Memory db

lighthouse/db/disk_db.rs

@@ -55,15 +55,7 @@ impl DiskDB {
             db,
         }
     }
-}
 
-impl From<RocksError> for DBError {
-    fn from(e: RocksError) -> Self {
-        Self { message: e.to_string() }
-    }
-}
-
-impl ClientDB for DiskDB {
     /// Create a RocksDB column family. Corresponds to the
     /// `create_cf()` function on the RocksDB API.
     fn create_col(&mut self, col: &str)
@@ -75,6 +67,15 @@ impl ClientDB for DiskDB {
         }
     }
 
+}
+
+impl From<RocksError> for DBError {
+    fn from(e: RocksError) -> Self {
+        Self { message: e.to_string() }
+    }
+}
+
+impl ClientDB for DiskDB {
     /// Get the value for some key on some column.
     ///
     /// Corresponds to the `get_cf()` method on the RocksDB API.

lighthouse/db/memory_db.rs

@@ -0,0 +1,179 @@
+use std::collections::{ HashSet, HashMap };
+use std::sync::RwLock;
+use super::blake2::blake2b::blake2b;
+use super::{
+    ClientDB,
+    DBValue,
+    DBError
+};
+
+type DBHashMap = HashMap<Vec<u8>, Vec<u8>>;
+type ColumnHashSet = HashSet<String>;
+
+/// An in-memory database implementing the ClientDB trait.
+///
+/// It is not particularily optimized, it exists for ease and speed of testing. It's not expected
+/// this DB would be used outside of tests.
+pub struct MemoryDB {
+    db: RwLock<DBHashMap>,
+    known_columns: RwLock<ColumnHashSet>
+}
+
+impl MemoryDB {
+    /// Open the in-memory database.
+    ///
+    /// All columns must be supplied initially, you will get an error if you try to access a column
+    /// that was not declared here. This condition is enforced artificially to simulate RocksDB.
+    pub fn open(columns: Option<&[&str]>) -> Self {
+        let db: DBHashMap = HashMap::new();
+        let mut known_columns: ColumnHashSet = HashSet::new();
+        if let Some(columns) = columns {
+            for col in columns {
+                known_columns.insert(col.to_string());
+            }
+        }
+        Self {
+            db: RwLock::new(db),
+            known_columns: RwLock::new(known_columns),
+        }
+    }
+
+    /// Hashes a key and a column name in order to get a unique key for the supplied column.
+    fn get_key_for_col(col: &str, key: &[u8]) -> Vec<u8> {
+        blake2b(32, col.as_bytes(), key).as_bytes().to_vec()
+    }
+}
+
+impl ClientDB for MemoryDB {
+    /// Get the value of some key from the database. Returns `None` if the key does not exist.
+    fn get(&self, col: &str, key: &[u8])
+        -> Result<Option<DBValue>, DBError>
+    {
+        // Panic if the DB locks are poisoned.
+        let db = self.db.read().unwrap();
+        let known_columns = self.known_columns.read().unwrap();
+
+        match known_columns.contains(&col.to_string()) {
+            false => Err(DBError{ message: "Unknown column".to_string() }),
+            true => {
+                let column_key = MemoryDB::get_key_for_col(col, key);
+                Ok(db.get(&column_key).and_then(|val| Some(val.clone())))
+            }
+        }
+    }
+
+    /// Puts a key in the database.
+    fn put(&self, col: &str, key: &[u8], val: &[u8])
+        -> Result<(), DBError>
+    {
+        // Panic if the DB locks are poisoned.
+        let mut db = self.db.write().unwrap();
+        let known_columns = self.known_columns.read().unwrap();
+
+        match known_columns.contains(&col.to_string()) {
+            false => Err(DBError{ message: "Unknown column".to_string() }),
+            true => {
+                let column_key = MemoryDB::get_key_for_col(col, key);
+                db.insert(column_key, val.to_vec());
+                Ok(())
+            }
+        }
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use super::super::ClientDB;
+    use std::thread;
+    use std::sync::Arc;
+
+    #[test]
+    fn test_memorydb_column_access() {
+        let col_a: &str = "ColumnA";
+        let col_b: &str = "ColumnB";
+
+        let column_families = vec![
+            col_a,
+            col_b,
+        ];
+
+        let db = MemoryDB::open(Some(&column_families));
+
+        /*
+         * Testing that if we write to the same key in different columns that
+         * there is not an overlap.
+         */
+        db.put(col_a, "same".as_bytes(), "cat".as_bytes()).unwrap();
+        db.put(col_b, "same".as_bytes(), "dog".as_bytes()).unwrap();
+
+        assert_eq!(db.get(col_a, "same".as_bytes()).unwrap().unwrap(), "cat".as_bytes());
+        assert_eq!(db.get(col_b, "same".as_bytes()).unwrap().unwrap(), "dog".as_bytes());
+
+
+    }
+
+    #[test]
+    fn test_memorydb_unknown_column_access() {
+        let col_a: &str = "ColumnA";
+        let col_x: &str = "ColumnX";
+
+        let column_families = vec![
+            col_a,
+            // col_x is excluded on purpose
+        ];
+
+        let db = MemoryDB::open(Some(&column_families));
+
+        /*
+         * Test that we get errors when using undeclared columns
+         */
+        assert!(db.put(col_a, "cats".as_bytes(), "lol".as_bytes()).is_ok());
+        assert!(db.put(col_x, "cats".as_bytes(), "lol".as_bytes()).is_err());
+
+        assert!(db.get(col_a, "cats".as_bytes()).is_ok());
+        assert!(db.get(col_x, "cats".as_bytes()).is_err());
+    }
+
+    #[test]
+    fn test_memorydb_threading() {
+        let col_name: &str = "TestColumn";
+        let column_families = vec![col_name];
+
+        let db = Arc::new(MemoryDB::open(Some(&column_families)));
+
+        let thread_count = 10;
+        let write_count = 10;
+
+        // We're execting the product of these numbers to fit in one byte.
+        assert!(thread_count * write_count <= 255);
+
+        let mut handles = vec![];
+        for t in 0..thread_count {
+            let wc = write_count;
+            let db = db.clone();
+            let col = col_name.clone();
+            let handle = thread::spawn(move || {
+                for w in 0..wc {
+                    let key = (t * w) as u8;
+                    let val = 42;
+                    db.put(&col, &vec![key], &vec![val]).unwrap();
+                }
+            });
+            handles.push(handle);
+        }
+
+        for handle in handles {
+            handle.join().unwrap();
+        }
+
+        for t in 0..thread_count {
+            for w in 0..write_count {
+                let key = (t * w) as u8;
+                let val = db.get(&col_name, &vec![key]).unwrap().unwrap();
+                assert_eq!(vec![42], val);
+            }
+        }
+    }
+}

lighthouse/db/mod.rs

@@ -1,9 +1,12 @@
 extern crate rocksdb;
+extern crate blake2_rfc as blake2;
 
 mod disk_db;
+mod memory_db;
 mod traits;
 
 pub use self::disk_db::DiskDB;
+pub use self::memory_db::MemoryDB;
 pub use self::traits::{
     DBError,
     DBValue,

lighthouse/db/traits.rs

@@ -18,9 +18,6 @@ impl DBError {
 /// program to use a persistent on-disk database during production,
 /// but use a transient database during tests.
 pub trait ClientDB: Sync + Send {
-    fn create_col(&mut self, col: &str)
-        -> Result<(), DBError>;
-
     fn get(&self, col: &str, key: &[u8])
         -> Result<Option<DBValue>, DBError>;