"sub_filter_once off" not working as advertised?

Tue Dec 12 16:34:36 UTC 2017

I have a rule like the following where I am trying to replace instances of /spf/ with /ec/apps/symmetry/spf/.   I’ve used sub_filter to do this sort of thing before and had luck with it.

        location /ec/apps/symmetry/ {

            proxy_pass http://stl-biz-d2-hrxsymmetry.devapp.c9.equifax.com:55943/;
            proxy_redirect / https://$host/ec/apps/symmetry/;

            #sub filter doesn't work if the upstream server returns compressed or zipped content.
            proxy_set_header Accept-Encoding identity;

            sub_filter once off;  # doesn’t seem to have an effect

            sub_filter '/spf/' '/ec/apps/symmetry/spf/';

            add_header X-nginx-rule /ec/apps/symmetry;
        }

The thing I am seeing here is that even though I specified sub_filter_once off I still only see the first link modified in the html that comes back.   When this html is returned

<html>
<head>
     <title> Welcome </title>

     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <meta name="robots" content="noindex,nofollow"/>
     <script type="text/javascript" src="/spf/resources/js/jquery.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/bootstrap.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/underscore.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/beautify-html.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/jquery-zoom.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/spf-new-all.js?v=spf_2017-R5"></script>
     <link href="/spf/resources/css/bootstrap.css?v=spf_2017-R5" type="text/css" media="all" rel="stylesheet">
     <link href="/spf/resources/css/main.css?v=spf_2017-R5" type="text/css" media="all" rel="stylesheet">

This is what I see coming out of nginx:

<html>
<head>
     <title> Welcome </title>

     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <meta name="robots" content="noindex,nofollow"/>
     <script type="text/javascript" src="/ec/apps/symmetry/spf/resources/js/jquery.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/bootstrap.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/underscore.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/beautify-html.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/jquery-zoom.js?v=spf_2017-R5"></script>
     <script type="text/javascript" src="/spf/resources/js/spf-new-all.js?v=spf_2017-R5"></script>
     <link href="/spf/resources/css/bootstrap.css?v=spf_2017-R5" type="text/css" media="all" rel="stylesheet">
     <link href="/spf/resources/css/main.css?v=spf_2017-R5" type="text/css" media="all" rel="stylesheet">

 I can see that “X-nginx-rule” header show up in the browser confirming that the request traversing this location block. The fact that anything is modified tells me that gzip and content-type are not getting in the way. sub_filter is filtering, it’s just only doing it one time ☺.

I was able to work around this by just accepting /spf/ in another location block but for future reference – has anyone seen sub_filter only make one substitution even when sub_filter once off is specified?

Jason Whittington | Architect, PD Shared Services
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jason.whittington at equifax.com<mailto:jason.whittington at equifax.com>

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