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    <p>Few things which will improve your Server code.</p> <p>First and foremost: The use of direct database access functions is discouraged in twisted, as they normally causes block. Twisted has nice abstraction for database access which provides twisted approach to db connection - <a href="http://twistedmatrix.com/documents/current/core/howto/rdbms.html" rel="nofollow">twisted.adbapi</a> </p> <p>Now on to reuse of db connection: If you want to reuse certain assets (like database connection) across a number of Protocol instances, you should initialize those in constructor of Factory or if you dont fancy initiating such things at a launch time, create an resource access method, which will initiate resource upon first method call then assign it to class variable and return that on subsequent calls. </p> <p>When Factory creates a specific Protocol intance, it will add a reference to itself inside the protocol, see <a href="http://twistedmatrix.com/trac/browser/tags/releases/twisted-11.0.0/twisted/internet/protocol.py#L97" rel="nofollow">line 97 of twisted.internet.protocol</a> </p> <p>Then within your Protocol instance, you can access shared database connection instance like: </p> <pre><code>self.factory.whatever_name_for_db_connection.doSomething() </code></pre> <p>Reworked Server code (I dont have python, twisted or even decent IDE available, so this is pretty much untested, some errors are to be expected)</p> <pre><code>from twisted.protocols import amp from twisted.internet import reactor from twisted.internet.protocol import Factory import time class AMPDBAccessProtocolFactory(Factory): def getDBConnection(self): if 'dbConnection' in dir(self): return self.dbConnection else: self.dbConnection = SQLLiteTestConnection(self.dbURL) return self.dbConnection class SQLLiteTestConnection(object): """ Provides abstraction for database access and some business functions. """ def __init__(self,dbURL): self.dbPool = adbapi.ConnectionPool("sqlite3" , dbURL, check_same_thread=False) def insertBTData4(self,data): query = "INSERT INTO btdata4(co2_data, patient_Id, sensor_Id) VALUES (%s,%s,%s)" tm=time.time() print "insert time:",tm chx=data PID=2 device_ID=5 dF = self.dbPool.runQuery(query,(chx, PID, device_ID)) dF.addCallback(self.onQuerySuccess,insert_data=data) return dF def onQuerySuccess(self,insert_data,*r): """ Here you can inspect query results or add any other valuable information to be parsed at client. For the test sake we will just return True to a customer if query was a success. original data available at kw argument insert_data """ return True class Insert(amp.Command): arguments = [('data', amp.Integer())] response = [('insert_result', amp.Integer())] class MyAMPProtocol(amp.AMP): @Insert.responder def dbInsert(self, data): db = self.factory.getDBConnection() dF = db.insertBTData4(data) dF.addErrback(self.onInsertError,data) return dF def onInsertError(self, error, data): """ Here you could do some additional error checking or inspect data which was handed for insert here. For now we will just throw the same exception again so that the client gets notified """ raise error if __name__=='__main__': pf = AMPDBAccessProtocolFactory() pf.protocol = MyAMPProtocol pf.dbURL='biomed1.db' reactor.listenTCP(1234, pf) reactor.run() </code></pre> <p>Now on to the client. IF AMP follows the overall RPC logic (cant test it currently) it should be able to peruse the same connection across a number of calls. So I have created a ServerProxy class which will hold that perusable protocol instance and provide abstraction for calls:</p> <pre><code>from twisted.internet import reactor from twisted.internet.protocol import ClientCreator from twisted.protocols import amp import time class Insert(amp.Command): arguments = [('data', amp.Integer())] response = [('insert_result', amp.Integer())] class ServerProxy(object): def connected(self,protocol): self.serverProxy = protocol # assign protocol as instance variable reactor.callLater(5,self.startMultipleInsert) #after five seconds start multiple insert procedure def remote_insert(self,data): return self.serverProxy.callRemote(Insert, data) def startMultipleInsert(self): for i in range (10): #send data over ten times dF = self.remote_insert(i) dF.addCallback(self.gotInsertResult) dF.addErrback(error) def gotInsertResult(self,result): print 'insert_result:', str(result) tm=time.time() print "stop", tm def error(reason): print "error", reason def main(): tm=time.time() print "start",tm serverProxy = ServerProxy() ClientCreator(reactor, amp.AMP).connectTCP('127.0.0.1', 1234).addCallback(serverProxy.connected).addErrback(error) reactor.run() if __name__=='__main__': main() </code></pre>
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    1. COThanks very much. I am currently working through your solution. I originally used the adbapi but what was happening was that by the time the adbapi returned the deferred, the AMP result had already returned a value. Basically I had two deferreds in series (the adbapi and the remote call) If I am waiting for the insert to complete from the client side then (as far as I can see) the adbapi gives no advantage. However, you might have found a way around this, so I will get your code running and see what happens. Many thanks.
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    2. COI suspect that you are thinking about twisted process in standart linear code way. This was the major obstacle I had to overcome, when first starting on twisted projects. In twisted you can not think of your execution flow as being linear. Therefore - you can, for example do a multiple database calls in a rapid sequence without waiting for their reply on the next line. Wherever you receive deferred, you have not executed anything yet (in most cases), you have put a job out for execution.
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    3. COI am new to Twisted so you are right. I ran your code and got this error: File "DBAserver4.py", line 48, in dbInsert db = self.protocol.getDBConnection() exceptions.AttributeError: 'MyAMPProtocol' object has no attribute 'protocol' - I tried various things to make it work but to no avail. I did a hack and was able to run but it got hung on the query format, which I will play around with. But I cannot see why it does not see the protocol in MyAMPProtocol. Thanks again.
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