rrd: try to load database if not already present in cache

Before, a call to `update` was necessary to load an existing database
into the cache. If `update` was never called, `extract_cached_data`
would simply return no data.

Signed-off-by: Lukas Wagner <l.wagner@proxmox.com>

proxmox-rrd/src/cache.rs

@@ -12,7 +12,7 @@ use crossbeam_channel::{bounded, TryRecvError};
 
 use proxmox_sys::fs::{create_path, CreateOptions};
 
-use crate::rrd::{AggregationFn, Archive, DataSourceType, Database};
+use crate::rrd::{AggregationFn, DataSourceType, Database};
 use crate::Entry;
 
 mod journal;
@@ -58,7 +58,8 @@ impl Cache {
         file_options: Option<CreateOptions>,
         dir_options: Option<CreateOptions>,
         apply_interval: f64,
-        load_rrd_cb: fn(path: &Path, rel_path: &str, dst: DataSourceType) -> Database,
+        load_rrd_cb: fn(path: &Path, rel_path: &str) -> Option<Database>,
+        create_rrd_cb: fn(dst: DataSourceType) -> Database,
     ) -> Result<Self, Error> {
         let basedir = basedir.as_ref().to_owned();
 
@@ -80,7 +81,7 @@ impl Cache {
         });
 
         let state = JournalState::new(Arc::clone(&config))?;
-        let rrd_map = RRDMap::new(Arc::clone(&config), load_rrd_cb);
+        let rrd_map = RRDMap::new(Arc::clone(&config), load_rrd_cb, create_rrd_cb);
 
         Ok(Self {
             config: Arc::clone(&config),
@@ -248,10 +249,24 @@ impl Cache {
         start: Option<u64>,
         end: Option<u64>,
     ) -> Result<Option<Entry>, Error> {
-        self.rrd_map
-            .read()
-            .unwrap()
-            .extract_cached_data(base, name, cf, resolution, start, end)
+        let res = {
+            let map = self.rrd_map.read().unwrap();
+            map.extract_cached_data(base, name, cf, resolution, start, end)?
+        };
+
+        match res {
+            Some(entry) => Ok(Some(entry)),
+            None => {
+                let mut map = self.rrd_map.write().unwrap();
+                let loaded = map.load(&format!("{base}/{name}"))?;
+
+                if loaded {
+                    map.extract_cached_data(base, name, cf, resolution, start, end)
+                } else {
+                    Ok(None)
+                }
+            }
+        }
     }
 }
 

proxmox-rrd/src/cache/rrd_map.rs

@@ -14,18 +14,21 @@ use crate::Entry;
 pub struct RRDMap {
     config: Arc<CacheConfig>,
     map: HashMap<String, Database>,
-    load_rrd_cb: fn(path: &Path, rel_path: &str, dst: DataSourceType) -> Database,
+    load_rrd_cb: fn(path: &Path, rel_path: &str) -> Option<Database>,
+    create_rrd_cb: fn(dst: DataSourceType) -> Database,
 }
 
 impl RRDMap {
     pub(crate) fn new(
         config: Arc<CacheConfig>,
-        load_rrd_cb: fn(path: &Path, rel_path: &str, dst: DataSourceType) -> Database,
+        load_rrd_cb: fn(path: &Path, rel_path: &str) -> Option<Database>,
+        create_rrd_cb: fn(dst: DataSourceType) -> Database,
     ) -> Self {
         Self {
             config,
             map: HashMap::new(),
             load_rrd_cb,
+            create_rrd_cb,
         }
     }
 
@@ -44,13 +47,18 @@ impl RRDMap {
         } else {
             let mut path = self.config.basedir.clone();
             path.push(rel_path);
+            let mut rrd = match (self.load_rrd_cb)(&path, rel_path) {
+                None => {
                     create_path(
                         path.parent().unwrap(),
                         Some(self.config.dir_options.clone()),
                         Some(self.config.dir_options.clone()),
                     )?;
 
-            let mut rrd = (self.load_rrd_cb)(&path, rel_path, dst);
+                    (self.create_rrd_cb)(dst)
+                }
+                Some(rrd) => rrd,
+            };
 
             if !new_only || time > rrd.last_update() {
                 rrd.update(time, value);
@@ -94,4 +102,21 @@ impl RRDMap {
             None => Ok(None),
         }
     }
+
+    pub fn load(&mut self, rel_path: &str) -> Result<bool, Error> {
+        if self.map.get(rel_path).is_some() {
+            // Already loaded, do nothing
+            return Ok(true);
+        }
+
+        let mut path = self.config.basedir.clone();
+        path.push(rel_path);
+
+        if let Some(rrd) = (self.load_rrd_cb)(&path, rel_path) {
+            self.map.insert(rel_path.to_string(), rrd);
+            return Ok(true);
+        } else {
+            return Ok(false);
+        }
+    }
 }