.. _multinode: Running Across Nodes ++++++++++++++++++++ *Cleanup needed yet* To run in multinode mode, Dragon must know what resources are available for its use on the compute backend. When using a workload manager (WLM) such as Slurm or PBS+Pals, Dragon normally obtains the list of available backend compute resources automatically from the active WLM allocation. However, when Dragon is used on a generic cluster without a traditional WLM, Dragon has no way to automatically ascertain what backend compute resources are available. In these cases Dragon can be run using a generic SSH launch. The following multinode configurations are supported: 1. :ref:`Running on a cluster or supercomputer that has been configured with a Work Load Manager (WLM), such has Slurm or PBS+Pals.` 2. :ref:`Running on a cluster without any Work Load Manager (WLM) using generic SSH launch.` .. _using_a_wlm: Running Dragon with a Workload Manager -------------------------------------- To launch a Dragon program on several compute nodes, a Work Load Manager job allocation obtained via `salloc`_ or `sbatch`_ (Slurm) or `qsub` (PBS+Pals) is required, eg: .. code-block:: bash $ salloc --nodes=2 $ dragon myprog.py arg1 arg2 ... In the event that Dragon is run outside of an active WLM allocation an exception is raised, and the program will not execute: .. code-block:: bash :caption: Dragon exception when no WLM allocation exists: $ dragon p2p_lat.py --iterations 100 --lg_max_message_size 12 --dragon RuntimeError: Executing in a Slurm environment, but with no job allocation. Resubmit as part of an 'salloc' or 'sbatch' execution To override this default behavior and execute a Dragon program on the same node as your shell, the `--single-node-override / -s` option is available. The Dragon service runtime assumes all nodes in an allocation are to be used unless the `--node-count` option is used. This limits the user program to executing on a smaller subset of nodes, potentially useful for execution of scaling benchmarks. For example, if the user has a job allocation for 4 nodes, but only wants to use 2 for their Dragon program, they may do the following: .. code-block:: bash $ salloc --nodes=4 $ dragon --nodes 2 p2p_lat.py --iterations 100 --lg_max_message_size 12 --dragon .. _using_ssh_launch: Running Dragon using generic SSH launch --------------------------------------- To use SSH launch, the following configuration options must be provided on the `dragon` launcher command line: 1. Select the SSH Workload Manager The `--wlm ssh / -w ssh` option tells the `dragon` launcher to use generic SSH launch semantics. 2. Provide available backend compute resources The list of available backend compute resources can be provided to the `dragon` launcher in one of several ways * :ref:`by providing a list of backend compute resources (either explicitly on the launcher command line or via a file)` or * :ref:`by providing a Dragon network configuration file` Note: Dragon requires that passwordless SSH is enabled for all backend compute resources. .. _hostlist_hostfile: Providing a Host List or Host File ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Providing a list of hosts to the `dragon` launcher can be done either by listing them explicitly on the `dragon` command-line or by providing the `dragon` launcher the name of a newline seperated text file containing the list of host names. To provide the available nodes explicitly on the `dragon` command line, specify the available backend hostnames as a comma-separated list, eg: `--hostlist host_1,host_2,host_3`. .. code-block:: shell :name: host_list :caption: **Providing a list of hosts via the command line** $ dragon -w ssh -t tcp --hostlist host_1,host_2,host_3 [PROG] To provide the available nodes via a text file, create a newline separated text file with each backend node's hostname on a separate line. Pass the name of the text file to the `dragon` launcher, eg: `--hostfile hosts.txt`. .. code-block:: shell :name: host_file :caption: **Providing a list of hosts via a text file** $ cat hosts.txt host_1 host_2 host_3 $ dragon -w ssh -t tcp --hostfile hosts.txt [PROG] NOTE: You cannot use both `--hostfile` and `--hostlist` on the commandline at the same time. When passing the list of available backend nodes in either of these ways, the `dragon` launcher needs to determine basic network configuration settings for each listed node before it can launch the Dragon user application. This is done by launching a utility application on each listed node to report the node's IP and other relevant information. Running this utility application slightly delays the startup of Dragon. To prevent this delay, you can instead generate a Dragon network-config file as explained below. .. _network_config: Providing a Dragon Network-Config File ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Dragon provides a utility application to gather and persist relevant network information from it's backend compute resorces. This utility can be used to generate a persistent YAML or JSON configuration which, when passed to the `dragon` launcher, provides all required information about a set of backend compute nodes. To generate a network configuration file for a given set of backend compute nodes, run the `dragon-network-config` tool as shown below: .. code-block:: shell :name: ex_run_network_config :caption: **Example of how to run the dragon-network-config tool** $ dragon-network-config -w ssh --hostlist host1,host2,host3,host4 -j $ ls ssh.json ssh.json Once you have a network configuration file, the name of the configuration file can be passed to the `dragon` launcher to identify the available backend compute resources: .. code-block:: shell :name: host_list :caption: **Providing a list of hosts via the command line** $ dragon -w ssh -t tcp --network-config ssh.json [PROG] *NOTE*: Changes to the backend compute node's IP addresses or other relevant network settings will invalidate the saved network config file. If this happens, please re-run the `dragon-network-config` tool to collect updated information. The `dragon-network-config` help is below: .. autodocstringonly:: dragon.launcher.network_config.main Formatting of the network-config file appears below for both JSON and YAML: .. code-block:: YAML :name: yaml_network_config :linenos: :caption: **Example of YAML formatted network configuration file** '0': h_uid: null host_id: 18446744071562724608 ip_addrs: - 10.128.0.5:6565 is_primary: true name: nid00004 num_cpus: 0 physical_mem: 0 shep_cd: '' state: 4 '1': h_uid: null host_id: 18446744071562724864 ip_addrs: - 10.128.0.6:6565 is_primary: false name: nid00005 num_cpus: 0 physical_mem: 0 shep_cd: '' state: 4 .. code-block:: JSON :name: json_network_config :linenos: :caption: **Example of JSON formatted network configuration file** { "0": { "state": 4, "h_uid": null, "name": "nid00004", "is_primary": true, "ip_addrs": [ "10.128.0.5:6565" ], "host_id": 18446744071562724608, "num_cpus": 0, "physical_mem": 0, "shep_cd": "" }, "1": { "state": 4, "h_uid": null, "name": "nid00005", "is_primary": false, "ip_addrs": [ "10.128.0.6:6565" ], "host_id": 18446744071562724864, "num_cpus": 0, "physical_mem": 0, "shep_cd": "" } } When nodes have multiple available NICs, attention should be paid to the number and order of IP addresses specified in the network configuration file. Because the `dragon-network-config` utility has no way of knowing which of the multiple NICs and IP addresses should be used preferentially on a given node, the list of "ip_addrs" specified in the network config YAML/JSON file may need to be manually adjusted to ensure the preferred IP address is first in the list. This manual review and ordering adjustment is only necessary when some NICs can and some NICs can not route to other nodes in the Dragon cluster. Although not specified as part of the network configuration, if the frontend node also has multiple NICs and only some have available routes to the compute nodes, it is possible to specify the routable IP address (and thereby NIC) to use on the frontend node for all communications with the compute nodes via the environment variable, `DRAGON_FE_IP_ADDR`. A toy example showcasing how to specify which NIC to use of the frontend / head node while simultaneously specifying which NICs to use on the compute nodes (via the network config JSON file): .. code-block:: bash # Note that the value "1.2.3.4" should be replaced with the appropriate local IP address. $ DRAGON_FE_IP_ADDR="1.2.3.4:6566" dragon --wlm ssh --network-config my_cluster_config.json --network-prefix '' my_user_code.py .. _transport_agents: High Speed Transport Agent (HSTA) --------------------------------- HSTA is a high-speed transport agent that provides MPI-like performance using Dragon Channels. HSTA uses libfrabric or libucp for communication over Slingshot or Infiniband high-speed interconnection networks. If you have one of these networks you can configure HSTA to run on it using the appropriate `dragon-config` options. See the :ref:`installation-guide` section for examples of how to configure Dragon to use HSTA. The HSTA transport agent is currently not available in the opensource version of Dragon. For inquiries about Dragon's high speed RDMA-based transport, please contact HPE by emailing dragonhpc@hpe.com. .. _tcp_transport_agent: TCP-based Transport Agent ------------------------- The TCP-based transport agent is the default transport agent for the Dragon opensource package. The TCP transport agent utilizes standard TCP for inter-node communication through Dragon Channels. When using a version of Dragon that includes the HSTA transport agent and you prefer to use the TCP transport agent, the `--transport tcp` option can be passed to the launcher (see: :ref:`FAQ ` and :ref:`Launcher options `). The dragon-config command can also be used to specify that the TCP transport should be used. To do that you run dragon-config as follows. .. code-block:: console dragon-config -a 'tcp-runtime=True' The TCP agent is configured to use port 7575 by default. If that port is blocked, it can be changed with the `--port` argument to `dragon`. If not specific, 7575 is used:, eg: .. code-block:: bash # Port 7575 used $ dragon --nodes 2 p2p_lat.py --iterations 100 --lg_max_message_size 12 --dragon # Port 7000 used $ dragon --port 7000 --nodes 2 p2p_lat.py --iterations 100 --lg_max_message_size 12 --dragon The TCP transport agent also favors known Cray high-speed interconnect networks by default. This is accomplished via regex specification of the network's named prefix matchin `ipogif` (Aries) or `hsn` (Slingshot): `r'^(hsn|ipogif)\d+$'`. To change, for example, to match only `hsn` networks, the `--network-prefix` argument could be used: .. code-block:: bash $ dragon --network-prefix hsn --nodes 2 p2p_lat.py --iterations 100 --lg_max_message_size 12 --dragon *Known Issue*: If a `--network-prefix` argument is given that doesn't actually exist, the Dragon runtime will enter a hung state. This will be fixed in future releases. For now, a `ctrl+z` and `kill` will be necessary to recover.