[PATCH 2/2] ttl: Support different TTL times based on cache-control

[john at keeping.me.uk (John Keeping)]

On Fri, Feb 26, 2016 at 02:57:09PM -0600, Tim Nordell wrote:
> Allow the client browser to pass in "max-age=0" and "no-cache"
> to control a separate TTL time on the server for each type of
> page.  This extends the TTL field to have the additional form
> of:
> 
>     some-ttl=5:1
> 
> where 5 is the number of minutes if the user were to simply
> load the page, and 1 is the number of minutes if the user were
> to reload the page in their web browser (hit refresh).

Firefox seems to always send "max-age=0" when it has its own cached data
(along with an If-Modified-Since header).  I don't think we want to use
the forced value when the user's browser has an existing cached value.

Overall I'm not convinced CGit should be dealing with this, for advanced
caching isn't it better to stick Varnish or nginx in front of CGit.

> Signed-off-by: Tim Nordell <tim.nordell at logicpd.com>
> 
> diff --git a/cgit.c b/cgit.c
> index 963aee8..0ca1baa 100644
> --- a/cgit.c
> +++ b/cgit.c
> @@ -29,6 +29,30 @@ static void add_mimetype(const char *name, const char *value)
>  
>  static void process_cached_repolist(const char *path);
>  
> +/**
> + * \brief Convert TTL field into a TTL structure
> + *
> + * \param value Value from field; should be one of the following forms:
> + *                      [normal]
> + *                      [normal]:[forced]
> + * \return Parsed TTL value
> + */
> +static struct cgit_ttl ttl_value(const char *value)
> +{
> +	char *param2;
> +	struct cgit_ttl ret;
> +
> +	ret.normal = atoi(value);
> +
> +	param2 = strchr(value, ':');
> +	if(NULL != param2)
> +		ret.forced = atoi(&param2[1]);
> +	else
> +		ret.forced = -1;
> +
> +	return ret;
> +}
> +
>  static void repo_config(struct cgit_repo *repo, const char *name, const char *value)
>  {
>  	struct string_list_item *item;
> @@ -187,19 +211,19 @@ static void config_cb(const char *name, const char *value)
>  	else if (!strcmp(name, "cache-root"))
>  		ctx.cfg.cache_root = xstrdup(expand_macros(value));
>  	else if (!strcmp(name, "cache-root-ttl"))
> -		ctx.cfg.cache_root_ttl = atoi(value);
> +		ctx.cfg.cache_root_ttl = ttl_value(value);
>  	else if (!strcmp(name, "cache-repo-ttl"))
> -		ctx.cfg.cache_repo_ttl = atoi(value);
> +		ctx.cfg.cache_repo_ttl = ttl_value(value);
>  	else if (!strcmp(name, "cache-scanrc-ttl"))
>  		ctx.cfg.cache_scanrc_ttl = atoi(value);
>  	else if (!strcmp(name, "cache-static-ttl"))
> -		ctx.cfg.cache_static_ttl = atoi(value);
> +		ctx.cfg.cache_static_ttl = ttl_value(value);
>  	else if (!strcmp(name, "cache-dynamic-ttl"))
> -		ctx.cfg.cache_dynamic_ttl = atoi(value);
> +		ctx.cfg.cache_dynamic_ttl = ttl_value(value);
>  	else if (!strcmp(name, "cache-about-ttl"))
> -		ctx.cfg.cache_about_ttl = atoi(value);
> +		ctx.cfg.cache_about_ttl = ttl_value(value);
>  	else if (!strcmp(name, "cache-snapshot-ttl"))
> -		ctx.cfg.cache_snapshot_ttl = atoi(value);
> +		ctx.cfg.cache_snapshot_ttl = ttl_value(value);
>  	else if (!strcmp(name, "case-sensitive-sort"))
>  		ctx.cfg.case_sensitive_sort = atoi(value);
>  	else if (!strcmp(name, "about-filter"))
> @@ -352,13 +376,19 @@ static void prepare_context(void)
>  	ctx.cfg.cache_size = 0;
>  	ctx.cfg.cache_max_create_time = 5;
>  	ctx.cfg.cache_root = CGIT_CACHE_ROOT;
> -	ctx.cfg.cache_about_ttl = 15;
> -	ctx.cfg.cache_snapshot_ttl = 5;
> -	ctx.cfg.cache_repo_ttl = 5;
> -	ctx.cfg.cache_root_ttl = 5;
> +	ctx.cfg.cache_about_ttl.normal = 15;
> +	ctx.cfg.cache_about_ttl.forced = -1;
> +	ctx.cfg.cache_snapshot_ttl.normal = 5;
> +	ctx.cfg.cache_snapshot_ttl.forced = -1;
> +	ctx.cfg.cache_repo_ttl.normal = 5;
> +	ctx.cfg.cache_repo_ttl.forced = -1;
> +	ctx.cfg.cache_root_ttl.normal = 5;
> +	ctx.cfg.cache_root_ttl.forced = -1;
>  	ctx.cfg.cache_scanrc_ttl = 15;
> -	ctx.cfg.cache_dynamic_ttl = 5;
> -	ctx.cfg.cache_static_ttl = -1;
> +	ctx.cfg.cache_dynamic_ttl.normal = 5;
> +	ctx.cfg.cache_dynamic_ttl.forced = -1;
> +	ctx.cfg.cache_static_ttl.normal = -1;
> +	ctx.cfg.cache_static_ttl.forced = -1;
>  	ctx.cfg.case_sensitive_sort = 1;
>  	ctx.cfg.branch_sort = 0;
>  	ctx.cfg.commit_sort = 0;
> @@ -405,6 +435,7 @@ static void prepare_context(void)
>  	ctx.env.server_port = getenv("SERVER_PORT");
>  	ctx.env.http_cookie = getenv("HTTP_COOKIE");
>  	ctx.env.http_referer = getenv("HTTP_REFERER");
> +	ctx.env.http_cache_control = getenv("HTTP_CACHE_CONTROL");
>  	ctx.env.content_length = getenv("CONTENT_LENGTH") ? strtoul(getenv("CONTENT_LENGTH"), NULL, 10) : 0;
>  	ctx.env.authenticated = 0;
>  	ctx.page.mimetype = "text/html";
> @@ -1006,7 +1037,7 @@ static void cgit_parse_args(int argc, const char **argv)
>  static int calc_ttl(void)
>  {
>  	const int ttl_conversion_multiplier = 60;
> -	int ttl;
> +	struct cgit_ttl ttl;
>  
>  	if (!ctx.repo)
>  		ttl = ctx.cfg.cache_root_ttl;
> @@ -1023,8 +1054,14 @@ static int calc_ttl(void)
>  	else
>  		ttl = ctx.cfg.cache_repo_ttl;
>  
> -	if (ttl >= 0)
> -		return ttl * ttl_conversion_multiplier;
> +	if(ttl.forced >= 0 && NULL != ctx.env.http_cache_control &&
> +	    (!strcmp(ctx.env.http_cache_control, "max-age=0") ||
> +	     !strcmp(ctx.env.http_cache_control, "no-cache"))
> +	  )
> +		return ttl.forced * ttl_conversion_multiplier;
> +
> +	if (ttl.normal >= 0)
> +		return ttl.normal * ttl_conversion_multiplier;
>  
>  	return 10 * 365 * 24 * 60 * 60; /* 10 years */
>  }
> diff --git a/cgit.h b/cgit.h
> index 325432b..350d25d 100644
> --- a/cgit.h
> +++ b/cgit.h
> @@ -185,6 +185,11 @@ struct cgit_query {
>  	char *vpath;
>  };
>  
> +struct cgit_ttl {
> +	int normal;
> +	int forced;
> +};
> +
>  struct cgit_config {
>  	char *agefile;
>  	char *cache_root;
> @@ -213,14 +218,14 @@ struct cgit_config {
>  	char *virtual_root;	/* Always ends with '/'. */
>  	char *strict_export;
>  	int cache_size;
> -	int cache_dynamic_ttl;
>  	int cache_max_create_time;
> -	int cache_repo_ttl;
> -	int cache_root_ttl;
>  	int cache_scanrc_ttl;
> -	int cache_static_ttl;
> -	int cache_about_ttl;
> -	int cache_snapshot_ttl;
> +	struct cgit_ttl cache_root_ttl;
> +	struct cgit_ttl cache_repo_ttl;
> +	struct cgit_ttl cache_about_ttl;
> +	struct cgit_ttl cache_static_ttl;
> +	struct cgit_ttl cache_dynamic_ttl;
> +	struct cgit_ttl cache_snapshot_ttl;
>  	int case_sensitive_sort;
>  	int embedded;
>  	int enable_filter_overrides;
> @@ -295,6 +300,7 @@ struct cgit_environment {
>  	const char *server_port;
>  	const char *http_cookie;
>  	const char *http_referer;
> +	const char *http_cache_control;
>  	unsigned int content_length;
>  	int authenticated;
>  };
> diff --git a/ui-shared.c b/ui-shared.c
> index 9a38aa9..2ab2fd9 100644
> --- a/ui-shared.c
> +++ b/ui-shared.c
> @@ -789,7 +789,7 @@ void cgit_print_docend(void)
>  void cgit_print_error_page(int code, const char *msg, const char *fmt, ...)
>  {
>  	va_list ap;
> -	ctx.page.expires = ctx.cfg.cache_dynamic_ttl;
> +	ctx.page.expires = ctx.cfg.cache_dynamic_ttl.normal;
>  	ctx.page.status = code;
>  	ctx.page.statusmsg = msg;
>  	cgit_print_http_headers();
> -- 
> 2.4.9
> 
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