Configure rsyslog for logs export using the spec (#11338)

- Work on https://github.com/neondatabase/cloud/issues/24896
- Cplane part https://github.com/neondatabase/cloud/pull/26808

Instead of reconfiguring rsyslog via an API endpoint [we have
agreed](https://neondb.slack.com/archives/C04DGM6SMTM/p1743513810964509?thread_ts=1743170369.865859&cid=C04DGM6SMTM)
to have a new `logs_export_host` field as part of the compute spec.

---------

Co-authored-by: Tristan Partin <tristan@neon.tech>

compute_tools/src/compute.rs

@@ -661,15 +661,8 @@ impl ComputeNode {
         }
 
         // Configure and start rsyslog for Postgres logs export
-        if self.has_feature(ComputeFeature::PostgresLogsExport) {
-            if let Some(ref project_id) = pspec.spec.cluster.cluster_id {
-                let host = PostgresLogsRsyslogConfig::default_host(project_id);
-                let conf = PostgresLogsRsyslogConfig::new(Some(&host));
-                configure_postgres_logs_export(conf)?;
-            } else {
-                warn!("not configuring rsyslog for Postgres logs export: project ID is missing")
-            }
-        }
+        let conf = PostgresLogsRsyslogConfig::new(pspec.spec.logs_export_host.as_deref());
+        configure_postgres_logs_export(conf)?;
 
         // Launch remaining service threads
         let _monitor_handle = launch_monitor(self);
@@ -1573,6 +1566,10 @@ impl ComputeNode {
             });
         }
 
+        // Reconfigure rsyslog for Postgres logs export
+        let conf = PostgresLogsRsyslogConfig::new(spec.logs_export_host.as_deref());
+        configure_postgres_logs_export(conf)?;
+
         // Write new config
         let pgdata_path = Path::new(&self.params.pgdata);
         config::write_postgres_conf(

compute_tools/src/config.rs

@@ -7,7 +7,7 @@ use std::io::prelude::*;
 use std::path::Path;
 
 use compute_api::responses::TlsConfig;
-use compute_api::spec::{ComputeAudit, ComputeFeature, ComputeMode, ComputeSpec, GenericOption};
+use compute_api::spec::{ComputeAudit, ComputeMode, ComputeSpec, GenericOption};
 
 use crate::pg_helpers::{
     GenericOptionExt, GenericOptionsSearch, PgOptionsSerialize, escape_conf_value,
@@ -255,7 +255,7 @@ pub fn write_postgres_conf(
 
     // We need Postgres to send logs to rsyslog so that we can forward them
     // further to customers' log aggregation systems.
-    if spec.features.contains(&ComputeFeature::PostgresLogsExport) {
+    if spec.logs_export_host.is_some() {
         writeln!(file, "log_destination='stderr,syslog'")?;
     }
 

compute_tools/src/http/openapi_spec.yaml

@@ -306,36 +306,6 @@ paths:
               schema:
                 $ref: "#/components/schemas/GenericError"
 
-  /configure_telemetry:
-    post:
-      tags:
-        - Configure
-      summary: Configure rsyslog
-      description: |
-        This API endpoint configures rsyslog to forward Postgres logs
-        to a specified otel collector.
-      operationId: configureTelemetry
-      requestBody:
-        required: true
-        content:
-          application/json:
-            schema:
-              type: object
-              properties:
-                logs_export_host:
-                  type: string
-                  description: |
-                    Hostname and the port of the otel collector. Leave empty to disable logs forwarding.
-                    Example: config-shy-breeze-123-collector-monitoring.neon-telemetry.svc.cluster.local:54526
-      responses:
-        204:
-          description: "Telemetry configured successfully"
-        500:
-          content:
-            application/json:
-              schema:
-                $ref: "#/components/schemas/GenericError"
-
 components:
   securitySchemes:
     JWT:

compute_tools/src/http/routes/configure.rs

@@ -1,11 +1,9 @@
 use std::sync::Arc;
 
-use axum::body::Body;
 use axum::extract::State;
 use axum::response::Response;
-use compute_api::requests::{ConfigurationRequest, ConfigureTelemetryRequest};
+use compute_api::requests::ConfigurationRequest;
 use compute_api::responses::{ComputeStatus, ComputeStatusResponse};
-use compute_api::spec::ComputeFeature;
 use http::StatusCode;
 use tokio::task;
 use tracing::info;
@@ -13,7 +11,6 @@ use tracing::info;
 use crate::compute::{ComputeNode, ParsedSpec};
 use crate::http::JsonResponse;
 use crate::http::extract::Json;
-use crate::rsyslog::{PostgresLogsRsyslogConfig, configure_postgres_logs_export};
 
 // Accept spec in JSON format and request compute configuration. If anything
 // goes wrong after we set the compute status to `ConfigurationPending` and
@@ -95,25 +92,3 @@ pub(in crate::http) async fn configure(
 
     JsonResponse::success(StatusCode::OK, body)
 }
-
-pub(in crate::http) async fn configure_telemetry(
-    State(compute): State<Arc<ComputeNode>>,
-    request: Json<ConfigureTelemetryRequest>,
-) -> Response {
-    if !compute.has_feature(ComputeFeature::PostgresLogsExport) {
-        return JsonResponse::error(
-            StatusCode::PRECONDITION_FAILED,
-            "Postgres logs export feature is not enabled".to_string(),
-        );
-    }
-
-    let conf = PostgresLogsRsyslogConfig::new(request.logs_export_host.as_deref());
-    if let Err(err) = configure_postgres_logs_export(conf) {
-        return JsonResponse::error(StatusCode::INTERNAL_SERVER_ERROR, err.to_string());
-    }
-
-    Response::builder()
-        .status(StatusCode::NO_CONTENT)
-        .body(Body::from(""))
-        .unwrap()
-}

compute_tools/src/http/server.rs

@@ -87,7 +87,6 @@ impl From<&Server> for Router<Arc<ComputeNode>> {
                 let authenticated_router = Router::<Arc<ComputeNode>>::new()
                     .route("/check_writability", post(check_writability::is_writable))
                     .route("/configure", post(configure::configure))
-                    .route("/configure_telemetry", post(configure::configure_telemetry))
                     .route("/database_schema", get(database_schema::get_schema_dump))
                     .route("/dbs_and_roles", get(dbs_and_roles::get_catalog_objects))
                     .route("/insights", get(insights::get_insights))

compute_tools/src/rsyslog.rs

@@ -119,16 +119,9 @@ impl<'a> PostgresLogsRsyslogConfig<'a> {
         };
         Ok(config_content)
     }
-
-    /// Returns the default host for otel collector that receives Postgres logs
-    pub fn default_host(project_id: &str) -> String {
-        format!(
-            "config-{}-collector.neon-telemetry.svc.cluster.local:10514",
-            project_id
-        )
-    }
 }
 
+/// Writes rsyslogd configuration for Postgres logs export and restarts rsyslog.
 pub fn configure_postgres_logs_export(conf: PostgresLogsRsyslogConfig) -> Result<()> {
     let new_config = conf.build()?;
     let current_config = PostgresLogsRsyslogConfig::current_config()?;
@@ -261,16 +254,5 @@ mod tests {
             let res = conf.build();
             assert!(res.is_err());
         }
-
-        {
-            // Verify config with default host
-            let host = PostgresLogsRsyslogConfig::default_host("shy-breeze-123");
-            let conf = PostgresLogsRsyslogConfig::new(Some(&host));
-            let res = conf.build();
-            assert!(res.is_ok());
-            let conf_str = res.unwrap();
-            assert!(conf_str.contains(r#"shy-breeze-123"#));
-            assert!(conf_str.contains(r#"port="10514""#));
-        }
     }
 }

control_plane/src/endpoint.rs

@@ -670,6 +670,7 @@ impl Endpoint {
             reconfigure_concurrency: self.reconfigure_concurrency,
             drop_subscriptions_before_start: self.drop_subscriptions_before_start,
             audit_log_level: ComputeAudit::Disabled,
+            logs_export_host: None::<String>,
         };
 
         // this strange code is needed to support respec() in tests

libs/compute_api/src/requests.rs

@@ -30,9 +30,3 @@ pub struct SetRoleGrantsRequest {
     pub privileges: Vec<Privilege>,
     pub role: PgIdent,
 }
-
-/// Request of the /configure_telemetry API
-#[derive(Debug, Deserialize, Serialize)]
-pub struct ConfigureTelemetryRequest {
-    pub logs_export_host: Option<String>,
-}

libs/compute_api/src/spec.rs

@@ -168,6 +168,10 @@ pub struct ComputeSpec {
     /// Extensions should be present in shared_preload_libraries
     #[serde(default)]
     pub audit_log_level: ComputeAudit,
+
+    /// Hostname and the port of the otel collector. Leave empty to disable Postgres logs forwarding.
+    /// Example: config-shy-breeze-123-collector-monitoring.neon-telemetry.svc.cluster.local:10514
+    pub logs_export_host: Option<String>,
 }
 
 /// Feature flag to signal `compute_ctl` to enable certain experimental functionality.
@@ -179,9 +183,6 @@ pub enum ComputeFeature {
     /// track short-lived connections as user activity.
     ActivityMonitorExperimental,
 
-    /// Allow to configure rsyslog for Postgres logs export
-    PostgresLogsExport,
-
     /// This is a special feature flag that is used to represent unknown feature flags.
     /// Basically all unknown to enum flags are represented as this one. See unit test
     /// `parse_unknown_features()` for more details.