tracing: Use json-subscriber crate for JSON logging

This allows us to flatten the span fields, which makes them a lot easier to use within Datadog.

Author: Turbo87

Cargo.lock

@@ -79,6 +79,7 @@ hyper = { version = "=1.5.0", features = ["client", "http1"] }
 indexmap = { version = "=2.6.0", features = ["serde"] }
 indicatif = "=0.17.8"
 ipnetwork = "=0.20.0"
+json-subscriber = "=0.2.1"
 tikv-jemallocator = { version = "=0.6.0", features = ['unprefixed_malloc_on_supported_platforms', 'profiling'] }
 lettre = { version = "=0.11.9", default-features = false, features = ["file-transport", "smtp-transport", "native-tls", "hostname", "builder"] }
 minijinja = "=2.3.1"

Cargo.toml

@@ -29,8 +29,9 @@ fn init_with_default_level(level: LevelFilter) {
         .unwrap_or_default();
 
     let log_layer = match log_format.as_deref() {
-        Some("json") => tracing_subscriber::fmt::layer()
-            .json()
+        Some("json") => json_subscriber::fmt::layer()
+            .flatten_event(true)
+            .with_flat_span_list(true)
             .with_filter(env_filter)
             .boxed(),
         _ => tracing_subscriber::fmt::layer()