ParaViewWeb, Python Launcher, and Apache, and 'Process did not properly start' Error


I’m working on spinning up an instance of ParaViewWeb Python Launcher with Apache as a front-end as described in your documentation, and am running into some confounding issues.

Basically, my current local setup is as follows:

Apache is set up to surface my server as a virtual host

<VirtualHost *:80>
    ServerName localhost.paraview
    DocumentRoot "{project_directory}/www/"
    ErrorLog "{logging_directory}/apache2/localhost.paraview-error_log"
    CustomLog "{logging_directory}/apache2/localhost.paraview-access_log" common
    Header set Access-Control-Allow-Origin "*"

    ### The following commented lines could be useful when running
    ### over https and wss:
    # SSLEngine On
    # SSLCertificateFile    /etc/apache2/ssl/your_certificate.crt
    # SSLCertificateKeyFile /etc/apache2/ssl/your_domain_key.key
    # SSLCertificateChainFile /etc/apache2/ssl/DigiCertCA.crt
    # <Location ${MY-DOCUMENT-ROOT} >
    #   SSLRequireSSL On
    #   SSLVerifyClient optional
    #   SSLVerifyDepth 1
    #   SSLOptions +StdEnvVars +StrictRequire
    # </Location>

    # Rule for ParaViewWeb launcher
    # ProxyPass /paraview http://localhost.paraview
    ProxyPass /paraview http://localhost:8080/paraview

    # Rewrite setup for ParaViewWeb
    RewriteEngine On

    # This is the path the mapping file Jetty creates
    RewriteMap session-to-port txt:{project_directory}/mapping-dir/proxy-mapping.txt

    # This is the rewrite condition. Look for anything with a sessionId=
    # in the query part of the URL and capture the value to use below.
    RewriteCond %{QUERY_STRING}     ^sessionId=(.*)&path=(.*)$ [NC]

    # This does the rewrite using the mapping file and the sessionId
    RewriteRule    ^/proxy.*$  ws://${session-to-port:%1}/%2  [P]

    <Directory "{project_directory}/www/">
        Options Indexes FollowSymLinks
        Order allow,deny
        Allow from all
        AllowOverride None
        #AllowOverride All
        Require all granted

where {logging_directory} and {project_directory} are paths on my system and everything else above is given directly as in my vhosts file.

Additionally my launcher.config is

  // ===============================
  // General launcher configuration
  // ===============================

  "configuration": {
    "host" : "localhost",
    "port" : 8080,
    "endpoint": "paraview",                   // SessionManager Endpoint
    //"content": "./www",                    // Optional: Directory shared over HTTP
    "proxy_file" : "./mapping-dir/proxy-mapping.txt",  // Proxy-Mapping file for Apache
    "sessionURL" : "ws://localhost:8080/proxy?sessionId=${id}&path=ws",
         // ws url used by the client to connect to the started process
    "timeout" : 25,                           // Wait time in second after process start
    "log_dir" : "./viz-logs",              // Directory for log files
    //"upload_dir" : "/.../data",               // If launcher should act as upload server, where to put files
    "fields" : ["file", "host", "port", "updir"] //,    // List of fields that should be send back to client
                                                     // include "secret" if you provide it as an --authKey to the app
    //"sanitize": {                             // Check information coming from the client
    //  "cmd": {
    //    "type": "inList",                 // 'cmd' must be one of the strings in 'list'
    //    "list": [
    //      "me", "you", "something/else/altogether", "nothing-to-do"
    //    ],
    //    "default": "nothing-to-do"        // If the string doesn't match, replace it with the default.
                                        // Include the default in your list
      //"cmd2": {                             // 'cmd2' must match the regexp provided, example: not a quote
      //  "type": "regexp",
      //  "regexp": "^[^"]*$",             // Make sure to include '^' and '$' to match the entire string!
      //  "default": "nothing"

  // ===============================
  // Useful session vars for client
  // ===============================

  "sessionData" : { "updir": "/Home" },      // Tells client which path to updateFileBrowser after uploads

  // ===============================
  // Resources list for applications
  // ===============================

  "resources" : [ { "host" : "localhost", "port_range" : [9001, 9003] } ],

  // ===============================
  // Set of properties for cmd line
  // ===============================

  "properties" : {
    "vtkpython" : "/.../VTK/build/bin/vtkpython",
    "pvpython" : "/.../ParaView/build/bin/pvpython",
    "vtk_python_path": "/.../VTK/build/Wrapping/Python/vtk/web",
    "pv_python_path": "/.../ParaView/build/lib/site-packages/paraview/web",
    "plugins_path": "/.../ParaView/build/lib",
    "dataDir": "/.../path/to/data/directory"

  // ===============================
  // Application list with cmd lines
  // ===============================

  "apps" : {
    "cone" : {
      "cmd" : [
        "${vtkpython}", "${vtk_python_path}/", "--port", "$port"
      "ready_line" : "Starting factory cone"
    "graph" : {
      "cmd" : [
          "${vtkpython}", "${vtk_python_path}/", "--port", "$port",
            "--vertices", "${numberOfVertices}", "--edges", "${numberOfEdges}"
      "ready_line" : "Starting factory graph"
    "phylotree" : {
      "cmd" : [
        "${vtkpython}", "${vtk_python_path}/", "--port", "$port",
          "--tree", "${dataDir}/visomics/${treeFile}", "--table", "${dataDir}/visomics/${tableFile}"
      "ready_line" : "Starting factory phylotree"
    "filebrowser" : {
      "cmd" : [
        "${vtkpython}", "${vtk_python_path}/",
          "--port", "${port}", "--data-dir", "${dataDir}"
      "ready_line" : "Starting factory filebrowser"
    "data_prober": {
      "cmd": [
        "${pvpython}", "-dr", "${pv_python_path}/",
          "--port", "${port}", "--data-dir", "${dataDir}", "-f"
      "ready_line" : "Starting factory data_prober"
    "visualizer": {
      "cmd": [
        "${pvpython}", "-dr", "${pv_python_path}/",
          "--plugins", "${plugins_path}/", "--port", "${port}",
          "--data-dir", "${dataDir}", "--load-file", "${dataDir}/${fileToLoad}",
          "--authKey", "${secret}", "-f"
      ],  // Use of ${secret} means it needs to be provided to the client, in "fields", above.
      "ready_line" : "Starting factory visualizer"
    "loader": {
      "cmd": [
        "${pvpython}", "-dr", "${pv_python_path}/",
          "--port", "${port}", "--data-dir", "${dataDir}",
          "--load-file", "${dataDir}/${fileToLoad}", "-f"
      "ready_line" : "Starting factory loader"
    "launcher" : {
      "cmd": [
          "${port}", "${client}", "${resources}", "${file}"
      "ready_line" : "Starting factory launcher"
    "server": {
      "cmd": [
        //"", "--resource-host", "${host}", "--resource-port", "${port}",
        //  "--session-id", "${id}", "--generated-password", "${secret}",
        //  "--application-key", "${application}"
        //"${python_exec}", "-dr", "./server/"
        "/Applications/ {project_directory}/server/ -p", "${port}"
      "ready_line": "Starting factory SERVER"

where again {project_directory} is a path on my system and everything else above is given directly as in my config file, and the ‘server’ command is the one that I’m trying to trigger from the launcher, to open multiple versions of the app for different users from a base login screen.

To use my ParaViewWeb app, I start up the launcher with a script in a terminal and then go to ‘localhost.paraview’, a base log in screen Apache serves up, and then ideally, at the push of a ‘Continue as guest’ button, the launcher should be triggered to start up a basic implemenation of my app at ‘localhost.paraview/paraview’, and the browser is forwarded there.

I can see by the mapping-dir/proxy-mapping.txt and the viz-logs/ that the launcher is attempting to trigger the start up of the app, and that the ports/ids are being apportioned, and the browser is forwarding to ‘localhost.paraview/paraview’ but I keep receiving the following error message:

In browser:

Request URL: http://localhost:8080/paraview
Request Method: POST
Status Code: 503 Service Unavailable

Request Payload : {
  sessionManagerURL: "http://localhost:8080/paraview", 
  application: "server", 
  app: "server"

Response: {
  "error": "The process did not properly start. ['/Applications/ /Development/labkey_em_viewer/server/ -p', '9002']"

And in the viz-logs:

2020-12-18 17:11:23,607:ERROR:root:The command line failed
2020-12-18 17:11:23,609:ERROR:root:/Applications/ /Development/labkey_em_viewer/server/ -p 9002

I’m not sure what’s going on here, if I’m not triggering the app from the launcher in the right way, or if apache isn’t interacting with the launcher properly, etc. I’ve trued several different strategies and I keep ending up back here.

Could anyone help me determine what sort of errors cause the launcher to behave this way?


You should try to deploy that already done demo available here. You will notice how the launcher config is setup. Please fix your path in that configuration file to match the inside docker path.

You might be interested to read that thread too.