Improve naming of metrics.

app.py

@@ -7,13 +7,13 @@
 app = Flask(__name__)
 
 # A counter to count the total number of HTTP requests
-REQUESTS = Counter('http_requests_total', 'Total HTTP Requests (count)', ['method', 'endpoint'])
+REQUESTS = Counter('http_request_total', 'Total HTTP Requests (count)', ['method', 'endpoint'])
 
 # A gauge (i.e. goes up and down) to monitor the total number of in progress requests
-IN_PROGRESS = Gauge('http_requests_inprogress', 'Number of in progress HTTP requests')
+IN_PROGRESS = Gauge('http_request_inprogress', 'Number of in progress HTTP requests')
 
 # A histogram to measure the latency of the HTTP requests
-TIMINGS = Histogram('http_requests_latency_seconds', 'HTTP request latency (seconds)')
+TIMINGS = Histogram('http_request_duration_seconds', 'HTTP request latency (seconds)')
 
 
 # Standard Flask route stuff.