add tracing feature

Cargo.toml

@@ -26,6 +26,7 @@ serde_derive = "1.0.0"
 serde_json = "1.0.0"
 slab = "0.4"
 tokio = { version = "1.0", features = ["rt", "time"], optional = true }
+tracing = { version = "0.1.30", optional = true }
 
 [dev-dependencies]
 async-std = { version = "1.9.0", features = ["attributes"] }
@@ -61,6 +62,7 @@ zstd = ["rdkafka-sys/zstd"]
 zstd-pkg-config = ["rdkafka-sys/zstd-pkg-config"]
 external-lz4 = ["rdkafka-sys/external-lz4"]
 external_lz4 = ["rdkafka-sys/external_lz4"]
+# tracing, optional dependency
 
 [package.metadata.docs.rs]
 # docs.rs doesn't allow writing to ~/.cargo/registry (reasonably), so we have to

src/admin.rs

@@ -17,14 +17,14 @@ use std::time::Duration;
 use futures_channel::oneshot;
 use futures_util::future::{self, Either, FutureExt};
 use futures_util::ready;
-use log::{trace, warn};
 
 use rdkafka_sys as rdsys;
 use rdkafka_sys::types::*;
 
 use crate::client::{Client, ClientContext, DefaultClientContext, NativeQueue};
 use crate::config::{ClientConfig, FromClientConfig, FromClientConfigAndContext};
 use crate::error::{IsError, KafkaError, KafkaResult};
+use crate::log::{trace, warn};
 use crate::util::{cstr_to_owned, AsCArray, ErrBuf, IntoOpaque, KafkaDrop, NativePtr, Timeout};
 
 //

src/client.rs

@@ -21,15 +21,14 @@ use std::slice;
 use std::string::ToString;
 use std::sync::Arc;
 
-use log::{debug, error, info, trace, warn};
-
 use rdkafka_sys as rdsys;
 use rdkafka_sys::types::*;
 
 use crate::config::{ClientConfig, NativeClientConfig, RDKafkaLogLevel};
 use crate::consumer::RebalanceProtocol;
 use crate::error::{IsError, KafkaError, KafkaResult};
 use crate::groups::GroupList;
+use crate::log::{debug, error, info, trace, warn};
 use crate::metadata::Metadata;
 use crate::statistics::Statistics;
 use crate::util::{ErrBuf, KafkaDrop, NativePtr, Timeout};

src/config.rs

@@ -28,13 +28,12 @@ use std::iter::FromIterator;
 use std::os::raw::c_char;
 use std::ptr;
 
-use log::{log_enabled, Level};
-
 use rdkafka_sys as rdsys;
 use rdkafka_sys::types::*;
 
 use crate::client::ClientContext;
 use crate::error::{IsError, KafkaError, KafkaResult};
+use crate::log::{enabled, DEBUG, INFO, WARN};
 use crate::util::{ErrBuf, KafkaDrop, NativePtr};
 
 /// The log levels supported by librdkafka.
@@ -286,11 +285,11 @@ impl Extend<(String, String)> for ClientConfig {
 
 /// Return the log level
 fn log_level_from_global_config() -> RDKafkaLogLevel {
-    if log_enabled!(target: "librdkafka", Level::Debug) {
+    if enabled!(target: "librdkafka", DEBUG) {
         RDKafkaLogLevel::Debug
-    } else if log_enabled!(target: "librdkafka", Level::Info) {
+    } else if enabled!(target: "librdkafka", INFO) {
         RDKafkaLogLevel::Info
-    } else if log_enabled!(target: "librdkafka", Level::Warn) {
+    } else if enabled!(target: "librdkafka", WARN) {
         RDKafkaLogLevel::Warning
     } else {
         RDKafkaLogLevel::Error

src/consumer/base_consumer.rs

@@ -7,8 +7,6 @@ use std::os::raw::c_void;
 use std::ptr;
 use std::sync::Arc;
 
-use log::trace;
-
 use rdkafka_sys as rdsys;
 use rdkafka_sys::types::*;
 
@@ -22,6 +20,7 @@ use crate::consumer::{
 };
 use crate::error::{IsError, KafkaError, KafkaResult};
 use crate::groups::GroupList;
+use crate::log::trace;
 use crate::message::{BorrowedMessage, Message};
 use crate::metadata::Metadata;
 use crate::topic_partition_list::{Offset, TopicPartitionList};

src/consumer/mod.rs

@@ -4,14 +4,13 @@ use std::ptr;
 use std::sync::Arc;
 use std::time::Duration;
 
-use log::{error, trace};
-
 use rdkafka_sys as rdsys;
 use rdkafka_sys::types::*;
 
 use crate::client::{Client, ClientContext, NativeClient};
 use crate::error::KafkaResult;
 use crate::groups::GroupList;
+use crate::log::{error, trace};
 use crate::message::BorrowedMessage;
 use crate::metadata::Metadata;
 use crate::topic_partition_list::{Offset, TopicPartitionList};

src/consumer/stream_consumer.rs

@@ -13,7 +13,7 @@ use futures_channel::oneshot;
 use futures_util::future::{self, Either, FutureExt};
 use futures_util::pin_mut;
 use futures_util::stream::{Stream, StreamExt};
-use log::trace;
+use crate::log::trace;
 use slab::Slab;
 
 use rdkafka_sys as rdsys;

src/lib.rs

@@ -207,9 +207,13 @@
 //!
 //! ## Debugging
 //!
-//! rust-rdkafka uses the [`log`] and [`env_logger`] crates to handle logging.
-//! Logging can be enabled using the `RUST_LOG` environment variable, for
-//! example:
+//! rust-rdkafka uses the [`log`] crate to handle logging.
+//! Optionally, enable the `tracing` feature to emit [`tracing`]
+//! events as opposed to [`log`] records.
+//!
+//! In test and examples, rust-rdkafka uses the  [`env_logger`] crate
+//! to format logs. In those contexts, logging can be enabled
+//! using the `RUST_LOG` environment variable, for example:
 //!
 //! ```bash
 //! RUST_LOG="librdkafka=trace,rdkafka::client=debug" cargo test
@@ -234,6 +238,7 @@
 //! [`StreamConsumer`]: https://docs.rs/rdkafka/*/rdkafka/consumer/stream_consumer/struct.StreamConsumer.html
 //! [`ThreadedProducer`]: https://docs.rs/rdkafka/*/rdkafka/producer/base_producer/struct.ThreadedProducer.html
 //! [`log`]: https://docs.rs/log
+//! [`tracing`]: https://docs.rs/tracing
 //! [`env_logger`]: https://docs.rs/env_logger
 //! [Apache Kafka]: https://kafka.apache.org
 //! [asynchronous processing example]: https://github.com/fede1024/rust-rdkafka/blob/master/examples/asynchronous_processing.rs
@@ -270,6 +275,7 @@ pub mod config;
 pub mod consumer;
 pub mod error;
 pub mod groups;
+pub(crate) mod log;
 pub mod message;
 pub mod metadata;
 pub mod producer;

src/log.rs

@@ -0,0 +1,21 @@
+//! A wrapper module to export logging functionality from
+//! [`log`] or [`tracing`] depending on the `tracing` feature.
+//!
+//! [`log`]: https://docs.rs/log
+//! [`tracing`]: https://docs.rs/tracing
+
+#[cfg(not(feature = "tracing"))]
+pub(crate) use log::{
+    debug, error, info, log_enabled as enabled, trace, warn, Level::Debug as DEBUG,
+    Level::Info as INFO, Level::Warn as WARN,
+};
+
+#[cfg(feature = "tracing")]
+pub(crate) use tracing::{debug, enabled, error, info, trace, warn};
+
+#[cfg(feature = "tracing")]
+pub const DEBUG: tracing::Level = tracing::Level::DEBUG;
+#[cfg(feature = "tracing")]
+pub const INFO: tracing::Level = tracing::Level::INFO;
+#[cfg(feature = "tracing")]
+pub const WARN: tracing::Level = tracing::Level::WARN;

src/util.rs

@@ -18,7 +18,8 @@ use std::time::{Duration, SystemTime, UNIX_EPOCH};
 use futures_channel::oneshot;
 #[cfg(feature = "naive-runtime")]
 use futures_util::future::{FutureExt, Map};
-use log::trace;
+
+use crate::log::trace;
 
 use rdkafka_sys as rdsys;