add a custom DB backend that provides system-level SQL profiling

run this command on _any_ node in an awx cluster:

$ awx-manage profile_sql --threshold=2.0 --minutes=1

...and for 1 minute, the timing for _every_ SQL query in _every_ awx
Python process that uses the Django ORM will be measured

queries that run longer than (in this example) 2 seconds will be
written to a per-process sqlite database in /var/lib/awx/profile, and
the file will contain an EXPLAIN VERBOSE for the query and the full
Python stack that led to that SQL query's execution (this includes not
just WSGI requests, but background processes like the runworker and
dispatcher)

$ awx-manage profile_sql --threshold=0

...can be used to disable profiling again (if you don't want to wait for
the minute to expire)

awx/main/db/profiled_pg/base.py

@@ -0,0 +1,155 @@
+import os
+import pkg_resources
+import sqlite3
+import sys
+import traceback
+import uuid
+
+from django.core.cache import cache
+from django.core.cache.backends.locmem import LocMemCache
+from django.db.backends.postgresql.base import DatabaseWrapper as BaseDatabaseWrapper
+
+from awx.main.utils import memoize
+
+__loc__ = LocMemCache(str(uuid.uuid4()), {})
+__all__ = ['DatabaseWrapper']
+
+
+class RecordedQueryLog(object):
+
+    def __init__(self, log, db, dest='/var/lib/awx/profile'):
+        self.log = log
+        self.db = db
+        self.dest = dest
+        try:
+            self.threshold = cache.get('awx-profile-sql-threshold')
+        except Exception:
+            # if we can't reach memcached, just assume profiling's off
+            self.threshold = None
+
+    def append(self, query):
+        ret = self.log.append(query)
+        try:
+            self.write(query)
+        except Exception:
+            # not sure what else to do her e- we can't really safely
+            # *use* our loggers because it'll just generate more DB queries
+            # and potentially recurse into this state again
+            _, _, tb = sys.exc_info()
+            traceback.print_tb(tb)
+        return ret
+
+    def write(self, query):
+        if self.threshold is None:
+            return
+        seconds = float(query['time'])
+
+        # if the query is slow enough...
+        if seconds >= self.threshold:
+            sql = query['sql']
+            if sql.startswith('EXPLAIN'):
+                return
+
+            # build a printable Python stack
+            bt = ' '.join(traceback.format_stack())
+
+            # and re-run the same query w/ EXPLAIN
+            explain = ''
+            cursor = self.db.cursor()
+            cursor.execute('EXPLAIN VERBOSE {}'.format(sql))
+            for line in cursor.fetchall():
+                explain += line[0] + '\n'
+
+            # write a row of data into a per-PID sqlite database
+            if not os.path.isdir(self.dest):
+                os.makedirs(self.dest)
+            progname = ' '.join(sys.argv)
+            for match in ('uwsgi', 'dispatcher', 'callback_receiver', 'runworker'):
+                if match in progname:
+                    progname = match
+                    break
+            else:
+                progname = os.path.basename(sys.argv[0])
+            filepath = os.path.join(
+                self.dest,
+                '{}.sqlite'.format(progname)
+            )
+            version = pkg_resources.get_distribution('awx').version
+            log = sqlite3.connect(filepath, timeout=3)
+            log.execute(
+                'CREATE TABLE IF NOT EXISTS queries ('
+                '   id INTEGER PRIMARY KEY,'
+                '   version TEXT,'
+                '   pid INTEGER,'
+                '   stamp DATETIME DEFAULT CURRENT_TIMESTAMP,'
+                '   argv REAL,'
+                '   time REAL,'
+                '   sql TEXT,'
+                '   explain TEXT,'
+                '   bt TEXT'
+                ');'
+            )
+            log.commit()
+            log.execute(
+                'INSERT INTO queries (pid, version, argv, time, sql, explain, bt) '
+                'VALUES (?, ?, ?, ?, ?, ?, ?);',
+                (os.getpid(), version, ' ' .join(sys.argv), seconds, sql, explain, bt)
+            )
+            log.commit()
+
+    def __len__(self):
+        return len(self.log)
+
+    def __iter__(self):
+        return iter(self.log)
+
+    def __getattr__(self, attr):
+        return getattr(self.log, attr)
+
+
+class DatabaseWrapper(BaseDatabaseWrapper):
+    """
+    This is a special subclass of Django's postgres DB backend which - based on
+    the value of a special flag in memcached - captures slow queries and
+    writes profile and Python stack metadata to the disk.
+    """
+
+    def __init__(self, *args, **kwargs):
+        super(DatabaseWrapper, self).__init__(*args, **kwargs)
+        # Django's default base wrapper implementation has `queries_log`
+        # which is a `collections.deque` that every query is appended to
+        #
+        # this line wraps the deque with a proxy that can capture each query
+        # and - if it's slow enough - record profiling metadata to the file
+        # system for debugging purposes
+        self.queries_log = RecordedQueryLog(self.queries_log, self)
+
+    @property
+    @memoize(ttl=1, cache=__loc__)
+    def force_debug_cursor(self):
+        # in Django's base DB implementation, `self.force_debug_cursor` is just
+        # a simple boolean, and this value is used to signal to Django that it
+        # should record queries into `self.queries_log` as they're executed (this
+        # is the same mechanism used by libraries like the django-debug-toolbar)
+        #
+        # in _this_ implementation, we represent it as a property which will
+        # check memcache for a special flag to be set (when the flag is set, it
+        # means we should start recording queries because somebody called
+        # `awx-manage profile_sql`)
+        #
+        # it's worth noting that this property is wrapped w/ @memoize because
+        # Django references this attribute _constantly_ (in particular, once
+        # per executed query); doing a memcached.get()  _at most_ once per
+        # second is a good enough window to detect when profiling is turned
+        # on/off by a system administrator
+        try:
+            threshold = cache.get('awx-profile-sql-threshold')
+        except Exception:
+            # if we can't reach memcached, just assume profiling's off
+            threshold = None
+        self.queries_log.threshold = threshold
+        return threshold is not None
+
+    @force_debug_cursor.setter
+    def force_debug_cursor(self, v):
+        return