1. Building Distributed Systems with Brazil (Project Firebird) Rob Englander President and Principal Engineer MindStream Software, Inc. rob@mindstrm.com www.mindstrm.com OReilly Conference on Enterprise Java – Westin Hotel, Santa Clara, CA

2. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.2 Brazil Overview Small, efficient HTTP stack Extensible architecture using dynamically loaded Java classes Conforms to existing standards and protocols Uses familiar URL syntax for requests Allows HTTP to be added to applications, rather than applications being added to an HTTP server.

3. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.3 Moving Toward Services Today content is king Tomorrow services will reign Major strategies and technologies include –Microsofts.NET –Suns ONE –SOAP, UDDI, WSDL Applications will be aggregations of services from a wide distribution of providers

4. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.4 Process Flow There are many ways to organize processes –Individual, unrelated services –Chains of services, as is used by the Brazil Chain Handler –Process trees, where each node passes the flow to 0..n child nodes. We use the tree, as it subsumes the others and provides an opportunity for parallelism

5. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.5 Forming a Process Tree Trees can be represented using a variety of programmatic data structures –this is the realm of software developers Trees can be created in a visual, or graphical, environment –this is the realm of integrators

6. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.6 A familiar paradigm Maps easily to the underlying structure Usable by non-programmers Rapid development Using Drawing Tools

7. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.7 Services A service is a named function available on a given server Services are responsible for performing some defined process, computation, etc. Services are designed to fit into the context of a service processing tree

8. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.8 Service Models, a.k.a Service Trees Each node represents a service at a specified address The model begins with a single root node Child nodes may be processed in parallel, in no particular order Child nodes are not aware of sibling nodes or the data resulting from sibling node processing

9. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.9 Service Models, cont. Results of processing a node are not returned until the results of all child nodes are obtained and included in the result Each node in the model can point to a different address, or nodes can point to common addresses, or any combination

10. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.10 Services Using Brazil The service model requires a new set of Brazil handlers to: –Provide meta data to describe the Services available on a server –Process the Service Model

11. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.11 Java Service Classes Implemented in standard Java Service names are mapped to Java classes resident on the server Service mappings are defined in the Brazil server configuration file Services are loaded dynamically

12. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.12 A Brazil Server Configuration File log=0 handler=serviceModel serviceModel.class=com.mindstream.firebird.serviceModelHandler Empty.class=com.mindstream.firebird.emptyServiceHandler Quote.class=com.mindstream.firebird.quoteServiceHandler News.class=com.mindstream.firebird.newsServiceHandler Analytic.class=com.mindstream.firebird.analyticServiceHandler

13. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.13 An Example Service Model

14. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.14 The Request URL Well pass the stock symbol IBM The request URL with the stock symbol and the tree is http://firebirdServer:8901/serviceModel&symbol=IBM&root=Empty& Empty.address=firebirdServer:8901&Empty.children=Quote,News& Quote.address=quotesRus.com:8901&Quote.children=Analytic& Analytic.address=www.cruncher.com&News.address=worldnews.com:8080

15. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.15 The Service Model Handler Puts the data to be processed into a Property list Creates a tree of service nodes –Each node contains a service name, address, and list of child service nodes Passes the data and the tree to an instance of a node processor class

16. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.16 package com.mindstream.firebird; import sunlabs.brazil.server.*; import java.util.*; public class serviceModelHandler implements Handler { Server _server = null; public serviceModelHandler() { } public boolean init (Server server, String prefix) { _server = server; return true; } public boolean respond (Request request) { try { if (!request.url.equals("/serviceModel")) return false; Hashtable ht = (Hashtable)request.getQueryData(); Some Service Model Handler code

17. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.17 // set up the result properties and put the symbol // into the collection Properties resultProps = new Properties(); resultProps.setProperty("symbol", (String)ht.get("symbol")); // build a process tree String name = (String)ht.get("root"); ProcessNode tree = BuildNode(name, ht); // now process the tree NodeProcessor np = new NodeProcessor(_server); np.process(tree, resultProps); request.sendResponse(BuildResponse(resultProps)); } catch (java.io.IOException e) { } return true; } Some Service Model Handler code

18. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.18 public ProcessNode BuildNode(String name, Hashtable ht) { ProcessNode node = new ProcessNode(name); node._address = (String)ht.get(name + ".address"); Vector v = GetChildren(name, ht); int cnt = v.size(); for (int i = 0; i < cnt; i++) { node._children.add(BuildNode((String)v.elementAt(i), ht)); } return node; } public Vector GetChildren(String name, Hashtable ht) { String kids = (String)ht.get(name + ".children"); Vector v = new Vector(); if (kids != null) { StringTokenizer tk = new StringTokenizer(kids, ","); while (tk.hasMoreTokens()) { v.add(tk.nextToken()); } return v; } Some Service Model Handler code

19. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.19 The Node Processor For local services –Loads an instance of the service class –Passes the data and the tree node to the service object for processing –Child node processing is invoked by the service itself via a method provided by a common service base class

20. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.20 package com.mindstream.firebird; import sunlabs.brazil.server.*; import java.util.*; import java.net.*; import java.io.*; public class NodeProcessor { Server _server = null; public NodeProcessor(Server server) { _server = server; } public void process(ProcessNode node, Properties props) { String serverName = (String)_server.props.get("serverName"); serverName += ":"; serverName += _server.listen.getLocalPort(); if (!serverName.equals(node._address)) { remoteCall(node, props); } Some Node Processor Code

21. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.21 The Node Processor, cont. For remote services –Treats the current node as the root of a tree –Unpacks its tree and data into a URL –Uses the URL in an http request to the remote Brazil server

22. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.22 else { try { String className = (String)_server.props.get(node._name + ".class"); Class c = Class.forName(className); serviceHandler s = (serviceHandler)c.newInstance(); s.setServer(_server); s.service(node, props); } catch (Exception e) { } } public void remoteCall(ProcessNode node, Properties props) { try { URL u = new URL("http://" + node._address + "/serviceModel"); HttpURLConnection c = (HttpURLConnection)u.openConnection(); c.setRequestMethod("POST"); Some Node Processor Code

23. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.23 c.setDoInput(true); c.setDoOutput(true); c.setUseCaches(false); c.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); String request = ""; String delim = ""; Enumeration e = props.keys(); while (e.hasMoreElements()) { String name = (String)e.nextElement(); String value = props.getProperty(name); request += delim + name + "=" + value; delim = "&"; } request += "&root=" + node._name; request = addTreeNode(request, node); DataOutputStream dos = new DataOutputStream(c.getOutputStream()); dos.writeBytes(request); dos.flush(); dos.close(); Some Node Processor Code

24. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.24 props.load(c.getInputStream()); } catch (Exception e) { } } String addTreeNode(String request, ProcessNode node) { request += "&" + node._name + ".address=" + node._address; int cnt = node._children.size(); String children = ""; for (int i = 0; i < cnt; i++) { if (i > 0) children += ","; children += ((ProcessNode)node._children.elementAt(i))._name; } if (cnt > 0) request += "&" + node._name + ".children=" + children; for (int i = 0; i < cnt; i++) request = addTreeNode(request, (ProcessNode)node._children.elementAt(i)); return request; } Some Node Processor Code

25. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.25 Service Processing A Service is asked to perform its function by invoking its service() method call When a Service completes its processing, it is responsible for invoking its child nodes

26. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.26 package com.mindstream.firebird; import sunlabs.brazil.server.*; import java.util.*; public class quoteServiceHandler extends serviceHandler { public quoteServiceHandler() { } public void service(ProcessNode node, Properties props) { // perform quote processing here... // service any child nodes serviceChildren(node, props); } Some Service Code

27. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.27 Child Node Processing Provided by the serviceHandler base class Each child node is processed on its own thread using a copy of the current state of the result data When all child nodes are complete, the resulting data is aggregated and returned Node processing is recursive; each node is visited using the same techniques as before

28. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.28 package com.mindstream.firebird; import sunlabs.brazil.server.*; import java.util.*; public abstract class serviceHandler { Server _server = null; Vector _childThreads = new Vector(); Vector _resultList = new Vector(); Object _monitor = new Object(); public abstract void service(ProcessNode node, Properties props); public void setServer(Server server) { _server = server; } public serviceHandler() { } Some Service Handler Base Class Code

29. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.29 public Object getMonitorObject() { return _monitor; } public void serviceChildren(ProcessNode node, Properties props) { int cnt = node._children.size(); if (cnt == 0) return; for (int i = 0; i < cnt; i++) { Properties p = (Properties)props.clone(); serviceThread st = new serviceThread(this, (ProcessNode)node._children.elementAt(i), p, _server); _childThreads.add(st); st.start(); } Some Service Handler Base Class Code

30. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.30 while (true) { if (_childThreads.size() == 0) break; try { synchronized (_monitor) { _monitor.wait(); } catch (Exception e) { } } // collect the results from the children and incorporate int l = _resultList.size(); for (int i = 0; i < l; i++) { Properties pp = (Properties)_resultList.elementAt(i); Enumeration e = pp.keys(); while (e.hasMoreElements()) { String name = (String)e.nextElement(); String value = pp.getProperty(name); props.setProperty(name, value); } Some Service Handler Base Class Code

31. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.31 public void childComplete(serviceThread c) { _childThreads.remove(c); _resultList.add(c.getResults()); synchronized (_monitor) { _monitor.notifyAll(); } class serviceThread extends Thread { serviceHandler _notifyTarget = null; ProcessNode _pnode = null; Properties _props = null; Server _server = null; Properties _results = null; public serviceThread(serviceHandler target, ProcessNode pnode, Properties props, Server server) { _notifyTarget = target; _pnode = pnode; _props = props; _server = server; } Some Service Handler Base Class Code

32. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.32 public Properties getResults() { return _results; } public void run() { NodeProcessor np = new NodeProcessor(_server); np.process(_pnode, _props); _results = _props; _notifyTarget.childComplete(this); } Some Service Handler Base Class Code

33. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.33 Returning the Results When the entire tree has been processed, the initial call to the node processor returns to the main serviceModelHandler The result data is packaged and sent back as the response to the initial request

34. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.34 public String BuildResponse(Properties p) { StringBuffer res = new StringBuffer(); Enumeration e = p.propertyNames(); while (e.hasMoreElements()) { String name = (String)e.nextElement(); String value = (String)p.getProperty(name); res.append(name + "=" + value + "\n"); } return res.toString(); } Some Service Model Handler code

35. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.35 An Interesting Alternative The client application is itself a Brazil server Client resident services are coupled with visual display elements, and data is displayed as part of the service processing Other client resident services can be used to add functionality not otherwise available

36. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.36 Integrating Other Technologies The Brazil handler used for this model, as well as the services themselves, are free to employ any technology necessary to complete their processing –JDBC, EJB, XML, JMS, etc This does not interfere in any way with the service model presented

37. Building Distributed Systems with Brazil - Rob Englander, MindStream Software, Inc.37 Summary Brazil can serve as a solid foundation for providing a distributed services mechanism The aggregation of services can be modeled as a processing tree The development of applications can be aided by a visual environment for defining the processing tree Emerging technologies such as SOAP, UDDI, WSDL, and XMLP may prove useful in building similar systems