Get metrics from StreamSets Data Collector and show them on the Raspberry Pi PiTFT screen

sdc_display.py

'''
With thanks to jeremyblythe for showing how to use pygame with
the PiTFT screen.
'''
import argparse
import pygame
import os
from time import sleep
import RPi.GPIO as GPIO
import locale
import json
import requests
import urllib

parser = argparse.ArgumentParser(description='Display SDC pipeline metrics.')
parser.add_argument('pipelineName', metavar='pipelineName', nargs=1,
                    help='The name of a pipeline in SDC')
args = parser.parse_args()

pipeline = urllib.quote(args.pipelineName[0])

locale.setlocale(locale.LC_ALL, '')

button_map = {23:(255,0,0), 22:(0,255,0), 27:(0,0,255), 17:(0,0,0)}

#Setup the GPIOs as inputs with Pull Ups since the buttons are connected to GND
GPIO.setmode(GPIO.BCM)
for k in button_map.keys():
    GPIO.setup(k, GPIO.IN, pull_up_down=GPIO.PUD_UP)

#Buttons
START_BUTTON = 17
STOP_BUTTON = 22

#Colours
BLACK = (0,0,0)
WHITE = (255,255,255)
BLUE = (31,119,180)
GREEN = (92,184,92)
RED = (255,51,51)

#Bars
BAR_WIDTH = 80
BAR_HEIGHT = 190
BAR_Y = 25
INPUT_X = 20
OUTPUT_X = 120
ERROR_X = 220

#UI
X_RES = 320
Y_RES = 240
TEXT_SIZE = 24

#PiTFT setup
os.putenv('SDL_FBDEV', '/dev/fb1')
pygame.init()
pygame.mouse.set_visible(False)
lcd = pygame.display.set_mode((X_RES, Y_RES))
lcd.fill(WHITE)
pygame.display.update()

font = pygame.font.Font(None, TEXT_SIZE)

#Draw a histogram bar
def drawBar(lcd, n, label, x, y, width, height, color):
    pygame.draw.rect(lcd, color, [x, Y_RES - y - height, width, height])
    text_surface = font.render(label, True, BLACK)
    rect = text_surface.get_rect(center=((x + (width/2),Y_RES - (y - (font.get_linesize() / 2)))))
    lcd.blit(text_surface, rect)
    text_surface = font.render(locale.format("%d", n, grouping=True), True, BLACK)
    rect = text_surface.get_rect(center=((x + (width/2),Y_RES - (y + height +(font.get_linesize() / 2)))))
    lcd.blit(text_surface, rect)

counter = 0
debounce = False

while True:
    if (not debounce):
        pressed = None;
        if (GPIO.input(START_BUTTON) == False):
            pressed = 'start'
        elif (GPIO.input(STOP_BUTTON) == False):
            pressed = 'stop'

        if (pressed is not None):
            print 'Sending {} request to {}'.format(pressed, pipeline)
            r = requests.post('http://localhost:18630/rest/v1/pipeline/{}/{}?rev=0'.format(pipeline, pressed), 
                auth=('admin', 'admin'), headers={'X-Requested-By': 'sdc'})
            print 'Status code {}'.format(r.status_code)
            debounce = True;
            continue

    counter += 1

    # Only poll SDC every second
    if (counter % 10 != 1):
        continue

    debounce = False
        
    lcd.fill(WHITE)

    r = requests.get('http://localhost:18630/rest/v1/pipeline/{}/metrics?rev=0'.format(pipeline), 
            auth=('admin', 'admin'), headers={'X-Requested-By': 'sdc'})

    input = 0
    output = 0
    error = 0

    if (r.status_code == 200):
        try:
            data = r.json()

            input  = data["meters"]["pipeline.batchInputRecords.meter"]["count"]
            output = data["meters"]["pipeline.batchOutputRecords.meter"]["count"]
            error  = data["meters"]["pipeline.batchErrorRecords.meter"]["count"]
        except ValueError:
            print 'Decoding JSON failed: {}'.format(r.text)

    max_val = max(input, output, error)

    if (max_val > 0):
        scale = BAR_HEIGHT / float(max_val)
    else:
        scale = 0

    drawBar(lcd, input, 'Input', INPUT_X, BAR_Y, BAR_WIDTH, input * scale, BLUE)
    drawBar(lcd, output, 'Output', OUTPUT_X, BAR_Y, BAR_WIDTH, output * scale, GREEN)
    drawBar(lcd, error, 'Error', ERROR_X, BAR_Y, BAR_WIDTH, error * scale, RED)
 
    pygame.display.update()

    sleep(0.1)