Add cli flag for logging to JSON file

beacon_node/client/Cargo.toml

@@ -21,8 +21,9 @@ serde_derive = "1.0"
 error-chain = "0.12.0"
 eth2_ssz = { path = "../../eth2/utils/ssz" }
 slog = { version = "^2.2.3" , features = ["max_level_trace", "release_max_level_debug"] }
-slog-term = "^2.4.0"
 slog-async = "^2.3.0"
+slog-json = "^2.3"
+slog-term = "^2.4.0"
 tokio = "0.1.15"
 clap = "2.32.0"
 dirs = "1.0.3"

beacon_node/client/src/config.rs

@@ -2,8 +2,10 @@ use clap::ArgMatches;
 use http_server::HttpServerConfig;
 use network::NetworkConfig;
 use serde_derive::{Deserialize, Serialize};
-use std::fs;
+use slog::{info, o, Drain};
+use std::fs::{self, OpenOptions};
 use std::path::PathBuf;
+use std::sync::Mutex;
 
 /// The core configuration of a Lighthouse beacon node.
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -11,6 +13,7 @@ pub struct Config {
     pub data_dir: PathBuf,
     pub db_type: String,
     db_name: String,
+    pub log_file: PathBuf,
     pub network: network::NetworkConfig,
     pub rpc: rpc::RPCConfig,
     pub http: HttpServerConfig,
@@ -20,6 +23,7 @@ impl Default for Config {
     fn default() -> Self {
         Self {
             data_dir: PathBuf::from(".lighthouse"),
+            log_file: PathBuf::from(""),
             db_type: "disk".to_string(),
             db_name: "chain_db".to_string(),
             // Note: there are no default bootnodes specified.
@@ -45,23 +49,64 @@ impl Config {
         Some(path)
     }
 
+    // Update the logger to output in JSON to specified file
+    fn update_logger(&mut self, log: &mut slog::Logger) -> Result<(), &'static str> {
+        let file = OpenOptions::new()
+            .create(true)
+            .write(true)
+            .truncate(true)
+            .open(&self.log_file);
+
+        if file.is_err() {
+            return Err("Cannot open log file");
+        }
+        let file = file.unwrap();
+
+        if let Some(file) = self.log_file.to_str() {
+            info!(
+                *log,
+                "Log file specified, output will now be written to {} in json.", file
+            );
+        } else {
+            info!(
+                *log,
+                "Log file specified output will now be written in json"
+            );
+        }
+
+        let drain = Mutex::new(slog_json::Json::default(file)).fuse();
+        let drain = slog_async::Async::new(drain).build().fuse();
+        *log = slog::Logger::root(drain, o!());
+
+        Ok(())
+    }
+
     /// Apply the following arguments to `self`, replacing values if they are specified in `args`.
     ///
     /// Returns an error if arguments are obviously invalid. May succeed even if some values are
     /// invalid.
-    pub fn apply_cli_args(&mut self, args: &ArgMatches) -> Result<(), String> {
+    pub fn apply_cli_args(
+        &mut self,
+        args: &ArgMatches,
+        log: &mut slog::Logger,
+    ) -> Result<(), String> {
         if let Some(dir) = args.value_of("datadir") {
             self.data_dir = PathBuf::from(dir);
         };
 
         if let Some(dir) = args.value_of("db") {
             self.db_type = dir.to_string();
-        }
+        };
 
         self.network.apply_cli_args(args)?;
         self.rpc.apply_cli_args(args)?;
         self.http.apply_cli_args(args)?;
 
+        if let Some(log_file) = args.value_of("logfile") {
+            self.log_file = PathBuf::from(log_file);
+            self.update_logger(log)?;
+        };
+
         Ok(())
     }
 }