view src/http/modules/ngx_http_not_modified_filter_module.c @ 7985:ec2e6893caaa

Simplified sendfile(SF_NODISKIO) usage. Starting with FreeBSD 11, there is no need to use AIO operations to preload data into cache for sendfile(SF_NODISKIO) to work. Instead, sendfile() handles non-blocking loading data from disk by itself. It still can, however, return EBUSY if a page is already being loaded (for example, by a different process). If this happens, we now post an event for the next event loop iteration, so sendfile() is retried "after a short period", as manpage recommends. The limit of the number of EBUSY tolerated without any progress is preserved, but now it does not result in an alert, since on an idle system event loop iteration might be very short and EBUSY can happen many times in a row. Instead, SF_NODISKIO is simply disabled for one call once the limit is reached. With this change, sendfile(SF_NODISKIO) is now used automatically as long as sendfile() is enabled, and no longer requires "aio on;".
author Maxim Dounin <mdounin@mdounin.ru>
date Mon, 27 Dec 2021 19:48:33 +0300
parents 8b6fa4842133
children
line wrap: on
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


static ngx_uint_t ngx_http_test_if_unmodified(ngx_http_request_t *r);
static ngx_uint_t ngx_http_test_if_modified(ngx_http_request_t *r);
static ngx_uint_t ngx_http_test_if_match(ngx_http_request_t *r,
    ngx_table_elt_t *header, ngx_uint_t weak);
static ngx_int_t ngx_http_not_modified_filter_init(ngx_conf_t *cf);


static ngx_http_module_t  ngx_http_not_modified_filter_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_http_not_modified_filter_init,     /* postconfiguration */

    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */

    NULL,                                  /* create server configuration */
    NULL,                                  /* merge server configuration */

    NULL,                                  /* create location configuration */
    NULL                                   /* merge location configuration */
};


ngx_module_t  ngx_http_not_modified_filter_module = {
    NGX_MODULE_V1,
    &ngx_http_not_modified_filter_module_ctx, /* module context */
    NULL,                                  /* module directives */
    NGX_HTTP_MODULE,                       /* module type */
    NULL,                                  /* init master */
    NULL,                                  /* init module */
    NULL,                                  /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};


static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;


static ngx_int_t
ngx_http_not_modified_header_filter(ngx_http_request_t *r)
{
    if (r->headers_out.status != NGX_HTTP_OK
        || r != r->main
        || r->disable_not_modified)
    {
        return ngx_http_next_header_filter(r);
    }

    if (r->headers_in.if_unmodified_since
        && !ngx_http_test_if_unmodified(r))
    {
        return ngx_http_filter_finalize_request(r, NULL,
                                                NGX_HTTP_PRECONDITION_FAILED);
    }

    if (r->headers_in.if_match
        && !ngx_http_test_if_match(r, r->headers_in.if_match, 0))
    {
        return ngx_http_filter_finalize_request(r, NULL,
                                                NGX_HTTP_PRECONDITION_FAILED);
    }

    if (r->headers_in.if_modified_since || r->headers_in.if_none_match) {

        if (r->headers_in.if_modified_since
            && ngx_http_test_if_modified(r))
        {
            return ngx_http_next_header_filter(r);
        }

        if (r->headers_in.if_none_match
            && !ngx_http_test_if_match(r, r->headers_in.if_none_match, 1))
        {
            return ngx_http_next_header_filter(r);
        }

        /* not modified */

        r->headers_out.status = NGX_HTTP_NOT_MODIFIED;
        r->headers_out.status_line.len = 0;
        r->headers_out.content_type.len = 0;
        ngx_http_clear_content_length(r);
        ngx_http_clear_accept_ranges(r);

        if (r->headers_out.content_encoding) {
            r->headers_out.content_encoding->hash = 0;
            r->headers_out.content_encoding = NULL;
        }

        return ngx_http_next_header_filter(r);
    }

    return ngx_http_next_header_filter(r);
}


static ngx_uint_t
ngx_http_test_if_unmodified(ngx_http_request_t *r)
{
    time_t  iums;

    if (r->headers_out.last_modified_time == (time_t) -1) {
        return 0;
    }

    iums = ngx_parse_http_time(r->headers_in.if_unmodified_since->value.data,
                               r->headers_in.if_unmodified_since->value.len);

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                 "http iums:%T lm:%T", iums, r->headers_out.last_modified_time);

    if (iums >= r->headers_out.last_modified_time) {
        return 1;
    }

    return 0;
}


static ngx_uint_t
ngx_http_test_if_modified(ngx_http_request_t *r)
{
    time_t                     ims;
    ngx_http_core_loc_conf_t  *clcf;

    if (r->headers_out.last_modified_time == (time_t) -1) {
        return 1;
    }

    clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);

    if (clcf->if_modified_since == NGX_HTTP_IMS_OFF) {
        return 1;
    }

    ims = ngx_parse_http_time(r->headers_in.if_modified_since->value.data,
                              r->headers_in.if_modified_since->value.len);

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http ims:%T lm:%T", ims, r->headers_out.last_modified_time);

    if (ims == r->headers_out.last_modified_time) {
        return 0;
    }

    if (clcf->if_modified_since == NGX_HTTP_IMS_EXACT
        || ims < r->headers_out.last_modified_time)
    {
        return 1;
    }

    return 0;
}


static ngx_uint_t
ngx_http_test_if_match(ngx_http_request_t *r, ngx_table_elt_t *header,
    ngx_uint_t weak)
{
    u_char     *start, *end, ch;
    ngx_str_t   etag, *list;

    list = &header->value;

    if (list->len == 1 && list->data[0] == '*') {
        return 1;
    }

    if (r->headers_out.etag == NULL) {
        return 0;
    }

    etag = r->headers_out.etag->value;

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http im:\"%V\" etag:%V", list, &etag);

    if (weak
        && etag.len > 2
        && etag.data[0] == 'W'
        && etag.data[1] == '/')
    {
        etag.len -= 2;
        etag.data += 2;
    }

    start = list->data;
    end = list->data + list->len;

    while (start < end) {

        if (weak
            && end - start > 2
            && start[0] == 'W'
            && start[1] == '/')
        {
            start += 2;
        }

        if (etag.len > (size_t) (end - start)) {
            return 0;
        }

        if (ngx_strncmp(start, etag.data, etag.len) != 0) {
            goto skip;
        }

        start += etag.len;

        while (start < end) {
            ch = *start;

            if (ch == ' ' || ch == '\t') {
                start++;
                continue;
            }

            break;
        }

        if (start == end || *start == ',') {
            return 1;
        }

    skip:

        while (start < end && *start != ',') { start++; }
        while (start < end) {
            ch = *start;

            if (ch == ' ' || ch == '\t' || ch == ',') {
                start++;
                continue;
            }

            break;
        }
    }

    return 0;
}


static ngx_int_t
ngx_http_not_modified_filter_init(ngx_conf_t *cf)
{
    ngx_http_next_header_filter = ngx_http_top_header_filter;
    ngx_http_top_header_filter = ngx_http_not_modified_header_filter;

    return NGX_OK;
}