: logging: default disable log forwarding (#1878)

Summary:

this diff sets the following defaults for hyperactor-mesh global configuration values:
- `MESH_ENABLE_LOG_FORWARDING=false`
- `MESH_ENABLE_FILE_CAPTURE=false`
- `MESH_TAIL_LOG_LINES=0`

the effect of this is to disable log forwarding, prevent allocating resources for log forwarding, no file capture at the hyperactor mesh level (including no "exit tail" capture), in fact, under these defaults there is no interception of child process stdio at all.

a workplace post is planned to announce this change in default configuration.

this diff is built on: D85783397 provide config for enabling/disabling hyperactor-mesh logging interception features, D85919326 for avoiding spinning up `LogForwardActor` meshes when log forwarding is enabled and D85969320 for some detailed testing.

Reviewed By: zdevito, vidhyav

Differential Revision: D86994420

Author: shayne-fletcher

hyperactor_mesh/src/bootstrap.rs

@@ -99,7 +99,7 @@ declare_attrs! {
         env_name: Some("HYPERACTOR_MESH_ENABLE_LOG_FORWARDING".to_string()),
         py_name: None,
     })
-    pub attr MESH_ENABLE_LOG_FORWARDING: bool = true;
+    pub attr MESH_ENABLE_LOG_FORWARDING: bool = false;
 
     /// When `true`: if stdio is piped, each child's `StreamFwder`
     /// also forwards lines to a host-scoped `FileAppender` managed by
@@ -124,7 +124,7 @@ declare_attrs! {
         env_name: Some("HYPERACTOR_MESH_ENABLE_FILE_CAPTURE".to_string()),
         py_name: None,
     })
-    pub attr MESH_ENABLE_FILE_CAPTURE: bool = true;
+    pub attr MESH_ENABLE_FILE_CAPTURE: bool = false;
 
     /// Maximum number of log lines retained in a proc's stderr/stdout
     /// tail buffer. Used by [`StreamFwder`] when wiring child
@@ -133,7 +133,7 @@ declare_attrs! {
         env_name: Some("HYPERACTOR_MESH_TAIL_LOG_LINES".to_string()),
         py_name: None,
     })
-    pub attr MESH_TAIL_LOG_LINES: usize = 100;
+    pub attr MESH_TAIL_LOG_LINES: usize = 0;
 
     /// If enabled (default), bootstrap child processes install
     /// `PR_SET_PDEATHSIG(SIGKILL)` so the kernel reaps them if the
@@ -3692,6 +3692,10 @@ mod tests {
     #[tokio::test]
     async fn exit_tail_is_attached_and_logged() {
         hyperactor_telemetry::initialize_logging_for_test();
+
+        let lock = hyperactor::config::global::lock();
+        let _guard = lock.override_key(MESH_TAIL_LOG_LINES, 100);
+
         // Spawn a child that writes to stderr then exits 7.
         let mut cmd = Command::new("sh");
         cmd.arg("-c")

hyperactor_mesh/src/v1/host_mesh.rs

@@ -1125,6 +1125,7 @@ mod tests {
 
     use super::*;
     use crate::Bootstrap;
+    use crate::bootstrap::MESH_TAIL_LOG_LINES;
     use crate::resource::Status;
     use crate::v1::ActorMesh;
     use crate::v1::testactor;
@@ -1321,6 +1322,9 @@ mod tests {
     #[tokio::test]
     #[cfg(fbcode_build)]
     async fn test_failing_proc_allocation() {
+        let lock = hyperactor::config::global::lock();
+        let _guard = lock.override_key(MESH_TAIL_LOG_LINES, 100);
+
         let program = crate::testresource::get("monarch/hyperactor_mesh/bootstrap");
 
         let hosts = vec![free_localhost_addr(), free_localhost_addr()];

monarch_hyperactor/src/v1/logging.rs

@@ -310,9 +310,9 @@ impl LoggingMeshClient {
             // re-spawning infra, which we deliberately don't do at
             // runtime.
             (None, true) => {
-                return Err(PyErr::new::<pyo3::exceptions::PyRuntimeError, _>(
-                    "log forwarding disabled by config at startup; cannot enable streaming_to_client",
-                ));
+                // return Err(PyErr::new::<pyo3::exceptions::PyRuntimeError, _>(
+                //     "log forwarding disabled by config at startup; cannot enable streaming_to_client",
+                // ));
             }
         }
 
@@ -592,6 +592,9 @@ mod tests {
                     );
                 }
 
+                /*
+                // Update (SF: 2025, 11, 13): We now ignore stream to client requests if
+                // log forwarding is enabled.
                 // (c) stream_to_client = true when forwarding was
                 //     never spawned -> Err
                 let res = client_ref.set_mode(&py_instance, true, None, 10);
@@ -606,6 +609,7 @@ mod tests {
                         "unexpected err when enabling streaming with no forwarders: {msg}"
                     );
                 }
+                */
             });
 
             drop(client_py); // See note "NOTE ON LIFECYCLE / CLEANUP"

python/monarch/_src/actor/v1/proc_mesh.py

@@ -365,8 +365,8 @@ def rank_tensors(self) -> Dict[str, "Tensor"]:
 
     async def logging_option(
         self,
-        stream_to_client: bool = True,
-        aggregate_window_sec: int | None = 3,
+        stream_to_client: bool = False,
+        aggregate_window_sec: int | None = None,
         level: int = logging.INFO,
     ) -> None:
         """