Houdini 20.0 How to use the help

Running a central help server

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Overview

A studio can set up a central help server to serve help to multiple users of Houdini, instead of each instance of Houdini starting up its own help server on each machine. This may be useful for sharing site-specific documentation between users.

Note

If the studio’s custom assets are served to users from a shard network location, then each individual Houdini instance will be able to browse the help in the assets without needing a central server (however a small amount of CPU time to index the asset docs will be duplicated across all machines). The central server is more useful if you want to centralize documentation besides node docs.

This document outlines a few solutions for providing Houdini help without running a full Houdini:

  • Running the help server. This simply runs the default Python server included with Houdini. This is the easiest option and should be the first thing you try. If you find it’s not sufficient for a large number of users, you can use one of the faster solutions below.

  • Running the Houdini help WSGI app inside an applicaiton server.

  • Serving static help. This pre-generates HTML files from the wiki files in the help, so you can serve them using a plain HTTP server.

    This is the fastest possible solution, and easy to set up, since it’s just serving plain static files, and does not require any license installation. This solution allows you to publish Houdini’s help from an existing web server. This does not provide dynamic content, search, or help embedded in nodes.

Licensing

The help server normally requires a Houdini license to run, since it uses HOM to read help embedded in nodes and tools.

You can run hython with any Houdini license, including an Apprentice license. The easiest thing to do is set up a central server machine and install just an Apprentice license on it, so the server process will use that.

You can ensure hython uses an Apprentice license by disallowing the other license types:

hhelp --skip-license-modes="commercial,indie,education" ...

Note that serving static help does not require ongoing use of a license, but has some drawbacks. See serving static help below for more information.

Running the default help server

The easiest way to set up a central help server is simply to run the default Python help server included with Houdini. The drawback is that the Python server can only uses a single process, and serves all files (images, stylesheets, and so on) using Python code. This is probably fast enough for small to medium sized studios, but for many users you may need to investigate using an application server or serving static files.

  • Easy to set up.

Tip

Previous versions of this document recommended usinga a proxy server to speed up the help, but Houdini/hython now serves static help files (such as icons and images) using native code, so loading pages is much faster and running a proxy server is probably not necessary unless you are serving many users and need multiple server threads/processes.

Command line

  1. Open a Houdini shell.

    Windows

    Click Start ▸ All programs ▸ Side Effects Software ▸ Houdini X.X.XXX ▸ Utilities ▸ Command line tools.

    Mac

    In the Finder, open Applications ▸ Houdini ▸ HoudiniX.X.X ▸ Utilities ▸ Houdini Terminal.

    Linux

    In a bash shell, cd to the Houdini install directory and source houdini_setup.

  2. In the Houdini shell, type:

    hhelp --skip-license-modes="commercial,indie,education" serve --host=0.0.0.0 --port=8080 -bgindex=true
    
  3. Open a browser and go to

    http://localhost:8080/
    

serve command

--host=0.0.0.0

The IP address for the server.

  • If your computer has multiple network controllers, you can specify which address you want the server to listen at.

  • Use 0.0.0.0 (the default) to make the server available to other computers.

  • Use localhost or 127.0.0.1 to make the server only available on your computer.

--port=8080

The port number for the server. Default is 8080.

--debug

Run the server with debugging information on.

--bgindex

Re-index changed documents in the background while the server is running.

--config=path

(Optional) a file to read configuration options from.

--logfile=path

(Optional) a file to write server log to.

--loglevel=DEBUG|INFO|WARNING|ERROR

(Optional) log messages at or above this level of severity.

index command

This command lets you manually update the search index (if you're not running a server with the --bgindex option). By default the command will only update changed files, unless you pass the --clean option.

hhelp --skip-license-modes="commercial,indie,education" index

--clean

Re-index all documents from scratch, whether they've changed or not.

--usages

Generate information about what nodes are used by example files.

--config=path

(Optional) a file to read configuration options from.

--logfile=path

(Optional) a file to write server log to.

--loglevel=DEBUG|INFO|WARNING|ERROR

(Optional) log messages at or above this level of severity.

Starting the server from code in hython

If you want to start the built-in server in code (in hython):

from houdinihelp.server import start_server

start_server(
    host="0.0.0.0",         # Network interface to listen to
    port=8080,             # Port to listen to
    debug=False,            # Whether to start the server in debug mode
    bgindex=None ,          # Whether to do background indexing
    config_file=None,       # String path to a config file
    use_houdini_path=True,  # See below
)
  • If config_file is None and use_houdini_path is True, the code will use hou to search the Houdini path for a config/Help/bookish.cfg configuration file (see configuration below). This will use a batch license if hou hasn’t already been imported. If you're specifying a configuration file in the arguments you don’t need worry about this.

  • The bgindex keyword argument can be True, False, or None. None means use the value from the configuration, whereas passing True or False will override the configuration.

Setting Houdini clients to use the central server

Once you have a central server set up, you can configure your Houdini clients to get help from it instead of starting up their own local help servers.

  • In the Houdini UI:

    1. In the main menus, choose Edit ▸ Preferences ▸ Miscellaneous.

    2. Turn on Use external help server.

    3. Set the External help URL to the URL of your central server (e.g. http://server.local:8080/houdini/).

    or

  • For studio-wide changes without using the UI, you can set these preferences directly in $HOUDINI_USER_PREF_DIR/houdini.pref using the keys misc.useexternalhelp.val := 1; and misc.externalhelpurl.val := "help_url".

Using a WSGI application server

The proxy server example above is relatively easy to set up because you can use hhelp to start Houdini’s help server as usual, then forward requests to the help server as needed.

However, the drawback is that communicating with the help server over HTTP is somewhat inefficient, and the Python help server is still single-process/single-threaded, limiting overall throughput.

Instead of running the help server and forwarding requests to it, this solution uses a WSGI application server such as uwsgi, gunicorn, or Apache with modwsgi, to run the Houdini help’s application code itself, so it can use multiprocessing and multithreading.

WSGI is a protocol that allows standalone HTTP servers to run a Python function to generate dynamic web content. The drawback is that the server usually wants to start the Python interpreter itself, so we can’t rely on hython setting up the path to Houdini’s libraries automatically. The application.py script listed in this section manipulates the Python path so the Houdini help app can run in plain Python.

  • Faster than the plain help server.

  • Can serve dynamic wiki help from directories you specify.

  • Can’t use hou, so this solution can’t serve help embedded inside assets or tools.

  • Slightly harder to set up, since you can’t use hython (which sets up the Python path automatically to use Houdini’s libraries).

Important notes:

  • Because the Houdini help app won’t can’t use HOM from the app server, it can’t serve help from inside nodes. To use this solution, you have to keep your node help in files on disk rather that embedded inside the assets.

  • You should still run the server in a Houdini shell environment, so it has environment variables such as $HFS available.

  • This document outlines general solutions and configurations that require installation and configuration of third party software. This document contains some examples, but unfortunately it can’t hope to cover all the possible combinations of platform, software, and configuration options. You may need to do your own research on the software you use, its configuration options, and how your chosen software uses standards such as WSGI.

Setting up an application server

  1. First, set up the directory structure as in setting up central server directories.

    This should give you a directory structure like this:

    central/
        files/
            icons/
                ...
            images/
                ...
            videos/
                ...
            static/
                ...
    
  2. The app server will require a script to create an application() function it will call to serve pages.

    The application server will run the script using Python, not hython, so it won’t automatically have the Houdini libraries available.

    The following example script manipulates the Python path so it can find Houdini’s libraries, and configures the application to find files under $HFS, before creating the application function.

    Save this to a file under central called application.py.

    Example central/application.py script

    import logging
    import sys
    from os.path import expandvars
    
    # Add Houdini libraries to Python path
    sys.path.append(expandvars("$HHP"))
    
    # Add Houdini's third-party Python libraries. Unfortunately this path is
    # platform-specific
    if sys.platform in ("linux", "linux2"):
       sys.path.append(expandvars("$HFS/python/lib/python2.7/site-packages-forced"))
    elif sys.platform == "darwin":
        sys.path.append(
            expandvars(
                "$HFS/Frameworks/Python.framework/Versions/Current/lib/python2.7/site-packages-forced"
            )
        )
    elif sys.platform in ("win32", "win64"):
        sys.path.append(expandvars("$HFS/python27/lib/site-packages-forced"))
    
    
    from houdinihelp.hconfig import HoudiniHfsConfig
    from houdinihelp.server import get_houdini_app
    
    
    class MyConfig(HoudiniHfsConfig):
        # The directories you want to serve from
        DOCUMENTS = [
            # "Loose" (unzipped) files under $HFS/houdini/help
            expandvars("$HFS/houdini/help"),
            {
                # This adds ability to read docs out of .zip files in
                # $HFS/houdini/help
                "type": "object",
                "classname": "bookish.stores.ZipTree",
                "args": {
                    "dirpath": expandvars("$HFS/houdini/help"),
                }
            },
            # This adds files under the help dir in your user prefs
            expandvars("$HOUDINI_USER_PREF_DIR/help"),
    
            # Add any other directories you want to add to the server here
            # "/my/dir",
        ]
    
        # Store the cache in the user's prefs dir
        CACHE_DIR = expandvars("$HOUDINI_USER_PREF_DIR/config/Help/cache")
    
        # The full-text index shipped with Houdini. If you want to use background
        # indexing, copy this directory somewhere writable, and set this to the path
        # of the writable directory.
        INDEX_DIR = expandvars("$HFS/houdini/config/Help/index")
    
        # True if the server should run an indexing thread in the background
        ENABLE_BACKGROUND_INDEXING = False
        # Number of seconds between background indexing runs
        BACKGROUND_INDEXING_INTERVAL = 60
    
        # Specify a page manager that doesn't use hou
        PAGES_CLASS = "houdinihelp.hpages.HoudiniPagesWithoutHou"
    
    
    application = get_houdini_app(
        use_houdini_path=False,
        config_obj=MyConfig,
        loglevel=logging.INFO,
        debug=False,
    )
    
  3. Install a WSGI application server.

    This step is specific to the server you want to use. We recommend a lightweight server such as uwsgi.

    How to install server software on your system is beyond the scope of this document. See the instructions for your chosen server for how to install it on different platforms. For uwsgi, you can install it using Python’s pip3 package manager (pip3 install uwsgi). This is the best installation method for uwsgi since it installs all necessary plugins as well as the base program.

  4. Set up your HTTP server to serve the static files directly, and use the application.py script to serve dynamic help pages.

    This is highly specific to the app server you use and how you want to configure the server. See the documentation for your application server for details of how it works with a WSGI function, and how you specify static directories.

uwsgi example

The following command runs uwsgi as an HTTP server, sets the listening address/port, specifies the directory to serve static files from (as set up above), and points to the script that creates the application’s WSGI function:

% uwsgi --http 0.0.0.0:9090 --check-static $CENTRAL/files $CENTRAL/application.py

Serving static help

  • Fastest, most robust solution

  • Can use any HTTP server, don’t need to configure application

  • Doesn’t require any Houdini license.

  • Only serves static pages, not dynamic wiki pages (that is, you can’t edit a wiki help file and reload to see the results immediately in the browser).

  • No search!

Pre-generate all help files

  1. First, set up the directory structure as in setting up central server directories above.

    This should give you a directory structure like this:

    central/
        files/
            icons/
                ...
            images/
                ...
            videos/
                ...
            static/
                ...
    
  2. In Houdini shell, cd to the central directory.

  3. Run the following command:

    hhelp generate files

    This will generate a static HTML file from every wiki file in the Houdin help. This can take a long time.

  4. Once you have generated the HTML files, you can point any HTTP server to serve the files in central/files.

Configuring the help server

  • You can specify a configuration file in the hhelp command line utility using the --config option, or in code using the config_file parameter of houdinihelp.server.get_houdini_app or houdinihelp.server.start_server.

  • If you don’t specify a configuration file and HOUDINIPATH/config/Help/bookish.cfg exists, the server will load it (unless you pass use_houdini_path=False).

  • The help server is based on Flask. Flask’s configuration files are actually Python.

For example, to add a directory of files at $HOME/myfiles, put the following in the configuration file:

EXTRA_DOCUMENTS = ["$HOME/myfiles/"]

See below for some useful configuration keys.

Useful configuration keys

DOCUMENTS = [...]

The default list of document sources includes help directories from the Houdini path, as well as special sources that allow reading help from inside assets and shelf tools. You can replace this with a list of directory paths to serve only your directories. For example:

DOCUMENTS = ["/my/dir"]

It’s possible to extend this list in your configuration file instead of replacing it, but in that case it’s easier to use EXTRA_DOCUMENTS (see below).

EXTRA_DOCUMENTS = []

A list of “extra” document sources to be added on to the defaults in DOCUMENTS. This is useful when you want the defaults but also want to serve from some additional directories

(Note that the default list includes the HOUDINIPATH/help, so you can extend the Houdini path to achieve the same thing.)

EXTRA_DOCUMENTS = ["/my/dir"]

ENABLE_BACKGROUND_INDEXING = False

Whether to run a thread to re-index changed content in the background. Overridden by the --bgindex option on the command line.

BACKGROUND_INDEXING_INTERVAL = 60

The number of seconds between re-indexes when background indexing is on.

EXTRA_SHORTCUTS = []

CACHE_DIR = "$HOUDINI_USER_PREF_DIR/config/Help"

Where the server caches .json files generated from wiki source files.

INDEX_DIR = "$HFS/houdini/config/Help/index"

Directory containing the search index.

How to use the help

Basics

Documenting nodes

Running a central help server