/// <summary>
/// 自动读写分离时，获取本次操作涉及到的Database
/// </summary>
/// <param name="statement"></param>
/// <returns></returns>
public static OperationalDatabases GetDatabasesByStatement(Statement statement)
{
OperationalDatabases result = null;
String databaseSet = statement.DatabaseSet;
if (!DALBootstrap.DatabaseSets.ContainsKey(databaseSet))
{
throw new ArgumentOutOfRangeException(String.Format(Properties.Resources.DatabaseSetDoesNotExistException, databaseSet));
}
var databaseSetWrapper = DALBootstrap.DatabaseSets[databaseSet];
if (databaseSetWrapper.DatabaseWrappers.Count == 0)
{
throw new System.Configuration.ConfigurationErrorsException(String.Format("DatabaseSet '{0}' doesn't contain any database.", databaseSetWrapper.Name));
}
if (databaseSetWrapper.EnableReadWriteSpliding)
{
if (readWriteSplit == null)
{
lock (Locker)
{
if (readWriteSplit == null)
{
readWriteSplit = RWSplittingManager.Instance;
}
}
result = readWriteSplit.GetOperationalDatabases(statement);
}
}
//如果没有合适的数据库
if (result == null || (result.FirstCandidate == null && result.OtherCandidates.Count == 0))
{
result = new OperationalDatabases();
Database master = databaseSetWrapper.DatabaseWrappers.Single(item => item.DatabaseType == DatabaseType.Master).Database;
result.FirstCandidate = master;
}
if (result.FirstCandidate == null && (result.OtherCandidates == null || result.OtherCandidates.Count == 0))
{
throw new ArgumentException("Specified database not found.");
}
return(result);
}
/// <summary>
/// 自动读写分离时，获取本次操作涉及到的Database
/// </summary>
/// <param name="statement"></param>
/// <returns></returns>
public static OperationalDatabases GetDatabasesByStatement(Statement statement)
{
#if !NETSTANDARD
if (Transaction.Current != null)
{
statement.OperationType = OperationType.Write;//如果是在事物中强制改成读写都走master
}
#endif
OperationalDatabases result = null;
String databaseSet = statement.DatabaseSet;
if (!DALBootstrap.DatabaseSets.ContainsKey(databaseSet))
{
throw new ArgumentOutOfRangeException(String.Format(Properties.Resources.DatabaseSetDoesNotExistException, databaseSet));
}
var databaseSetWrapper = DALBootstrap.DatabaseSets[databaseSet];
if (databaseSetWrapper.DatabaseWrappers.Count == 0)
{
throw new DalException(String.Format("DatabaseSet '{0}' doesn't contain any database.", databaseSetWrapper.Name));
}
String shard = statement.ShardID ?? String.Empty;
if (shard.Length > 0 && !databaseSetWrapper.TotalRatios.ContainsKey(shard))
{
throw new ArgumentOutOfRangeException(String.Format("Shard '{0}' doesn't exist.", shard));
}
if (databaseSetWrapper.EnableReadWriteSpliding)
{
if (readWriteSplit == null)
{
lock (Locker)
{
if (readWriteSplit == null)
{
readWriteSplit = RWSplittingManager.Instance;
}
}
}
result = readWriteSplit.GetOperationalDatabases(statement);
}
//如果没有合适的数据库
if (result == null || (result.FirstCandidate == null && result.OtherCandidates.Count == 0))
{
result = new OperationalDatabases();
Database master = databaseSetWrapper.DatabaseWrappers.Single(item => item.DatabaseType == DatabaseType.Master && item.Sharding == shard).Database;
if (databaseSetWrapper.EnableReadWriteSpliding && statement.OperationType == OperationType.Read)
{
//首先选出所有Slave
var slaves = databaseSetWrapper.DatabaseWrappers.Where(item => item.DatabaseType == DatabaseType.Slave && item.Sharding == shard).ToList();
var count = slaves.Count();
//如果多于1个Slave，随机选择一个
if (count > 0)
{
//用来动态选择slave数据库
var index = ThreadLocalRandom.Current.Next(0, count);
result.OtherCandidates = new List <Database>();
for (var i = 0; i < count; i++)
{
if (i == index)
{
result.FirstCandidate = slaves.ElementAt(index).Database;
}
else
{
result.OtherCandidates.Add(slaves.ElementAt(i).Database);
}
}
//将主库加入作为最后的备选
result.OtherCandidates.Add(master);
}
}
else
{
//如果强制到写库，仅作Retry，不做Fail Over，因此不提供Candidate Slaves
result.FirstCandidate = master;
}
}
if (result.FirstCandidate == null && (result.OtherCandidates == null || result.OtherCandidates.Count == 0))
{
throw new ArgumentException("Specified database not found.");
}
return(result);
}
