Validator log filter may now be reconfigured at runtime (#5473)

* Log filter may now be reconfigured at runtime

* Add RPC API and bash script to reconfigure the log filter

logger/src/lib.rs

@@ -1,19 +1,41 @@
-//! The `logger` module provides a setup function for `env_logger`. Its only function,
-//! `setup()` may be called multiple times.
+//! The `logger` module configures `env_logger`
 
-use env_logger;
-use std::sync::Once;
+use lazy_static::lazy_static;
+use std::sync::{Arc, RwLock};
 
-static INIT: Once = Once::new();
-
-pub fn setup_with_filter(filter: &str) {
-    INIT.call_once(|| {
-        env_logger::Builder::from_env(env_logger::Env::new().default_filter_or(filter))
-            .default_format_timestamp_nanos(true)
-            .init();
-    });
+lazy_static! {
+    static ref LOGGER: Arc<RwLock<env_logger::Logger>> =
+        { Arc::new(RwLock::new(env_logger::Logger::from_default_env())) };
 }
 
+struct LoggerShim {}
+
+impl log::Log for LoggerShim {
+    fn enabled(&self, metadata: &log::Metadata) -> bool {
+        LOGGER.read().unwrap().enabled(metadata)
+    }
+
+    fn log(&self, record: &log::Record) {
+        LOGGER.read().unwrap().log(record);
+    }
+
+    fn flush(&self) {}
+}
+
+// Configures logging with a specific filter.
+// May be called at any time to re-configure the log filter
+pub fn setup_with_filter(filter: &str) {
+    let logger = env_logger::Builder::from_env(env_logger::Env::new().default_filter_or(filter))
+        .default_format_timestamp_nanos(true)
+        .build();
+    let max_level = logger.filter();
+    log::set_max_level(max_level);
+    let mut rw = LOGGER.write().unwrap();
+    std::mem::replace(&mut *rw, logger);
+    let _ = log::set_boxed_logger(Box::new(LoggerShim {}));
+}
+
+// Configures logging with the default filter ("error")
 pub fn setup() {
     setup_with_filter("error");
 }