Take clients in a ID -> Client handle dictionary.

src/networking.c

@@ -75,6 +75,8 @@ void linkClient(client *c) {
      * this way removing the client in unlinkClient() will not require
      * a linear scan, but just a constant time operation. */
     c->client_list_node = listLast(server.clients);
+    uint64_t id = htonu64(c->id);
+    raxInsert(server.clients_index,(unsigned char*)&id,sizeof(id),c,NULL);
 }
 
 client *createClient(int fd) {
@@ -720,6 +722,8 @@ void unlinkClient(client *c) {
     if (c->fd != -1) {
         /* Remove from the list of active clients. */
         if (c->client_list_node) {
+            uint64_t id = htonu64(c->id);
+            raxRemove(server.clients_index,(unsigned char*)&id,sizeof(id),NULL);
             listDelNode(server.clients,c->client_list_node);
             c->client_list_node = NULL;
         }

src/server.c

@@ -1890,6 +1890,7 @@ void initServer(void) {
     server.pid = getpid();
     server.current_client = NULL;
     server.clients = listCreate();
+    server.clients_index = raxNew();
     server.clients_to_close = listCreate();
     server.slaves = listCreate();
     server.monitors = listCreate();

src/server.h

@@ -952,6 +952,7 @@ struct redisServer {
     list *clients_pending_write; /* There is to write or install handler. */
     list *slaves, *monitors;    /* List of slaves and MONITORs */
     client *current_client; /* Current client, only used on crash report */
+    rax *clients_index;         /* Active clients dictionary by client ID. */
     int clients_paused;         /* True if clients are currently paused */
     mstime_t clients_pause_end_time; /* Time when we undo clients_paused */
     char neterr[ANET_ERR_LEN];   /* Error buffer for anet.c */