include timeline ids in tenant details response (#6166)

Part of getpage@lsn benchmark epic:
https://github.com/neondatabase/neon/issues/5771

This allows getting the list of tenants and timelines without triggering
initial logical size calculation by requesting the timeline details API
response, which would skew our results.

libs/pageserver_api/src/models.rs

@@ -370,6 +370,14 @@ pub struct TenantInfo {
     pub attachment_status: TenantAttachmentStatus,
 }
 
+#[derive(Serialize, Deserialize, Clone)]
+pub struct TenantDetails {
+    #[serde(flatten)]
+    pub tenant_info: TenantInfo,
+
+    pub timelines: Vec<TimelineId>,
+}
+
 /// This represents the output of the "timeline_detail" and "timeline_list" API calls.
 #[derive(Debug, Serialize, Deserialize, Clone)]
 pub struct TimelineInfo {

pageserver/client/src/mgmt_api.rs

@@ -64,6 +64,18 @@ impl Client {
         resp.json().await.map_err(Error::ReceiveBody)
     }
 
+    pub async fn tenant_details(
+        &self,
+        tenant_id: TenantId,
+    ) -> Result<pageserver_api::models::TenantDetails> {
+        let uri = format!("{}/v1/tenant/{tenant_id}", self.mgmt_api_endpoint);
+        self.get(uri)
+            .await?
+            .json()
+            .await
+            .map_err(Error::ReceiveBody)
+    }
+
     pub async fn list_timelines(
         &self,
         tenant_id: TenantId,

pageserver/src/http/routes.rs

@@ -14,6 +14,7 @@ use hyper::header;
 use hyper::StatusCode;
 use hyper::{Body, Request, Response, Uri};
 use metrics::launch_timestamp::LaunchTimestamp;
+use pageserver_api::models::TenantDetails;
 use pageserver_api::models::{
     DownloadRemoteLayersTaskSpawnRequest, LocationConfigMode, TenantAttachRequest,
     TenantLoadRequest, TenantLocationConfigRequest,
@@ -857,11 +858,14 @@ async fn tenant_status(
         }
 
         let state = tenant.current_state();
-        Result::<_, ApiError>::Ok(TenantInfo {
-            id: tenant_shard_id,
-            state: state.clone(),
-            current_physical_size: Some(current_physical_size),
-            attachment_status: state.attachment_status(),
+        Result::<_, ApiError>::Ok(TenantDetails {
+            tenant_info: TenantInfo {
+                id: tenant_shard_id,
+                state: state.clone(),
+                current_physical_size: Some(current_physical_size),
+                attachment_status: state.attachment_status(),
+            },
+            timelines: tenant.list_timeline_ids(),
         })
     }
     .instrument(info_span!("tenant_status_handler",

pageserver/src/tenant.rs

@@ -1552,6 +1552,10 @@ impl Tenant {
             .collect()
     }
 
+    pub fn list_timeline_ids(&self) -> Vec<TimelineId> {
+        self.timelines.lock().unwrap().keys().cloned().collect()
+    }
+
     /// This is used to create the initial 'main' timeline during bootstrapping,
     /// or when importing a new base backup. The caller is expected to load an
     /// initial image of the datadir to the new timeline after this.