Rendering of pages having many static connect macros (without caching) can cause a gateway timeout if the rendering takes longer than 60 seconds.

We ran into this when one of our customers exported a single page having a lot of multi-excerpt macros (those are static connect macros).
Calling the /contentbody/convert/export_view REST API apparently took longer than one minute so the gateway closed the connection.

This is a critical issue for us, because customers don't think of timeouts when adding (connect) macros on their pages.

Steps to reproduce:

1. Install an addon providing a 'dummy' static content macro that sleeps three seconds (contact cli@atlassian.com for this) 
2. Insert 20 of the dummy macros into a Confluence page. Alternatively, POST the following JSON containing twenty of these macros to <your- site>/wiki/rest/api/contentbody/convert/export_view

   {
       "value" : "<p>before</p> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <ac:structured-macro ac:name=\"dummy\" ac:schema-version=\"1\" ac:macro-id=\"c9a41198-7f37-4009-842f-d263f02409d6\"/> <p>after</p>",
       "representation" : "storage"
   }

1. You'll run into a '504 Gateway Time-out' after exactly one minute.

Investigation Results: 

I think the problem is that currently the Confluence page waits for all macros on the page to send back a response before rendering all of them. Because of this, when one macro times out, the entire page cannot be rendered.

Solution:

Refer to Steven's comment.