Regression in SolrDispatchFilter.java concerning the getOutputStream vs
getWriter
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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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