tushargarud / 3_Phase_Commit

3 Phase Commit Protocol Simulation

3 Phase Commit Protocol Simulation

This is a Java Swing and MySQL based project. The server communicates with its clients using HTTP protocol and sockets. Server: Server just acts as a medium for transferring messages from sender and receiver. All the received GET and POST requests are displayed on the server’s user interface. A sender process sends a message in a HTTP POST request and a receiver process polls the server to receive its messages using HTTP GET request. The server temporarily stores the message in a database table until they are delivered to the receiver as a response to its GET request. Coordinator: The coordinator process sends an arbitrary string to all participant process which the participants will write to their log file after a distributed commit. After sending the string, the coordinator will send a vote request message to every participant and waits for the reply. If any participant votes for abort, then coordinator will send a GLOBAL_ABORT to everyone. If every participant vote for commit, then coordinator will send a PREPARE_COMMIT to everyone. After receiving acknowledge from every participant, the coordinator will send a GLOBAL_COMMIT to everyone to commit the transaction. Participants: Run 3 instances of the HTTPMultithreadedSocketClient class which will act as the participant processes. These processes will receive a string from coordinator and wait for a vote request. When a vote request is received from the coordinator, then the buttons to vote for commit or abort will be enabled. After user clicks on a button, the vote is sent to the coordinator and participant waits for a next message from the coordinator. If the next message is a GLOBAL_ABORT then the string will not be written to file and transaction will be aborted. If the message is PREPARE_COMMIT then participant will send an acknowledge to the coordinator. Then after receiving GLOBAL_COMMIT from coordinator, every participant will write the string to file thereby committing the transaction.

To run the project:

1. Create a table named ‘messages’ in your MySQL database using the file ‘http_socket_db.sql’ provided in the zip.
2. Update the connection string in connectToMySql() method of ‘HTTPMultithreadedSocketServer.java’.
3. Include the library ‘mysql-connector-java-5.1.45-bin.jar’ in your classpath. It is a JDBC library for MySQL connectivity.
4. Start the server process by running ‘HTTPMultithreadedSocketServer.java’.
5. Start the coordinator process by running ‘HTTPMultithreadedSocketCoordinator.java’.
6. Start 3 client processes by running ‘HTTPMultithreadedSocketClient.java’.
7. Click on the ‘Start Transaction’ button on coordinator user interface to initiate a transaction.
8. Click on either ‘Pre-Commit’ or ‘Abort’ button on participant user interfaces.
9. If PREPARE_COMMIT is received from server, click on ‘Acknowledge’ button.
10. The transaction will commit or abort as per the 3-phase commit protocol.
11. To disconnect the client, send a message as ‘exit’.