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How to return a simple page

Let’s see what we need to do in order to return a simple page to a client using Nginx module. We need to generate a header and a body of the response. To send a response header we use function ngx_http_send_header:

#include <ngx_http.h>

ngx_int_t ngx_http_send_header(ngx_http_request_t *r);

The only argument r is the request for which you want to generate and send a header. This function serializes headers from the list of response headers r->headers_out into a buffer and sends this buffer to a client or queues this buffer into output queue r->out if the client socket is not writeable. The HTTP version in the status line will be determined for you automatically. The HTTP status code is taken from r->headers_out.status and the status text will be filled according to the status code.

Lets see how we can add some custom header line to our response header. Continue reading “How to return a simple page”

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HTTP request processing phases in Nginx

Nginx processes HTTP requests in multiple phases. In each of the phases there might be 0 or more handlers called. In the Nginx source code phases have specific constants associated with them. Here is a list of all phases:

  1. NGX_HTTP_SERVER_REWRITE_PHASE — the phase of request URI transformation on virtual server level;
  2. NGX_HTTP_FIND_CONFIG_PHASE — the phase of configuration location lookup;
  3. NGX_HTTP_REWRITE_PHASE — the phase of request URI transformation on location level;
  4. NGX_HTTP_POST_REWRITE_PHASE — request URI transformation post-processing phase;
  5. NGX_HTTP_PREACCESS_PHASE — access restrictions check preprocessing phase;
  6. NGX_HTTP_ACCESS_PHASE — access restrictions check phase;
  7. NGX_HTTP_POST_ACCESS_PHASE — access restrictions check post-processing phase;
  8. NGX_HTTP_TRY_FILES_PHASE — try_files directive processing phase;
  9. NGX_HTTP_CONTENT_PHASE — content generation phase;
  10. NGX_HTTP_LOG_PHASE — logging phase.

On every phase you can register any number of your handlers. Continue reading “HTTP request processing phases in Nginx”