[performance] replace domain block cache with an in-memory radix trie (#1714)

* replace domain block cache with an in-memory radix tree

Signed-off-by: kim <grufwub@gmail.com>

* fix domain block cache init

Signed-off-by: kim <grufwub@gmail.com>

---------

Signed-off-by: kim <grufwub@gmail.com>

internal/cache/domain/domain.go

@@ -19,151 +19,206 @@
 
 import (
 	"fmt"
-	"time"
+	"strings"
+	"sync/atomic"
+	"unsafe"
 
-	"codeberg.org/gruf/go-cache/v3/ttl"
+	"golang.org/x/exp/slices"
-	"github.com/miekg/dns"
 )
 
 // BlockCache provides a means of caching domain blocks in memory to reduce load
 // on an underlying storage mechanism, e.g. a database.
 //
-// It consists of a TTL primary cache that stores calculated domain string to block results,
-// that on cache miss is filled by calculating block status by iterating over a list of all of
-// the domain blocks stored in memory. This reduces CPU usage required by not need needing to
-// iterate through a possible 100-1000s long block list, while saving memory by having a primary
-// cache of limited size that evicts stale entries. The raw list of all domain blocks should in
-// most cases be negligible when it comes to memory usage.
-//
 // The in-memory block list is kept up-to-date by means of a passed loader function during every
 // call to .IsBlocked(). In the case of a nil internal block list, the loader function is called to
-// hydrate the cache with the latest list of domain blocks. The .Clear() function can be used to invalidate
+// hydrate the cache with the latest list of domain blocks. The .Clear() function can be used to
-// the cache, e.g. when a domain block is added / deleted from the database. It will drop the current
+// invalidate the cache, e.g. when a domain block is added / deleted from the database.
-// list of domain blocks and clear all entries from the primary cache.
 type BlockCache struct {
-	pcache *ttl.Cache[string, bool] // primary cache of domains -> block results
+	// atomically updated ptr value to the
-	blocks []block                  // raw list of all domain blocks, nil => not loaded.
+	// current domain block cache radix trie.
-}
+	rootptr unsafe.Pointer
-
-// New returns a new initialized BlockCache instance with given primary cache capacity and TTL.
-func New(pcap int, pttl time.Duration) *BlockCache {
-	c := new(BlockCache)
-	c.pcache = new(ttl.Cache[string, bool])
-	c.pcache.Init(0, pcap, pttl)
-	return c
-}
-
-// Start will start the cache background eviction routine with given sweep frequency. If already running or a freq <= 0 provided, this is a no-op. This will block until the eviction routine has started.
-func (b *BlockCache) Start(pfreq time.Duration) bool {
-	return b.pcache.Start(pfreq)
-}
-
-// Stop will stop cache background eviction routine. If not running this is a no-op. This will block until the eviction routine has stopped.
-func (b *BlockCache) Stop() bool {
-	return b.pcache.Stop()
 }
 
 // IsBlocked checks whether domain is blocked. If the cache is not currently loaded, then the provided load function is used to hydrate it.
-// NOTE: be VERY careful using any kind of locking mechanism within the load function, as this itself is ran within the cache mutex lock.
 func (b *BlockCache) IsBlocked(domain string, load func() ([]string, error)) (bool, error) {
-	var blocked bool
+	// Load the current root pointer value.
+	ptr := atomic.LoadPointer(&b.rootptr)
 
-	// Acquire cache lock
+	if ptr == nil {
-	b.pcache.Lock()
+		// Cache is not hydrated.
-	defer b.pcache.Unlock()
-
-	// Check primary cache for result
-	entry, ok := b.pcache.Cache.Get(domain)
-	if ok {
-		return entry.Value, nil
-	}
-
-	if b.blocks == nil {
-		// Cache is not hydrated
 		//
-		// Load domains from callback
+		// Load domains from callback.
 		domains, err := load()
 		if err != nil {
 			return false, fmt.Errorf("error reloading cache: %w", err)
 		}
 
-		// Drop all domain blocks and recreate
+		// Allocate new radix trie
-		b.blocks = make([]block, len(domains))
+		// node to store matches.
+		root := new(root)
 
-		for i, domain := range domains {
+		// Add each domain to the trie.
-			// Store pre-split labels for each domain block
+		for _, domain := range domains {
-			b.blocks[i].labels = dns.SplitDomainName(domain)
+			root.Add(domain)
 		}
+
+		// Sort the trie.
+		root.Sort()
+
+		// Store the new node ptr.
+		ptr = unsafe.Pointer(root)
+		atomic.StorePointer(&b.rootptr, ptr)
 	}
 
-	// Split domain into it separate labels
+	// Look for a match in the trie node.
-	labels := dns.SplitDomainName(domain)
+	return (*root)(ptr).Match(domain), nil
-
-	// Compare this to our stored blocks
-	for _, block := range b.blocks {
-		if block.Blocks(labels) {
-			blocked = true
-			break
-		}
-	}
-
-	// Store block result in primary cache
-	b.pcache.Cache.Set(domain, &ttl.Entry[string, bool]{
-		Key:    domain,
-		Value:  blocked,
-		Expiry: time.Now().Add(b.pcache.TTL),
-	})
-
-	return blocked, nil
 }
 
-// Clear will drop the currently loaded domain list, and clear the primary cache.
+// Clear will drop the currently loaded domain list,
-// This will trigger a reload on next call to .IsBlocked().
+// triggering a reload on next call to .IsBlocked().
 func (b *BlockCache) Clear() {
-	// Drop all blocks.
+	atomic.StorePointer(&b.rootptr, nil)
-	b.pcache.Lock()
-	b.blocks = nil
-	b.pcache.Unlock()
-
-	// Clear needs to be done _outside_ of
-	// lock, as also acquires a mutex lock.
-	b.pcache.Clear()
 }
 
-// block represents a domain block, and stores the
+// root is the root node in the domain
-// deconstructed labels of a singular domain block.
+// block cache radix trie. this is the
-// e.g. []string{"gts", "superseriousbusiness", "org"}.
+// singular access point to the trie.
-type block struct {
+type root struct{ root node }
-	labels []string
+
+// Add will add the given domain to the radix trie.
+func (r *root) Add(domain string) {
+	r.root.add(strings.Split(domain, "."))
 }
 
-// Blocks checks whether the separated domain labels of an
+// Match will return whether the given domain matches
-// incoming domain matches the stored (receiving struct) block.
+// an existing stored domain block in this radix trie.
-func (b block) Blocks(labels []string) bool {
+func (r *root) Match(domain string) bool {
-	// Calculate length difference
+	return r.root.match(strings.Split(domain, "."))
-	d := len(labels) - len(b.labels)
+}
-	if d < 0 {
+
+// Sort will sort the entire radix trie ensuring that
+// child nodes are stored in alphabetical order. This
+// MUST be done to finalize the block cache in order
+// to speed up the binary search of node child parts.
+func (r *root) Sort() {
+	r.root.sort()
+}
+
+type node struct {
+	part  string
+	child []*node
+}
+
+func (n *node) add(parts []string) {
+	if len(parts) == 0 {
+		panic("invalid domain")
+	}
+
+	for {
+		// Pop next domain part.
+		i := len(parts) - 1
+		part := parts[i]
+		parts = parts[:i]
+
+		var nn *node
+
+		// Look for existing child node
+		// that matches next domain part.
+		for _, child := range n.child {
+			if child.part == part {
+				nn = child
+				break
+			}
+		}
+
+		if nn == nil {
+			// Alloc new child node.
+			nn = &node{part: part}
+			n.child = append(n.child, nn)
+		}
+
+		if len(parts) == 0 {
+			// Drop all children here as
+			// this is a higher-level block
+			// than that we previously had.
+			nn.child = nil
+			return
+		}
+
+		// Re-iter with
+		// child node.
+		n = nn
+	}
+}
+
+func (n *node) match(parts []string) bool {
+	if len(parts) == 0 {
+		// Invalid domain.
 		return false
 	}
 
-	// Iterate backwards through domain block's
+	for {
-	// labels, omparing against the incoming domain's.
+		// Pop next domain part.
-	//
+		i := len(parts) - 1
-	// So for the following input:
+		part := parts[i]
-	// labels   = []string{"mail", "google", "com"}
+		parts = parts[:i]
-	// b.labels = []string{"google", "com"}
+
-	//
+		// Look for existing child
-	// These would be matched in reverse order along
+		// that matches next part.
-	// the entirety of the block object's labels:
+		nn := n.getChild(part)
-	// "com"    => match
+
-	// "google" => match
+		if nn == nil {
-	//
+			// No match :(
-	// And so would reach the end and return true.
-	for i := len(b.labels) - 1; i >= 0; i-- {
-		if b.labels[i] != labels[i+d] {
 			return false
 		}
+
+		if len(nn.child) == 0 {
+			// It's a match!
+			return true
+		}
+
+		// Re-iter with
+		// child node.
+		n = nn
+	}
+}
+
+// getChild fetches child node with given domain part string
+// using a binary search. THIS ASSUMES CHILDREN ARE SORTED.
+func (n *node) getChild(part string) *node {
+	i, j := 0, len(n.child)
+
+	for i < j {
+		// avoid overflow when computing h
+		h := int(uint(i+j) >> 1)
+		// i ≤ h < j
+
+		if n.child[h].part < part {
+			// preserves:
+			// n.child[i-1].part != part
+			i = h + 1
+		} else {
+			// preserves:
+			// n.child[h].part == part
+			j = h
+		}
 	}
 
-	return true
+	if i >= len(n.child) || n.child[i].part != part {
+		return nil // no match
+	}
+
+	return n.child[i]
+}
+
+func (n *node) sort() {
+	// Sort this node's slice of child nodes.
+	slices.SortFunc(n.child, func(i, j *node) bool {
+		return i.part < j.part
+	})
+
+	// Sort each child node's children.
+	for _, child := range n.child {
+		child.sort()
+	}
 }

internal/cache/domain/domain_test.go

@@ -20,13 +20,12 @@
 import (
 	"errors"
 	"testing"
-	"time"
 
 	"github.com/superseriousbusiness/gotosocial/internal/cache/domain"
 )
 
 func TestBlockCache(t *testing.T) {
-	c := domain.New(100, time.Second)
+	c := new(domain.BlockCache)
 
 	blocks := []string{
 		"google.com",

internal/cache/gts.go

@@ -72,12 +72,6 @@ func (c *GTSCaches) Init() {
 func (c *GTSCaches) Start() {
 	tryStart(c.account, config.GetCacheGTSAccountSweepFreq())
 	tryStart(c.block, config.GetCacheGTSBlockSweepFreq())
-	tryUntil("starting domain block cache", 5, func() bool {
-		if sweep := config.GetCacheGTSDomainBlockSweepFreq(); sweep > 0 {
-			return c.domainBlock.Start(sweep)
-		}
-		return true
-	})
 	tryStart(c.emoji, config.GetCacheGTSEmojiSweepFreq())
 	tryStart(c.emojiCategory, config.GetCacheGTSEmojiCategorySweepFreq())
 	tryStart(c.follow, config.GetCacheGTSFollowSweepFreq())
@@ -102,7 +96,6 @@ func (c *GTSCaches) Start() {
 func (c *GTSCaches) Stop() {
 	tryStop(c.account, config.GetCacheGTSAccountSweepFreq())
 	tryStop(c.block, config.GetCacheGTSBlockSweepFreq())
-	tryUntil("stopping domain block cache", 5, c.domainBlock.Stop)
 	tryStop(c.emoji, config.GetCacheGTSEmojiSweepFreq())
 	tryStop(c.emojiCategory, config.GetCacheGTSEmojiCategorySweepFreq())
 	tryStop(c.follow, config.GetCacheGTSFollowSweepFreq())
@@ -233,10 +226,7 @@ func (c *GTSCaches) initBlock() {
 }
 
 func (c *GTSCaches) initDomainBlock() {
-	c.domainBlock = domain.New(
+	c.domainBlock = new(domain.BlockCache)
-		config.GetCacheGTSDomainBlockMaxSize(),
-		config.GetCacheGTSDomainBlockTTL(),
-	)
 }
 
 func (c *GTSCaches) initEmoji() {