account for truncated/expanded static files

When running a static file server, we must account for filesystem
activity outside of our control where files may grow/shrink as
they're being served.

For truncated files, we must abort any persistent connections
downloading a truncated file to avoid confusing clients because
the Content-Length header was already set to the big value.

We also must ensure (we already did so before this commit,
this just adds a test for it) we do not send additional data
when a file grows on us after we've started sending the response.

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/yahns/wbuf_common.rb b/lib/yahns/wbuf_common.rb
index cfafaa2..b3a4502 100644
--- a/lib/yahns/wbuf_common.rb
+++ b/lib/yahns/wbuf_common.rb
@@ -14,8 +14,16 @@ module Yahns::WbufCommon # :nodoc:
       @sf_offset += rv # keep going otherwise
     when :wait_writable, :wait_readable
       return rv
+    when nil
+      # response got truncated, drop the connection
+      # this may happens when using Rack::File or similar, we can't
+      # keep the connection alive because we already sent our Content-Length
+      # header the client would be confused.
+      @wbuf_persist = false
+      return wbuf_close(client)
     else
-      raise "BUG: #{rv.nil? ? "EOF" : rv.inspect} on tmpio=#{@tmpio.inspect} " \
+      raise "BUG: rv=#{rv.inspect} " \
+            "on tmpio=#{@tmpio.inspect} " \
             "sf_offset=#@sf_offset sf_count=#@sf_count"
     end while true
   end