From e70efb2c36493dd9413d76cd7a1a60bbfb8cdfd6 Mon Sep 17 00:00:00 2001
From: Timotej Lazar <timotej.lazar@araneo.org>
Date: Thu, 20 Aug 2015 17:45:38 +0200
Subject: Add a timeout option for prolog.engine requests

---
 prolog/engine.py | 43 +++++++++++++++++++++++++++++--------------
 1 file changed, 29 insertions(+), 14 deletions(-)

diff --git a/prolog/engine.py b/prolog/engine.py
index f6ce103..bdbca21 100644
--- a/prolog/engine.py
+++ b/prolog/engine.py
@@ -13,43 +13,57 @@ def strip_html(text):
 # Create a new pengine, initialize it with [code] and return Prolog's reply.
 # The engine is destroyed after answering one query. If [query] is given, the
 # first answer is returned and the engine destroyed.
-def create(code='', query=''):
+def create(code='', query='', timeout=10):
     opts = {'format': 'json-html', 'destroy': True, 'src_text': code}
     if query:
         opts['ask'] = query
-    reply, output = request('POST', '/pengine/create', body=json.dumps(opts))
+    reply, output = request('POST', '/pengine/create', body=json.dumps(opts), timeout=timeout)
 
     # If query was given, the actual reply is nested in create/destroy objects.
     if query:
         reply = reply['answer']['data']
     return reply, output
 
-def ask(engine, query):
-    return send(engine, 'ask(({}),[])'.format(query))
+def abort(engine):
+    params = urllib.parse.urlencode({
+        'id': engine,
+        'format': 'json-html'})
+    try:
+        # We don't care about the answer here, so don't wait for it.
+        request('GET', '/pengine/abort?' + params, timeout=0.01)
+    except:
+        pass
+
+def ask(engine, query, timeout=10):
+    return send(engine, 'ask(({}),[])'.format(query), timeout=timeout)
 
-def next(engine, n=1):
-    return send(engine, 'next({})'.format(n))
+def next(engine, n=1, timeout=10):
+    return send(engine, 'next({})'.format(n), timeout=timeout)
 
-def stop(engine):
-    return send(engine, 'stop')
+def stop(engine, timeout=10):
+    return send(engine, 'stop', timeout=timeout)
 
 def destroy(engine):
-    return send(engine, 'destroy')
+    try:
+        # We don't care about the answer here, so don't wait for it.
+        send(engine, 'destroy([force(true)])', timeout=0.01)
+    except:
+        pass
 
-def send(engine, event):
+def send(engine, event, timeout=10):
     params = urllib.parse.urlencode({
         'id': engine,
         'event': event,
         'format': 'json-html'})
-    return request('GET', '/pengine/send?' + params)
+    return request('GET', path='/pengine/send?' + params, timeout=timeout)
 
 # Return the main reply and pull potential output replies.
 address, port = 'localhost', 3030  # TODO put this somewhere sane
-def request(method, path, body=None):
+def request(method, path, body=None, timeout=10):
     headers = {'Content-Type': 'application/json;charset=utf-8'}
     messages = []
     try:
-        conn = http.client.HTTPConnection(address, port, timeout=10)
+        conn = http.client.HTTPConnection(address, port, timeout=timeout)
         conn.request(method, path, body, headers=headers)
         while True:
             response = conn.getresponse()
@@ -60,7 +74,8 @@ def request(method, path, body=None):
             if reply.get('event') == 'output':
                 messages.append(get_message(reply))
 
-                # Request next reply.
+                # Pull the next output. These requests should return instantly
+                # as no additional processing needs to be done in the pengine.
                 params = urllib.parse.urlencode({
                     'id': reply['id'],
                     'format': 'json-html'})
-- 
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