Error for Graph Traversal using Streaming Expressions

[Zheng Lin Edwin Yeo]

Hi,

I am getting this error when I tried to run a query for Graph Traversal
using Streaming Expressions:

{
  "result-set":{
    "docs":[{
        "EXCEPTION":"java.util.concurrent.ExecutionException:
java.lang.RuntimeException: java.io.IOException:
java.util.concurrent.ExecutionException: java.io.IOException: -->
http://localhost:8983/solr/email/: An exception has occurred on the server,
refer to server log for details.",
        "EOF":true,
        "RESPONSE_TIME":11}]}}


Below is my query:

http://locahost:8983/solr/email/stream?expr=gatherNodes(email,
            walk="ed...@mail.com->from",
            gather="to")&indent=true

What could be the reason?

I'm using Solr 6.4.1 at the moment.

Regards,
Edwin