libdb/examples/csharp/excs_txn/excs_txn.cs

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2009, 2011 Oracle and/or its affiliates.  All rights reserved.
 *
 */
using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using System.Threading;

using BerkeleyDB;

namespace excs_txn {
        public class excs_txn {
		private DatabaseEnvironment env;
		private Database db;
		private Random generator = new Random();
		private bool inMem;
		private string dbName, home;
		private const int NUMTHREADS = 5;

		public static void Main(string[] args) {
			/*
			 * excs_txn is meant to be run from build_windows\AnyCPU, 
			 * in either the Debug or Release directory. The 
			 * required core libraries, however, are in either 
			 * build_windows\Win32 or build_windows\x64, depending 
			 * upon the platform.  That location needs to be added 
			 * to the PATH environment variable for the P/Invoke 
			 * calls to work.
			 */
			try {
				String pwd = Environment.CurrentDirectory;
				pwd = Path.Combine(pwd, "..");
				pwd = Path.Combine(pwd, "..");
				pwd = Path.Combine(pwd, "..");
				pwd = Path.Combine(pwd, "build_windows");
				if (IntPtr.Size == 4)
					pwd = Path.Combine(pwd, "Win32");
				else
					pwd = Path.Combine(pwd, "x64");
#if DEBUG
				pwd = Path.Combine(pwd, "Debug");
#else
				pwd = Path.Combine(pwd, "Release");
#endif
				pwd += ";" + Environment.GetEnvironmentVariable("PATH");
				Environment.SetEnvironmentVariable("PATH", pwd);
			} catch (Exception e) {
				Console.WriteLine(
				    "Unable to set the PATH environment variable.");
				Console.WriteLine(e.Message);
				return;
			}

			excs_txn obj = new excs_txn();
			obj.RunExample(args);
		}

		private void RunExample(string[] args) {
			dbName = "excs_txn.db";
			home = "TESTDIR";

			if (!ParseArgs(args)) {
				Usage();
				return;
			}

			try {
				Open();

				// Start the threads.
				Thread[] threadArray = new Thread[NUMTHREADS];
				for (int i = 0; i < NUMTHREADS; i++) {
					threadArray[i] = new Thread(
                                            new ThreadStart(WriteData));
					threadArray[i].Name = "Thread " + i;
					threadArray[i].Start();
				}

				for (int i = 0; i < NUMTHREADS; i++) {
					threadArray[i].Join();
					Console.WriteLine("Thread " + i + " finished.");
				}

			} catch (DatabaseException e) {
				Console.WriteLine("Caught exception: {0}", e.Message);
				Console.WriteLine(e.StackTrace);
			} finally {
				Close();
			}
		}

		private void Open() {
			Console.WriteLine("Opening environment and database");

			// Set up the environment.
			DatabaseEnvironmentConfig envCfg = new DatabaseEnvironmentConfig();
			envCfg.Create = true;
			envCfg.UseMPool = true;
			envCfg.UseLocking = true;
			envCfg.UseLogging = true;
			envCfg.UseTxns = true;

			// Allow multiple threads visit to the environment handle.
			envCfg.FreeThreaded = true;

			if (inMem)
				envCfg.Private = true;
			else 
				envCfg.RunRecovery = true;

			/* 
			 * Indicate that we want db to internally perform 
			 * deadlock detection, aborting the transaction that 
			 * has performed the least amount of WriteData activity 
			 * in the event of a deadlock.
			 */
			envCfg.LockSystemCfg = new LockingConfig();
			envCfg.LockSystemCfg.DeadlockResolution =
			    DeadlockPolicy.MIN_WRITE;

			if (inMem) {
				// Specify in-memory logging.
				envCfg.LogSystemCfg = new LogConfig();
				envCfg.LogSystemCfg.InMemory = true;

				/* 
				 * Specify the size of the in-memory log buffer
				 * Must be large enough to handle the log data
				 * created by the largest transaction.
				 */
				envCfg.LogSystemCfg.BufferSize = 10 * 1024 * 1024;

				/* 
				 * Specify the size of the in-memory cache, 
				 * large enough to avoid paging to disk.
				 */
				envCfg.MPoolSystemCfg = new MPoolConfig();
				envCfg.MPoolSystemCfg.CacheSize =
				    new CacheInfo(0, 10 * 1024 * 1024, 1);
			}

			// Set up the database.
			BTreeDatabaseConfig dbCfg = new BTreeDatabaseConfig();
			dbCfg.AutoCommit = true;
			dbCfg.Creation = CreatePolicy.IF_NEEDED;
			dbCfg.Duplicates = DuplicatesPolicy.SORTED;
			dbCfg.FreeThreaded = true;
			dbCfg.ReadUncommitted = true;

			/*
                         * Open the environment. Any errors will be caught
                         * by the caller.
                         */                          
			env = DatabaseEnvironment.Open(home, envCfg);

			/*
			 * Open the database. Do not provide a txn handle. This 
			 * Open is autocommitted because BTreeDatabaseConfig.AutoCommit
			 * is true.
			 */
			dbCfg.Env = env;
			db = BTreeDatabase.Open(dbName, dbCfg);

		}

		private void Close() {
			Console.WriteLine("Closing environment and database");
			if (db != null) {
				try {
					db.Close();
				} catch (DatabaseException e) {
					Console.WriteLine("Error closing db: " + e.ToString());
					Console.WriteLine(e.StackTrace);
				}
			}

			if (env != null) {
				try {
					env.Close();
				} catch (DatabaseException e) {
					Console.WriteLine("Error closing env: " + e.ToString());
					Console.WriteLine(e.StackTrace);
				}
			}
		}

		/*
		 * This simply counts the number of records contained in the
		 * database and returns the result. You can use this method
		 * in three ways:
		 * 
		 * First call it with an active txn handle.
		 * Secondly, configure the cursor for dirty reads
		 * Third, call countRecords AFTER the writer has committed
		 * its transaction.
		 * 
		 * If you do none of these things, the writer thread will
		 * self-deadlock.
		 * 
		 * Note that this method exists only for illustrative purposes.
		 * A more straight-forward way to count the number of records in
		 * a database is to use the Database.getStats() method.
		 */
		private int CountRecords(Transaction txn) {
			int count = 0;
			Cursor cursor = null;

			try {
				// Get the cursor.
				CursorConfig cc = new CursorConfig();
				
				/*
				 * Isolation degree one is ignored if the 
				 * database was not opened for uncommitted 
				 * read support. TxnGuide opens its database
				 * in this way and TxnGuideInMemory does not.
				 */
				cc.IsolationDegree = Isolation.DEGREE_ONE;
				cursor = db.Cursor(cc, txn);
				while (cursor.MoveNext())
					count++;
			} finally {
				if (cursor != null)
					cursor.Close();
			}

			return count;
		}

		private bool ParseArgs(string[] args) {
			for (int i = 0; i < args.Length; i++) {
				string s = args[i];
				if (s[0] != '-') {
					Console.Error.WriteLine(
					    "Unrecognized option: " + args[i]);
					return false;
				}
				
				switch (s[1]) {
					case 'h':
						home = args[++i];
						break;
					case 'm':
						inMem = true;
						break;
					default:
						Console.Error.WriteLine(
						    "Unrecognized option: " + args[i]);
						return false;
				}
			}
			return true;
		}

		private void Usage() {
			Console.WriteLine("excs_txn [-h <env directory>] [-m]");
			Console.WriteLine("\t -h home (Set environment directory.)");
			Console.WriteLine("\t -m (Run in memory, do not write to disk.)");
		}

		private void WriteData() {
			/*
			 * Write a series of records to the database using transaction 
			 * protection. Deadlock handling is demonstrated here.
			 */
			BinaryFormatter formatter = new BinaryFormatter();
			MemoryStream ms = new MemoryStream();
			Random generator = new Random();
			Transaction txn = null;

			string[] keys = {"key 1", "key 2", "key 3", "key 4",
			    "key 5", "key 6", "key 7", "key 8", "key 9", "key 10"};

			// Perform 20 transactions.
			int iters = 0;
			int retry_count = 0;
			int maxRetry = 20;
			while (iters < 50) {
				try {
					// Get a transaction.
					txn = env.BeginTransaction();

					// Write 10 records to the db for each transaction.
					for (int j = 0; j < 10; j++) {
						// Get the key.
						DatabaseEntry key;
						key = new DatabaseEntry(
						    ASCIIEncoding.ASCII.GetBytes(keys[j]));

						// Get the data.
						PayloadData pd = new PayloadData(
                                                    iters + j,
						    Thread.CurrentThread.Name,
						    generator.NextDouble());

						formatter.Serialize(ms, pd);
						Byte[] bytes = ms.GetBuffer();
						DatabaseEntry data = new DatabaseEntry(bytes);

						// Put key/data pair within the transaction.
						db.Put(key, data, txn);
					}

					// Commit the transaction.
					Console.WriteLine("{0} committing txn: {1}",
					    Thread.CurrentThread.Name, iters);

					int recCount = CountRecords(inMem ? txn : null);
					Console.WriteLine("{0} found {1} records in the database.",
					    Thread.CurrentThread.Name, recCount);

					try {
						txn.Commit();
						txn = null;
					} catch (DatabaseException e) {
						Console.WriteLine(
                                                    "Error on txn commit: " + 
                                                    e.ToString());
					}

					iters++;
					retry_count = 0;
				} catch (DeadlockException) {
					Console.WriteLine(
					    "##### {0} deadlocked.", Thread.CurrentThread.Name);

					// Retry if necessary.
					if (retry_count < maxRetry) {
						Console.WriteLine("{0} retrying.",
						    Thread.CurrentThread.Name);
						retry_count++;
					} else {
						Console.WriteLine("{0} out of retries. Giving up.",
						    Thread.CurrentThread.Name);
						iters++;
						retry_count = 0;
					}
				} catch (DatabaseException e) {
					// Abort and don't retry.
					iters++;
					retry_count = 0;
					Console.WriteLine(Thread.CurrentThread.Name +
					    " : caught exception: " + e.ToString());
					Console.WriteLine(Thread.CurrentThread.Name +
					    " : errno: " + e.ErrorCode);
					Console.WriteLine(e.StackTrace);
				} finally {
					if (txn != null) {
						try {
							txn.Abort();
						} catch (DatabaseException e) {
							Console.WriteLine("Error aborting transaction: " +
							    e.ToString());
							Console.WriteLine(e.StackTrace);
						}
					}
				}
			}
		}
	}
}