Support client side caching when using sync interface

src/sw/redis++/command.h

@@ -47,6 +47,14 @@ inline void hello(Connection &connection, long long version) {
     connection.send("HELLO %lld", version);
 }
 
+inline void client_tracking(Connection &connection, bool on) {
+  if (on) {
+    connection.send("CLIENT TRACKING ON");
+  } else {
+    connection.send("CLIENT TRACKING OFF");
+  }
+}
+
 inline void echo(Connection &connection, const StringView &msg) {
     connection.send("ECHO %b", msg.data(), msg.size());
 }

src/sw/redis++/connection.cpp

@@ -275,6 +275,15 @@ void Connection::_set_options() {
     if (_opts.readonly) {
         _enable_readonly();
     }
+
+#ifdef REDIS_PLUS_PLUS_RESP_VERSION_3
+    if (_opts.resp > 2 && _opts.client_tracking && _opts.push_cb) {
+      _context()->privdata = _opts.privdata;
+      _context()->free_privdata = _opts.privdata_dtor;
+      set_push_callback(_opts.push_cb);
+      _set_client_tracking(true);
+    }
+#endif
 }
 
 void Connection::_enable_readonly() {
@@ -297,6 +306,16 @@ void Connection::_set_resp_version() {
     // TODO: parse hello reply.
 }
 
+void Connection::_set_client_tracking(bool on) {
+    cmd::client_tracking(*this, on);
+
+    auto reply = recv();
+
+    assert(reply);
+
+    // TODO: parse reply.
+}
+
 void Connection::_auth() {
     const std::string DEFAULT_USER = "default";
 

src/sw/redis++/connection.h

@@ -87,6 +87,18 @@ struct ConnectionOptions {
     // RESP version.
     int resp = 2;
 
+#ifdef REDIS_PLUS_PLUS_RESP_VERSION_3
+    // https://redis.io/docs/manual/client-side-caching/
+    bool client_tracking = false;
+
+    // Optional user defined data/destructor
+    void *privdata = nullptr;
+    void (*privdata_dtor)(void *) = nullptr;
+
+    // A user defined PUSH message callback
+    redisPushFn *push_cb = nullptr;
+#endif
+
     // For internal use, and might be removed in the future. DO NOT use it in client code.
     std::string _server_info() const;
 };
@@ -182,6 +194,8 @@ class Connection {
 
     void _set_resp_version();
 
+    void _set_client_tracking(bool);
+
     redisContext* _context();
 
     ContextUPtr _ctx;

src/sw/redis++/connection_pool.cpp

@@ -30,6 +30,12 @@ ConnectionPool::ConnectionPool(const ConnectionPoolOptions &pool_opts,
         throw Error("CANNOT create an empty pool");
     }
 
+#ifdef REDIS_PLUS_PLUS_RESP_VERSION_3
+    if (_opts.client_tracking && _pool_opts.size > 1) {
+        throw Error("CANNOT enable client tracking with pool size greater than 1");
+    }
+#endif
+
     // Lazily create connections.
 }