Using PyKX as a `q` Server

The purpose of this example is to provide a quick start for setting up PyKX as a q server that other q and PyKX sessions can connect to.

To follow along with this example please feel free to download this zip archive that contains a copy of the python script and this writeup.

Quick start

To run this example simply run the server.py script and it will launch a PyKX server on port 5000 or you can run server_async.py to run an asyncronous version of the server. The server will print out any queries it receives as well as the result of executing the query before replying.

python server.py
// or
python server_async.py

Extra Configuration Options

User Validation

It is possible to add a function to validate users when they try to connect to the server. This can be done by overriding the .z.pw function. By default all connection attempts will be accepted.

The function will be passed 2 arguments when a user connects, the first will be the username, and the second will be the password (if no password is provided None/:: will be passed in place of a password).

Note: The function needs to be overridden using EmbeddedQ not on the q connection.

Here is an example of overriding it using a python function as a validation function.

def validate(user, password):
    if password == 'password':
        return True # Correct password allow the connection
    return False # Incorrect password deny the connection

kx.q.z.pw = validate

Here is an example of overriding it using a q function as a validation function.

kx.q.z.pw = kx.q('{[user; password] $[password=`password; 1b; 0b]}')

Message Handler

The message handler can be overridden to apply custom logic to incoming queries. By default it just returns the result of calling kx.q.value() on the incoming query. This function will be passed a CharVector containing the incoming query.

Note: The function needs to be overridden using EmbeddedQ not on the q connection.

Here is an example of overriding it using a python function as a message handler.

def qval(query):
    res = kx.q.value(query)
    print(f'{query}\n{res}\n')
    return res

kx.q.z.pg = qval

Here is an example of overriding it using a q function as a message handler.

kx.q.z.pg = kx.q('{[x] show x; show y: value x; y}')

For async messages kx.q.z.ps can be managed in the same fashion.

Connection Garbage Collection Frequency

One of the keyword arguments you can use when creating a server is conn_gc_time this argument takes a float as input and the value denotes how often the server will attempt to clear old closed connections. By default the value is 0.0 and this will cause the list of connections to be cleaned on every call to poll_recv, with lots of incoming connections this can cause performance to deteriorate. If you set the conn_gc_time to 10.0 then this clean-up will happen at most every 10 seconds.

Using PyKX as a q Server