|
|
@@ -15,6 +15,13 @@ pub struct Entry {
|
|
|
pub expires_at: Option<Instant>,
|
|
|
}
|
|
|
|
|
|
+/// Database Entry
|
|
|
+///
|
|
|
+/// A database entry is a Value associated with an optional expiration time.
|
|
|
+///
|
|
|
+/// The database will never return an entry if has expired already, by having
|
|
|
+/// this promise we can run the purge process every few seconds instead of doing
|
|
|
+/// so more frequently.
|
|
|
impl Entry {
|
|
|
pub fn new(value: Value) -> Self {
|
|
|
Self {
|
|
|
@@ -23,6 +30,8 @@ impl Entry {
|
|
|
}
|
|
|
}
|
|
|
|
|
|
+ /// Changes the value that is wrapped in this entry, the TTL (expired_at) is
|
|
|
+ /// not affected.
|
|
|
pub fn change_value(&mut self, value: Value) {
|
|
|
self.value = value;
|
|
|
}
|
|
|
@@ -35,6 +44,10 @@ impl Entry {
|
|
|
&self.value
|
|
|
}
|
|
|
|
|
|
+ /// If the Entry should be taken as valid, if this function returns FALSE
|
|
|
+ /// the callee should behave as if the key was not found. By having this
|
|
|
+ /// behaviour we can schedule the purge thread to run every few seconds or
|
|
|
+ /// even minutes instead of once every second.
|
|
|
pub fn is_valid(&self) -> bool {
|
|
|
self.expires_at.map_or(true, |x| x > Instant::now())
|
|
|
}
|
|
|
@@ -42,8 +55,24 @@ impl Entry {
|
|
|
|
|
|
#[derive(Debug)]
|
|
|
pub struct Db {
|
|
|
+ /// A vector of hashmaps.
|
|
|
+ ///
|
|
|
+ /// Instead of having a single HashMap, and having all threads fighting for
|
|
|
+ /// blocking the single HashMap, we have a vector of N HashMap
|
|
|
+ /// (configurable), which in theory allow to have faster reads and writes.
|
|
|
+ ///
|
|
|
+ /// Because all operations are always key specific, the key is used to hash
|
|
|
+ /// and select to which HashMap the data might be stored.
|
|
|
entries: Vec<RwLock<HashMap<Bytes, Entry>>>,
|
|
|
+ /// B-Tree Map of expiring keys
|
|
|
+ ///
|
|
|
+ /// This B-Tree has the name of expiring entries, and they are sorted by the
|
|
|
+ /// Instant where the entries are expiring.
|
|
|
+ ///
|
|
|
+ /// Because it is possible that two entries expire at the same Instant, a
|
|
|
+ /// counter is introduced to avoid collisions on this B-Tree.
|
|
|
expirations: RwLock<BTreeMap<(Instant, u64), String>>,
|
|
|
+ /// Number of HashMaps that are available.
|
|
|
slots: usize,
|
|
|
}
|
|
|
|
