Deployment scenarios#

To make your application into a user-friendly service, you’ll have to deploy your work. This subsection explores various aspects of deployment.

Standalone Bokeh server#

You can have the Bokeh server running on a network for users to interact with your app directly. This can be a simple solution for local network deployment, provided the capabilities of the hardware running the server match your app requirements and the expected number of users.

However, if you have authentication, scaling, or uptime requirements, you’ll have to consider more sophisticated deployment configurations.

Integrating Bokeh server into other web services#

Bokeh server is frequently used to create plots and dashboards embedded within larger parent applications. For instance, in a financial context, this may involve incorporating Bokeh-backed trendlines that chart account balances over time into a web-based trading platform. In a supply-chain context, a Bokeh view could be integrated into an existing inventory management system to interactively monitor a store’s item supplies.

To meet this use-case, the bokeh.embed module offers the server_document() and server_session() methods. Refer to Bokeh applications for a detailed discussion of their usage, with examples. In short, these methods return the text of an HTML script tag that loads a view from Bokeh server, and adds the view to the DOM of any page that the script tag is placed in.

If the parent service you wish to integrate with is not Python-based, you can still integrate with Bokeh through the server_document / server_session methods. However, you will need to do so by calling out to a small, long-lived Python script that returns the text contents of those methods via any standard form of IPC.

To allow your parent application to display embedded Bokeh views, you must configure the parent application to permit cross-origin requests to your Bokeh server instance. This is accomplished by adding the public hostname and port number of your Bokeh server to the script-src and connect-src directives of the parent service’s content security policy (CSP), for both the HTTP(S) and WS(S) protocols. The exact procedure for configuring the CSP will depend on the toolkit or framework your parent service is built with, so reference the specific documentation for that software. As a measure of last resort, CSP headers can be overwritten by a reverse-proxy as well.

Warning

Do not run Bokeh server over HTTP while running the parent service over HTTPS, or vice-versa. Bokeh’s loader code determines which protocol to load resources over on the client-side, via window.location.protocol, so if the protocol of the parent service does not match the protocol of your Bokeh server instance, the loader script’s requests to Bokeh server will fail.

If your parent application is Python-based, and you don’t mind tightly integrating your Bokeh server application into your parent application’s codebase, Bokeh also supports running its underlying Tornado web server through a thread launched by your parent application. Practical examples are linked under Bokeh server APIs. This approach still requires the use of server_document or server_session, but may simplify CSP configuration as well as deployment of your Bokeh server app.

SSH tunnels#

To run a standalone instance of the Bokeh server on a host with restricted access, use SSH to “tunnel” to the server.

In the simplest scenario, the user accesses the Bokeh server from another location, such as a laptop with no intermediary machines.

Run the server as usual on the remote host.

bokeh serve

Next, issue the following command on the local machine to establish an SSH tunnel to the remote host:

ssh -NfL localhost:5006:localhost:5006 user@remote.host

Replace user with your username on the remote host and remote.host with the hostname or IP address of the system hosting the Bokeh server. The remote system may prompt you for login credentials. Once you are connected, you will be able to navigate to localhost:5006 as though the Bokeh server were running on the local machine.

A slightly more complicated scenario involves a gateway between the server and the local machine. In that situation, a reverse tunnel must be established from the server to the gateway with another tunnel connecting the gateway with the local machine.

Issue the following commands on the remote host where the Bokeh server will be running:

nohup bokeh server &
ssh -NfR 5006:localhost:5006 user@gateway.host

Replace user with your username on the gateway and gateway.host with the hostname or IP address of the gateway. The gateway may prompt you for login credentials.

To setup the tunnel between the local machine and the gateway, run the following command on the local machine:

ssh -NfL localhost:5006:localhost:5006 user@gateway.host

Again, replace user with your username on the gateway and gateway.host with the hostname or IP address of the gateway.

You should now be able to access the Bokeh server from the local machine by navigating to localhost:5006. You can even set up client connections from a Jupyter notebook running on the local machine.

Note

We intend to expand this section with more guidance for other tools and configurations. If you have experience with other web deployment scenarios and wish to contribute your knowledge here, please contact us on https://discourse.bokeh.org

SSL termination#

You can configure the Bokeh server to terminate SSL connections and serve secure HTTPS and WSS sessions directly. To do so, you’ll have to supply the --ssl-certfile argument with the value of the path to a single PEM file containing a certificate as well as any number of CA certificates needed to establish the certificate’s authenticity.

bokeh serve --ssl-certfile /path/to/cert.pem

You can also supply a path to the certificate file by setting the environment variable BOKEH_SSL_CERTFILE.

If the private key is stored separately, you can supply its location by setting the --ssl-keyfile command line argument or by setting the BOKEH_SSL_KEYFILE environment variable. If the private key requires a password, supply it by setting the BOKEH_SSL_PASSWORD environment variable.

Alternatively, you may wish to run a Bokeh server behind a proxy and have the proxy terminate SSL connections. See the next subsection for details.

Basic reverse proxy setup#

To serve a web application to the general internet, you may wish to host your app on an internal network and proxy connections to it through some dedicated HTTP server. This subsection provides guidance on how to configure some common reverse proxies.

Nginx#

One very common HTTP and reverse-proxying server is Nginx. Here’s an example of a server configuration stanza:

server {
    listen 80 default_server;
    server_name _;

    access_log  /tmp/bokeh.access.log;
    error_log   /tmp/bokeh.error.log debug;

    location / {
        proxy_pass http://127.0.0.1:5100;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_http_version 1.1;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host:$server_port;
        proxy_buffering off;
    }

}

The above server block sets up Nginx to proxy incoming connections to 127.0.0.1 on port 80 over to 127.0.0.1 on port 5100. To work in this configuration, you need to use some of the command line options to configure the Bokeh server. In particular, use --port to have the Bokeh server listen on port 5100.

bokeh serve myapp.py --port 5100

The basic server block above does not configure any special handling for static resources, such as Bokeh JS and CSS files. This means that the Bokeh server serves these files directly.

Although this is a viable option, it requires that the Bokeh server do extra work that is better handled with Nginx. To serve static assets with Nginx, add the following sub-block to the code above, substituting the path to your static assets for /path/to/bokeh/server/static:

location /static {
    alias /path/to/bokeh/server/static;
}

Make sure that the account running Nginx has permissions to access Bokeh resources. Alternatively, you can copy the resources to a global static directory during the deployment.

To communicate cookies and headers across processes, Bokeh may include this information in a JSON web token, sending it via a WebSocket. In certain cases this token can grow very large causing Nginx to drop the request. You may have to work around this by overriding the default Nginx setting large_client_header_buffers:

large_client_header_buffers 4 24k;

Apache#

Another common HTTP server and proxy is Apache. Here is an example configuration for a Bokeh server running behind Apache:

<VirtualHost *:80>
    ServerName localhost

    CustomLog "/path/to/logs/access_log" combined
    ErrorLog "/path/to/logs/error_log"

    ProxyPreserveHost On
    ProxyPass /myapp/ws ws://127.0.0.1:5100/myapp/ws
    ProxyPassReverse /myapp/ws ws://127.0.0.1:5100/myapp/ws

    ProxyPass /myapp http://127.0.0.1:5100/myapp
    ProxyPassReverse /myapp http://127.0.0.1:5100/myapp

    <Directory />
        Require all granted
        Options -Indexes
    </Directory>

    Alias /static /path/to/bokeh/server/static
    <Directory /path/to/bokeh/server/static>
        # directives to effect the static directory
        Options +Indexes
    </Directory>

</VirtualHost>

The above configuration aliases /static to the location of the Bokeh static resources directory. However, it is also possible (and probably preferable) to copy the static resources to whatever standard location for static files you configure for Apache as part of the deployment.

You may also need to enable some modules for the above configuration:

a2enmod proxy
a2enmod proxy_http
a2enmod proxy_wstunnel
apache2ctl restart

Depending on your system, you may have to use sudo to run the above.

As before, run the Bokeh server with the following command:

bokeh serve myapp.py --port 5100

Unix sockets with proxies#

In some cases, you might want to connect the proxied Bokeh server to the proxy using a Unix socket, rather than a websocket. You can bind the Bokeh server to a Unix socket and use Nginx or Apache to proxy to a Unix domain socket.

Note

Binding to a Unix socket is not supported on Windows.

bokeh serve --unix-socket /path/to/socket.sock

A Nginx config could look like this example:

upstream myserver {
    server unix:/path/to/socket.sock;
}

server {
    listen 80 default_server;
    server_name _;

    access_log  /tmp/bokeh.access.log;
    error_log   /tmp/bokeh.error.log debug;

    location / {
        proxy_pass http://myserver;
    }

}

Please be aware that Bokeh server network options such as websocket origins and SSL configuration are incompatible with Unix sockets. It would be up to the proxy to enforce these restrictions at the front end.

If there are multiple users who share the host, you can restrict the file permissions on the socket to restrict access to the proxied server.

Reverse proxying with Nginx and SSL#

To deploy a Bokeh server behind an SSL-terminated Nginx proxy, you need a few additional customizations. In particular, you have to configure the Bokeh server with the --use-xheaders flag.

bokeh serve myapp.py --port 5100 --use-xheaders

The --use-xheaders flag causes Bokeh to override the remote IP and URI scheme/protocol for all requests with X-Real-Ip, X-Forwarded-For, X-Scheme, and X-Forwarded-Proto headers when they are available.

You also need to customize Nginx. In particular, you have to configure Nginx to send X-Forwarded-Proto headers and use SSL termination. Optionally, you may want to redirect all HTTP traffic to HTTPS.

The complete details of this configuration, such as how and where to install SSL certificates and keys, varies by platform and the following is only a reference nginx.conf setup:

# redirect HTTP traffic to HTTPS (optional)
server {
    listen      80;
    server_name foo.com;
    return      301 https://$server_name$request_uri;
}

server {
    listen      443 default_server;
    server_name foo.com;

    # adds Strict-Transport-Security to prevent man-in-the-middle attacks
    add_header Strict-Transport-Security "max-age=31536000";

    ssl on;

    # SSL installation details vary by platform
    ssl_certificate /etc/ssl/certs/my-ssl-bundle.crt;
    ssl_certificate_key /etc/ssl/private/my_ssl.key;

    # enables all versions of TLS, but not the deprecated SSLv2 or v3
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

    # disables all weak ciphers
    ssl_ciphers "ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4";

    ssl_prefer_server_ciphers on;

    location / {
        proxy_pass http://127.0.0.1:5100;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_http_version 1.1;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host:$server_port;
        proxy_buffering off;
    }

}

This configuration will proxy all incoming HTTPS connections to foo.com over to a Bokeh server running internally on http://127.0.0.1:5100.

Load balancing#

The Bokeh server is scalable by design. If you need more capacity, you can simply run additional servers. In this case, you’ll generally want to run all the Bokeh server instances behind a load balancer so that new connections are distributed among individual servers.

../../../_images/bokeh_serve_scale.svg — The Bokeh server is horizontally scalable. To add more capacity, you can run more servers behind a load balancer.#

You can run as many Bokeh servers as you need. The following examples are based on a setup with three Bokeh servers running on three different ports:

bokeh serve myapp.py --port 5100
bokeh serve myapp.py --port 5101
bokeh serve myapp.py --port 5102

The sections below propose basic configurations based on this setup. See the Nginx load balancer documentation or the Apache proxy balancer module documentation for more detailed information. For instance, there are different strategies available to define how incoming connections are distributed among server instances.

Nginx#

First, you need to add an upstream stanza to the Nginx configuration. This typically goes above the server stanza and looks something like the following:

upstream myapp {
    least_conn;            # Use the least-connected strategy
    server 127.0.0.1:5100;
    server 127.0.0.1:5101;
    server 127.0.0.1:5102;
}

The rest of the configuration uses the name myapp to refer to the above upstream stanza, which lists the internal connection information for the three Bokeh server instances.

Next, in the location stanza for the Bokeh server, change the proxy_pass value to refer to the upstream stanza above. The code below uses proxy_pass http://myapp;.

server {

    location / {
        proxy_pass http://myapp;

        # all other settings unchanged
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_http_version 1.1;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host:$server_port;
        proxy_buffering off;
    }

}

Apache#

First, make sure you have enabled the proxy_balancer and rewrite modules.

Add balancers for both http and websocket protocols:

<Proxy "balancer://myapp_http">
    BalancerMember "http://127.0.0.1:5100/myapp"
    BalancerMember "http://127.0.0.1:5101/myapp"
    BalancerMember "http://127.0.0.1:5102/myapp"
    ProxySet lbmethod=bybusyness
</Proxy>

<Proxy "balancer://myapp_ws">
    BalancerMember "ws://127.0.0.1:5100/myapp"
    BalancerMember "ws://127.0.0.1:5101/myapp"
    BalancerMember "ws://127.0.0.1:5102/myapp"
    ProxySet lbmethod=bybusyness
</Proxy>

The bybusyness load balancing method ensures that an incoming connection is assigned to the instance that has the fewest active connections at that time. It should yield better results than other available algorithms such as byrequests. You may have to enable mod_lbmethod_bybusyness.

Finally, you can proxy websocket and http requests to the corresponding balancers:

RewriteEngine On
RewriteCond %{HTTP:Upgrade} =websocket [NC]
RewriteRule /myapp(.*)    balancer://myapp_ws$1 [P,L]
RewriteCond %{HTTP:Upgrade} !=websocket [NC]
RewriteRule /myapp(.*)    balancer://myapp_http$1 [P,L]

Authentication#

The Bokeh server itself does not have any facilities for authentication or authorization. However, you can configure the Bokeh server with an “auth provider” that hooks into Tornado’s underlying capabilities. For background information, see the Tornado docs for Authentication and security. The rest of this section assumes some familiarity with that material.

Auth module#

You can configure the Bokeh server to only allow authenticated users to connect. To do so, provide a path to the module that implements the necessary functions on the command line.

bokeh serve --auth-module=/path/to/auth.py

Alternatively, you can set the BOKEH_AUTH_MODULE environment variable to this path.

The module must contain one of the following two functions that return the current user (or None):

def get_user(request_handler):
    pass

async def get_user_async(request_handler):
    pass

The module passes the function to the Tornado RequestHandler that can inspect cookies or request headers to determine the authenticated user. If there is no authenticated user, these functions should return None.

Additionally, the module must specify where to redirect unauthenticated users by including either:

a module attribute login_url and (optionally) a LoginHandler class
a function definition for get_login_url

login_url = "..."

class LoginHandler(RequestHandler):
    pass

def get_login_url(request_handler):
    pass

If the module provides a relative login_url, it can also provide an optional LoginHandler class, which the Bokeh server will incorporate automatically.

The get_login_url function is useful in cases where the login URL must vary based on the request, cookies, or other factors. You can also specify a LoginHandler when defining the get_url_function.

To define an endpoint for logging users out, you can also use optional logout_url and LogoutHandler parameters, similar to the login options.

If you don’t provide an authentication module, the configuration will not require any authentication to access Bokeh server endpoints.

Warning

The configuration executes the contents of the authentication module.

Secure cookies#

If you want to use Tornado’s set_secure_cookie and get_secure_cookie functions in your auth module, you’ll have to set a cookie secret. To do so, use the BOKEH_COOKIE_SECRET environment variable.

export BOKEH_COOKIE_SECRET=<cookie secret value>

The value should be a long, random sequence of bytes.

Security#

By default, the Bokeh server will accept any incoming connections with an allowed WebSocket origin. If you specify a session ID, and a session with that ID already exists on the server, the server will connect to that session. Otherwise, the server will automatically create and use a new session.

If you are deploying an embedded Bokeh app within a large organization or to the wider internet, you may want to limit who can initiate sessions, and from where. Bokeh lets you manage session creation privileges.

WebSocket origin#

When a Bokeh server receives an HTTP request, it immediately returns a script that initiates a WebSocket connection. All subsequent communication happens over the WebSocket.

To reduce the risk of cross-site misuse, the Bokeh server will only initiate WebSocket connections from the origins that are explicitly allowed. Requests with Origin headers that are not on the allowed list will generate HTTP 403 error responses.

By default, only localhost:5006 is allowed, making the following two invocations identical:

bokeh serve --show myapp.py

and

bokeh serve --show --allow-websocket-origin=localhost:5006 myapp.py

Both of these open your default browser to the default application URL localhost:5006 and, since localhost:5006 is on the list of allowed WebSocket origins, the Bokeh server creates and displays a new session.

When you embed a Bokeh server in another web page with server_document() or server_session(), the Origin header for the request to the Bokeh server is the URL of the page that hosts your Bokeh content.

For example, if a user navigates to your page at https://acme.com/products, the origin header reported by the browser will be acme.com. In this case, you’d typically restrict the Bokeh server to honoring only the requests that originate from the acme.com page, preventing other pages from embedding your Bokeh app without your knowledge.

You can do so by setting the --allow-websocket-origin command line argument as follows:

bokeh serve --show --allow-websocket-origin=acme.com myapp.py

This will prevent other sites from embedding your Bokeh application in their pages because requests from users viewing those pages will report a different origin than acme.com, causing the Bokeh server to reject them.

Warning

Bear in mind that this only prevents other web pages from embedding your Bokeh app without your knowledge.

If you require multiple allowed origins, you can pass multiple instances of --allow-websocket-origin on the command line.

You can also configure the Bokeh server to allow all connections regardless of origin:

bokeh serve --show --allow-websocket-origin='*' myapp.py

This option is only suitable for testing, experimentation, and local notebook usage.

Signed session IDs#

By default, the Bokeh server will automatically create new sessions for all new requests from allowed WebSocket origins, even if you provide no session ID.

When embedding a Bokeh app inside another web application, such as Flask or Django, make sure that only your web application is capable of generating viable requests to the Bokeh server, which you can configure to only create sessions with a cryptographically signed session ID.

First, use the bokeh secret command to create a secret to sign session IDs.

export BOKEH_SECRET_KEY=`bokeh secret`

Then set BOKEH_SIGN_SESSIONS to yes when starting the Bokeh server. You’ll typically also want to set the allowed WebSocket origin at this point.

BOKEH_SIGN_SESSIONS=yes bokeh serve --allow-websocket-origin=acme.com myapp.py

Then, in your web application, explicitly provide signed session IDs with generate_session_id:

from bokeh.util.token import generate_session_id

script = server_session(url='http://localhost:5006/bkapp',
                        session_id=generate_session_id())
return render_template("embed.html", script=script, template="Flask")

Make sure to set identical BOKEH_SECRET_KEY environment variables both for the Bokeh server and for the web app processes, such as Flask, Django, or any other tool you are using.

Note

Signed session IDs serve as access tokens. As with any token system, security is predicated on keeping the token secret. You should also run the Bokeh server behind a proxy that terminates SSL connections, or configure the Bokeh server to terminate SSL directly. This lets you securely transmit session IDs to the client browsers.

XSRF cookies#

Bokeh server can use Tornado’s cross-site request forgery protection. To turn this feature on, use the --enable-xsrf-cookies option or set the environment variable BOKEH_XSRF_COOKIES to yes.

With this setting, you’ll have to properly instrument all PUT, POST, and DELETE operations on custom and login handlers in order for them to function. Typically, this means adding the following code to all HTML form submission templates:

{% module xsrf_form_html() %}

For full details, see the Tornado documentation on XSRF Cookies.

Scaling the server#

You can fork multiple server processes with the num-procs option. For example, run the following command to fork 3 processes:

bokeh serve --num-procs 3

Note that the forking operation happens in the underlying Tornado server. For further information, see the Tornado docs.