add FIFO compaction for persistent-cache descriptor; comments/cleanup

Signed-off-by: Jason Volk <jason@zemos.net>

src/database/engine/cf_opts.rs

@@ -1,8 +1,8 @@
 use conduwuit::{Config, Result, err, utils::math::Expected};
 use rocksdb::{
 	BlockBasedIndexType, BlockBasedOptions, BlockBasedPinningTier, Cache,
-	DBCompressionType as CompressionType, DataBlockIndexType, LruCacheOptions, Options,
-	UniversalCompactOptions, UniversalCompactionStopStyle,
+	DBCompressionType as CompressionType, DataBlockIndexType, FifoCompactOptions,
+	LruCacheOptions, Options, UniversalCompactOptions, UniversalCompactionStopStyle,
 };
 
 use super::descriptor::{CacheDisp, Descriptor};
@@ -16,7 +16,7 @@ pub(super) const SENTINEL_COMPRESSION_LEVEL: i32 = 32767;
 pub(crate) fn cf_options(ctx: &Context, opts: Options, desc: &Descriptor) -> Result<Options> {
 	let cache = get_cache(ctx, desc);
 	let config = &ctx.server.config;
-	descriptor_cf_options(opts, desc.clone(), config, cache.as_ref())
+	descriptor_cf_options(opts, *desc, config, cache.as_ref())
 }
 
 fn descriptor_cf_options(
@@ -46,6 +46,7 @@ fn descriptor_cf_options(
 	opts.set_compaction_style(desc.compaction);
 	opts.set_compaction_pri(desc.compaction_pri);
 	opts.set_universal_compaction_options(&uc_options(&desc));
+	opts.set_fifo_compaction_options(&fifo_options(&desc));
 
 	let compression_shape: Vec<_> = desc
 		.compression_shape
@@ -142,6 +143,13 @@ fn set_compression(desc: &mut Descriptor, config: &Config) {
 	}
 }
 
+fn fifo_options(desc: &Descriptor) -> FifoCompactOptions {
+	let mut opts = FifoCompactOptions::default();
+	opts.set_max_table_files_size(desc.limit_size);
+
+	opts
+}
+
 fn uc_options(desc: &Descriptor) -> UniversalCompactOptions {
 	let mut opts = UniversalCompactOptions::default();
 	opts.set_stop_style(UniversalCompactionStopStyle::Total);

src/database/engine/descriptor.rs

@@ -6,14 +6,8 @@ use rocksdb::{
 
 use super::cf_opts::SENTINEL_COMPRESSION_LEVEL;
 
+/// Column Descriptor
 #[derive(Debug, Clone, Copy)]
-pub(crate) enum CacheDisp {
-	Unique,
-	Shared,
-	SharedWith(&'static str),
-}
-
-#[derive(Debug, Clone)]
 pub(crate) struct Descriptor {
 	pub(crate) name: &'static str,
 	pub(crate) dropped: bool,
@@ -30,6 +24,7 @@ pub(crate) struct Descriptor {
 	pub(crate) file_shape: i32,
 	pub(crate) level0_width: i32,
 	pub(crate) merge_width: (i32, i32),
+	pub(crate) limit_size: u64,
 	pub(crate) ttl: u64,
 	pub(crate) compaction: CompactionStyle,
 	pub(crate) compaction_pri: CompactionPri,
@@ -46,7 +41,16 @@ pub(crate) struct Descriptor {
 	pub(crate) auto_readahead_max: usize,
 }
 
-pub(crate) static BASE: Descriptor = Descriptor {
+/// Cache Disposition
+#[derive(Debug, Clone, Copy)]
+pub(crate) enum CacheDisp {
+	Unique,
+	Shared,
+	SharedWith(&'static str),
+}
+
+/// Base descriptor supplying common defaults to all derived descriptors.
+static BASE: Descriptor = Descriptor {
 	name: EMPTY,
 	dropped: false,
 	cache_disp: CacheDisp::Shared,
@@ -62,6 +66,7 @@ pub(crate) static BASE: Descriptor = Descriptor {
 	file_shape: 2,
 	level0_width: 2,
 	merge_width: (2, 16),
+	limit_size: 0,
 	ttl: 60 * 60 * 24 * 21,
 	compaction: CompactionStyle::Level,
 	compaction_pri: CompactionPri::MinOverlappingRatio,
@@ -78,6 +83,10 @@ pub(crate) static BASE: Descriptor = Descriptor {
 	auto_readahead_max: 1024 * 1024 * 2,
 };
 
+/// Tombstone descriptor for columns which have been or will be deleted.
+pub(crate) static DROPPED: Descriptor = Descriptor { dropped: true, ..BASE };
+
+/// Descriptor for large datasets with random updates across the keyspace.
 pub(crate) static RANDOM: Descriptor = Descriptor {
 	compaction_pri: CompactionPri::OldestSmallestSeqFirst,
 	write_size: 1024 * 1024 * 32,
@@ -88,6 +97,7 @@ pub(crate) static RANDOM: Descriptor = Descriptor {
 	..BASE
 };
 
+/// Descriptor for large datasets with updates to the end of the keyspace.
 pub(crate) static SEQUENTIAL: Descriptor = Descriptor {
 	compaction_pri: CompactionPri::OldestLargestSeqFirst,
 	write_size: 1024 * 1024 * 64,
@@ -101,6 +111,7 @@ pub(crate) static SEQUENTIAL: Descriptor = Descriptor {
 	..BASE
 };
 
+/// Descriptor for small datasets with random updates across the keyspace.
 pub(crate) static RANDOM_SMALL: Descriptor = Descriptor {
 	compaction: CompactionStyle::Universal,
 	write_size: 1024 * 1024 * 16,
@@ -117,6 +128,7 @@ pub(crate) static RANDOM_SMALL: Descriptor = Descriptor {
 	..RANDOM
 };
 
+/// Descriptor for small datasets with updates to the end of the keyspace.
 pub(crate) static SEQUENTIAL_SMALL: Descriptor = Descriptor {
 	compaction: CompactionStyle::Universal,
 	write_size: 1024 * 1024 * 16,
@@ -132,3 +144,14 @@ pub(crate) static SEQUENTIAL_SMALL: Descriptor = Descriptor {
 	compressed_index: false,
 	..SEQUENTIAL
 };
+
+/// Descriptor for small persistent caches with random updates. Oldest entries
+/// are deleted after limit_size reached.
+pub(crate) static RANDOM_SMALL_CACHE: Descriptor = Descriptor {
+	compaction: CompactionStyle::Fifo,
+	cache_disp: CacheDisp::Unique,
+	limit_size: 1024 * 1024 * 64,
+	ttl: 60 * 60 * 24 * 14,
+	file_shape: 2,
+	..RANDOM_SMALL
+};

src/database/engine/open.rs

@@ -101,13 +101,11 @@ fn configure_cfds(
 		debug!("Creating new column {name:?} not previously found in existing database.");
 	});
 
-	let missing_descriptors = missing
-		.clone()
-		.map(|_| Descriptor { dropped: true, ..descriptor::BASE });
+	let missing_descriptors = missing.clone().map(|_| descriptor::DROPPED);
 
 	let cfopts: Vec<_> = desc
 		.iter()
-		.cloned()
+		.copied()
 		.chain(missing_descriptors)
 		.map(|ref desc| cf_options(ctx, db_opts.clone(), desc))
 		.collect::<Result<_>>()?;

src/database/maps.rs

@@ -233,7 +233,7 @@ pub(super) static MAPS: &[Descriptor] = &[
 	},
 	Descriptor {
 		name: "servername_destination",
-		..descriptor::RANDOM_SMALL
+		..descriptor::RANDOM_SMALL_CACHE
 	},
 	Descriptor {
 		name: "servername_educount",
@@ -241,7 +241,7 @@ pub(super) static MAPS: &[Descriptor] = &[
 	},
 	Descriptor {
 		name: "servername_override",
-		..descriptor::RANDOM_SMALL
+		..descriptor::RANDOM_SMALL_CACHE
 	},
 	Descriptor {
 		name: "servernameevent_data",