forked from cerc-io/plugeth
p2p/dnsdisc: rate limit resolving before checking cache (#22566)
This makes the rate limit apply regardless of whether the node is already cached.
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15e6c27f8b
commit
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@ -37,9 +37,10 @@ import (
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// Client discovers nodes by querying DNS servers.
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// Client discovers nodes by querying DNS servers.
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type Client struct {
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type Client struct {
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cfg Config
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cfg Config
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clock mclock.Clock
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clock mclock.Clock
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entries *lru.Cache
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entries *lru.Cache
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ratelimit *rate.Limiter
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}
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}
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// Config holds configuration options for the client.
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// Config holds configuration options for the client.
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@ -97,8 +98,12 @@ func NewClient(cfg Config) *Client {
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panic(err)
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panic(err)
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}
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}
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rlimit := rate.NewLimiter(rate.Limit(cfg.RateLimit), 10)
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rlimit := rate.NewLimiter(rate.Limit(cfg.RateLimit), 10)
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cfg.Resolver = &rateLimitResolver{cfg.Resolver, rlimit}
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return &Client{
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return &Client{cfg: cfg, entries: cache, clock: mclock.System{}}
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cfg: cfg,
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entries: cache,
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clock: mclock.System{},
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ratelimit: rlimit,
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}
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}
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}
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// SyncTree downloads the entire node tree at the given URL.
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// SyncTree downloads the entire node tree at the given URL.
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@ -157,6 +162,13 @@ func parseAndVerifyRoot(txt string, loc *linkEntry) (rootEntry, error) {
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// resolveEntry retrieves an entry from the cache or fetches it from the network
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// resolveEntry retrieves an entry from the cache or fetches it from the network
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// if it isn't cached.
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// if it isn't cached.
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func (c *Client) resolveEntry(ctx context.Context, domain, hash string) (entry, error) {
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func (c *Client) resolveEntry(ctx context.Context, domain, hash string) (entry, error) {
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// The rate limit always applies, even when the result might be cached. This is
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// important because it avoids hot-spinning in consumers of node iterators created on
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// this client.
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if err := c.ratelimit.Wait(ctx); err != nil {
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return nil, err
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}
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cacheKey := truncateHash(hash)
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cacheKey := truncateHash(hash)
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if e, ok := c.entries.Get(cacheKey); ok {
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if e, ok := c.entries.Get(cacheKey); ok {
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return e.(entry), nil
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return e.(entry), nil
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@ -196,19 +208,6 @@ func (c *Client) doResolveEntry(ctx context.Context, domain, hash string) (entry
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return nil, nameError{name, errNoEntry}
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return nil, nameError{name, errNoEntry}
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}
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}
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// rateLimitResolver applies a rate limit to a Resolver.
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type rateLimitResolver struct {
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r Resolver
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limiter *rate.Limiter
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}
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func (r *rateLimitResolver) LookupTXT(ctx context.Context, domain string) ([]string, error) {
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if err := r.limiter.Wait(ctx); err != nil {
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return nil, err
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}
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return r.r.LookupTXT(ctx, domain)
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}
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// randomIterator traverses a set of trees and returns nodes found in them.
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// randomIterator traverses a set of trees and returns nodes found in them.
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type randomIterator struct {
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type randomIterator struct {
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cur *enode.Node
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cur *enode.Node
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