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From "Nick Veenhof (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (SOLR-2878) Regression in SolrDispatchFilter.java concerning the getOutputStream vs getWriter
Date Fri, 04 Nov 2011 23:33:52 GMT
Regression in SolrDispatchFilter.java concerning the getOutputStream vs getWriter
---------------------------------------------------------------------------------

                 Key: SOLR-2878
                 URL: https://issues.apache.org/jira/browse/SOLR-2878
             Project: Solr
          Issue Type: Bug
          Components: Build, Response Writers
    Affects Versions: 3.4
         Environment: Any unix system, it's a  global problem
            Reporter: Nick Veenhof
             Fix For: 3.5, 4.0


In solr 1.4 we used getWriter in the writeResponse for solrDispatchFilter::doFilter which
invoked writeResponse.
This code looked in summary like this :
<code>
private void writeResponse(SolrQueryResponse solrRsp, ServletResponse response, QueryResponseWriter
responseWriter, SolrQueryRequest solrReq, Method reqMethod) throws IOException {
 PrintWriter out = response.getWriter();
 responseWriter.write(out, solrReq, solrRsp);
</code>

In solr 3.x this has changed to something like this 
<code>
private void writeResponse(SolrQueryResponse solrRsp, ServletResponse response,QueryResponseWriter
responseWriter, SolrQueryRequest solrReq, Method reqMethod) throws IOException {
...
String charset = ContentStreamBase.getCharsetFromContentType(ct);
Writer out = (charset == null || charset.equalsIgnoreCase("UTF-8"))
  ? new OutputStreamWriter(response.getOutputStream(), UTF8)
  : new OutputStreamWriter(response.getOutputStream(), charset);
out = new FastWriter(out);
responseWriter.write(out, solrReq, solrRsp);
out.flush();
</code>

Now, when we add another filter that tries to modify the output it is being blocked by the
out.flush(). 
flush() is telling our outputstream that it can write directly to the destination (similar
to the out.close()), since this normally happens automatically there shouldn't be a need to
execute this flush.
In our case this secondary filter is trying to add headers to the response object. When we
were using getwriter() it was not closing the writer so we could still modify this output.
Since the flush happens now we are no longer able to modify the headers accordingly. 
It would be an easy fix if the flush could be commented out and everything would work but
that is not the case. The headers are working when this happens but there is no more output.
When I modify both classes to use getWriter() everything is working as expected.

This is a severe regression for our use of solr.

Our code that is used in the filter
<code>
public void doFilter(ServletRequest req, ServletResponse res,FilterChain chain) throws IOException,
ServletException {
...
Writer out = new OutputStreamWriter(response.getOutputStream(), "UTF8"); //auto flush
out = new FastWriter(out);
// convert to a chartext
CharResponseWrapper wrapper = new CharResponseWrapper((HttpServletResponse) response);
chain.doFilter(request, wrapper);
String responseBody = wrapper.toString();
//write the outgoing header. Only succeeds when flush of solrDispatchFilter is commented out
response.addHeader("pragma", "somevalue;");
out.write(responseBody);
...
</code>

Sources :
<quote>SRV.5.5 Closure of Response Object
When a response is closed, the container must immediately flush all remaining content in the
response buffer to the client. The following events indicate that the servlet has satisfied
the request and that the response object is to be closed:
• The termination of the service method of the servlet. 
• The amount of content specified in the setContentLength method of the response has been
written to the response. 
• The sendError method is called. 
• The sendRedirect method is called.
</quote>

Solr 1.4 https://svn.apache.org/repos/asf/lucene/solr/branches/branch-1.4/src/webapp/src/org/apache/solr/servlet/SolrDispatchFilter.java
Solr 3.4 https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_3_4/solr/core/src/java/org/apache/solr/servlet/SolrDispatchFilter.java

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