"""Renders vital stats about a single App Engine instance.
Intended for developers, not users. To turn on concurrent request recording, add the middleware and InfoHandler to your WSGI application, eg::
from oauth_dropins.webutil.instance_info import concurrent_requests_wsgi_middleware, info
application = concurrent_requests_wsgi_middleware(WSGIApplication([
...
('/_info', info),
])
"""
import collections
import heapq
import os
import threading
from flask import render_template
from . import util
CONCURRENTS_SIZE = 20
# A time when there was more than one request running at once. count is the
# first field so that instances compare by count, since they're stored in a
# heap, so that we keep the highest count instances.
Concurrent = collections.namedtuple('Concurrent', ('count', 'when'))
# globals
current_requests = set() # stores string request IDs
current_requests_lock = threading.Lock()
concurrents = [] # a heapq. stores Concurrents
[docs]
def info():
"""Flask handler that renders current instance info."""
return render_template(
os.path.join(os.path.dirname(__file__), 'templates/instance_info.html'),
concurrents=concurrents,
current_requests=current_requests,
os=os,
runtime=os.getenv('GAE_RUNTIME'),
)
[docs]
def concurrent_requests_wsgi_middleware(app):
"""WSGI middleware for per request instance info instrumentation.
Follows the WSGI standard. Details: http://www.python.org/dev/peps/pep-0333/
"""
def wrapper(environ, start_response):
req_id = os.environ['REQUEST_LOG_ID']
global current_requests, current_requests_lock, concurrents
with current_requests_lock:
current_requests.add(req_id)
if len(current_requests) > 1:
heapq.heappush(concurrents, Concurrent(count=len(current_requests),
when=util.now()))
if len(concurrents) > CONCURRENTS_SIZE:
heapq.heappop(concurrents)
ret = app(environ, start_response)
with current_requests_lock:
current_requests.remove(req_id)
return ret
return wrapper