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package sources
import (
"context"
"net"
"sync"
"github.com/ethereum-optimism/optimism/op-service/client"
"github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/rpc"
"golang.org/x/sync/semaphore"
)
type limitClient struct {
mutex sync.Mutex
closed bool
c client.RPC
sema *semaphore.Weighted
wg sync.WaitGroup
}
// joinWaitGroup will add the caller to the waitgroup if the client has not
// already been told to shutdown. If the client has shut down, false is
// returned, otherwise true.
func (lc *limitClient) joinWaitGroup() bool {
lc.mutex.Lock()
defer lc.mutex.Unlock()
if lc.closed {
return false
}
lc.wg.Add(1)
return true
}
// LimitRPC limits concurrent RPC requests (excluding subscriptions) to a given number by wrapping the client with a semaphore.
func LimitRPC(c client.RPC, concurrentRequests int) client.RPC {
return &limitClient{
c: c,
// the capacity of the channel determines how many go-routines can concurrently execute requests with the wrapped client.
sema: semaphore.NewWeighted(int64(concurrentRequests)),
}
}
func (lc *limitClient) BatchCallContext(ctx context.Context, b []rpc.BatchElem) error {
if !lc.joinWaitGroup() {
return net.ErrClosed
}
defer lc.wg.Done()
if err := lc.sema.Acquire(ctx, 1); err != nil {
return err
}
defer lc.sema.Release(1)
return lc.c.BatchCallContext(ctx, b)
}
func (lc *limitClient) CallContext(ctx context.Context, result any, method string, args ...any) error {
if !lc.joinWaitGroup() {
return net.ErrClosed
}
defer lc.wg.Done()
if err := lc.sema.Acquire(ctx, 1); err != nil {
return err
}
defer lc.sema.Release(1)
return lc.c.CallContext(ctx, result, method, args...)
}
func (lc *limitClient) EthSubscribe(ctx context.Context, channel any, args ...any) (ethereum.Subscription, error) {
if !lc.joinWaitGroup() {
return nil, net.ErrClosed
}
defer lc.wg.Done()
// subscription doesn't count towards request limit
return lc.c.EthSubscribe(ctx, channel, args...)
}
func (lc *limitClient) Close() {
lc.mutex.Lock()
lc.closed = true // No new waitgroup members after this is set
lc.mutex.Unlock()
lc.wg.Wait() // All waitgroup members exited, means no more dereferences of the client
lc.c.Close()
}