make database config a sum type

This way we don't need to construct the entire configuration to load a
database or database engine.

The other advantage is that it allows having options that are unique to
each database backend.

The one thing I don't like about this is `DatabaseConfig::path`, whose
existence implies all databases will have a file path, which is not
true for out-of-process databases. The only thing this is really used
for is creating the media directory. I think we should restructure the
configuration in the future to resolve this.

src/cli/serve.rs

@@ -76,7 +76,7 @@ pub(crate) async fn run(args: ServeArgs) -> Result<(), error::ServeCommand> {
 
     info!("Loading database");
     let db = Box::leak(Box::new(
-        KeyValueDatabase::load_or_create(&config)
+        KeyValueDatabase::load_or_create(&config.database)
             .map_err(Error::DatabaseError)?,
     ));
 

src/config.rs

@@ -216,35 +216,53 @@ impl Default for TurnConfig {
     }
 }
 
-#[derive(Clone, Copy, Debug, Deserialize)]
-#[serde(rename_all = "lowercase")]
-pub(crate) enum DatabaseBackend {
-    #[cfg(feature = "rocksdb")]
-    Rocksdb,
-    #[cfg(feature = "sqlite")]
-    Sqlite,
+#[cfg(feature = "rocksdb")]
+#[derive(Clone, Debug, Deserialize)]
+pub(crate) struct RocksdbConfig {
+    pub(crate) path: PathBuf,
+    #[serde(default = "default_rocksdb_max_open_files")]
+    pub(crate) max_open_files: i32,
+    #[serde(default = "default_rocksdb_cache_capacity_bytes")]
+    pub(crate) cache_capacity_bytes: usize,
 }
 
-impl Display for DatabaseBackend {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match *self {
+#[cfg(feature = "sqlite")]
+#[derive(Clone, Debug, Deserialize)]
+pub(crate) struct SqliteConfig {
+    pub(crate) path: PathBuf,
+    #[serde(default = "default_sqlite_cache_capacity_kilobytes")]
+    pub(crate) cache_capacity_kilobytes: u32,
+}
+
+#[derive(Clone, Debug, Deserialize)]
+#[serde(rename_all = "lowercase", tag = "backend")]
+pub(crate) enum DatabaseConfig {
+    #[cfg(feature = "rocksdb")]
+    Rocksdb(RocksdbConfig),
+    #[cfg(feature = "sqlite")]
+    Sqlite(SqliteConfig),
+}
+
+impl DatabaseConfig {
+    pub(crate) fn path(&self) -> &Path {
+        match self {
             #[cfg(feature = "rocksdb")]
-            DatabaseBackend::Rocksdb => write!(f, "RocksDB"),
+            DatabaseConfig::Rocksdb(x) => &x.path,
             #[cfg(feature = "sqlite")]
-            DatabaseBackend::Sqlite => write!(f, "SQLite"),
+            DatabaseConfig::Sqlite(x) => &x.path,
         }
     }
 }
 
-#[derive(Clone, Debug, Deserialize)]
-pub(crate) struct DatabaseConfig {
-    pub(crate) backend: DatabaseBackend,
-    pub(crate) path: String,
-    #[serde(default = "default_db_cache_capacity_mb")]
-    pub(crate) cache_capacity_mb: f64,
-    #[cfg(feature = "rocksdb")]
-    #[serde(default = "default_rocksdb_max_open_files")]
-    pub(crate) rocksdb_max_open_files: i32,
+impl Display for DatabaseConfig {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            #[cfg(feature = "rocksdb")]
+            DatabaseConfig::Rocksdb(_) => write!(f, "RocksDB"),
+            #[cfg(feature = "sqlite")]
+            DatabaseConfig::Sqlite(_) => write!(f, "SQLite"),
+        }
+    }
 }
 
 #[derive(Clone, Debug, Default, Deserialize)]
@@ -377,10 +395,6 @@ fn default_port() -> u16 {
     6167
 }
 
-fn default_db_cache_capacity_mb() -> f64 {
-    300.0
-}
-
 fn default_cache_capacity_modifier() -> f64 {
     1.0
 }
@@ -390,6 +404,16 @@ fn default_rocksdb_max_open_files() -> i32 {
     1000
 }
 
+#[cfg(feature = "rocksdb")]
+fn default_rocksdb_cache_capacity_bytes() -> usize {
+    300 * 1024 * 1024
+}
+
+#[cfg(feature = "sqlite")]
+fn default_sqlite_cache_capacity_kilobytes() -> u32 {
+    300 * 1024
+}
+
 fn default_pdu_cache_capacity() -> usize {
     150_000
 }

src/database.rs

@@ -14,7 +14,7 @@ use ruma::{
 use tracing::{debug, error, info, info_span, warn, Instrument};
 
 use crate::{
-    config::DatabaseBackend,
+    config::DatabaseConfig,
     service::{
         media::MediaFileKey,
         rooms::{
@@ -22,7 +22,7 @@ use crate::{
             state_compressor::CompressedStateEvent,
         },
     },
-    services, utils, Config, Error, Result,
+    services, utils, Error, Result,
 };
 
 pub(crate) mod abstraction;
@@ -233,20 +233,20 @@ pub(crate) struct KeyValueDatabase {
 
 impl KeyValueDatabase {
     pub(crate) fn load_or_create_engine(
-        config: &Config,
+        config: &DatabaseConfig,
     ) -> Result<Arc<dyn KeyValueDatabaseEngine>> {
         #[cfg(not(any(feature = "rocksdb", feature = "sqlite")))]
         return Err(Error::BadConfig(
             "Compiled without support for any databases",
         ));
 
-        let x: Arc<dyn KeyValueDatabaseEngine> = match config.database.backend {
+        let x: Arc<dyn KeyValueDatabaseEngine> = match config {
             #[cfg(feature = "sqlite")]
-            DatabaseBackend::Sqlite => {
+            DatabaseConfig::Sqlite(config) => {
                 Arc::new(Arc::new(abstraction::sqlite::Engine::open(config)?))
             }
             #[cfg(feature = "rocksdb")]
-            DatabaseBackend::Rocksdb => {
+            DatabaseConfig::Rocksdb(config) => {
                 Arc::new(Arc::new(abstraction::rocksdb::Engine::open(config)?))
             }
         };
@@ -260,7 +260,9 @@ impl KeyValueDatabase {
         allow(unreachable_code)
     )]
     #[allow(clippy::too_many_lines)]
-    pub(crate) fn load_or_create(config: &Config) -> Result<KeyValueDatabase> {
+    pub(crate) fn load_or_create(
+        config: &DatabaseConfig,
+    ) -> Result<KeyValueDatabase> {
         let builder = Self::load_or_create_engine(config)?;
 
         let db = Self {
@@ -943,7 +945,7 @@ impl KeyValueDatabase {
             );
 
             info!(
-                backend = %services().globals.config.database.backend,
+                backend = %services().globals.config.database,
                 version = latest_database_version,
                 "Loaded database",
             );
@@ -956,7 +958,7 @@ impl KeyValueDatabase {
             services().admin.create_admin_room().await?;
 
             info!(
-                backend = %services().globals.config.database.backend,
+                backend = %services().globals.config.database,
                 version = latest_database_version,
                 "Created new database",
             );

src/database/abstraction/rocksdb.rs

@@ -12,10 +12,8 @@ use rocksdb::{
 };
 use tracing::Level;
 
-use super::{
-    super::Config, watchers::Watchers, KeyValueDatabaseEngine, KvTree,
-};
-use crate::{utils, Result};
+use super::{watchers::Watchers, KeyValueDatabaseEngine, KvTree};
+use crate::{config::RocksdbConfig, utils, Result};
 
 pub(crate) struct Engine {
     rocks: DBWithThreadMode<MultiThreaded>,
@@ -70,43 +68,35 @@ fn db_options(max_open_files: i32, rocksdb_cache: &Cache) -> Options {
 }
 
 impl Engine {
-    pub(crate) fn open(config: &Config) -> Result<Self> {
+    pub(crate) fn open(config: &RocksdbConfig) -> Result<Self> {
         #[allow(
             clippy::as_conversions,
             clippy::cast_sign_loss,
             clippy::cast_possible_truncation
         )]
-        let cache_capacity_bytes =
-            (config.database.cache_capacity_mb * 1024.0 * 1024.0) as usize;
-        let rocksdb_cache = Cache::new_lru_cache(cache_capacity_bytes);
+        let rocksdb_cache = Cache::new_lru_cache(config.cache_capacity_bytes);
 
-        let db_opts =
-            db_options(config.database.rocksdb_max_open_files, &rocksdb_cache);
+        let db_opts = db_options(config.max_open_files, &rocksdb_cache);
 
-        let cfs = DBWithThreadMode::<MultiThreaded>::list_cf(
-            &db_opts,
-            &config.database.path,
-        )
-        .map(|x| x.into_iter().collect::<HashSet<_>>())
-        .unwrap_or_default();
+        let cfs =
+            DBWithThreadMode::<MultiThreaded>::list_cf(&db_opts, &config.path)
+                .map(|x| x.into_iter().collect::<HashSet<_>>())
+                .unwrap_or_default();
 
         let db = DBWithThreadMode::<MultiThreaded>::open_cf_descriptors(
             &db_opts,
-            &config.database.path,
+            &config.path,
             cfs.iter().map(|name| {
                 ColumnFamilyDescriptor::new(
                     name,
-                    db_options(
-                        config.database.rocksdb_max_open_files,
-                        &rocksdb_cache,
-                    ),
+                    db_options(config.max_open_files, &rocksdb_cache),
                 )
             }),
         )?;
 
         Ok(Engine {
             rocks: db,
-            max_open_files: config.database.rocksdb_max_open_files,
+            max_open_files: config.max_open_files,
             cache: rocksdb_cache,
             old_cfs: cfs,
             new_cfs: Mutex::default(),

src/database/abstraction/sqlite.rs

@@ -13,7 +13,7 @@ use thread_local::ThreadLocal;
 use tracing::debug;
 
 use super::{watchers::Watchers, KeyValueDatabaseEngine, KvTree};
-use crate::{database::Config, Result};
+use crate::{config::SqliteConfig, Result};
 
 thread_local! {
     static READ_CONNECTION: RefCell<Option<&'static Connection>> =
@@ -63,39 +63,26 @@ pub(crate) struct Engine {
     read_iterator_conn_tls: ThreadLocal<Connection>,
 
     path: PathBuf,
-    cache_size_per_thread: u32,
+    cache_capacity_kilobytes: u32,
 }
 
 impl Engine {
-    pub(crate) fn open(config: &Config) -> Result<Self> {
-        fs::create_dir_all(&config.database.path)?;
+    pub(crate) fn open(config: &SqliteConfig) -> Result<Self> {
+        fs::create_dir_all(&config.path)?;
 
-        let path = Path::new(&config.database.path).join("sqlite.db");
+        let path = config.path.join("sqlite.db");
 
-        // calculates cache-size per permanent connection
-        // 1. convert MB to KiB
-        // 2. divide by permanent connections + permanent iter connections +
-        //    write connection
-        // 3. round down to nearest integer
-        #[allow(
-            clippy::as_conversions,
-            clippy::cast_possible_truncation,
-            clippy::cast_precision_loss,
-            clippy::cast_sign_loss
-        )]
-        let cache_size_per_thread =
-            ((config.database.cache_capacity_mb * 1024.0)
-                / ((num_cpus::get() as f64 * 2.0) + 1.0)) as u32;
-
-        let writer =
-            Mutex::new(Engine::prepare_conn(&path, cache_size_per_thread)?);
+        let writer = Mutex::new(Engine::prepare_conn(
+            &path,
+            config.cache_capacity_kilobytes,
+        )?);
 
         Ok(Engine {
             writer,
             read_conn_tls: ThreadLocal::new(),
             read_iterator_conn_tls: ThreadLocal::new(),
             path,
-            cache_size_per_thread,
+            cache_capacity_kilobytes: config.cache_capacity_kilobytes,
         })
     }
 
@@ -121,13 +108,15 @@ impl Engine {
 
     fn read_lock(&self) -> &Connection {
         self.read_conn_tls.get_or(|| {
-            Self::prepare_conn(&self.path, self.cache_size_per_thread).unwrap()
+            Self::prepare_conn(&self.path, self.cache_capacity_kilobytes)
+                .unwrap()
         })
     }
 
     fn read_lock_iterator(&self) -> &Connection {
         self.read_iterator_conn_tls.get_or(|| {
-            Self::prepare_conn(&self.path, self.cache_size_per_thread).unwrap()
+            Self::prepare_conn(&self.path, self.cache_capacity_kilobytes)
+                .unwrap()
         })
     }
 

src/service/globals.rs

@@ -609,7 +609,7 @@ impl Service {
 
     pub(crate) fn get_media_folder(&self) -> PathBuf {
         let mut r = PathBuf::new();
-        r.push(self.config.database.path.clone());
+        r.push(self.config.database.path());
         r.push("media");
         r
     }