[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>
This commit is contained in:
kim 2023-05-01 11:36:46 +01:00 committed by GitHub
parent 66f09a8d93
commit 3ff1391a9d
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3 changed files with 166 additions and 122 deletions

View file

@ -19,151 +19,206 @@ package domain
import (
"fmt"
"time"
"strings"
"sync/atomic"
"unsafe"
"codeberg.org/gruf/go-cache/v3/ttl"
"github.com/miekg/dns"
"golang.org/x/exp/slices"
)
// 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
// the cache, e.g. when a domain block is added / deleted from the database. It will drop the current
// list of domain blocks and clear all entries from the primary cache.
// hydrate the cache with the latest list of domain blocks. The .Clear() function can be used to
// invalidate the cache, e.g. when a domain block is added / deleted from the database.
type BlockCache struct {
pcache *ttl.Cache[string, bool] // primary cache of domains -> block results
blocks []block // raw list of all domain blocks, nil => not loaded.
}
// 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()
// atomically updated ptr value to the
// current domain block cache radix trie.
rootptr unsafe.Pointer
}
// 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
b.pcache.Lock()
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
if ptr == 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
b.blocks = make([]block, len(domains))
// Allocate new radix trie
// node to store matches.
root := new(root)
for i, domain := range domains {
// Store pre-split labels for each domain block
b.blocks[i].labels = dns.SplitDomainName(domain)
// Add each domain to the trie.
for _, domain := range domains {
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
labels := dns.SplitDomainName(domain)
// 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
// Look for a match in the trie node.
return (*root)(ptr).Match(domain), nil
}
// Clear will drop the currently loaded domain list, and clear the primary cache.
// This will trigger a reload on next call to .IsBlocked().
// Clear will drop the currently loaded domain list,
// triggering a reload on next call to .IsBlocked().
func (b *BlockCache) Clear() {
// Drop all blocks.
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()
atomic.StorePointer(&b.rootptr, nil)
}
// block represents a domain block, and stores the
// deconstructed labels of a singular domain block.
// e.g. []string{"gts", "superseriousbusiness", "org"}.
type block struct {
labels []string
// root is the root node in the domain
// block cache radix trie. this is the
// singular access point to the trie.
type root struct{ root node }
// 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
// incoming domain matches the stored (receiving struct) block.
func (b block) Blocks(labels []string) bool {
// Calculate length difference
d := len(labels) - len(b.labels)
if d < 0 {
// Match will return whether the given domain matches
// an existing stored domain block in this radix trie.
func (r *root) Match(domain string) bool {
return r.root.match(strings.Split(domain, "."))
}
// 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
// labels, omparing against the incoming domain's.
//
// So for the following input:
// labels = []string{"mail", "google", "com"}
// b.labels = []string{"google", "com"}
//
// These would be matched in reverse order along
// the entirety of the block object's labels:
// "com" => match
// "google" => 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] {
for {
// Pop next domain part.
i := len(parts) - 1
part := parts[i]
parts = parts[:i]
// Look for existing child
// that matches next part.
nn := n.getChild(part)
if nn == nil {
// No match :(
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()
}
}

View file

@ -20,13 +20,12 @@ package domain_test
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",

12
internal/cache/gts.go vendored
View file

@ -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(
config.GetCacheGTSDomainBlockMaxSize(),
config.GetCacheGTSDomainBlockTTL(),
)
c.domainBlock = new(domain.BlockCache)
}
func (c *GTSCaches) initEmoji() {