From ed5d7561f9c4087f825ac7aa03e287182d87b35d Mon Sep 17 00:00:00 2001
From: Pablo Hoffman <pablo@pablohoffman.com>
Date: Fri, 11 Jun 2010 17:22:14 -0300
Subject: [PATCH] Added SQS Execution Queue, and example script to add spiders
 to the queue

---
 bin/scrapy-sqs.py                | 30 +++++++++++++++++++
 scrapy/commands/start.py         |  7 +++--
 scrapy/conf/default_settings.py  |  7 +++++
 scrapy/contrib/queue/__init__.py |  0
 scrapy/contrib/queue/sqs.py      | 49 ++++++++++++++++++++++++++++++++
 scrapy/core/queue.py             |  2 +-
 6 files changed, 91 insertions(+), 4 deletions(-)
 create mode 100755 bin/scrapy-sqs.py
 create mode 100644 scrapy/contrib/queue/__init__.py
 create mode 100644 scrapy/contrib/queue/sqs.py

diff --git a/bin/scrapy-sqs.py b/bin/scrapy-sqs.py
new file mode 100755
index 000000000..e710aebb8
--- /dev/null
+++ b/bin/scrapy-sqs.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+
+import sys
+
+from boto.sqs.connection import SQSConnection
+from boto.sqs.message import Message
+
+from scrapy.utils.py26 import json
+from scrapy.conf import settings
+
+qname = settings['SQS_QUEUE']
+
+if len(sys.argv) <= 1:
+    print "usage: %s <command> [args]" % sys.argv[0]
+    print
+    print "available commands:"
+    print "  put <spider_name> - append spider to queue"
+    print
+    print "SQS queue: %s" % qname
+    print
+    sys.exit()
+
+cmd, args = sys.argv[1], sys.argv[2:]
+
+if cmd == 'put':
+    conn = SQSConnection(settings['AWS_ACCESS_KEY_ID'], \
+        settings['AWS_SECRET_ACCESS_KEY'])
+    q = conn.create_queue(qname)
+    msg = Message(body=json.dumps({'name': args[0]}))
+    q.write(msg)
diff --git a/scrapy/commands/start.py b/scrapy/commands/start.py
index 3c32abcc6..efe21bd64 100644
--- a/scrapy/commands/start.py
+++ b/scrapy/commands/start.py
@@ -1,6 +1,7 @@
-from scrapy.core.queue import KeepAliveExecutionQueue
 from scrapy.command import ScrapyCommand
 from scrapy.core.manager import scrapymanager
+from scrapy.utils.misc import load_object
+from scrapy.conf import settings
 
 class Command(ScrapyCommand):
 
@@ -10,6 +11,6 @@ class Command(ScrapyCommand):
         return "Start the Scrapy manager but don't run any spider (idle mode)"
 
     def run(self, args, opts):
-        q = KeepAliveExecutionQueue()
-        scrapymanager.queue = q
+        queue_class = load_object(settings['SERVICE_QUEUE'])
+        scrapymanager.queue = queue_class()
         scrapymanager.start()
diff --git a/scrapy/conf/default_settings.py b/scrapy/conf/default_settings.py
index d2983f898..e53d8be90 100644
--- a/scrapy/conf/default_settings.py
+++ b/scrapy/conf/default_settings.py
@@ -185,6 +185,8 @@ SCHEDULER_MIDDLEWARES_BASE = {
 
 SCHEDULER_ORDER = 'DFO'
 
+SERVICE_QUEUE = 'scrapy.core.queue.KeepAliveExecutionQueue'
+
 SPIDER_MANAGER_CLASS = 'scrapy.contrib.spidermanager.TwistedPluginSpiderManager'
 
 SPIDER_MIDDLEWARES = {}
@@ -205,6 +207,11 @@ SPIDER_MODULES = []
 
 SPIDERPROFILER_ENABLED = False
 
+SQS_QUEUE = 'scrapy'
+SQS_VISIBILITY_TIMEOUT = 7200
+SQS_POLLING_DELAY = 30
+SQS_REGION = 'us-east-1'
+
 STATS_CLASS = 'scrapy.stats.collector.MemoryStatsCollector'
 STATS_ENABLED = True
 STATS_DUMP = False
diff --git a/scrapy/contrib/queue/__init__.py b/scrapy/contrib/queue/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/scrapy/contrib/queue/sqs.py b/scrapy/contrib/queue/sqs.py
new file mode 100644
index 000000000..69ce2dc7c
--- /dev/null
+++ b/scrapy/contrib/queue/sqs.py
@@ -0,0 +1,49 @@
+import threading
+
+from twisted.internet import threads
+from boto.sqs.connection import SQSConnection
+from boto.sqs import regions
+
+from scrapy.core.queue import ExecutionQueue
+from scrapy.utils.py26 import json
+from scrapy.conf import settings
+
+class SQSExecutionQueue(ExecutionQueue):
+
+    polling_delay = settings.getint('SQS_POLLING_DELAY')
+    queue_name = settings['SQS_QUEUE']
+    region_name = settings['SQS_REGION']
+    visibility_timeout = settings.getint('SQS_VISIBILITY_TIMEOUT')
+    aws_access_key_id = settings['AWS_ACCESS_KEY_ID']
+    aws_secret_access_key = settings['AWS_SECRET_ACCESS_KEY']
+
+    def __init__(self, *a, **kw):
+        super(SQSExecutionQueue, self).__init__(*a, **kw)
+        self.region = self._get_region()
+        self._tls = threading.local()
+
+    def _append_next(self):
+        return threads.deferToThread(self._append_next_from_sqs)
+
+    def _append_next_from_sqs(self):
+        q = self._get_sqs_queue()
+        msgs = q.get_messages(1, visibility_timeout=self.visibility_timeout)
+        if msgs:
+            msg = msgs[0]
+            msg.delete()
+            spargs = json.loads(msg.get_body())
+            spname = spargs.pop('name')
+            self.append_spider_name(spname, **spargs)
+
+    def _get_sqs_queue(self):
+        if not hasattr(self._tls, 'queue'):
+            c = SQSConnection(self.aws_access_key_id, self.aws_secret_access_key, \
+                region=self.region)
+            self._tls.queue = c.create_queue(self.queue_name)
+        return self._tls.queue
+
+    def _get_region(self, name=region_name):
+        return [r for r in regions() if r.name == name][0]
+
+    def is_finished(self):
+        return False
diff --git a/scrapy/core/queue.py b/scrapy/core/queue.py
index f8dd340df..354f3a135 100644
--- a/scrapy/core/queue.py
+++ b/scrapy/core/queue.py
@@ -15,7 +15,7 @@ class ExecutionQueue(object):
         self._spiders = _spiders
 
     def _append_next(self):
-        """Called when there are no more itemsl left in self.spider_requests.
+        """Called when there are no more items left in self.spider_requests.
         This method is meant to be overriden in subclasses to add new (spider,
         requests) tuples to self.spider_requests. It can return a Deferred.
         """