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It is possible to connect local ecflow_ui running on your mac/pc to the remote servers running at the Centre via ECMWF Teleport SSH gateway. You will be able to run ecflow_ui on your laptop at home and interact with ecFlow servers and suites as if you were at the Centre.

Setting up Teleport access

You will need to install Teleport client on your laptop. Follow instructions on the Centre's User Documentation pages how to install and set up the client.

You also need a valid Teleport SSH certificate on your laptop. Certificates expire after 12 hours. Fresh certificate is obtained from the Centre's Teleport service by executing "tsh login" command in a terminal. You may be asked for your ECMWF login credentials. If you already have a valid certificate, the authentication prompt will be skipped.

Connecting to ecFlow servers at the Centre

Here we describe two methods how to connect ecflow_ui running on a laptop with ecFlow servers running at the Centre. Both methods rely on the Teleport service.

Method #1: Local Port Forwarding

Once you have installed and set up Teleport client, you can start the SSH local port forwarding session. The session will tunnel network traffic between your ecflow_ui and the Centre's servers:

  • ecflow_ui ↔ ECMWF ecFlow servers
  • ecflow_ui ↔ ECMWF logservers (but see the "Limitations" section)

Start your SSH port forwarding session

Here I wish to connect to ECMWF workstation hostname machine1 where I have a ecflow server running on port 4141, also wish to connect to host machine2 where I have a ecflow server running on port 3142 (replace "user1" with your ECMWF username and "machine1", "machine2" with real ECMWF hostnames). To start the SSH tunnel on your laptop, execute:

ssh -J user1@shell.ecmwf.int user1@machine1 -C -N -L 4141:machine1:4141 -L 3142:machine2:3142

The ssh session will keep running in the terminal, listening on ports 4141 and 3142 and printing various log messages as it forwards your ecflow network traffic to the Centre.

To access HPC job output via the log server, you need to create a tunnel access for this as well. Here we use 'logserver' as an example (replace this with your actual logserver).

ssh -J user1@shell.ecmwf.int user1@machine1 -C -N -L 4141:machine1:4141 -L 3142:machine2:3142 -L 9316:logserver:9316

Configure your ecflow_ui

Next, configure the connection settings for the two ecflow servers in your ecflow_ui. Make sure you use "localhost" in "Host" fields, not the actual ECMWF hostnames. 

You will also need to add "127.0.0.1 logserver" alias in /etc/hosts on your laptop, so that connections from your ecflow_ui to logserver actually go to localhost (replace "logserver" with an actual ECMWF logserver name).

Limitations of Local Port Forwarding

In practice we can only connect to a single ECMWF logserver. This is because:

  • different logservers at the Centre use the same port number (9316).
  • we cannot map all of them to a single 127.0.0.1:9316 local endpoint
  • we could map each logserver:9316 to a different local port number, but we cannot reconfigure ecflow_ui to use these local port numbers (i.e. we cannot change ECF_LOGPORT=9316 defined on the ecFlow server without affecting other users).

Method #2: Dynamic Port Forwarding

SSH offers Dynamic Port Forwarding, i.e. it can act as a SOCKS proxy. This method has some advantages over Local Port Forwarding:

  • There is no need to manually specify port number mapping for each ecflow server
  • You can use original host names in the ecFlow servers connection settigs, instead of 'localhost'
  • You are not limited to a single logserver; there is also no need to modify /etc/hosts file.

However, to use Dynamic Port Forwarding, the client application (ecflow_ui) must understand SOCKS protocol. Here we will show how to start SOCKS proxy and how to make ecflow_ui speak SOCKS. The proxy will tunnel all network traffic from ecflow_ui to the servers running inside the Centre:

  • ecflow_ui ↔ ECMWF ecFlow servers
  • ecflow_ui ↔ ECMWF ecFlow logservers
  • ecflow_ui ↔ ECMWF DNS servers

NOTE: if you were using Local Port Forwarding method, you will now need to:

  • remove "127.0.0.1 logserver" from your /etc/hosts
  • use actual ECMWF hostnames in the "Host" fields of ecflow_ui connection settings, instead of "localhost".

Start your SOCKS proxy

In a terminal, start the SOCKS proxy SSH session with:

% ssh -v -C -N -D9050 -J myecuser@shell.ecmwf.int myecuser@myecworkstation

(replace "myecuser" and "myecworkstation" with your real ECMWF username and workstation name).

The ssh session will keep running in the terminal, listening on port 9050 and printing various log messages as it forwards your network traffic to the Centre.

SOCKS-ify your ecflow_ui

Applications which want to use SOCKS proxy must speak SOCKS protocol. Some application can be "SOCKS-ified" using a tool called proxychains. The tool intercepts the application's network traffic, adds SOCKS protocol layer and redirects traffic to the proxy. Luckily, the ecflow_ui.x executable can be SOCKS-ified this way.

On MacOS, you can install proxychains tool with "brew install proxychains-ng". Many Linux distributions come with proxychains tool preinstalled.

By default, proxychains tool sends network traffic to localhost:9050. If your SOCKS proxy is listening on a different port, adjust /usr/local/etc/proxychains.conf configuration file (MacOS) accordingly.

Now edit the ecflow_ui launch script. Towards the end of the script, replace the "$exe" with proxychains4 "$exe". On my machine, the ecflow_ui launch script is installed as /opt/miniconda3/bin/ecflow_ui.

You should now be able to start ecflow_ui and interact with ecFlow servers and suites as if you were at the Centre.

Accessing restricted ecFlow servers

Servers with username-based access control

Many ecFlow servers at the Centre use a whitelist to only allow authorized users in. This creates a problem when connecting remotely - typically your username on the laptop will be different from your authorized ECMWF username.

There are two possible ways to access these servers:

  • you can ask the ecFlow server administrator to add your laptop username to the server's whitelist, or
  • you can create a new user account on your laptop, setting username to match the ECMWF username.

If you create new user account for ecflow_ui but want to keep using your regular account, here is a handy script. This example uses Dynamic Port Forwarding method, but can be easily adapted to use Local Port Forwarding method.

A script for starting SSH tunnel + ecflow_ui on a laptop as another user 
#!/bin/bash
set -e
# --------------------------------------------------------------
# A script for starting SSH SOCKS proxy and ecFlow UI as another user.
# Prerequisites:
#   * User named "myecuser" must exist on the laptop
#   * "myecuser" has set up their Teleport client to access ECMWF.
# --------------------------------------------------------------

ECMWF_USER=myecuser              # your ECMWF username
ECMWF_HOST=myecworkstation       # your ECMWF workstation name

xhost + || :
sudo -i -u "$ECMWF_USER" -- sh << SUDO

    set -e

    # Starting ssh-agent for $ECMWF_USER.
    # Teleport service requires ssh-agent running.

    ssh-agent -- sh << SSH_AGENT

        set -e

        # "tsh login" will fetch SSH certificate from
        # shell.ecmwf.int and load it onto the ssh-agent.

        tsh login -d

        # "ssh -f" will start SSH tunnel in the background.
        # The trap will terminate the tunnel on exit.

        trap 'pkill -f ssh.*-f' 0 1 2 3 15
        ssh -f -N -v -C -D9050 -J "$ECMWF_USER@shell.ecmwf.int" "$ECMWF_USER@$ECMWF_HOST"

        # finally, start the local ecFlow UI
        /Volumes/Macintosh\ HD/opt/miniconda3/bin/ecflow_ui
SSH_AGENT
SUDO

Servers with password-based access control

As an alternative to username-based access control, ecFlow offers password-based access control. See: Security(custom user).

The password-based access control must be enabled on the ecFlow server side first. Discuss with your server administrator to set it up. 

When the server-side setup is done by the administrator, configure the connection settings in your ecflow_ui: 

Replace "host1" with a real ECMWF ecFlow server hostname and "myecflowuser" with your authorised ecFlow username.

Known issues

  • Sometimes ecflow_ui fails to fetch the job output, job script and .sub files from the logserver. Refreshing the tab usually fixes the issue. The initial error looks like: "Output directory: [1] Failed to fetch from cca-log@9316 error: The remote host closed the connection. [2] No access to path on disk!"
  • For some suites the ecflow_ui cannot retrieve job output, job script and .sub files no matter what. It happens when the log server at the centre doesn't have access to these files. ecflow_uis running at the centre have direct access to the files on disk so no problem, but remote ecflow_ui cannot access them.
  • The timeline and server load functionality currently doesn't work
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