Make app middlewares not require specific instances of app
diff --git a/scripts/run_clang_tidy.py b/scripts/run_clang_tidy.py
new file mode 100755
index 0000000..c42463b
--- /dev/null
+++ b/scripts/run_clang_tidy.py
@@ -0,0 +1,218 @@
+#!/usr/bin/env python3
+#
+# ===- run-clang-tidy.py - Parallel clang-tidy runner ---------*- python -*--===#
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+# ===------------------------------------------------------------------------===#
+# FIXME: Integrate with clang-tidy-diff.py
+
+"""
+Parallel clang-tidy runner
+==========================
+
+Runs clang-tidy over all files in a compilation database. Requires clang-tidy
+and clang-apply-replacements in $PATH.
+
+Example invocations.
+- Run clang-tidy on all files in the current working directory with a default
+  set of checks and show warnings in the cpp files and all project headers.
+    run-clang-tidy.py $PWD
+
+- Fix all header guards.
+    run-clang-tidy.py -fix -checks=-*,llvm-header-guard
+
+- Fix all header guards included from clang-tidy and header guards
+  for clang-tidy headers.
+    run-clang-tidy.py -fix -checks=-*,llvm-header-guard extra/clang-tidy \
+                      -header-filter=extra/clang-tidy
+
+Compilation database setup:
+http://clang.llvm.org/docs/HowToSetupToolingForLLVM.html
+"""
+
+import argparse
+import json
+import multiprocessing
+import os
+import queue
+import re
+import shutil
+import subprocess
+import sys
+import tempfile
+import threading
+
+
+def find_compilation_database(path):
+    """Adjusts the directory until a compilation database is found."""
+    result = './'
+    while not os.path.isfile(os.path.join(result, path)):
+        if os.path.realpath(result) == '/':
+            print('Error: could not find compilation database.')
+            sys.exit(1)
+        result += '../'
+    return os.path.realpath(result)
+
+
+def get_tidy_invocation(f, clang_tidy_binary, checks, tmpdir, build_path,
+                        header_filter, extra_arg, extra_arg_before, quiet):
+    """Gets a command line for clang-tidy."""
+    start = [clang_tidy_binary]
+    if header_filter is not None:
+        start.append('-header-filter=' + header_filter)
+    else:
+        # Show warnings in all in-project headers by default.
+        start.append('-header-filter=^' + build_path + '/.*')
+    if checks:
+        start.append('-checks=' + checks)
+    if tmpdir is not None:
+        start.append('-export-fixes')
+        # Get a temporary file. We immediately close the handle so clang-tidy can
+        # overwrite it.
+        (handle, name) = tempfile.mkstemp(suffix='.yaml', dir=tmpdir)
+        os.close(handle)
+        start.append(name)
+    for arg in extra_arg:
+        start.append('-extra-arg=%s' % arg)
+    for arg in extra_arg_before:
+        start.append('-extra-arg-before=%s' % arg)
+    start.append('-p=' + build_path)
+    if quiet:
+        start.append('-quiet')
+    start.append(f)
+    return start
+
+
+def apply_fixes(args, tmpdir):
+    """Calls clang-apply-fixes on a given directory. Deletes the dir when done."""
+    invocation = [args.clang_apply_replacements_binary]
+    if args.format:
+        invocation.append('-format')
+    invocation.append(tmpdir)
+    subprocess.call(invocation)
+    shutil.rmtree(tmpdir)
+
+
+def run_tidy(args, tmpdir, build_path, this_queue):
+    """Takes filenames out of queue and runs clang-tidy on them."""
+    while True:
+        name = this_queue.get()
+        invocation = get_tidy_invocation(
+            name, args.clang_tidy_binary, args.checks,
+                                         tmpdir, build_path, args.header_filter,
+                                         args.extra_arg, args.extra_arg_before,
+                                         args.quiet)
+        sys.stdout.write(' '.join(invocation) + '\n')
+        subprocess.call(invocation)
+        this_queue.task_done()
+
+
+def main():
+    parser = argparse.ArgumentParser(description='Runs clang-tidy over all files '
+                                     'in a compilation database. Requires '
+                                     'clang-tidy and clang-apply-replacements in '
+                                     '$PATH.')
+    parser.add_argument('-clang-tidy-binary', metavar='PATH',
+                        default='clang-tidy',
+                        help='path to clang-tidy binary')
+    parser.add_argument('-clang-apply-replacements-binary', metavar='PATH',
+                        default='clang-apply-replacements',
+                        help='path to clang-apply-replacements binary')
+    parser.add_argument('-checks', default=None,
+                        help='checks filter, when not specified, use clang-tidy '
+                        'default')
+    parser.add_argument('-header-filter', default=None,
+                        help='regular expression matching the names of the '
+                        'headers to output diagnostics from. Diagnostics from '
+                        'the main file of each translation unit are always '
+                        'displayed.')
+    parser.add_argument('-j', type=int, default=0,
+                        help='number of tidy instances to be run in parallel.')
+    parser.add_argument('files', nargs='*', default=['.*'],
+                        help='files to be processed (regex on path)')
+    parser.add_argument('-fix', action='store_true', help='apply fix-its')
+    parser.add_argument('-format', action='store_true', help='Reformat code '
+                        'after applying fixes')
+    parser.add_argument('-p', dest='build_path',
+                        help='Path used to read a compile command database.')
+    parser.add_argument('-extra-arg', dest='extra_arg',
+                        action='append', default=[],
+                        help='Additional argument to append to the compiler '
+                        'command line.')
+    parser.add_argument('-extra-arg-before', dest='extra_arg_before',
+                        action='append', default=[],
+                        help='Additional argument to prepend to the compiler '
+                        'command line.')
+    parser.add_argument('-quiet', action='store_true',
+                        help='Run clang-tidy in quiet mode')
+    args = parser.parse_args()
+
+    db_path = 'compile_commands.json'
+
+    if args.build_path is not None:
+        build_path = args.build_path
+    else:
+        # Find our database
+        build_path = find_compilation_database(db_path)
+
+    try:
+        invocation = [args.clang_tidy_binary, '-list-checks']
+        invocation.append('-p=' + build_path)
+        if args.checks:
+            invocation.append('-checks=' + args.checks)
+        invocation.append('-')
+        print(subprocess.check_output(invocation))
+    except:
+        print("Unable to run clang-tidy.", file=sys.stderr)
+        sys.exit(1)
+
+    # Load the database and extract all files.
+    database = json.load(open(os.path.join(build_path, db_path)))
+    files = [entry['file'] for entry in database]
+
+    max_task = args.j
+    if max_task == 0:
+        max_task = multiprocessing.cpu_count()
+
+    tmpdir = None
+    if args.fix:
+        tmpdir = tempfile.mkdtemp()
+
+    # Build up a big regexy filter from all command line arguments.
+    file_name_re = re.compile('|'.join(args.files))
+
+    try:
+        # Spin up a bunch of tidy-launching threads.
+        this_queue = queue.Queue(max_task)
+        for _ in range(max_task):
+            t = threading.Thread(target=run_tidy,
+                                 args=(args, tmpdir, build_path, this_queue))
+            t.daemon = True
+            t.start()
+
+        # Fill the queue with files.
+        for name in files:
+            if file_name_re.search(name):
+                this_queue.put(name)
+
+        # Wait for all threads to be done.
+        this_queue.join()
+
+    except KeyboardInterrupt:
+        # This is a sad hack. Unfortunately subprocess goes
+        # bonkers with ctrl-c and we start forking merrily.
+        print('\nCtrl-C detected, goodbye.')
+        if args.fix:
+            shutil.rmtree(tmpdir)
+        os.kill(0, 9)
+
+    if args.fix:
+        print('Applying fixes ...')
+        apply_fixes(args, tmpdir)
+
+if __name__ == '__main__':
+    main()