Merge "lmdb: add max_readers and additional_dbs fields to NostrLmdbBuilder"

Add max_readers and additional_dbs configuration options to NostrLmdbBuilder to allow fine-tuning of LMDB environment settings.

- **max_readers**: Controls the maximum number of reader threads (defaults to 126)
- **additional_dbs**: Specifies additional database slots beyond the 9 internal ones (defaults to 0)

This addresses part of the feedback from PR #992 where the reviewer suggested changing the parameter name to `additional_dbs` since 9 databases are already defined internally.

### Notes to the reviewers

- Following the same pattern as the existing `map_size` field
- All parameters cascade through: NostrLmdbBuilder → Store → Lmdb
- Uses sensible defaults (126 for max_readers, 0 for additional_dbs)
- No breaking changes - all existing code continues to work

Pull-Request: #1003
Acked-by: Yuki Kishimoto <[email protected]>
Signed-off-by: Yuki Kishimoto <[email protected]>

Author: yukibtc

database/nostr-lmdb/CHANGELOG.md

@@ -32,6 +32,7 @@
 ### Added
 
 - Add NostrLmdbBuilder and allow setting a custom map size (https://github.com/rust-nostr/nostr/pull/970)
+- Add `max_readers` and `additional_dbs` fields to `NostrLmdbBuilder`
 
 ## v0.42.0 - 2025/05/20
 

database/nostr-lmdb/src/lib.rs

@@ -37,6 +37,14 @@ pub struct NostrLmdbBuilder {
     /// - 32GB for 64-bit arch
     /// - 4GB for 32-bit arch
     pub map_size: Option<usize>,
+    /// Maximum number of reader threads
+    ///
+    /// Defaults to 126 if not set
+    pub max_readers: Option<u32>,
+    /// Number of additional databases to allocate beyond the 9 internal ones
+    ///
+    /// Defaults to 0 if not set
+    pub additional_dbs: Option<u32>,
 }
 
 impl NostrLmdbBuilder {
@@ -48,6 +56,8 @@ impl NostrLmdbBuilder {
         Self {
             path: path.as_ref().to_path_buf(),
             map_size: None,
+            max_readers: None,
+            additional_dbs: None,
         }
     }
 
@@ -61,10 +71,29 @@ impl NostrLmdbBuilder {
         self
     }
 
+    /// Maximum number of reader threads
+    ///
+    /// Defaults to 126 if not set
+    pub fn max_readers(mut self, max_readers: u32) -> Self {
+        self.max_readers = Some(max_readers);
+        self
+    }
+
+    /// Number of additional databases to allocate beyond the 9 internal ones
+    ///
+    /// Defaults to 0 if not set
+    pub fn additional_dbs(mut self, additional_dbs: u32) -> Self {
+        self.additional_dbs = Some(additional_dbs);
+        self
+    }
+
     /// Build
     pub fn build(self) -> Result<NostrLMDB, DatabaseError> {
         let map_size: usize = self.map_size.unwrap_or(MAP_SIZE);
-        let db: Store = Store::open(self.path, map_size).map_err(DatabaseError::backend)?;
+        let max_readers: u32 = self.max_readers.unwrap_or(126);
+        let additional_dbs: u32 = self.additional_dbs.unwrap_or(0);
+        let db: Store = Store::open(self.path, map_size, max_readers, additional_dbs)
+            .map_err(DatabaseError::backend)?;
         Ok(NostrLMDB { db })
     }
 }

database/nostr-lmdb/src/store/lmdb/mod.rs

@@ -48,15 +48,21 @@ pub(crate) struct Lmdb {
 }
 
 impl Lmdb {
-    pub(super) fn new<P>(path: P, map_size: usize) -> Result<Self, Error>
+    pub(super) fn new<P>(
+        path: P,
+        map_size: usize,
+        max_readers: u32,
+        additional_dbs: u32,
+    ) -> Result<Self, Error>
     where
         P: AsRef<Path>,
     {
         // Construct LMDB env
         let env: Env = unsafe {
             EnvOpenOptions::new()
                 .flags(EnvFlags::NO_TLS)
-                .max_dbs(9)
+                .max_dbs(9 + additional_dbs)
+                .max_readers(max_readers)
                 .map_size(map_size)
                 .open(path)?
         };

database/nostr-lmdb/src/store/mod.rs

@@ -27,7 +27,12 @@ pub struct Store {
 }
 
 impl Store {
-    pub(super) fn open<P>(path: P, map_size: usize) -> Result<Store, Error>
+    pub(super) fn open<P>(
+        path: P,
+        map_size: usize,
+        max_readers: u32,
+        additional_dbs: u32,
+    ) -> Result<Store, Error>
     where
         P: AsRef<Path>,
     {
@@ -36,7 +41,7 @@ impl Store {
         // Create the directory if it doesn't exist
         fs::create_dir_all(path)?;
 
-        let db: Lmdb = Lmdb::new(path, map_size)?;
+        let db: Lmdb = Lmdb::new(path, map_size, max_readers, additional_dbs)?;
         let ingester: Sender<IngesterItem> = Ingester::run(db.clone());
 
         Ok(Self { db, ingester })