add support for multiple log formats

this commit adds the tracing-subscriber crate and use its formatters to
support multiple log formats.

More details in
#464 (comment)

Signed-off-by: Sebastian Webber <sebastian@swebber.me>

Author: sebastianwebber

Cargo.lock

@@ -47,6 +47,8 @@ tokio-test = "0.4.2"
 serde_json = "1"
 itertools = "0.10"
 clap = { version = "4.3.1", features = ["derive", "env"] }
+tracing = "0.1.37"
+tracing-subscriber = { version = "0.3.17", features = ["json"]}
 
 [target.'cfg(not(target_env = "msvc"))'.dependencies]
 jemallocator = "0.5.0"

Cargo.toml

@@ -1,17 +1,27 @@
-use clap::Parser;
-use log::LevelFilter;
+use clap::{Parser, ValueEnum};
+use tracing::Level;
 
 /// PgCat: Nextgen PostgreSQL Pooler
 #[derive(Parser, Debug)]
 #[command(author, version, about, long_about = None)]
-pub(crate) struct Args {
+pub struct Args {
     #[arg(default_value_t = String::from("pgcat.toml"), env)]
     pub config_file: String,
 
-    #[arg(short, long, default_value_t = LevelFilter::Info, env)]
-    pub log_level: log::LevelFilter,
+    #[arg(short, long, default_value_t = tracing::Level::INFO, env)]
+    pub log_level: Level,
+
+    #[clap(short='F', long, value_enum, default_value_t=LogFormat::Text, env)]
+    pub log_format: LogFormat,
 }
 
-pub(crate) fn parse() -> Args {
+pub fn parse() -> Args {
     return Args::parse();
 }
+
+#[derive(ValueEnum, Clone, Debug)]
+pub enum LogFormat {
+    Text,
+    Structured,
+    Debug,
+}

src/cmd_args.rs

@@ -1,13 +1,13 @@
 pub mod admin;
 pub mod auth_passthrough;
 pub mod client;
+pub mod cmd_args;
 pub mod config;
 pub mod constants;
 pub mod dns_cache;
 pub mod errors;
 pub mod messages;
 pub mod mirrors;
-pub mod multi_logger;
 pub mod plugins;
 pub mod pool;
 pub mod prometheus;

src/lib.rs

@@ -61,18 +61,31 @@ use std::str::FromStr;
 use std::sync::Arc;
 use tokio::sync::broadcast;
 
+use pgcat::cmd_args;
+use pgcat::cmd_args::LogFormat;
 use pgcat::config::{get_config, reload_config, VERSION};
 use pgcat::dns_cache;
 use pgcat::messages::configure_socket;
 use pgcat::pool::{ClientServerMap, ConnectionPool};
 use pgcat::prometheus::start_metric_server;
 use pgcat::stats::{Collector, Reporter, REPORTER};
-
-mod cmd_args;
+use tracing_subscriber;
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     let args = cmd_args::parse();
-    pgcat::multi_logger::MultiLogger::init(args.log_level).unwrap();
+    match args.log_format {
+        LogFormat::Structured => tracing_subscriber::fmt()
+            .json()
+            .with_max_level(args.log_level)
+            .init(),
+        LogFormat::Debug => tracing_subscriber::fmt()
+            .pretty()
+            .with_max_level(args.log_level)
+            .init(),
+        _ => tracing_subscriber::fmt()
+            .with_max_level(args.log_level)
+            .init(),
+    };
 
     info!("Welcome to PgCat! Meow. (Version {})", VERSION);