缓冲时来自服务器的WCF InsufficientMemoryException

Question

I am getting this error on my server.

System.InsufficientMemoryException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089

Failed to allocate a managed memory buffer of 536870912 bytes. The amount of available memory may be low.

This happens after the last statement return myCollection . when myCollection is around 45k items.

Server Config:

<binding name="LargeTCPBinding"
         closeTimeout="00:30:00"
         openTimeout="00:30:00"
         receiveTimeout="01:00:00"
         sendTimeout="01:00:00"
         hostNameComparisonMode="StrongWildcard"
         maxBufferPoolSize="2147483647"
         maxReceivedMessageSize="2147483647"
         maxBufferSize="2147483647">
  <readerQuotas maxDepth="2147483647"
                maxStringContentLength="2147483647"
                maxArrayLength="2147483647"
                maxBytesPerRead="2147483647"
                maxNameTableCharCount="2147483647" />
  <security mode="Transport">
    <transport clientCredentialType="Windows" />
  </security>
</binding>

i did some basic memory profiling GC.GetTotalMemory(false) and the difference after getting my collection into memory is about 170 MB.

The exception happens after returning the collection (so it appears to happen during buffering for send).

If i switch my wcf connection config to Streamed , this fixes the exception, but the call goes from 25 seconds to 1:05 minutes.

Just trying to understand what is happening here because that collection is not that big. This is running on WCF 4.0, 64bit cpu.

Answer 1

What's important here is not the SIZE of the collection but the COMPLEXITY of the object graph. If your collection contains a reference type with many fields and/or properties, this is a more complex/deeper graph.

Before WCF can send a response to you, it must serialize the object graph into binary, send it over the wire, and the client deserializes it.

Buffered means the collection is serialized to a structure in memory, and then sent as one big chunk. Streamed means that the collection is sent as it is serialized.

Your object may not be large, but the serialized representation of it may be quite massive, simply due to the SOAP envelope created for your data and the XML representation, etc.

This is why Streamed solves your issue: buffered cannot represent the entire object graph in serialized form in memory at one time.