AppEngine gzip compressing

Question

I'm trying to gzip responses from GAE server, but receive null in Content-Encoding.

I have the following code:

connection = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type", 
          "application/json; charset=utf-8"); //"application/json; charset=utf-8"
connection.setRequestProperty("Accept-Encoding", "gzip");
connection.setRequestProperty("User-Agent", "gzip");
connection.setUseCaches (false);
connection.setDoInput(true);
connection.setDoOutput(true);

//write
//read

System.out.println("Content-Encoding " + connection.getContentEncoding());

I've read that on GAE servers do compressing automatically. So what can be the problem?

GAE doesn't take any notice of whether you ask it to compress or not. How big is the file in this case? From experience, anything over 1MB is never compressed. — Frodo Baggins, Dec 12 '11 at 13:31

score 10 · Accepted Answer · answered Dec 15 '11 at 00:04

10

The App Engine frontend servers rely on a number of factors, including the Accept-Encoding and User-Agent headers to determine if they should compress responses. They do this because there are a number of user agents out there that claim to accept gzipped responses, but actually can't understand them.

Try setting your user agent to something sensible (and not 'gzip', which isn't a real user agent), and see if that makes any difference.

answered Dec 15 '11 at 00:04

Nick Johnson

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https://developers.google.com/appengine/kb/general#compression states "To force gzipped content to be served, clients may supply 'gzip' as the value of both the Accept-Encoding and User-Agent request headers.". Some people report it working, others not. Basically, nobody seems to know the real answer. – Frodo Baggins Dec 23 '12 at 11:44
Modified client to send `Accept-Encoding: gzip`, but App Engine still responded uncompressed. Then appended gzip to UA, `User-Agent: Our Real UA String; gzip` and that (along with `Accept-Encoding: gzip`) finally forced App Engine to respond compressed. – Zach Young Dec 05 '16 at 18:28
Can we do this without sending in Request ? like setting these values inside code ? – Sunil Rk Apr 25 '17 at 06:25

score 0 · Answer 2 · answered Jun 18 '19 at 15:22

In my case, the problem was that the servlet wasn't specifying a value for the Content-Type header. Specifying it explicitly was all I needed to do:

public void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws IOException, ServletException {
    ...
    resp.setHeader("Content-Type", "application/json");
    ...

AppEngine gzip compressing

2 Answers2

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