Mercurial > hg > nginx
view src/http/modules/ngx_http_not_modified_filter_module.c @ 7281:bd6563e81cea
Limit req: improved handling of negative times.
Negative times can appear since workers only update time on an event
loop iteration start. If a worker was blocked for a long time during
an event loop iteration, it is possible that another worker already
updated the time stored in the node. As such, time since last update
of the node (ms) will be negative.
Previous code used ngx_abs(ms) in the calculations. That is, negative
times were effectively treated as positive ones. As a result, it was
not possible to maintain high request rates, where the same node can be
updated multiple times from during an event loop iteration.
In particular, this affected setups with many SSL handshakes, see
http://mailman.nginx.org/pipermail/nginx/2018-May/056291.html.
Fix is to only update the last update time stored in the node if the
new time is larger than previously stored one. If a future time is
stored in the node, we preserve this time as is.
To prevent breaking things on platforms without monotonic time available
if system time is updated backwards, a safety limit of 60 seconds is
used. If the time stored in the node is more than 60 seconds in the future,
we assume that the time was changed backwards and update lr->last
to the current time.
author | Maxim Dounin <mdounin@mdounin.ru> |
---|---|
date | Wed, 30 May 2018 15:40:34 +0300 |
parents | 8b6fa4842133 |
children |
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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; }