CACHE_DECLARE(int) ap_cache_check_freshness(cache_handle_t *h,
request_rec *r)
{
apr_int64_t age, maxage_req, maxage_cresp, maxage, smaxage, maxstale;
apr_int64_t minfresh;
int age_in_errhdr = 0;
const char *cc_cresp, *cc_ceresp, *cc_req;
const char *agestr = NULL;
const char *expstr = NULL;
char *val;
apr_time_t age_c = 0;
cache_info *info = &(h->cache_obj->info);
/*
* We now want to check if our cached data is still fresh. This depends
* on a few things, in this order:
*
* - RFC2616 14.9.4 End to end reload, Cache-Control: no-cache. no-cache in
* either the request or the cached response means that we must
* revalidate the request unconditionally, overriding any expiration
* mechanism. It's equivalent to max-age=0,must-revalidate.
*
* - RFC2616 14.32 Pragma: no-cache This is treated the same as
* Cache-Control: no-cache.
*
* - RFC2616 14.9.3 Cache-Control: max-stale, must-revalidate,
* proxy-revalidate if the max-stale request header exists, modify the
* stale calculations below so that an object can be at most <max-stale>
* seconds stale before we request a revalidation, _UNLESS_ a
* must-revalidate or proxy-revalidate cached response header exists to
* stop us doing this.
*
* - RFC2616 14.9.3 Cache-Control: s-maxage the origin server specifies the
* maximum age an object can be before it is considered stale. This
* directive has the effect of proxy|must revalidate, which in turn means
* simple ignore any max-stale setting.
*
* - RFC2616 14.9.4 Cache-Control: max-age this header can appear in both
* requests and responses. If both are specified, the smaller of the two
* takes priority.
*
* - RFC2616 14.21 Expires: if this request header exists in the cached
* entity, and it's value is in the past, it has expired.
*
*/
cc_cresp = apr_table_get(h->resp_hdrs, "Cache-Control");
cc_ceresp = apr_table_get(h->resp_err_hdrs, "Cache-Control");
cc_req = apr_table_get(h->req_hdrs, "Cache-Control");
if ((agestr = apr_table_get(h->resp_hdrs, "Age"))) {
age_c = apr_atoi64(agestr);
}
else if ((agestr = apr_table_get(h->resp_err_hdrs, "Age"))) {
age_c = apr_atoi64(agestr);
age_in_errhdr = 1;
}
if (!(expstr = apr_table_get(h->resp_err_hdrs, "Expires"))) {
expstr = apr_table_get(h->resp_hdrs, "Expires");
}
/* calculate age of object */
age = ap_cache_current_age(info, age_c, r->request_time);
/* extract s-maxage */
if (cc_cresp && ap_cache_liststr(r->pool, cc_cresp, "s-maxage", &val)) {
smaxage = apr_atoi64(val);
}
else if (cc_ceresp && ap_cache_liststr(r->pool, cc_ceresp, "s-maxage", &val)) {
smaxage = apr_atoi64(val);
}
else {
smaxage = -1;
}
/* extract max-age from request */
if (cc_req && ap_cache_liststr(r->pool, cc_req, "max-age", &val)) {
maxage_req = apr_atoi64(val);
}
else {
maxage_req = -1;
}
/* extract max-age from response */
if (cc_cresp && ap_cache_liststr(r->pool, cc_cresp, "max-age", &val)) {
maxage_cresp = apr_atoi64(val);
}
else if (cc_ceresp && ap_cache_liststr(r->pool, cc_ceresp, "max-age", &val)) {
maxage_cresp = apr_atoi64(val);
}
else
{
maxage_cresp = -1;
}
/*
* if both maxage request and response, the smaller one takes priority
*/
if (-1 == maxage_req) {
maxage = maxage_cresp;
}
else if (-1 == maxage_cresp) {
maxage = maxage_req;
}
else {
maxage = MIN(maxage_req, maxage_cresp);
}
/* extract max-stale */
if (cc_req && ap_cache_liststr(r->pool, cc_req, "max-stale", &val)) {
maxstale = apr_atoi64(val);
}
else {
maxstale = 0;
}
/* extract min-fresh */
if (cc_req && ap_cache_liststr(r->pool, cc_req, "min-fresh", &val)) {
minfresh = apr_atoi64(val);
}
else {
minfresh = 0;
}
/* override maxstale if must-revalidate or proxy-revalidate */
if (maxstale && ((cc_cresp &&
ap_cache_liststr(NULL, cc_cresp,
"must-revalidate", NULL)) ||
(cc_cresp &&
ap_cache_liststr(NULL, cc_cresp,
"proxy-revalidate", NULL)) ||
(cc_ceresp &&
ap_cache_liststr(NULL, cc_ceresp,
"must-revalidate", NULL)) ||
(cc_ceresp &&
ap_cache_liststr(NULL, cc_ceresp,
"proxy-revalidate", NULL)))) {
maxstale = 0;
}
/* handle expiration */
if (((smaxage != -1) && (age < (smaxage - minfresh))) ||
((maxage != -1) && (age < (maxage + maxstale - minfresh))) ||
((smaxage == -1) && (maxage == -1) &&
(info->expire != APR_DATE_BAD) &&
(age < (apr_time_sec(info->expire - info->date) + maxstale - minfresh)))) {
const char *warn_head;
apr_table_t *head_ptr;
warn_head = apr_table_get(h->resp_hdrs, "Warning");
if (warn_head != NULL) {
head_ptr = h->resp_hdrs;
}
else {
warn_head = apr_table_get(h->resp_err_hdrs, "Warning");
head_ptr = h->resp_err_hdrs;
}
/* it's fresh darlings... */
/* set age header on response */
if (age_in_errhdr) {
apr_table_set(h->resp_err_hdrs, "Age",
apr_psprintf(r->pool, "%lu", (unsigned long)age));
}
else {
apr_table_set(h->resp_hdrs, "Age",
apr_psprintf(r->pool, "%lu", (unsigned long)age));
}
/* add warning if maxstale overrode freshness calculation */
if (!(((smaxage != -1) && age < smaxage) ||
((maxage != -1) && age < maxage) ||
(info->expire != APR_DATE_BAD &&
(info->expire - info->date) > age))) {
/* make sure we don't stomp on a previous warning */
if ((warn_head == NULL) ||
((warn_head != NULL) && (ap_strstr_c(warn_head, "110") == NULL))) {
apr_table_merge(head_ptr, "Warning", "110 Response is stale");
}
}
/*
* If none of Expires, Cache-Control: max-age, or Cache-Control:
* s-maxage appears in the response, and the respose header age
* calculated is more than 24 hours add the warning 113
*/
if ((maxage_cresp == -1) && (smaxage == -1) &&
(expstr == NULL) && (age > 86400)) {
/* Make sure we don't stomp on a previous warning, and don't dup
* a 113 marning that is already present. Also, make sure to add
* the new warning to the correct *headers_out location.
*/
if ((warn_head == NULL) ||
((warn_head != NULL) && (ap_strstr_c(warn_head, "113") == NULL))) {
apr_table_merge(head_ptr, "Warning", "113 Heuristic expiration");
}
}
return 1; /* Cache object is fresh (enough) */
}
return 0; /* Cache object is stale */
}
CACHE_DECLARE(int) ap_cache_check_freshness(cache_handle_t *h,
request_rec *r)
{
apr_int64_t age, maxage_req, maxage_cresp, maxage, smaxage, maxstale;
apr_int64_t minfresh;
const char *cc_cresp, *cc_req;
const char *pragma;
const char *agestr = NULL;
const char *expstr = NULL;
char *val;
apr_time_t age_c = 0;
cache_info *info = &(h->cache_obj->info);
cache_server_conf *conf =
(cache_server_conf *)ap_get_module_config(r->server->module_config,
&cache_module);
/*
* We now want to check if our cached data is still fresh. This depends
* on a few things, in this order:
*
* - RFC2616 14.9.4 End to end reload, Cache-Control: no-cache. no-cache in
* either the request or the cached response means that we must
* revalidate the request unconditionally, overriding any expiration
* mechanism. It's equivalent to max-age=0,must-revalidate.
*
* - RFC2616 14.32 Pragma: no-cache This is treated the same as
* Cache-Control: no-cache.
*
* - RFC2616 14.9.3 Cache-Control: max-stale, must-revalidate,
* proxy-revalidate if the max-stale request header exists, modify the
* stale calculations below so that an object can be at most <max-stale>
* seconds stale before we request a revalidation, _UNLESS_ a
* must-revalidate or proxy-revalidate cached response header exists to
* stop us doing this.
*
* - RFC2616 14.9.3 Cache-Control: s-maxage the origin server specifies the
* maximum age an object can be before it is considered stale. This
* directive has the effect of proxy|must revalidate, which in turn means
* simple ignore any max-stale setting.
*
* - RFC2616 14.9.4 Cache-Control: max-age this header can appear in both
* requests and responses. If both are specified, the smaller of the two
* takes priority.
*
* - RFC2616 14.21 Expires: if this request header exists in the cached
* entity, and it's value is in the past, it has expired.
*
*/
/* This value comes from the client's initial request. */
cc_req = apr_table_get(r->headers_in, "Cache-Control");
pragma = apr_table_get(r->headers_in, "Pragma");
if (ap_cache_liststr(NULL, pragma, "no-cache", NULL)
|| ap_cache_liststr(NULL, cc_req, "no-cache", NULL)) {
if (!conf->ignorecachecontrol) {
/* Treat as stale, causing revalidation */
return 0;
}
ap_log_error(APLOG_MARK, APLOG_INFO, 0, r->server,
"Incoming request is asking for a uncached version of "
"%s, but we know better and are ignoring it",
r->unparsed_uri);
}
/* These come from the cached entity. */
cc_cresp = apr_table_get(h->resp_hdrs, "Cache-Control");
expstr = apr_table_get(h->resp_hdrs, "Expires");
if (ap_cache_liststr(NULL, cc_cresp, "no-cache", NULL)) {
/*
* The cached entity contained Cache-Control: no-cache, so treat as
* stale causing revalidation
*/
return 0;
}
if ((agestr = apr_table_get(h->resp_hdrs, "Age"))) {
age_c = apr_atoi64(agestr);
}
/* calculate age of object */
age = ap_cache_current_age(info, age_c, r->request_time);
/* extract s-maxage */
if (cc_cresp && ap_cache_liststr(r->pool, cc_cresp, "s-maxage", &val)
&& val != NULL) {
smaxage = apr_atoi64(val);
}
else {
smaxage = -1;
}
/* extract max-age from request */
if (!conf->ignorecachecontrol
&& cc_req && ap_cache_liststr(r->pool, cc_req, "max-age", &val)
&& val != NULL) {
maxage_req = apr_atoi64(val);
}
else {
maxage_req = -1;
}
/* extract max-age from response */
if (cc_cresp && ap_cache_liststr(r->pool, cc_cresp, "max-age", &val)
&& val != NULL) {
maxage_cresp = apr_atoi64(val);
}
else {
maxage_cresp = -1;
}
/*
* if both maxage request and response, the smaller one takes priority
*/
if (maxage_req == -1) {
maxage = maxage_cresp;
}
else if (maxage_cresp == -1) {
maxage = maxage_req;
}
else {
maxage = MIN(maxage_req, maxage_cresp);
}
/* extract max-stale */
if (cc_req && ap_cache_liststr(r->pool, cc_req, "max-stale", &val)) {
if(val != NULL) {
maxstale = apr_atoi64(val);
}
else {
/*
* If no value is assigned to max-stale, then the client is willing
* to accept a stale response of any age (RFC2616 14.9.3). We will
* set it to one year in this case as this situation is somewhat
* similar to a "never expires" Expires header (RFC2616 14.21)
* which is set to a date one year from the time the response is
* sent in this case.
*/
maxstale = APR_INT64_C(86400*365);
}
}
else {
maxstale = 0;
}
/* extract min-fresh */
if (!conf->ignorecachecontrol
&& cc_req && ap_cache_liststr(r->pool, cc_req, "min-fresh", &val)
&& val != NULL) {
minfresh = apr_atoi64(val);
}
else {
minfresh = 0;
}
/* override maxstale if must-revalidate or proxy-revalidate */
if (maxstale && ((cc_cresp &&
ap_cache_liststr(NULL, cc_cresp,
"must-revalidate", NULL)) ||
(cc_cresp &&
ap_cache_liststr(NULL, cc_cresp,
"proxy-revalidate", NULL)))) {
maxstale = 0;
}
/* handle expiration */
if (((smaxage != -1) && (age < (smaxage - minfresh))) ||
((maxage != -1) && (age < (maxage + maxstale - minfresh))) ||
((smaxage == -1) && (maxage == -1) &&
(info->expire != APR_DATE_BAD) &&
(age < (apr_time_sec(info->expire - info->date) + maxstale - minfresh)))) {
const char *warn_head;
warn_head = apr_table_get(h->resp_hdrs, "Warning");
/* it's fresh darlings... */
/* set age header on response */
apr_table_set(h->resp_hdrs, "Age",
apr_psprintf(r->pool, "%lu", (unsigned long)age));
/* add warning if maxstale overrode freshness calculation */
if (!(((smaxage != -1) && age < smaxage) ||
((maxage != -1) && age < maxage) ||
(info->expire != APR_DATE_BAD &&
(apr_time_sec(info->expire - info->date)) > age))) {
/* make sure we don't stomp on a previous warning */
if ((warn_head == NULL) ||
((warn_head != NULL) && (ap_strstr_c(warn_head, "110") == NULL))) {
apr_table_merge(h->resp_hdrs, "Warning",
"110 Response is stale");
}
}
/*
* If none of Expires, Cache-Control: max-age, or Cache-Control:
* s-maxage appears in the response, and the respose header age
* calculated is more than 24 hours add the warning 113
*/
if ((maxage_cresp == -1) && (smaxage == -1) &&
(expstr == NULL) && (age > 86400)) {
/* Make sure we don't stomp on a previous warning, and don't dup
* a 113 marning that is already present. Also, make sure to add
* the new warning to the correct *headers_out location.
*/
if ((warn_head == NULL) ||
((warn_head != NULL) && (ap_strstr_c(warn_head, "113") == NULL))) {
apr_table_merge(h->resp_hdrs, "Warning",
"113 Heuristic expiration");
}
}
return 1; /* Cache object is fresh (enough) */
}
return 0; /* Cache object is stale */
}
int cache_check_freshness(cache_handle_t *h, cache_request_rec *cache,
request_rec *r)
{
apr_status_t status;
apr_int64_t age, maxage_req, maxage_cresp, maxage, smaxage, maxstale;
apr_int64_t minfresh;
const char *cc_req;
const char *pragma;
const char *agestr = NULL;
apr_time_t age_c = 0;
cache_info *info = &(h->cache_obj->info);
const char *warn_head;
cache_server_conf *conf =
(cache_server_conf *)ap_get_module_config(r->server->module_config,
&cache_module);
/*
* We now want to check if our cached data is still fresh. This depends
* on a few things, in this order:
*
* - RFC2616 14.9.4 End to end reload, Cache-Control: no-cache. no-cache
* in either the request or the cached response means that we must
* perform the request unconditionally, and ignore cached content. We
* should never reach here, but if we do, mark the content as stale,
* as this is the best we can do.
*
* - RFC2616 14.32 Pragma: no-cache This is treated the same as
* Cache-Control: no-cache.
*
* - RFC2616 14.9.3 Cache-Control: max-stale, must-revalidate,
* proxy-revalidate if the max-stale request header exists, modify the
* stale calculations below so that an object can be at most <max-stale>
* seconds stale before we request a revalidation, _UNLESS_ a
* must-revalidate or proxy-revalidate cached response header exists to
* stop us doing this.
*
* - RFC2616 14.9.3 Cache-Control: s-maxage the origin server specifies the
* maximum age an object can be before it is considered stale. This
* directive has the effect of proxy|must revalidate, which in turn means
* simple ignore any max-stale setting.
*
* - RFC2616 14.9.4 Cache-Control: max-age this header can appear in both
* requests and responses. If both are specified, the smaller of the two
* takes priority.
*
* - RFC2616 14.21 Expires: if this request header exists in the cached
* entity, and it's value is in the past, it has expired.
*
*/
/* This value comes from the client's initial request. */
cc_req = apr_table_get(r->headers_in, "Cache-Control");
pragma = apr_table_get(r->headers_in, "Pragma");
ap_cache_control(r, &cache->control_in, cc_req, pragma, r->headers_in);
if (cache->control_in.no_cache) {
if (!conf->ignorecachecontrol) {
/* Treat as stale, causing revalidation */
return 0;
}
ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(00781)
"Incoming request is asking for a uncached version of "
"%s, but we have been configured to ignore it and "
"serve a cached response anyway",
r->unparsed_uri);
}
/* These come from the cached entity. */
if (h->cache_obj->info.control.no_cache
|| h->cache_obj->info.control.invalidated) {
/*
* The cached entity contained Cache-Control: no-cache, or a
* no-cache with a header present, or a private with a header
* present, or the cached entity has been invalidated in the
* past, so treat as stale causing revalidation.
*/
return 0;
}
if ((agestr = apr_table_get(h->resp_hdrs, "Age"))) {
char *endp;
apr_off_t offt;
if (!apr_strtoff(&offt, agestr, &endp, 10)
&& endp > agestr && !*endp) {
age_c = offt;
}
}
/* calculate age of object */
age = ap_cache_current_age(info, age_c, r->request_time);
/* extract s-maxage */
smaxage = h->cache_obj->info.control.s_maxage_value;
/* extract max-age from request */
maxage_req = -1;
if (!conf->ignorecachecontrol) {
maxage_req = cache->control_in.max_age_value;
}
/*
* extract max-age from response, if both s-maxage and max-age, s-maxage
* takes priority
*/
if (smaxage != -1) {
maxage_cresp = smaxage;
}
else {
maxage_cresp = h->cache_obj->info.control.max_age_value;
}
/*
* if both maxage request and response, the smaller one takes priority
*/
if (maxage_req == -1) {
maxage = maxage_cresp;
}
else if (maxage_cresp == -1) {
maxage = maxage_req;
}
else {
maxage = MIN(maxage_req, maxage_cresp);
}
/* extract max-stale */
if (cache->control_in.max_stale) {
if(cache->control_in.max_stale_value != -1) {
maxstale = cache->control_in.max_stale_value;
}
else {
/*
* If no value is assigned to max-stale, then the client is willing
* to accept a stale response of any age (RFC2616 14.9.3). We will
* set it to one year in this case as this situation is somewhat
* similar to a "never expires" Expires header (RFC2616 14.21)
* which is set to a date one year from the time the response is
* sent in this case.
*/
maxstale = APR_INT64_C(86400*365);
}
}
else {
maxstale = 0;
}
/* extract min-fresh */
if (!conf->ignorecachecontrol && cache->control_in.min_fresh) {
minfresh = cache->control_in.min_fresh_value;
}
else {
minfresh = 0;
}
/* override maxstale if must-revalidate, proxy-revalidate or s-maxage */
if (maxstale && (h->cache_obj->info.control.must_revalidate
|| h->cache_obj->info.control.proxy_revalidate || smaxage != -1)) {
maxstale = 0;
}
/* handle expiration */
if (((maxage != -1) && (age < (maxage + maxstale - minfresh))) ||
((smaxage == -1) && (maxage == -1) &&
(info->expire != APR_DATE_BAD) &&
(age < (apr_time_sec(info->expire - info->date) + maxstale - minfresh)))) {
warn_head = apr_table_get(h->resp_hdrs, "Warning");
/* it's fresh darlings... */
/* set age header on response */
apr_table_set(h->resp_hdrs, "Age",
apr_psprintf(r->pool, "%lu", (unsigned long)age));
/* add warning if maxstale overrode freshness calculation */
if (!(((maxage != -1) && age < maxage) ||
(info->expire != APR_DATE_BAD &&
(apr_time_sec(info->expire - info->date)) > age))) {
/* make sure we don't stomp on a previous warning */
if ((warn_head == NULL) ||
((warn_head != NULL) && (ap_strstr_c(warn_head, "110") == NULL))) {
apr_table_mergen(h->resp_hdrs, "Warning",
"110 Response is stale");
}
}
/*
* If none of Expires, Cache-Control: max-age, or Cache-Control:
* s-maxage appears in the response, and the response header age
* calculated is more than 24 hours add the warning 113
*/
if ((maxage_cresp == -1) && (smaxage == -1) && (apr_table_get(
h->resp_hdrs, "Expires") == NULL) && (age > 86400)) {
/* Make sure we don't stomp on a previous warning, and don't dup
* a 113 marning that is already present. Also, make sure to add
* the new warning to the correct *headers_out location.
*/
if ((warn_head == NULL) ||
((warn_head != NULL) && (ap_strstr_c(warn_head, "113") == NULL))) {
apr_table_mergen(h->resp_hdrs, "Warning",
"113 Heuristic expiration");
}
}
return 1; /* Cache object is fresh (enough) */
}
/*
* At this point we are stale, but: if we are under load, we may let
* a significant number of stale requests through before the first
* stale request successfully revalidates itself, causing a sudden
* unexpected thundering herd which in turn brings angst and drama.
*
* So.
*
* We want the first stale request to go through as normal. But the
* second and subsequent request, we must pretend to be fresh until
* the first request comes back with either new content or confirmation
* that the stale content is still fresh.
*
* To achieve this, we create a very simple file based lock based on
* the key of the cached object. We attempt to open the lock file with
* exclusive write access. If we succeed, woohoo! we're first, and we
* follow the stale path to the backend server. If we fail, oh well,
* we follow the fresh path, and avoid being a thundering herd.
*
* The lock lives only as long as the stale request that went on ahead.
* If the request succeeds, the lock is deleted. If the request fails,
* the lock is deleted, and another request gets to make a new lock
* and try again.
*
* At any time, a request marked "no-cache" will force a refresh,
* ignoring the lock, ensuring an extended lockout is impossible.
*
* A lock that exceeds a maximum age will be deleted, and another
* request gets to make a new lock and try again.
*/
status = cache_try_lock(conf, cache, r);
if (APR_SUCCESS == status) {
/* we obtained a lock, follow the stale path */
ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(00782)
"Cache lock obtained for stale cached URL, "
"revalidating entry: %s",
r->unparsed_uri);
return 0;
}
else if (APR_STATUS_IS_EEXIST(status)) {
/* lock already exists, return stale data anyway, with a warning */
ap_log_rerror(APLOG_MARK, APLOG_DEBUG, status, r, APLOGNO(00783)
"Cache already locked for stale cached URL, "
"pretend it is fresh: %s",
r->unparsed_uri);
/* make sure we don't stomp on a previous warning */
warn_head = apr_table_get(h->resp_hdrs, "Warning");
if ((warn_head == NULL) ||
((warn_head != NULL) && (ap_strstr_c(warn_head, "110") == NULL))) {
apr_table_mergen(h->resp_hdrs, "Warning",
"110 Response is stale");
}
return 1;
}
else {
/* some other error occurred, just treat the object as stale */
ap_log_rerror(APLOG_MARK, APLOG_DEBUG, status, r, APLOGNO(00784)
"Attempt to obtain a cache lock for stale "
"cached URL failed, revalidating entry anyway: %s",
r->unparsed_uri);
return 0;
}
}
