我正在使用Cassandra 0.8.7,Aquiles作为C#客户端和Thrift 0.7,我试图从具有以下定义的SuperColumnFamily中获取大量数据:
create column family SCF with column_type=Super and comparator=TimeUUIDType and subcomparator=AsciiType;
我想将从Cassandra获取的数据插入到DataTable中,这样我就能过滤行并根据它生成一些报告,但我总是得到一个OutOfMemoryException。
[OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.]
Thrift.Transport.TFramedTransport.ReadFrame() +191
Thrift.Transport.TFramedTransport.Read(Byte[] buf, Int32 off, Int32 len) +101
Thrift.Transport.TTransport.ReadAll(Byte[] buf, Int32 off, Int32 len) +76
Thrift.Protocol.TBinaryProtocol.ReadAll(Byte[] buf, Int32 off, Int32 len) +66
Thrift.Protocol.TBinaryProtocol.ReadI32() +47
Thrift.Protocol.TBinaryProtocol.ReadMessageBegin() +75
Apache.Cassandra.Client.recv_multiget_slice() in D:\apache-cassandra-0.8.0-beta2\interface\gen-csharp\Apache\Cassandra\Cassandra.cs:304
Apache.Cassandra.Client.multiget_slice(List`1 keys, ColumnParent column_parent, SlicePredicate predicate, ConsistencyLevel consistency_level) in D:\apache-cassandra-0.8.0-beta2\interface\gen-csharp\Apache\Cassandra\Cassandra.cs:286
我尝试了几种方法来优化我的代码,我的最终版本是分割一段时间(如果它们超过前缀数字,那么键的数量)我用来在较小的范围内切割SuperColumn但是没有,最终我总是得到同样的例外。
它可能是Thrift库的错误吗?当我得到异常时,它始终指向Thrift.Transport.TFramedTransport内的代码的以下部分:
private void ReadFrame()
{
byte[] i32rd = new byte[header_size];
transport.ReadAll(i32rd, 0, header_size);
int size =
((i32rd[0] & 0xff) << 24) |
((i32rd[1] & 0xff) << 16) |
((i32rd[2] & 0xff) << 8) |
((i32rd[3] & 0xff));
byte[] buff = new byte[size]; //Here the exception is thrown
transport.ReadAll(buff, 0, size);
readBuffer = new MemoryStream(buff);
}
以下是我尝试运行的代码:
string columnFamily = "SCF";
ICluster cluster = AquilesHelper.RetrieveCluster(ConfigurationManager.AppSettings["CLUSTERNAME"].ToString());
ColumnParent columnParent = new ColumnParent()
{
Column_family = columnFamily
};
List<byte[]> keys = //Function that return the list of the key i want to query
SlicePredicate predicate = new SlicePredicate();
foreach (DateTime[] dates in dateList)
{
from = GuidGenerator.GenerateTimeBasedGuid(dates[0]);
to = GuidGenerator.GenerateTimeBasedGuid(dates[1]);
predicate = new SlicePredicate()
{
Slice_range = new SliceRange()
{
Count = int.MaxValue,
Reversed = false,
Start = Aquiles.Helpers.Encoders.ByteEncoderHelper.UUIDEnconder.ToByteArray(from),
Finish = Aquiles.Helpers.Encoders.ByteEncoderHelper.UUIDEnconder.ToByteArray(to)
},
};
cluster.Execute(new ExecutionBlock(delegate(CassandraClient client)
{
int maxKeys = Convert.ToInt32(ConfigurationManager.AppSettings["maxKeys"]);
CassandraMethods.TableCreator(ref dt, columnParent, predicate, keys, client, maxKeys);
return null;
}), ConfigurationManager.AppSettings["KEYSPACE"].ToString());
}
这是应该将cassandra中的数据插入DataTable的函数:
public static DataTable TableCreator(ref DataTable dt, ColumnParent columnParent, SlicePredicate predicate, List<byte[]> keys, CassandraClient client, int maxKeys)
{
int keyCount = keys.Count;
if (keyCount < maxKeys)
CassandraMethods.CassandraToDataTable(ref dt, client.multiget_slice(keys, columnParent, predicate, ConsistencyLevel.ONE));
else
{
int counter = 0;
while (counter < keyCount)
{
if (counter + maxKeys <= keyCount)
CassandraMethods.CassandraToDataTable(ref dt, client.multiget_slice(keys.GetRange(counter, maxKeys), columnParent, predicate, ConsistencyLevel.ONE));
else
CassandraMethods.CassandraToDataTable(ref dt, client.multiget_slice(keys.GetRange(counter, keyCount - counter), columnParent, predicate, ConsistencyLevel.ONE));
counter += maxKeys;
}
}
return dt;
}
我错过了什么吗?我做错了什么?
更新1:我还尝试使用Cassandra 1.0,Aquiles 1.0,版本0.6和0.7的Thrift,但没有,仍然是相同的例外。
更新2:问题已解决,请阅读下面的答案
答案 0 :(得分:1)
问题解决了:) 我玩弄了内存使用和垃圾收集器,我解决了这个问题。
发生的事情是,每当我的应用程序达到1.5 GB的Ram时,由于visual studio将其编译为32位应用程序,因此抛出异常。
编译并运行x64解决了已发布的问题,为了确保不使用太多内存,我现在在每次Cassandra multiget_slice调用之前添加了以下3行代码。
GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
GC.WaitForPendingFinalizers();
GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
谢谢,N。
答案 1 :(得分:0)
SuperColumnFamily中的数据有多大? Thrift的默认最大帧大小为15 Mb。这是在/etc/cassandra/conf/cassandra.yaml
中设置的 - 你可以尝试增加它吗?
请注意,无法将数据拆分为小于单个超级列。