cache: resolution-persistent r/w transactions

this is a little hacked, I'd like to do list of nested
transactions later and short-lived read transactions.

knot-resolver.files

@@ -22,5 +22,7 @@ lib/rplan.c
 lib/layer/stats.h
 lib/layer/stats.c
 lib/defines.h
+lib/layer/itercache.h
+lib/layer/itercache.c
 lib/cache.h
 lib/cache.c

knot-resolver.includes

 .
-include
\ No newline at end of file
+include
+lib/layer
+lib

lib/cache.c

@@ -20,6 +20,7 @@ struct kr_cache
 struct kr_txn
 {
 	MDB_dbi dbi;
+	unsigned flags;
 	MDB_txn *txn;
 	MDB_txn *parent;
 	mm_ctx_t *mm;
@@ -233,7 +234,7 @@ void kr_cache_close(struct kr_cache *cache)
 	mm_free(cache->pool, cache);
 }
 
-struct kr_txn *kr_cache_txn_begin(struct kr_cache *cache, struct kr_txn *parent, mm_ctx_t *mm)
+struct kr_txn *kr_cache_txn_begin(struct kr_cache *cache, struct kr_txn *parent, unsigned flags, mm_ctx_t *mm)
 {
 	struct kr_txn *txn = mm_alloc(mm, sizeof(struct kr_txn));
 	if (txn == NULL) {
@@ -247,7 +248,13 @@ struct kr_txn *kr_cache_txn_begin(struct kr_cache *cache, struct kr_txn *parent,
 		txn->parent = parent->txn;
 	}
 
-	int ret = mdb_txn_begin(cache->env, txn->parent, 0, &txn->txn);
+	unsigned mdb_flags = 0;
+	txn->flags = flags;
+	if (flags & KR_CACHE_RDONLY) {
+	   mdb_flags |= MDB_RDONLY;
+	}	   
+
+	int ret = mdb_txn_begin(cache->env, txn->parent, mdb_flags, &txn->txn);
 	if (ret != 0) {
 		mm_free(mm, txn);
 		return NULL;
@@ -256,7 +263,7 @@ struct kr_txn *kr_cache_txn_begin(struct kr_cache *cache, struct kr_txn *parent,
 #ifndef NDEBUG
 	MDB_stat stat;
 	mdb_stat(txn->txn, txn->dbi, &stat);
-	DEBUG_MSG("TX_BEGIN, %zu entries\n", stat.ms_entries);
+	DEBUG_MSG("TX_BEGIN, flags=%u, %zu entries\n", flags, stat.ms_entries);
 #endif
 
 	return txn;

lib/cache.h

@@ -17,16 +17,21 @@ limitations under the License.
 
 #include <libknot/rrset.h>
 
+enum kr_cache_flag {
+	KR_CACHE_NOFLAG = 0,
+	KR_CACHE_RDONLY = 1 << 0
+};
+
 struct kr_cache;
 struct kr_txn;
 
 struct kr_cache *kr_cache_open(const char *handle, unsigned flags, mm_ctx_t *mm);
 void kr_cache_close(struct kr_cache *cache);
 
-struct kr_txn *kr_cache_txn_begin(struct kr_cache *cache, struct kr_txn *parent, mm_ctx_t *mm);
+struct kr_txn *kr_cache_txn_begin(struct kr_cache *cache, struct kr_txn *parent, unsigned flags, mm_ctx_t *mm);
 int kr_cache_txn_commit(struct kr_txn *txn);
 void kr_cache_txn_abort(struct kr_txn *txn);
 
 int kr_cache_query(struct kr_txn *txn, knot_rrset_t *rr);
 int kr_cache_insert(struct kr_txn *txn, const knot_rrset_t *rr, unsigned flags);
-int kr_cache_remove(struct kr_txn *txn, const knot_rrset_t *rr);
\ No newline at end of file
+int kr_cache_remove(struct kr_txn *txn, const knot_rrset_t *rr);

lib/context.c

@@ -21,10 +21,20 @@ int kr_context_init(struct kr_context *ctx, mm_ctx_t *mm)
 
 int kr_context_reset(struct kr_context *ctx)
 {
+	/* Finalize transactions. */
+	if (ctx->txn.write) {
+		kr_cache_txn_commit(ctx->txn.write);
+	}
+	if (ctx->txn.read) {
+		kr_cache_txn_abort(ctx->txn.read);
+	}
+
 	ctx->state = 0;
 	ctx->resolved_qry = NULL;
 	ctx->current_ns = NULL;
 	ctx->query = NULL;
+	ctx->txn.read = NULL;
+	ctx->txn.write = NULL;
 	kr_rplan_clear(&ctx->rplan);
 
 	return 0;
@@ -38,12 +48,29 @@ int kr_context_deinit(struct kr_context *ctx)
 	return -1;
 }
 
+struct kr_txn *kr_context_txn_acquire(struct kr_context *ctx, unsigned flags)
+{
+	struct kr_txn **txn = &ctx->txn.write;
+	if (flags & KR_CACHE_RDONLY) {
+		txn = &ctx->txn.read;	
+	}
+
+	if (*txn != NULL) {
+		return *txn;
+	}
+
+	return *txn = kr_cache_txn_begin(ctx->cache, NULL, flags, ctx->pool);
+}
+
+void kr_context_txn_release(struct kr_txn *txn)
+{
+}
+
 int kr_result_init(struct kr_context *ctx, struct kr_result *result)
 {
 	memset(result, 0, sizeof(struct kr_result));
 
 	/* Initialize answer packet. */
-
 	knot_pkt_t *ans = knot_pkt_new(NULL, KNOT_WIRE_MAX_PKTSIZE, ctx->pool);
 	if (ans == NULL) {
 		return -1;
@@ -61,20 +88,12 @@ int kr_result_init(struct kr_context *ctx, struct kr_result *result)
 
 	result->ans = ans;
 
-	/* Start cache transaction. */
-	result->txn = kr_cache_txn_begin(ctx->cache, NULL, ctx->pool);
-	if (result->txn == NULL) {
-		knot_pkt_free(&ans);
-		return -1;
-	}
-
 	return 0;
 }
 
 int kr_result_deinit(struct kr_result *result)
 {
 	knot_pkt_free(&result->ans);
-	kr_cache_txn_commit(result->txn);
 
 	return 0;
 }

lib/context.h

@@ -30,7 +30,6 @@ struct kr_result {
 	struct timeval t_start, t_end;
 	unsigned total_rtt;
 	unsigned nr_queries;
-	struct kr_txn *txn;
 };
 
 /*! \brief Name resolution context. */
@@ -42,6 +41,10 @@ struct kr_context
 	struct kr_rplan rplan;
 	struct kr_delegmap dp_map;
 	struct kr_cache *cache;
+	struct {
+		struct kr_txn *read;
+		struct kr_txn *write;
+	} txn;
 	mm_ctx_t *pool;
 	unsigned state;
 	unsigned options;
@@ -50,6 +53,8 @@ struct kr_context
 int kr_context_init(struct kr_context *ctx, mm_ctx_t *mm);
 int kr_context_reset(struct kr_context *ctx);
 int kr_context_deinit(struct kr_context *ctx);
+struct kr_txn *kr_context_txn_acquire(struct kr_context *ctx, unsigned flags);
+void kr_context_txn_release(struct kr_txn *txn);
 
 int kr_result_init(struct kr_context *ctx, struct kr_result *result);
-int kr_result_deinit(struct kr_result *result);
\ No newline at end of file
+int kr_result_deinit(struct kr_result *result);

lib/layer/iterate.c

@@ -209,7 +209,9 @@ static int resolve_auth(knot_pkt_t *pkt, struct kr_layer_param *param)
 		}
 
 		/* Update cache. */
-		kr_cache_insert(result->txn, &an->rr[i], 0);
+		struct kr_txn *txn = kr_context_txn_acquire(resolve, 0);
+		kr_cache_insert(txn, &an->rr[i], 0);
+		kr_context_txn_release(txn);
 
 		/* Check canonical name. */
 		follow_cname_chain(&cname, &an->rr[i], param);
@@ -272,10 +274,11 @@ static int prepare_query(knot_layer_t *ctx, knot_pkt_t *pkt)
 		return -1;
 	}
 
-	/* TODO: hacked cache */
+	struct kr_txn *txn = kr_context_txn_acquire(resolve, KR_CACHE_RDONLY);
 	knot_rrset_t cached_reply;
 	knot_rrset_init(&cached_reply, next->sname, next->stype, next->sclass);
-	if (kr_cache_query(result->txn, &cached_reply) == 0) {
+
+	if (kr_cache_query(txn, &cached_reply) == 0) {
 		/* Solve this from cache. */
 		update_result(next, result, &cached_reply);
 		knot_rdataset_clear(&cached_reply.rrs, resolve->pool);
@@ -283,9 +286,11 @@ static int prepare_query(knot_layer_t *ctx, knot_pkt_t *pkt)
 		/* Resolved current SNAME. */
 		knot_wire_set_rcode(result->ans->wire, KNOT_RCODE_NOERROR);
 		resolve->resolved_qry = next;
+		kr_context_txn_release(txn);
 		return NS_PROC_DONE;
 	}
 	knot_rdataset_clear(&cached_reply.rrs, resolve->pool);
+	kr_context_txn_release(txn);
 
 	knot_pkt_clear(pkt);