Revive network-test logs files in CI (#7459)

https://github.com/sigp/lighthouse/issues/7187


  This PR adds a writer that implements `tracing_subscriber::fmt::MakeWriter`, which writes logs to separate files for each test.

beacon_node/beacon_chain/src/test_utils.rs

@@ -69,8 +69,6 @@ use types::{typenum::U4294967296, *};
 pub const HARNESS_GENESIS_TIME: u64 = 1_567_552_690;
 // Environment variable to read if `fork_from_env` feature is enabled.
 pub const FORK_NAME_ENV_VAR: &str = "FORK_NAME";
-// Environment variable to read if `ci_logger` feature is enabled.
-pub const CI_LOGGER_DIR_ENV_VAR: &str = "CI_LOGGER_DIR";
 
 // Pre-computed data column sidecar using a single static blob from:
 // `beacon_node/execution_layer/src/test_utils/fixtures/mainnet/test_blobs_bundle.ssz`

beacon_node/network/Cargo.toml

@@ -57,4 +57,3 @@ disable-backfill = []
 fork_from_env = ["beacon_chain/fork_from_env"]
 portable = ["beacon_chain/portable"]
 test_logger = []
-ci_logger = []

beacon_node/network/src/sync/tests/lookups.rs

@@ -107,6 +107,8 @@ impl TestRig {
         // deterministic seed
         let rng = ChaCha20Rng::from_seed([0u8; 32]);
 
+        init_tracing();
+
         TestRig {
             beacon_processor_rx,
             beacon_processor_rx_queue: vec![],

beacon_node/network/src/sync/tests/mod.rs

@@ -9,9 +9,14 @@ use beacon_processor::WorkEvent;
 use lighthouse_network::NetworkGlobals;
 use rand_chacha::ChaCha20Rng;
 use slot_clock::ManualSlotClock;
-use std::sync::Arc;
+use std::fs::OpenOptions;
+use std::io::Write;
+use std::sync::{Arc, Once};
 use store::MemoryStore;
 use tokio::sync::mpsc;
+use tracing_subscriber::fmt::MakeWriter;
+use tracing_subscriber::layer::SubscriberExt;
+use tracing_subscriber::util::SubscriberInitExt;
 use types::{ChainSpec, ForkName, MinimalEthSpec as E};
 
 mod lookups;
@@ -65,3 +70,55 @@ struct TestRig {
     fork_name: ForkName,
     spec: Arc<ChainSpec>,
 }
+
+// Environment variable to read if `fork_from_env` feature is enabled.
+pub const FORK_NAME_ENV_VAR: &str = "FORK_NAME";
+// Environment variable specifying the log output directory in CI.
+pub const CI_LOGGER_DIR_ENV_VAR: &str = "CI_LOGGER_DIR";
+
+static INIT_TRACING: Once = Once::new();
+
+pub fn init_tracing() {
+    INIT_TRACING.call_once(|| {
+        if std::env::var(CI_LOGGER_DIR_ENV_VAR).is_ok() {
+            // Enable logging to log files for each test and each fork.
+            tracing_subscriber::registry()
+                .with(
+                    tracing_subscriber::fmt::layer()
+                        .with_ansi(false)
+                        .with_writer(CILogWriter),
+                )
+                .init();
+        }
+    });
+}
+
+// CILogWriter writes logs to separate files for each test and each fork.
+struct CILogWriter;
+
+impl<'a> MakeWriter<'a> for CILogWriter {
+    type Writer = Box<dyn Write + Send>;
+
+    // fmt::Layer calls this method each time an event is recorded.
+    fn make_writer(&'a self) -> Self::Writer {
+        let log_dir = std::env::var(CI_LOGGER_DIR_ENV_VAR).unwrap();
+        let fork_name = std::env::var(FORK_NAME_ENV_VAR)
+            .map(|s| format!("{s}_"))
+            .unwrap_or_default();
+
+        // The current test name can be got via the thread name.
+        let test_name = std::thread::current()
+            .name()
+            .unwrap_or("unnamed")
+            .replace(|c: char| !c.is_alphanumeric(), "_");
+
+        let file_path = format!("{log_dir}/{fork_name}{test_name}.log");
+        let file = OpenOptions::new()
+            .append(true)
+            .create(true)
+            .open(&file_path)
+            .expect("failed to open a log file");
+
+        Box::new(file)
+    }
+}