Flushing responses in nginx modules

[Johan Andersson]

Hi everyone,

I have some issues writing my nginx modules.

I am on Debian Stretch, installed nginx with the default configuration, 
and took the hello_world module. It works without a hitch. Then I 
changed the handler to send three "hello world" responses, and sleep for 
one second between each response.

However, when I look at the result in my browser, the page loads, pauses 
for three seconds, and then displays all three "hello world" messages at 
once.

Actually I was flushing each response, so I expected each "hello world" 
message to appear one after the other, with one second pause between 
them.

Am I doing something wrong? Is this event the correct way to achieve 
this? All functions return NGX_OK. This is my code:

static ngx_int_t ngx_http_hello_world_handler(ngx_http_request_t *r)
{
     ngx_buf_t *b;
     ngx_chain_t out;
     ngx_int_t result;

     r->headers_out.content_type.len = sizeof("text/html") - 1;
     r->headers_out.content_type.data = (u_char *) "text/html";
     r->headers_out.status = NGX_HTTP_OK;
     //r->headers_out.content_length_n = sizeof(ngx_hello_world);
     ngx_http_send_header(r);

     for(int i = 0; i < 3; i++)
     {
         b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));

         out.buf = b;
         out.next = NULL;

         b->pos = ngx_hello_world;
         b->last = ngx_hello_world + sizeof(ngx_hello_world);
         b->memory = 1;
         b->flush = 1;
         b->last_buf = (i == 2);

         result = ngx_http_output_filter(r, &out);
         ngx_http_send_special(r, NGX_HTTP_FLUSH);

         sleep(1);
     }

     return result;
}

Cheers
Johann