse();
-        let drain = slog_async::Async::new(drain).build();
+        let log_format = log_format.unwrap_or("JSON");
+        let drain = match log_format.to_uppercase().as_str() {
+            "JSON" => {
+                let drain = slog_json::Json::default(file).fuse();
+                slog_async::Async::new(drain).build()
+            }
+            _ => return Err("Logging format provided is not supported".to_string()),
+        };
 
         let drain = match debug_level {
             "info" => drain.filter_level(Level::Info),

lighthouse/src/main.rs

@@ -42,7 +42,17 @@ fn main() {
             Arg::with_name("logfile")
                 .long("logfile")
                 .value_name("FILE")
-                .help("File path where output will be written.")
+                .help(
+                    "File path where output will be written. Default file logging format is JSON.",
+                )
+                .takes_value(true),
+        )
+        .arg(
+            Arg::with_name("log-format")
+                .long("log-format")
+                .value_name("FORMAT")
+                .help("Specifies the format used for logging.")
+                .possible_values(&["JSON"])
                 .takes_value(true),
         )
         .arg(
@@ -99,8 +109,10 @@ fn run<E: EthSpec>(
         .value_of("debug-level")
         .ok_or_else(|| "Expected --debug-level flag".to_string())?;
 
+    let log_format = matches.value_of("log-format");
+
     let mut environment = environment_builder
-        .async_logger(debug_level)?
+        .async_logger(debug_level, log_format)?
         .multi_threaded_tokio_runtime()?
         .build()?;
 
@@ -110,7 +122,7 @@ fn run<E: EthSpec>(
         let path = log_path
             .parse::<PathBuf>()
             .map_err(|e| format!("Failed to parse log path: {:?}", e))?;
-        environment.log_to_json_file(path, debug_level)?;
+        environment.log_to_json_file(path, debug_level, log_format)?;
     }
 
     if std::mem::size_of::<usize>() != 8 {

tests/beacon_chain_sim/src/main.rs

@@ -41,6 +41,7 @@ fn main() {
     let nodes = 4;
     let validators_per_node = 20;
     let log_level = "debug";
+    let log_format = None;
     let speed_up_factor = 4;
     let end_after_checks = true;
 
@@ -49,6 +50,7 @@ fn main() {
         validators_per_node,
         speed_up_factor,
         log_level,
+        log_format,
         end_after_checks,
     ) {
         Ok(()) => println!("Simulation exited successfully"),
@@ -64,10 +66,11 @@ fn async_sim(
     validators_per_node: usize,
     speed_up_factor: u64,
     log_level: &str,
+    log_format: Option<&str>,
     end_after_checks: bool,
 ) -> Result<(), String> {
     let mut env = EnvironmentBuilder::minimal()
-        .async_logger(log_level)?
+        .async_logger(log_level, log_format)?
         .multi_threaded_tokio_runtime()?
         .build()?;