Add cache_methods directive: cache the specified request methods only. (#504)

Related to issue #494.

Author: keshonok

README.md

@@ -78,7 +78,8 @@ The file location is determined by the `TFW_CFG_PATH` environment variable:
 
 By default, the `tempesta_fw.conf` from this directory is used.
 
-See `tempesta_fw.conf` for the list of available options and their descriptions.
+See `tempesta_fw.conf` for the list of available configuration directives,
+options and their descriptions.
 
 
 ### Listening address
@@ -126,7 +127,7 @@ keepalive_timeout 75;
 ### Caching
 
 Tempesta caches Web-content by default, i.e. works as reverse proxy.
-Configuration option `cache` manages the cache befavior:
+Configuration directive `cache` manages the cache befavior:
 
 * `0` - no caching at all, pure proxying mode;
 * `1` - cache sharding when each NUMA node contains independent shard
@@ -152,6 +153,17 @@ yet) of each Tempesta DB file used as Web cache storage. The size must be
 multiple of 2MB (Tempesta DB extent size). Default value is `268435456`
 (256MB).
 
+`cache_methods` specifies the list of cacheable request methods. Responses
+to requests with these methods will be cached. If this directive is skipped,
+then the default cacheable request method is `GET`. Note that not all of
+HTTP request methods are cacheable by the HTTP standards. Besides, some
+request methods may be cachable only when certain additional restrictions
+are satisfied. Also, note that not all HTTP request methods may be supported
+by Tempesta at this time. Below is an example of this directive:
+```
+cache_methods GET HEAD;
+```
+
 
 ### Server Load Balancing
 
@@ -320,8 +332,8 @@ HTTP requests from a client. Default behaviour is that Tempesta sticky cookies
 are not used.
 
 The use and behaviour of Tempesta sticky cookies is controlled by a single
-configuration option that can have several parameters. The full form of
-the option and parameters is as follows:
+configuration directive that can have several parameters. The full form of
+the directive and parameters is as follows:
 ```
 sticky [name=<COOKIE_NAME>] [enforce];
 ```
@@ -336,7 +348,7 @@ response from Tempesta that redirects the client to the same URI, and prompts
 that Tempesta sticky cookie is set in requests from the client.
 
 
-Below are examples of Tempesta sticky cookie option.
+Below are examples of Tempesta sticky cookie directive.
 
 * **sticky;**
 Enable Tempesta sticky cookie. Default cookie name is used. Tempesta expects

tempesta_fw/cache.c

@@ -97,6 +97,7 @@ typedef struct {
 
 static struct {
 	int cache;
+	unsigned int methods;
 	unsigned int db_size;
 	const char *db_path;
 } cache_cfg __read_mostly;
@@ -158,6 +159,38 @@ static TfwStr g_crlf = { .ptr = S_CRLF, .len = SLEN(S_CRLF) };
 	}								\
 	for ( ; c != h_end; ++c, c = (c == u_end) ? h_start : c)
 
+/*
+ * The mask of non-cacheable methods per RFC 7231 4.2.3.
+ * Currently none of the non-cacheable methods are supported.
+ * Note: POST method is cacheable but not supported at this time.
+ */
+static unsigned int tfw_cache_nc_methods = (1 << TFW_HTTP_METH_POST);
+
+static inline bool
+__cache_method_nc_test(tfw_http_meth_t method)
+{
+	return tfw_cache_nc_methods & (1 << method);
+}
+
+static inline void
+__cache_method_add(tfw_http_meth_t method)
+{
+	cache_cfg.methods |= (1 << method);
+}
+
+static inline bool
+__cache_method_test(tfw_http_meth_t method)
+{
+	return cache_cfg.methods & (1 << method);
+}
+
+static inline bool
+tfw_cache_msg_cacheable(TfwHttpReq *req)
+{
+	return __cache_method_test(req->method);
+}
+
+
 static bool
 tfw_cache_entry_key_eq(TDB *db, TfwHttpReq *req, TfwCacheEntry *ce)
 {
@@ -535,7 +568,7 @@ tfw_cache_add(TfwHttpResp *resp, TfwHttpReq *req)
 {
 	unsigned long key;
 
-	if (!cache_cfg.cache)
+	if (!cache_cfg.cache || !tfw_cache_msg_cacheable(req))
 		return true;
 
 	key = tfw_http_req_key_calc(req);
@@ -575,7 +608,7 @@ tfw_cache_process(TfwHttpReq *req, TfwHttpResp *resp,
 	TfwWorkTasklet *ct;
 	TfwCWork cw;
 
-	if (!cache_cfg.cache) {
+	if (!cache_cfg.cache || !tfw_cache_msg_cacheable(req)) {
 		action(req, resp);
 		return 0;
 	}
@@ -942,13 +975,56 @@ tfw_cache_stop(void)
 		tdb_close(c_nodes[i].db);
 }
 
+static int
+tfw_cache_cfg_method(TfwCfgSpec *cs, TfwCfgEntry *ce)
+{
+	unsigned int i, method;
+	const char *val;
+
+	BUILD_BUG_ON(sizeof(cache_cfg.methods) * 8 < _TFW_HTTP_METH_COUNT);
+
+	TFW_CFG_ENTRY_FOR_EACH_VAL(ce, i, val) {
+		if (!strcasecmp(val, "GET")) {
+			method = TFW_HTTP_METH_GET;
+		} else if (!strcasecmp(val, "HEAD")) {
+			method = TFW_HTTP_METH_HEAD;
+		} else if (!strcasecmp(val, "POST")) {
+			method = TFW_HTTP_METH_POST;
+		} else {
+			TFW_ERR("%s: unsupported method: '%s'\n",
+				cs->name, val);
+			return -EINVAL;
+		}
+		if (__cache_method_nc_test(method)) {
+			TFW_ERR("%s: non-cacheable method: '%s'\n",
+				cs->name, val);
+			return -EINVAL;
+		}
+		if (__cache_method_test(method)) {
+			TFW_WARN("%s: duplicate method: '%s'\n",
+				 cs->name, val);
+			continue;
+		}
+		__cache_method_add(method);
+	}
+
+	return 0;
+}
+
 static TfwCfgSpec tfw_cache_cfg_specs[] = {
 	{
 		"cache",
 		"2",
 		tfw_cfg_set_int,
 		&cache_cfg.cache
 	},
+	{
+		"cache_methods",
+		"GET",
+		tfw_cache_cfg_method,
+		.allow_none = true,
+		.allow_repeat = false,
+	},
 	{
 		"cache_size",
 		"268435456",

tempesta_fw/http.h

@@ -260,7 +260,7 @@ typedef struct {
 	TfwStr			userinfo;
 	TfwStr			host;
 	TfwStr			uri_path;
-	unsigned char		method;
+	tfw_http_meth_t		method;
 	unsigned short		node;
 	unsigned int		frang_st;
 	unsigned int		chunk_cnt;