Varnish Breaking Social Sharing

Question

Facebook uses a curl with range option to retrieve HTML of a page for sharing. Varnish is only returning page header info and not the html. This is the result I would say 75% to 80% of the time. Every once in a while it returns the correct Result

Anyone have an Idea how to fix this.

Example

#curl -v -H Range:bytes=0-524288 http://americanactionnews.com/articles/huge-protest-calls-for-death-to-usa-demands-isis-control
*   Trying 52.45.101.42...
* TCP_NODELAY set
* Connected to americanactionnews.com (52.45.101.42) port 80 (#0)
> GET /articles/huge-protest-calls-for-death-to-usa-demands-isis-control HTTP/1.1
> Host: americanactionnews.com
> User-Agent: curl/7.51.0
> Accept: */*
> Range:bytes=0-524288
>
< HTTP/1.1 206 Partial Content
< Content-Type: text/html; charset=utf-8
< Status: 200 OK
< X-Frame-Options: SAMEORIGIN
< X-XSS-Protection: 1; mode=block
< X-Content-Type-Options: nosniff
< Date: Fri, 23 Dec 2016 16:39:46 GMT
< Cache-Control: max-age=300, public
< X-Request-Id: 8007fb76-3878-430d-845c-06a8710ae1ae
< X-Runtime: 0.247333
< X-Powered-By: Phusion Passenger 4.0.55
< Server: nginx/1.6.2 + Phusion Passenger 4.0.55
< X-Varnish-TTL: 300.000
< X-Varnish: 65578
< Age: 0
< Via: 1.1 varnish-v4
< X-Cache: MISS
< Transfer-Encoding: chunked
< Connection: keep-alive
< Accept-Ranges: bytes
< Content-Range: bytes 0-15/16
<
* Curl_http_done: called premature == 0
* Connection #0 to host americanactionnews.com left intact 

Answer 1

We have found the answer and made some modifications to our varnish based on the following link and it seems to be working. https://info.varnish-software.com/blog/caching-partial-objects-varnish

Answer 2

It looks like it is actually your backend server (Nginx) that is the problem. Especially considering your mentioned hit-rate-like success rate :) Plus, the failure's example is a MISS (delivered from backend server).

Make sure that you don't have anything in your Nginx configuration that prevents range requests, i.e. one popular thing that breaks it is:

ssi on;
ssi_types *;