How to make Flask/ keep Ajax HTTP connection alive?
ajax, flask, keep-alive, werkzeug
Solution
Werkzeug's integrated web server builds on BaseHTTPServer from Python's standard library. BaseHTTPServer seems to support Keep-Alives if you set its HTTP protocol version to 1.1.
Werkzeug doesn't do it but if you're ready to hack into the machinery that Flask uses to instantiate Werkzeug's BaseWSGIServer, you can do it yourself. See `Flask.run()` which calls `werkzeug.serving.run_simple()`. What you have to do boils down to `BaseWSGIServer.protocol_version = "HTTP/1.1"`.
I haven't tested the solution. I suppose you do know that Flask's web server ought to be used for development only.
Problem
I have a jQuery Ajax call, like so: ``` $("#tags").keyup(function(event) { $.ajax({url: "/terms", type: "POST", contentType: "application/json", data: JSON.stringify({"prefix": $("#tags").val() }), dataType: "json", success: function(response) { display_terms(response.terms); }, }); ``` I have a Flask method like so: ``` @app.route("/terms", methods=["POST"]) def terms_by_prefix(): req = flask.request.json tlist = terms.find_by_prefix(req["prefix"]) return flask.jsonify({'terms': tlist}) ``` tcpdump shows the HTTP dialog: ``` POST /terms HTTP/1.1 Host: 127.0.0.1:5000 User-Agent: Mozilla/5.0 (X11; Linux i686; rv:12.0) Gecko/20100101 Firefox/12.0 Accept: application/json, text/javascript, */*; q=0.01 Accept-Language: en-us,en;q=0.5 Accept-Encoding: gzip, deflate Connection: keep-alive Content-Type: application/json; charset=UTF-8 X-Requested-With: XMLHttpRequest Referer: http://127.0.0.1:5000/ Content-Length: 27 Pragma: no-cache Cache-Control: no-cache {"prefix":"foo"} ``` However, Flask replies without keep-alive. ``` HTTP/1.0 200 OK Content-Type: application/json Content-Length: 445 Server: Werkzeug/0.8.3 Python/2.7.2+ Date: Wed, 09 May 2012 17:55:04 GMT {"terms": [...]} ``` Is it really the case that keep-alive is not implemented?