Logging: Set tracing subscriber globally

Set default tracing subscriber globally for all threads for the duration
of the entire program. This can be set only once, so subsequent attemps
to set the log level through `cass_log_set_level` will be ignored. The logging
configuration must be done before any other driver function is called,
otherwise, the default logging callback will be used, and logs will
appear on stderr.

Fixes scylladb#110

scylla-rust-wrapper/src/lib.rs

@@ -1,12 +1,10 @@
 #![allow(clippy::missing_safety_doc)]
 
-use crate::logging::set_tracing_subscriber_with_level;
 use crate::logging::stderr_log_callback;
 use crate::logging::Logger;
 use lazy_static::lazy_static;
 use std::sync::RwLock;
 use tokio::runtime::Runtime;
-use tracing::dispatcher::DefaultGuard;
 
 #[macro_use]
 mod binding;
@@ -40,9 +38,6 @@ lazy_static! {
         cb: Some(stderr_log_callback),
         data: std::ptr::null_mut(),
     });
-    pub static ref LOG: RwLock<Option<DefaultGuard>> = RwLock::new(Some(
-        set_tracing_subscriber_with_level(tracing::Level::WARN)
-    ));
 }
 
 // To send a Rust object to C:

scylla-rust-wrapper/src/logging.rs

@@ -1,14 +1,12 @@
 use crate::argconv::{arr_to_cstr, ptr_to_cstr, ptr_to_ref, str_to_arr};
 use crate::types::size_t;
-use crate::LOG;
 use crate::LOGGER;
 use std::convert::TryFrom;
 use std::fmt::Debug;
 use std::fmt::Write;
 use std::os::raw::{c_char, c_void};
 use std::time::{SystemTime, UNIX_EPOCH};
 use tracing::debug;
-use tracing::dispatcher::DefaultGuard;
 use tracing::field::Field;
 use tracing::Level;
 use tracing_subscriber::layer::Context;
@@ -143,41 +141,31 @@ where
     }
 }
 
-// Sets tracing subscriber with specified `level` and returns `DefaultGuard`.
-// The subscriber is valid for the duration of the lifetime of the returned `DefaultGuard`.
-pub fn set_tracing_subscriber_with_level(level: Level) -> DefaultGuard {
-    tracing::subscriber::set_default(
+// Sets tracing subscriber with specified `level`.
+// The subscriber is valid for the duration of the entire program.
+pub fn set_tracing_subscriber_with_level(level: Level) {
+    tracing::subscriber::set_global_default(
         tracing_subscriber::registry()
             .with(
                 tracing_subscriber::EnvFilter::from_default_env()
                     .add_directive(level.to_owned().into()),
             )
             .with(CustomLayer),
     )
-}
-
-pub fn init_logging() {
-    let _log = (*LOG.read().unwrap()).as_ref().unwrap();
+    .unwrap_or(()) // Ignore if it is set already
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn cass_log_set_level(log_level: CassLogLevel) {
     if log_level == CassLogLevel::CASS_LOG_DISABLED {
         debug!("Logging is disabled!");
-        *LOG.write().unwrap() = None;
         return;
     }
 
     let level = Level::try_from(log_level).unwrap_or(Level::WARN);
 
-    // Drops the `DefaultGuard` of the current tracing subscriber making it invalid.
-    // Setting LOG to None is vital, otherwise, the new tracing subscriber created in
-    // `set_tracing_subscriber_with_level` will be ignored as the previous `DefaultGuard` is
-    // still alive.
-    *LOG.write().unwrap() = None;
     // Sets the tracing subscriber with new log level.
-    *LOG.write().unwrap() = Some(set_tracing_subscriber_with_level(level));
-
+    set_tracing_subscriber_with_level(level);
     debug!("Log level is set to {}", level);
 }
 

scylla-rust-wrapper/src/session.rs

@@ -5,7 +5,6 @@ use crate::cass_types::{get_column_type, CassDataType, UDTDataType};
 use crate::cluster::build_session_builder;
 use crate::cluster::CassCluster;
 use crate::future::{CassFuture, CassResultValue};
-use crate::logging::init_logging;
 use crate::metadata::create_table_metadata;
 use crate::metadata::{CassKeyspaceMeta, CassMaterializedViewMeta, CassSchemaMeta};
 use crate::query_result::Value::{CollectionValue, RegularValue};
@@ -29,8 +28,6 @@ pub type CassSession = RwLock<Option<Session>>;
 
 #[no_mangle]
 pub unsafe extern "C" fn cass_session_new() -> *const CassSession {
-    init_logging();
-
     let session = Arc::new(RwLock::new(None));
     Arc::into_raw(session)
 }