# Ray start --head Unable to connect to GCS **URL:** \ **Category:** Ray Core\ **Created:** [March 31, 2022, 12:19am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619 "2022-03-31T00:19:09Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![david.waterworth](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@david.waterworth](https://discuss.ray.io/u/david.waterworth)\ **Post date:** [March 31, 2022, 12:19am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/1 "2022-03-31T00:19:09Z")
**How severe does this issue affect your experience of using Ray?** - Medium: It contributes to significant difficulty to complete my task, but I can work around it. I’m working through the ray[serve] tutorials but I’m unable to start and run them `detached` because `ray start --head` fails. If I used method 1 from [https://docs.ray.io/en/master/serve/deployment.html#deploying-on-a-single-node](https://docs.ray.io/en/master/serve/deployment.html#deploying-on-a-single-node) (i.e. serve.start() then loop to prevent the script exiting) the examples work. However I wanted to experiment with method 2, starting the head node from the console. However every time I run `$ ray start --head` I get the error ```auto Local node IP: 10.0.102.40 2022-03-31 11:03:14,134 WARNING node.py:1501 -- Unable to connect to GCS at 10.0.102.40:6379. Check that (1) Ray GCS with matching version started successfully at the specified address, and (2) there is no firewall setting preventing access. ``` Via `lsof -i :6379` I’ve confirmed the port isn’t in use. The contents of `gcs_server.out` are below. Can anyone point me in the correct direction, for now I’m just trying to start a single node cluster. > [2022-03-31 11:03:09,119 I 11416 11416] (gcs\_server) io\_service\_pool.cc:35: IOServicePool is running with 1 io\_service. > [2022-03-31 11:03:09,119 I 11416 11416] (gcs\_server) gcs\_server.cc:51: GCS storage type is memory > [2022-03-31 11:03:09,119 I 11416 11416] (gcs\_server) gcs\_server.cc:52: gRPC based pubsub is enabled > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:42: Loading job table data. > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:54: Loading node table data. > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:66: Loading cluster resources table data. > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:93: Loading actor table data. > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:79: Loading placement group table data. > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:46: Finished loading job table data, size = 0 > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:58: Finished loading node table data, size = 0 > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:70: Finished loading cluster resources table data, size = 0 > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:97: Finished loading actor table data, size = 0 > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_init\_data.cc:84: Finished loading placement group table data, size = 0 > [2022-03-31 11:03:09,120 I 11416 11416] (gcs\_server) gcs\_heartbeat\_manager.cc:30: GcsHeartbeatManager start, num\_heartbeats\_timeout=30 > [2022-03-31 11:03:09,143 C 11416 11416] (gcs\_server) grpc\_server.cc:93: Check failed: server\_ Failed to start the grpc server. The specified port is 6379. This means that Ray’s core components will not be able to function correctly. If the server startup error message is `Address already in use`, it indicates the server fails to start because the port is already used by other processes (such as --node-manager-port, --object-manager-port, --gcs-server-port, and ports between --min-worker-port, --max-worker-port). Try running lsof -i :6379 to check if there are other processes listening to the port. > \*\*\* StackTrace Information \*\*\* > ray::SpdLogMessage::Flush() > ray::RayLog::~RayLog() > ray::rpc::GrpcServer::Run() > ray::gcs::GcsServer::DoStart() > std::\_Function\_handler\<\>::\_M\_invoke() > EventTracker::RecordExecution() > std::\_Function\_handler\<\>::\_M\_invoke() > boost::asio::detail::completion\_handler\<\>::do\_complete() > boost::asio::detail::scheduler::do\_run\_one() > boost::asio::detail::scheduler::run() > boost::asio::io\_context::run() > main > \_\_libc\_start\_main ---
**Author:** ![zyc-bit](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/zyc-bit/32/2496_2.png) [@zyc-bit](https://discuss.ray.io/u/zyc-bit)\ **Post date:** [May 7, 2022, 3:57pm UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/2 "2022-05-07T15:57:34Z")
I have the same problem, I can not `ray start --head` . It is also unable to connect to GCS. ---
**Author:** ![Mingwei](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/mingwei/32/997_2.png) [@Mingwei](https://discuss.ray.io/u/Mingwei)\ **Post date:** [May 7, 2022, 8:42pm UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/3 "2022-05-07T20:42:23Z")
@zyc-bit, can you specify the Ray and Python version being used, and post the content of `gcs_server.out`? @david.waterworth sorry for missing the issue earlier! From the log message the issue is most likely related to registering port at 6379, but as you confirmed there is no process currently using the port … Can you try if starting another service, e.g. Redis, on the same port (6379) would work? ---
**Author:** ![david.waterworth](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@david.waterworth](https://discuss.ray.io/u/david.waterworth)\ **Post date:** [May 8, 2022, 10:29pm UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/4 "2022-05-08T22:29:09Z")
@Mingwei thanks - my question was answered [here](https://discuss.ray.io/t/required-redis-version/5638) - there actually was something using the port. ---
**Author:** ![zyc-bit](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/zyc-bit/32/2496_2.png) [@zyc-bit](https://discuss.ray.io/u/zyc-bit)\ **Post date:** [May 9, 2022, 5:09am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/5 "2022-05-09T05:09:57Z")
@Mingwei , thank you vary much for your reply. When I run `ray start --head`, I got an error: ```auto $ ray start --head Usage stats collection will be enabled by default in the next release. See https://github.com/ray-project/ray/issues/20857 for more details. Local node IP: 10.140.0.32 2022-05-08 22:32:27,173 WARNING utils.py:1249 -- Unable to connect to GCS at 10.140.0.32:6379. Check that (1) Ray GCS with matching version started successfully at the specified address, and (2) there is no firewall setting preventing access. 2022-05-08 22:32:27,173 WARNING utils.py:1249 -- Unable to connect to GCS at 10.140.0.32:6379. Check that (1) Ray GCS with matching version started successfully at the specified address, and (2) there is no firewall setting preventing access. ``` And sorry for the lack of `gcs-server.out` . I do not know how to get the content of `gcs_server.out` Looking forword for your reply! ---
**Author:** ![Mingwei](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/mingwei/32/997_2.png) [@Mingwei](https://discuss.ray.io/u/Mingwei)\ **Post date:** [May 9, 2022, 5:24am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/6 "2022-05-09T05:24:20Z")
Hi @zyc-bit, `gcs-server.out` is most likely at `/tmp/ray/session_latest/logs/gcs_server.out` on Linux and MacOS. Btw, can you also try `lsof -i :6379` to see if there is a port conflict? ---
**Author:** ![zyc-bit](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/zyc-bit/32/2496_2.png) [@zyc-bit](https://discuss.ray.io/u/zyc-bit)\ **Post date:** [May 9, 2022, 5:27am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/7 "2022-05-09T05:27:36Z")
I run `lsof -i :6379` . And it gave me nothing. And my ray is 1.12.0, and my python is 3.7. ---
**Author:** ![zyc-bit](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/zyc-bit/32/2496_2.png) [@zyc-bit](https://discuss.ray.io/u/zyc-bit)\ **Post date:** [May 9, 2022, 5:33am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/8 "2022-05-09T05:33:29Z")
Hi @Mingwei , my ` gcs_server.out` shows blow, ```auto [2022-05-08 22:32:21,865 I 129461 129461] (gcs_server) io_service_pool.cc:35: IOServicePool is running with 1 io_service. [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_server.cc:55: GCS storage type is memory [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_server.cc:56: gRPC based pubsub is enabled [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:42: Loading job table data. [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:54: Loading node table data. [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:66: Loading cluster resources table data. [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:93: Loading actor table data. [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:79: Loading placement group table data. [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:46: Finished loading job table data, size = 0 [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:58: Finished loading node table data, size = 0 [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:70: Finished loading cluster resources table data, size = 0 [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:97: Finished loading actor table data, size = 0 [2022-05-08 22:32:21,866 I 129461 129461] (gcs_server) gcs_init_data.cc:84: Finished loading placement group table data, size = 0 [2022-05-08 22:32:21,867 I 129461 129461] (gcs_server) gcs_heartbeat_manager.cc:31: GcsHeartbeatManager start, num_heartbeats_timeout=30 [2022-05-08 22:32:21,892 C 129461 129461] (gcs_server) grpc_server.cc:95: Check failed: server_ Failed to start the grpc server. The specified port is 6379. This means that Ray's core components will not be able to function correctly. If the server startup error message is `Address already in use`, it indicates the server fails to start because the port is already used by other processes (such as --node-manager-port, --object-manager-port, --gcs-server-port, and ports between --min-worker-port, --max-worker-port). Try running lsof -i :6379 to check if there are other processes listening to the port. ***StackTrace Information*** ray::SpdLogMessage::Flush() ray::RayLog::~RayLog() ray::rpc::GrpcServer::Run() ray::gcs::GcsServer::DoStart() ray::gcs::GcsTable<>::GetAll()::{lambda()#1}::operator()() EventTracker::RecordExecution() std::_Function_handler<>::_M_invoke() boost::asio::detail::completion_handler<>::do_complete() boost::asio::detail::scheduler::do_run_one() boost::asio::detail::scheduler::run() boost::asio::io_context::run() main __libc_start_main ``` Thank you very much for taking the time to answer my questions. ---
**Author:** ![zyc-bit](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/zyc-bit/32/2496_2.png) [@zyc-bit](https://discuss.ray.io/u/zyc-bit)\ **Post date:** [May 9, 2022, 7:06am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/9 "2022-05-09T07:06:54Z")
Hi @Mingwei , I successed. Command `lsof -i :6379` always returned nothing. So I thought there was no port conflict. But the fact is that my colleague told me he just stop his ray process. (I still do not understand why `lsof -i :6379` returned nothing before.) So mine worked. Thank you a lot. ---
**Author:** ![Mingwei](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/mingwei/32/997_2.png) [@Mingwei](https://discuss.ray.io/u/Mingwei)\ **Post date:** [May 9, 2022, 6:49pm UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/10 "2022-05-09T18:49:36Z")
Great that you found the issue. It seems only using `sudo lsof -i :6379` can show processes from other users. We can update log messages and documentations in Ray. ---
**Author:** ![xcy](https://avatars.discourse-cdn.com/v4/letter/x/46a35a/32.png) [@xcy](https://discuss.ray.io/u/xcy)\ **Post date:** [June 19, 2022, 10:36pm UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/11 "2022-06-19T22:36:27Z")
Hi! I am now facing the same problem. And port 6739 can not be used. ![WechatIMG251](https://us1.discourse-cdn.com/flex020/uploads/ray/original/2X/e/e6cf3b1b486891ed162004ae80eb558ec6f843ed.jpeg) And could you give me some advice about this problem. Thank you very much! ---
**Author:** ![zyc-bit](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/zyc-bit/32/2496_2.png) [@zyc-bit](https://discuss.ray.io/u/zyc-bit)\ **Post date:** [June 21, 2022, 3:38am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/12 "2022-06-21T03:38:00Z")
Hi, @xcy are you using you PC instead of a cluster? Have you ever started ray succeessful before? You can run `ray stop` first to make sure there is no other ray process. ---
**Author:** ![xcy](https://avatars.discourse-cdn.com/v4/letter/x/46a35a/32.png) [@xcy](https://discuss.ray.io/u/xcy)\ **Post date:** [June 21, 2022, 4:15am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/13 "2022-06-21T04:15:06Z")
Thank you for your reply. I think I don’t start the ray. Because this is the code from my professor. And what I should do is to run the train code. And I should input two params. One is gpus and the other is port. But after I do this, there was a warning message like this. So i don’t know how to solve this ---
**Author:** ![zyc-bit](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ray.io/zyc-bit/32/2496_2.png) [@zyc-bit](https://discuss.ray.io/u/zyc-bit)\ **Post date:** [June 21, 2022, 5:02am UTC](https://discuss.ray.io/t/ray-start-head-unable-to-connect-to-gcs/5619/14 "2022-06-21T05:02:57Z")
I understood. Firstly the code your professor provided should be proved correct. Make sure the code can be run successful on other machine before. Secondly, you need to start ray by run `ray start --head` in your cmd. Try to start ray in the cmd by running `ray start --head` to see if the ray can be start successfully.