Fix memory allocate during request processing

Before introducing a txn memory region box_txn_alloc()
allocates memory using the fiber.gc region and can be
used without box_txn_begin(). Now the similar trick
doesn't work (a transaction must be started).
To allocate memory on region without start a transaction,
the region was added to struct memcached_connection.

Fixes #53

Author: LeonidVas

memcached/internal/memcached.c

@@ -78,6 +78,17 @@ memcached_flush(struct memcached_connection *con) {
 	return total;
 }
 
+static void
+memcached_connection_gc(struct memcached_connection *con)
+{
+	if (region_used(&con->gc) < 128 * 1024) {
+		region_reset(&con->gc);
+		return;
+	}
+
+	region_free(&con->gc);
+}
+
 static inline int
 memcached_loop_read(struct memcached_connection *con, size_t to_read)
 {
@@ -176,7 +187,10 @@ memcached_loop(struct memcached_connection *con)
 		}
 		assert(!con->close_connection);
 		rc = 0;
-		if (!con->noprocess) rc = con->cb.process_request(con);
+		if (!con->noprocess) {
+			rc = con->cb.process_request(con);
+			memcached_connection_gc(con);
+		}
 		con->write_end = obuf_create_svp(con->out);
 		memcached_skip_request(con);
 		if (rc == -1)
@@ -233,6 +247,8 @@ memcached_handler(struct memcached_service *p, int fd)
 		assert(0); /* unreacheable */
 	}
 
+	region_create(&con.gc, cord_slab_cache());
+
 	/* read-write cycle */
 	con.cfg->stat.curr_conns++;
 	con.cfg->stat.total_conns++;
@@ -242,6 +258,7 @@ memcached_handler(struct memcached_service *p, int fd)
 	iobuf_delete(con.in, con.out);
 	memcached_sasl_connection_destroy(&con);
 	free((void *)con.sasl_ctx);
+	region_destroy(&con.gc);
 	const box_error_t *err = box_error_last();
 	if (err)
 		say_error("%s", box_error_message(err));

memcached/internal/memcached.h

@@ -11,6 +11,7 @@
 
 
 #include <small/obuf.h>
+#include <small/region.h>
 #include "constants.h"
 
 struct memcached_connection;
@@ -142,6 +143,8 @@ struct memcached_connection {
 		memcached_loop_func_t     process_request;
 		memcached_error_func_t    process_error;
 	} cb; /* protocol specific callbacks */
+	/* A garbage collected memory pool used in request processing. */
+	struct region gc;
 };
 
 struct memcached_stat *

memcached/internal/memcached_layer.c

@@ -71,7 +71,7 @@ memcached_tuple_set(struct memcached_connection *con,
 		       mp_sizeof_str  (vlen)   +
 		       mp_sizeof_uint (cas)    +
 		       mp_sizeof_uint (flags);
-	char *begin  = (char *)box_txn_alloc(len);
+	char *begin = (char *)region_alloc(&con->gc, len);
 	if (begin == NULL) {
 		memcached_error_ENOMEM(len, "tuple");
 		return -1;
@@ -95,7 +95,7 @@ memcached_tuple_get(struct memcached_connection *con,
 	/* Create key for getting previous tuple from space */
 	uint32_t len = mp_sizeof_array(1) +
 		       mp_sizeof_str  (key_len);
-	char *begin  = (char *)box_txn_alloc(len);
+	char *begin = (char *)region_alloc(&con->gc, len);
 	if (begin == NULL) {
 		memcached_error_ENOMEM(len, "key");
 		return -1;

memcached/internal/proto_bin.c

@@ -324,7 +324,7 @@ memcached_bin_process_delete(struct memcached_connection *con)
 	con->cfg->stat.cmd_delete++;
 	uint32_t len = mp_sizeof_array(1) +
 		       mp_sizeof_str  (b->key_len);
-	char *begin = (char *)box_txn_alloc(len);
+	char *begin = (char *)region_alloc(&con->gc, len);
 	if (begin == NULL) {
 		memcached_error_ENOMEM(len, "key");
 		return -1;
@@ -682,7 +682,7 @@ memcached_bin_process_pend(struct memcached_connection *con)
 	mp_next(&pos); /* skip cas */
 	flags            = mp_decode_uint(&pos);
 
-	char *begin = (char *)box_txn_alloc(b->val_len + vlen);
+	char *begin = (char *)region_alloc(&con->gc, b->val_len + vlen);
 	if (begin == NULL) {
 		memcached_error_ENOMEM(b->val_len + vlen, "value");
 		return -1;

memcached/internal/proto_txt.c

@@ -288,7 +288,7 @@ memcached_txt_process_pend(struct memcached_connection *con)
 	mp_next(&pos); /* skip cas */
 	flags            = mp_decode_uint(&pos);
 
-	char *begin = (char *)box_txn_alloc(data_len + vlen);
+	char *begin = (char *)region_alloc(&con->gc, data_len + vlen);
 	if (begin == NULL) {
 		memcached_error_ENOMEM(data_len + vlen, "value");
 		return -1;
@@ -322,7 +322,7 @@ memcached_txt_process_delete(struct memcached_connection *con)
 	con->cfg->stat.cmd_delete++;
 	uint32_t len = mp_sizeof_array(1) +
 		       mp_sizeof_str  (key_len);
-	char *begin = (char *)box_txn_alloc(len);
+	char *begin = (char *)region_alloc(&con->gc, len);
 	if (begin == NULL) {
 		memcached_error_ENOMEM(len, "key");
 		return -1;