设置
我正在使用Titan Rexster（titan-server-0.4.4.zip）和Elasticsearch后端在Ubuntu 12.4服务器上实现推荐系统。为了连接Rexster服务器，我使用python的Bulbflow库。
Beta版似乎运行了3周，但是随着负载“增加”（只有几个用户约10个），Rexster服务器停止响应。我不知道我的rexster配置是否有误或者我是否正确使用了Bulbflow库。
Rexster / Titan配置
这是我的rexster-cassandra-es.xml文件：
<?xml version="1.0" encoding="UTF-8"?>
<rexster>
<http>
<server-port>8182</server-port>
<server-host>0.0.0.0</server-host>
<base-uri>http://MY_IP</base-uri>
<web-root>public</web-root>
<character-set>UTF-8</character-set>
<enable-jmx>false</enable-jmx>
<enable-doghouse>true</enable-doghouse>
<max-post-size>2097152</max-post-size>
<max-header-size>8192</max-header-size>
<upload-timeout-millis>30000</upload-timeout-millis>
<thread-pool>
<worker>
<core-size>20</core-size>
<max-size>40</max-size>
</worker>
<kernal>
<core-size>10</core-size>
<max-size>20</max-size>
</kernal>
</thread-pool>
<io-strategy>leader-follower</io-strategy>
</http>
<rexpro>
<server-port>8184</server-port>
<server-host>0.0.0.0</server-host>
<session-max-idle>1790000</session-max-idle>
<session-check-interval>3000000</session-check-interval>
<connection-max-idle>180000</connection-max-idle>
<connection-check-interval>3000000</connection-check-interval>
<enable-jmx>false</enable-jmx>
<thread-pool>
<worker>
<core-size>8</core-size>
<max-size>8</max-size>
</worker>
<kernal>
<core-size>4</core-size>
<max-size>4</max-size>
</kernal>
</thread-pool>
<io-strategy>leader-follower</io-strategy>
</rexpro>
<shutdown-port>8183</shutdown-port>
<shutdown-host>127.0.0.1</shutdown-host>
<script-engines>
<script-engine>
<name>gremlin-groovy</name>
<reset-threshold>-1</reset-threshold>
<imports>com.tinkerpop.gremlin.*,com.tinkerpop.gremlin.java.*,com.tinkerpop.gremlin.pipes.filter.*,com.tinkerpop.gremlin.pipes.sideeffect.*,com.tinkerpop.gremlin.pipes.transform.*,com.tinkerpop.blueprints.*,com.tinkerpop.blueprints.impls.*,com.tinkerpop.blueprints.impls.tg.*,com.tinkerpop.blueprints.impls.neo4j.*,com.tinkerpop.blueprints.impls.neo4j.batch.*,com.tinkerpop.blueprints.impls.orient.*,com.tinkerpop.blueprints.impls.orient.batch.*,com.tinkerpop.blueprints.impls.dex.*,com.tinkerpop.blueprints.impls.rexster.*,com.tinkerpop.blueprints.impls.sail.*,com.tinkerpop.blueprints.impls.sail.impls.*,com.tinkerpop.blueprints.util.*,com.tinkerpop.blueprints.util.io.*,com.tinkerpop.blueprints.util.io.gml.*,com.tinkerpop.blueprints.util.io.graphml.*,com.tinkerpop.blueprints.util.io.graphson.*,com.tinkerpop.blueprints.util.wrappers.*,com.tinkerpop.blueprints.util.wrappers.batch.*,com.tinkerpop.blueprints.util.wrappers.batch.cache.*,com.tinkerpop.blueprints.util.wrappers.event.*,com.tinkerpop.blueprints.util.wrappers.event.listener.*,com.tinkerpop.blueprints.util.wrappers.id.*,com.tinkerpop.blueprints.util.wrappers.partition.*,com.tinkerpop.blueprints.util.wrappers.readonly.*,com.tinkerpop.blueprints.oupls.sail.*,com.tinkerpop.blueprints.oupls.sail.pg.*,com.tinkerpop.blueprints.oupls.jung.*,com.tinkerpop.pipes.*,com.tinkerpop.pipes.branch.*,com.tinkerpop.pipes.filter.*,com.tinkerpop.pipes.sideeffect.*,com.tinkerpop.pipes.transform.*,com.tinkerpop.pipes.util.*,com.tinkerpop.pipes.util.iterators.*,com.tinkerpop.pipes.util.structures.*,org.apache.commons.configuration.*,com.thinkaurelius.titan.core.*,com.thinkaurelius.titan.core.attribute.*,com.thinkaurelius.titan.core.util.*,com.thinkaurelius.titan.example.*,org.apache.commons.configuration.*,com.tinkerpop.gremlin.Tokens.T,com.tinkerpop.gremlin.groovy.*</imports>
<static-imports>com.tinkerpop.blueprints.Direction.*,com.tinkerpop.blueprints.TransactionalGraph$Conclusion.*,com.tinkerpop.blueprints.Compare.*,com.thinkaurelius.titan.core.attribute.Geo.*,com.thinkaurelius.titan.core.attribute.Text.*,com.thinkaurelius.titan.core.TypeMaker$UniquenessConsistency.*,com.tinkerpop.blueprints.Query$Compare.*</static-imports>
</script-engine>
</script-engines>
<security>
<authentication>
<type>none</type>
<configuration>
<users>
<user>
<username>rexster</username>
<password>rexster</password>
</user>
</users>
</configuration>
</authentication>
</security>
<metrics>
<reporter>
<type>jmx</type>
</reporter>
<reporter>
<type>http</type>
</reporter>
<reporter>
<type>console</type>
<properties>
<rates-time-unit>SECONDS</rates-time-unit>
<duration-time-unit>SECONDS</duration-time-unit>
<report-period>10</report-period>
<report-time-unit>MINUTES</report-time-unit>
<includes>http.rest.*</includes>
<excludes>http.rest.*.delete</excludes>
</properties>
</reporter>
</metrics>
<graphs>
<graph>
<graph-name>newspaper</graph-name>
<graph-type>com.thinkaurelius.titan.tinkerpop.rexster.TitanGraphConfiguration</graph-type>
<!-- <graph-location>/tmp/titan</graph-location> -->
<graph-read-only>false</graph-read-only>
<properties>
<storage.backend>cassandra</storage.backend>
<storage.index.search.backend>elasticsearch</storage.index.search.backend>
<storage.index.search.hostname>localhost</storage.index.search.hostname>
<storage.index.search.client-only>true</storage.index.search.client-only>
<storage.index.search.local-mode>false</storage.index.search.local-mode>
</properties>
<extensions>
<allows>
<allow>tp:gremlin</allow>
</allows>
</extensions>
</graph>
</graphs>
</rexster>
我已经改变了线程池的核心大小和最大大小，如果不做这些更改，Rexster服务器会更快地挂起/无响应。
核心大小和最大大小的合适值是什么？
Bulbflow用法
为了使用bulbflow，我每次需要执行请求时都会创建一个新的Graph对象。有很多请求，因此这些对象经常被创建。
我是否真的应该为每个新请求创建一个新的Graph对象？
是否可能只创建一个Graph对象，并在发送新请求到图形数据库时重复使用它，或者会遇到会话问题？
错误消息
当一切都卡住了，并且我强制终止程序（ctrl-c），我会得到以下堆栈跟踪：
Exception happened during processing of request from ('my_ip', 57489)
Traceback (most recent call last):
File "/usr/lib/python2.7/SocketServer.py", line 284, in _handle_request_noblock
self.process_request(request, client_address)
File "/usr/lib/python2.7/SocketServer.py", line 310, in process_request
self.finish_request(request, client_address)
File "/usr/lib/python2.7/SocketServer.py", line 323, in finish_request
self.RequestHandlerClass(request, client_address, self)
File "/usr/lib/python2.7/SocketServer.py", line 638, in __init__
self.handle()
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/werkzeug/serving.py", line 200, in handle
rv = BaseHTTPRequestHandler.handle(self)
File "/usr/lib/python2.7/BaseHTTPServer.py", line 340, in handle
self.handle_one_request()
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/werkzeug/serving.py", line 235, in handle_one_request
return self.run_wsgi()
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/werkzeug/serving.py", line 177, in run_wsgi
execute(self.server.app)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/werkzeug/serving.py", line 165, in execute
application_iter = app(environ, start_response)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/home/user/dir/recommender/project/api/start.py", line 65, in put_user
graphdb.insert_user(user_id)
File "project/api/graphdb.py", line 14, in insert_user
user_with_id = g.users.index.lookup(user_sqlid=user_id)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/bulbs/titan/index.py", line 270, in lookup
resp = self.client.lookup_vertex(self.index_name,key,value)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/bulbs/titan/client.py", line 348, in lookup_vertex
return self.request.get(path,params)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/bulbs/rest.py", line 101, in get
return self.request(GET, path, params)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/bulbs/rest.py", line 184, in request
http_resp = self.http.request(uri, method, body, headers)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/httplib2/__init__.py", line 1593, in request
(response, content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/httplib2/__init__.py", line 1335, in _request
(response, content) = self._conn_request(conn, request_uri, method, body, headers)
File "/home/user/dir/env/venv_python/local/lib/python2.7/site-packages/httplib2/__init__.py", line 1291, in _conn_request
response = conn.getresponse()
File "/usr/lib/python2.7/httplib.py", line 1030, in getresponse
response.begin()
File "/usr/lib/python2.7/httplib.py", line 407, in begin
version, status, reason = self._read_status()
File "/usr/lib/python2.7/httplib.py", line 365, in _read_status
line = self.fp.readline()
File "/usr/lib/python2.7/socket.py", line 430, in readline
data = recv(1)
恢复
为了进行恢复，我需要关闭rexster/titan并重启。每次停止Rexster服务器(./bin/titan -c cassandra-es stop)时，我会收到以下输出：
Killing Titan + Rexster (pid 26779)...
Rexster shutdown timeout exceeded (60 seconds)
Killing Cassandra (pid 26201)...
Rexster完全卡住了。 期待得到一些有用的指导。