http_server.py

#!/usr/bin/env python3
# this serves a simple queue so that 2 to 3 teams can communicate
#
# https://docs.cherrypy.org/en/latest/tutorials.html#tutorial-6-what-about-my-javascripts-css-and-images
# https://stackoverflow.com/questions/3743769/how-to-receive-json-in-a-post-request-in-cherrypy


import os.path
import sys
import cherrypy
import json
from datetime import datetime
from http_util import IP_ADDRESS, IP_PORT
from threading import Lock
import logging


dt_pattern = '%Y-%m-%d %H:%M:%S'
fifo = {}   # key is primarily a serial number, but other non-numeric keys are allowed
index = 0   # index that is used to store and retrieve a value.  This unique
            # and is passed to the various clients
debugging = False
count = 0
lock = Lock()

def get_time_stamp():
    s = datetime.now().strftime(dt_pattern)
    return s

class IndexPage:
    @cherrypy.expose
    def index(self):
        with open("res/index.html", "r") as f:
            s = f.read()
        return s
 
    @cherrypy.expose
    def echo(self, text='whatever'):
        return(text)
    
    @cherrypy.expose
    def reset_fifo(self):
        global fifo, index
        lock.acquire()
        fifo = {}
        lock.release()
    
    @cherrypy.expose
    @cherrypy.tools.json_out()
    @cherrypy.tools.json_in()
    def fifo_in(self):
        global index, fifo
        lock.acquire()
        value = cherrypy.request.json   # already converted to Python dict
        index += 1
        if debugging: 
            print(f'fifo_in POST value ({index})', value)
        else:
            print(f'[{get_time_stamp()}] ' +
                  f'POST /fifo_in: ({index}, {str(value)[:55]}...)')
        d = {index: value}
        fifo.update(d)
        # Responses are serialized to JSON (because of the json_out decorator)
        result = {"index": index}
        lock.release()
        return result
    
    @cherrypy.expose
    @cherrypy.tools.json_out()    
    def fifo_out(self, index=None):
        # assume that index (integer) is the item being requested
        # fifo_out returns all dictionary items that are equal and newer
        global count
        lock.acquire()
        count += 1
        keys = sorted(fifo.keys())
        index = int(index)
        result = {k: fifo[k] for k in keys if k >= index}
        if debugging and result: 
            print(f'server.fifo_out ({count}, {index})', result)
        elif result:
            print(f'[{get_time_stamp()}] ' +
                  f'GET /fifo_out: ({index}, {str(result)[:55]}...)')
        lock.release()
        return result


#mainconf = os.path.join(os.path.dirname(__file__), 'main.conf')
conf = {
    'global':{
        'server.socket_host': IP_ADDRESS,
        'server.socket_port': IP_PORT,
        'server.thread_pool': 10
        },
    '/': {
        'tools.sessions.on': True,
        'tools.staticdir.root': os.path.abspath(os.getcwd())
        },
    '/static': {
        'tools.staticdir.on': True,
        'tools.staticdir.dir': './res'
    }
}

class IgnoreURLFilter(logging.Filter):
    # used to suppress the many repeated "GET" requests
    def __init__(self, ignore):
        self.ignore = ignore
    
    def filter(self, record):
        msg = record.getMessage()
        return self.ignore not in msg

def main(arg = None):
    my_app = IndexPage()
    app = cherrypy.tree.mount(my_app, "/", conf)  # config=mainconf ?
    app.log.access_log.addFilter(IgnoreURLFilter('GET /fifo_out'))
    app.log.access_log.addFilter(IgnoreURLFilter('POST /fifo_in'))
    cherrypy.engine.start()
    return


if __name__ == "__main__":
    main(sys.argv)