From 05886f8dcba52a5ac7a206eb6177eb0dc47ada00 Mon Sep 17 00:00:00 2001
From: Jade Ellis <jade@ellis.link>
Date: Sun, 26 Oct 2025 17:30:42 +0000
Subject: [PATCH] feat: Add option to control WAL compression

Also enables zstd compression by default
---
 conduwuit-example.toml         | 15 +++++++++++++++
 src/core/config/mod.rs         | 19 +++++++++++++++++++
 src/database/engine/db_opts.rs | 20 ++++++++++++++++++--
 3 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/conduwuit-example.toml b/conduwuit-example.toml
index 4b50c067..aebe3be9 100644
--- a/conduwuit-example.toml
+++ b/conduwuit-example.toml
@@ -957,6 +957,21 @@
 #
 #rocksdb_bottommost_compression = true
 
+# Compression algorithm for RocksDB's Write-Ahead-Log (WAL).
+#
+# At present, only ZSTD compression is supported by RocksDB for WAL
+# compression. Enabling this can reduce WAL size at the expense of some
+# CPU usage during writes.
+#
+# The options are:
+# - "none" = No compression
+# - "zstd" = ZSTD compression
+#
+# For more information on WAL compression, see:
+# https://github.com/facebook/rocksdb/wiki/WAL-Compression
+#
+#rocksdb_wal_compression = "zstd"
+
 # Database recovery mode (for RocksDB WAL corruption).
 #
 # Use this option when the server reports corruption and refuses to start.
diff --git a/src/core/config/mod.rs b/src/core/config/mod.rs
index a5fdc320..fbb29357 100644
--- a/src/core/config/mod.rs
+++ b/src/core/config/mod.rs
@@ -1128,6 +1128,23 @@ pub struct Config {
 	#[serde(default = "true_fn")]
 	pub rocksdb_bottommost_compression: bool,
 
+	/// Compression algorithm for RocksDB's Write-Ahead-Log (WAL).
+	///
+	/// At present, only ZSTD compression is supported by RocksDB for WAL
+	/// compression. Enabling this can reduce WAL size at the expense of some
+	/// CPU usage during writes.
+	///
+	/// The options are:
+	/// - "none" = No compression
+	/// - "zstd" = ZSTD compression
+	///
+	/// For more information on WAL compression, see:
+	/// https://github.com/facebook/rocksdb/wiki/WAL-Compression
+	///
+	/// default: "zstd"
+	#[serde(default = "default_rocksdb_wal_compression")]
+	pub rocksdb_wal_compression: String,
+
 	/// Database recovery mode (for RocksDB WAL corruption).
 	///
 	/// Use this option when the server reports corruption and refuses to start.
@@ -2454,6 +2471,8 @@ fn default_rocksdb_compression_algo() -> String {
 		.to_owned()
 }
 
+fn default_rocksdb_wal_compression() -> String { "zstd".to_owned() }
+
 /// Default RocksDB compression level is 32767, which is internally read by
 /// RocksDB as the default magic number and translated to the library's default
 /// compression level as they all differ. See their `kDefaultCompressionLevel`.
diff --git a/src/database/engine/db_opts.rs b/src/database/engine/db_opts.rs
index 91620ec4..d6092cbf 100644
--- a/src/database/engine/db_opts.rs
+++ b/src/database/engine/db_opts.rs
@@ -1,7 +1,9 @@
 use std::{cmp, convert::TryFrom};
 
-use conduwuit::{Config, Result, utils};
-use rocksdb::{Cache, DBRecoveryMode, Env, LogLevel, Options, statistics::StatsLevel};
+use conduwuit::{Config, Result, utils, warn};
+use rocksdb::{
+	Cache, DBCompressionType, DBRecoveryMode, Env, LogLevel, Options, statistics::StatsLevel,
+};
 
 use super::{cf_opts::cache_size_f64, logger::handle as handle_log};
 
@@ -58,6 +60,20 @@ pub(crate) fn db_options(config: &Config, env: &Env, row_cache: &Cache) -> Resul
 	opts.set_max_total_wal_size(1024 * 1024 * 512);
 	opts.set_writable_file_max_buffer_size(1024 * 1024 * 2);
 
+	// WAL compression
+	let wal_compression = match config.rocksdb_wal_compression.as_ref() {
+		| "zstd" => DBCompressionType::Zstd,
+		| "none" => DBCompressionType::None,
+		| value => {
+			warn!(
+				"Invalid rocksdb_wal_compression value '{value}'. Supported values are 'none' \
+				 or 'zstd'. Defaulting to 'none'."
+			);
+			DBCompressionType::None
+		},
+	};
+	opts.set_wal_compression_type(wal_compression);
+
 	// Misc
 	opts.set_disable_auto_compactions(!config.rocksdb_compaction);
 	opts.create_missing_column_families(true);