feat: perform full checkpoints and truncate WAL every 2k events

src/db.rs

@@ -38,9 +38,10 @@ pub struct SubmittedEvent {
 
 /// Database file
 pub const DB_FILE: &str = "nostr.db";
-/// How many persisted events before optimization is triggered
-pub const EVENT_COUNT_OPTIMIZE_TRIGGER: usize = 500;
-/// How many persisted events before we pause for backups
+/// How many persisted events before DB maintenannce is triggered.
+pub const EVENT_COUNT_MAINTENANCE_TRIGGER: usize = 2000;
+/// How many persisted events before we pause for backups.
+/// It isn't clear this is enough to make the online backup API work yet.
 pub const EVENT_COUNT_BACKUP_PAUSE_TRIGGER: usize = 1000;
 
 /// Build a database connection pool.
@@ -95,6 +96,38 @@ pub fn optimize_db(conn: &mut PooledConnection) -> Result<()> {
     conn.execute_batch("PRAGMA optimize;")?;
     Ok(())
 }
+#[derive(Debug)]
+enum SqliteReturnStatus {
+    SqliteOk,
+    SqliteBusy,
+    SqliteError,
+    SqliteOther(u64),
+}
+
+/// Checkpoint/Truncate WAL
+pub fn checkpoint_db(conn: &mut PooledConnection) -> Result<()> {
+    let query = "PRAGMA wal_checkpoint(TRUNCATE);";
+    let start = Instant::now();
+    let (cp_result, wal_size, _frames_checkpointed) = conn.query_row(query, [], |row| {
+        let checkpoint_result: u64 = row.get(0)?;
+        let wal_size: u64 = row.get(1)?;
+        let frames_checkpointed: u64 = row.get(2)?;
+        Ok((checkpoint_result, wal_size, frames_checkpointed))
+    })?;
+    let result = match cp_result {
+        0 => SqliteReturnStatus::SqliteOk,
+        1 => SqliteReturnStatus::SqliteBusy,
+        2 => SqliteReturnStatus::SqliteError,
+        x => SqliteReturnStatus::SqliteOther(x),
+    };
+    info!(
+        "checkpoint ran in {:?} (result: {:?}, WAL size: {})",
+        start.elapsed(),
+        result,
+        wal_size
+    );
+    Ok(())
+}
 
 /// Spawn a database writer that persists events to the SQLite store.
 pub async fn db_writer(
@@ -135,9 +168,12 @@ pub async fn db_writer(
         let rps_setting = settings.limits.messages_per_sec;
         let mut most_recent_rate_limit = Instant::now();
         let mut lim_opt = None;
-        // Keep rough track of events so we can run optimize eventually.
-        let mut optimize_counter: usize = 0;
-        // Constant writing has interfered with online backups.  Keep track of how long since we've given the backups a chance to run.
+        // Keep rough track of events so we can run maintenance
+        // eventually.
+        let mut maintenance_counter: usize = 0;
+        // Constant writing has interfered with online backups.  Keep
+        // track of how long since we've given the backups a chance to
+        // run.
         let mut backup_pause_counter: usize = 0;
         let clock = governor::clock::QuantaClock::default();
         if let Some(rps) = rps_setting {
@@ -279,12 +315,14 @@ pub async fn db_writer(
                     backup_pause_counter = 0
                 }
 
-                // Use this as a trigger to do optimization
-                optimize_counter += 1;
-                if optimize_counter > EVENT_COUNT_OPTIMIZE_TRIGGER {
-                    info!("running database optimizer");
-                    optimize_counter = 0;
+                // Use this as a trigger to do optimization & checkpointing
+                maintenance_counter += 1;
+                if maintenance_counter > EVENT_COUNT_MAINTENANCE_TRIGGER {
+                    debug!("running database optimizer");
+                    maintenance_counter = 0;
                     optimize_db(&mut pool.get()?).ok();
+                    debug!("running wal_checkpoint(TRUNCATE)");
+                    checkpoint_db(&mut pool.get()?).ok();
                 }
             }