Examples: add logging_log example

This example demonstrates usage of `env_logger` to listen to driver logs.

examples/Cargo.toml

@@ -12,7 +12,7 @@ rustyline = "9"
 rustyline-derive = "0.6"
 scylla = {path = "../scylla", features = ["ssl", "cloud", "chrono", "time", "num-bigint-03", "num-bigint-04", "bigdecimal-04"]}
 tokio = {version = "1.1.0", features = ["full"]}
-tracing = "0.1.25"
+tracing = { version = "0.1.25" , features = ["log"] }
 tracing-subscriber = { version = "0.3.14", features = ["env-filter"] }
 chrono = { version = "0.4", default-features = false }
 time = { version = "0.3.22" }
@@ -21,6 +21,7 @@ tower = "0.4"
 stats_alloc = "0.1"
 clap = { version = "3.2.4", features = ["derive"] }
 rand = "0.8.5"
+env_logger = "0.10"
 
 [[example]]
 name = "auth"
@@ -34,6 +35,10 @@ path = "basic.rs"
 name = "logging"
 path = "logging.rs"
 
+[[example]]
+name = "logging_log"
+path = "logging_log.rs"
+
 [[example]]
 name = "tls"
 path = "tls.rs"

examples/logging_log.rs

@@ -0,0 +1,27 @@
+use anyhow::Result;
+use scylla::transport::session::Session;
+use scylla::SessionBuilder;
+use std::env;
+use tracing::info;
+
+// To run this example, and view logged messages, RUST_LOG env var needs to be set
+// This can be done using shell command presented below
+// RUST_LOG=info cargo run --example logging_log
+#[tokio::main]
+async fn main() -> Result<()> {
+    // Driver uses tracing for logging purposes, but it's possible to use `log`
+    // ecosystem to view the messages. This requires adding `tracing` crate to
+    // dependencies and enabling it's "log" feature. Then you will be able to use
+    // loggers like `env_logger` to see driver's messages.
+    env_logger::init();
+
+    let uri = env::var("SCYLLA_URI").unwrap_or_else(|_| "127.0.0.1:9042".to_string());
+    info!("Connecting to {}", uri);
+
+    let session: Session = SessionBuilder::new().known_node(uri).build().await?;
+    session.query("CREATE KEYSPACE IF NOT EXISTS examples_ks WITH REPLICATION = {'class' : 'NetworkTopologyStrategy', 'replication_factor' : 1}", &[]).await?;
+
+    session.query("USE examples_ks", &[]).await?;
+
+    Ok(())
+}