From 5da80c7631f07913f5d5568046089c91a0deb7d2 Mon Sep 17 00:00:00 2001
From: iximeow <me@iximeow.net>
Date: Sun, 2 Jul 2023 01:01:39 -0700
Subject: clean up old stale jobs for clients that have gone away

---
 src/ci_driver.rs | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++-----
 src/dbctx.rs     | 11 ++++++++++
 src/sql.rs       |  2 +-
 3 files changed, 73 insertions(+), 7 deletions(-)

diff --git a/src/ci_driver.rs b/src/ci_driver.rs
index 439b4d4..d41cb75 100644
--- a/src/ci_driver.rs
+++ b/src/ci_driver.rs
@@ -1,5 +1,6 @@
 use std::process::Command;
-use std::sync::RwLock;
+use std::collections::HashMap;
+use std::sync::{Mutex, RwLock};
 use lazy_static::lazy_static;
 use std::io::Read;
 use serde_derive::{Deserialize, Serialize};
@@ -8,7 +9,7 @@ use std::fmt;
 use std::path::{Path, PathBuf};
 use tokio::spawn;
 use tokio_stream::wrappers::ReceiverStream;
-use std::sync::Arc;
+use std::sync::{Arc, Weak};
 use std::time::{SystemTime, UNIX_EPOCH};
 use axum_server::tls_rustls::RustlsConfig;
 use axum::body::StreamBody;
@@ -28,12 +29,13 @@ mod sql;
 mod notifier;
 mod io;
 
-use crate::dbctx::{DbCtx, PendingRun, Job};
+use crate::dbctx::{DbCtx, PendingRun, Job, Run};
 use crate::sql::JobResult;
 use crate::sql::RunState;
 
 lazy_static! {
     static ref AUTH_SECRET: RwLock<Option<String>> = RwLock::new(None);
+    static ref ACTIVE_TASKS: Mutex<HashMap<u64, Weak<()>>> = Mutex::new(HashMap::new());
 }
 
 fn reserve_artifacts_dir(run: u64) -> std::io::Result<PathBuf> {
@@ -140,7 +142,9 @@ struct ClientJob {
     remote_git_url: String,
     sha: String,
     task: PendingRun,
-    client: RunnerClient
+    client: RunnerClient,
+    // exists only as confirmation this `ClientJob` is somewhere, still alive and being processed.
+    task_witness: Arc<()>,
 }
 
 impl ClientJob {
@@ -304,13 +308,16 @@ impl RunnerClient {
                 if resp == serde_json::json!({
                     "status": "started"
                 }) {
+                    let task_witness = Arc::new(());
+                    ACTIVE_TASKS.lock().unwrap().insert(job.id, Arc::downgrade(&task_witness));
                     eprintln!("resp: {:?}", resp);
                     Ok(Some(ClientJob {
                         task: job.clone(),
                         dbctx: Arc::clone(dbctx),
                         sha: sha.to_string(),
                         remote_git_url: remote_git_url.to_string(),
-                        client: self
+                        client: self,
+                        task_witness,
                     }))
                 } else {
                     Err("client rejected job".to_string())
@@ -498,11 +505,59 @@ async fn main() {
 
     let dbctx = Arc::new(DbCtx::new(&driver_config.config_path, &driver_config.db_path));
 
+    dbctx.create_tables().unwrap();
+
     let (api_server, mut channel) = make_api_server(Arc::clone(&dbctx)).await;
     spawn(axum_server::bind_rustls(driver_config.server_addr.parse().unwrap(), config)
           .serve(api_server.into_make_service()));
 
-    dbctx.create_tables().unwrap();
+async fn old_task_reaper(dbctx: Arc<DbCtx>) {
+    let mut potentially_stale_tasks = dbctx.get_active_runs().unwrap();
+
+    let active_tasks = ACTIVE_TASKS.lock().unwrap();
+
+    for (id, witness) in active_tasks.iter() {
+        if let Some(idx) = potentially_stale_tasks.iter().position(|task| task.id == *id) {
+            potentially_stale_tasks.swap_remove(idx);
+        }
+    }
+
+    std::mem::drop(active_tasks);
+
+    // ok, so we have tasks that are not active, now if the task is started we know someone should
+    // be running it and they are not. retain only those tasks, as they are ones we may want to
+    // mark dead.
+    //
+    // further, filter out any tasks created in the last 60 seconds. this is a VERY generous grace
+    // period for clients that have accepted a job but for some reason we have not recorded them as
+    // active (perhaps they are slow to ack somehow).
+
+    let stale_threshold = crate::io::now_ms() - 60_000;
+
+    let stale_tasks: Vec<Run> = potentially_stale_tasks.into_iter().filter(|task| {
+        match (task.state, task.start_time) {
+            // `run` is atomically set to `Started` and adorned with a `start_time`. disagreement
+            // between the two means this run is corrupt and should be reaped.
+            (RunState::Started, None) => {
+                true
+            },
+            (RunState::Started, Some(start_time)) => {
+                start_time < stale_threshold
+            }
+            // and if it's not `started`, it's either pending (not assigned yet, so not stale), or
+            // one of the complete statuses.
+            _ => {
+                false
+            }
+        }
+    }).collect();
+
+    for task in stale_tasks.iter() {
+        dbctx.reap_task(task.id).expect("works");
+    }
+}
+
+    spawn(old_task_reaper(Arc::clone(&dbctx)));
 
     loop {
         let runs = dbctx.get_pending_runs().unwrap();
diff --git a/src/dbctx.rs b/src/dbctx.rs
index 0e999f3..3eb68bd 100644
--- a/src/dbctx.rs
+++ b/src/dbctx.rs
@@ -384,6 +384,17 @@ impl DbCtx {
         Ok(run_id)
     }
 
+    pub fn reap_task(&self, task_id: u64) -> Result<(), String> {
+        let conn = self.conn.lock().unwrap();
+
+        conn.execute(
+            "update runs set final_status=\"lost signal\", state=4 where id=?1;",
+            [task_id]
+        ).unwrap();
+
+        Ok(())
+    }
+
     pub fn metrics_for_run(&self, run: u64) -> Result<Vec<MetricRecord>, String> {
         let conn = self.conn.lock().unwrap();
 
diff --git a/src/sql.rs b/src/sql.rs
index e911c96..a09e4bf 100644
--- a/src/sql.rs
+++ b/src/sql.rs
@@ -11,7 +11,7 @@ pub enum JobResult {
     Fail = 1,
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Copy, Clone, PartialEq)]
 pub enum RunState {
     Pending = 0,
     Started = 1,
-- 
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