X-Git-Url: https://git.tokkee.org/?p=sysdb.git;a=blobdiff_plain;f=src%2Fcore%2Fstore.c;h=7671e9800f13a0ac0a81e2b24817d95b0f0a83ef;hp=6befce7e5acd8933a3f054336974f8bf32229733;hb=742c60b383c9373b2156c3af5ff9e7605c056e60;hpb=794d7a5a42401a5bf0645b36162c3d05fbd81a99

diff --git a/src/core/store.c b/src/core/store.c
index 6befce7..7671e98 100644
--- a/src/core/store.c
+++ b/src/core/store.c
@@ -43,23 +43,62 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <math.h>
 #include <pthread.h>
 
 /*
  * private variables
  */
 
-static sdb_avltree_t *hosts = NULL;
-static pthread_rwlock_t host_lock = PTHREAD_RWLOCK_INITIALIZER;
+typedef struct {
+	sdb_object_t super;
+
+	/* hosts are the top-level entries and
+	 * reference everything else */
+	sdb_avltree_t *hosts;
+	pthread_rwlock_t host_lock;
+} sdb_store_t;
+#define ST(obj) ((sdb_store_t *)(obj))
+
+sdb_store_t *global_store = NULL;
 
 /*
  * private types
  */
 
-static sdb_type_t sdb_host_type;
-static sdb_type_t sdb_service_type;
-static sdb_type_t sdb_metric_type;
-static sdb_type_t sdb_attribute_type;
+static sdb_type_t host_type;
+static sdb_type_t service_type;
+static sdb_type_t metric_type;
+static sdb_type_t attribute_type;
+
+static int
+store_init(sdb_object_t *obj, va_list __attribute__((unused)) ap)
+{
+	int err;
+	if (! (ST(obj)->hosts = sdb_avltree_create()))
+		return -1;
+	if ((err = pthread_rwlock_init(&ST(obj)->host_lock, /* attr = */ NULL))) {
+		char errbuf[128];
+		sdb_log(SDB_LOG_ERR, "store: Failed to initialize lock: %s",
+				sdb_strerror(err, errbuf, sizeof(errbuf)));
+		return -1;
+	}
+	return 0;
+} /* store_init */
+
+static void
+store_destroy(sdb_object_t *obj)
+{
+	int err;
+	if ((err = pthread_rwlock_destroy(&ST(obj)->host_lock))) {
+		char errbuf[128];
+		sdb_log(SDB_LOG_ERR, "store: Failed to destroy lock: %s",
+				sdb_strerror(err, errbuf, sizeof(errbuf)));
+		return;
+	}
+	sdb_avltree_destroy(ST(obj)->hosts);
+	ST(obj)->hosts = NULL;
+} /* store_destroy */
 
 static int
 store_obj_init(sdb_object_t *obj, va_list ap)
@@ -88,12 +127,14 @@ store_obj_destroy(sdb_object_t *obj)
 	sobj->backends = NULL;
 	sobj->backends_num = 0;
 
-	if (sobj->parent)
-		sdb_object_deref(SDB_OBJ(sobj->parent));
+	// We don't currently keep an extra reference for parent objects to
+	// avoid circular self-references which are not handled correctly by
+	// the ref-count base management layer.
+	//sdb_object_deref(SDB_OBJ(sobj->parent));
 } /* store_obj_destroy */
 
 static int
-sdb_host_init(sdb_object_t *obj, va_list ap)
+host_init(sdb_object_t *obj, va_list ap)
 {
 	sdb_host_t *sobj = HOST(obj);
 	int ret;
@@ -113,10 +154,10 @@ sdb_host_init(sdb_object_t *obj, va_list ap)
 	if (! sobj->attributes)
 		return -1;
 	return 0;
-} /* sdb_host_init */
+} /* host_init */
 
 static void
-sdb_host_destroy(sdb_object_t *obj)
+host_destroy(sdb_object_t *obj)
 {
 	sdb_host_t *sobj = HOST(obj);
 	assert(obj);
@@ -129,10 +170,10 @@ sdb_host_destroy(sdb_object_t *obj)
 		sdb_avltree_destroy(sobj->metrics);
 	if (sobj->attributes)
 		sdb_avltree_destroy(sobj->attributes);
-} /* sdb_host_destroy */
+} /* host_destroy */
 
 static int
-sdb_service_init(sdb_object_t *obj, va_list ap)
+service_init(sdb_object_t *obj, va_list ap)
 {
 	sdb_service_t *sobj = SVC(obj);
 	int ret;
@@ -146,10 +187,10 @@ sdb_service_init(sdb_object_t *obj, va_list ap)
 	if (! sobj->attributes)
 		return -1;
 	return 0;
-} /* sdb_service_init */
+} /* service_init */
 
 static void
-sdb_service_destroy(sdb_object_t *obj)
+service_destroy(sdb_object_t *obj)
 {
 	sdb_service_t *sobj = SVC(obj);
 	assert(obj);
@@ -158,10 +199,10 @@ sdb_service_destroy(sdb_object_t *obj)
 
 	if (sobj->attributes)
 		sdb_avltree_destroy(sobj->attributes);
-} /* sdb_service_destroy */
+} /* service_destroy */
 
 static int
-sdb_metric_init(sdb_object_t *obj, va_list ap)
+metric_init(sdb_object_t *obj, va_list ap)
 {
 	sdb_metric_t *sobj = METRIC(obj);
 	int ret;
@@ -177,10 +218,10 @@ sdb_metric_init(sdb_object_t *obj, va_list ap)
 
 	sobj->store.type = sobj->store.id = NULL;
 	return 0;
-} /* sdb_metric_init */
+} /* metric_init */
 
 static void
-sdb_metric_destroy(sdb_object_t *obj)
+metric_destroy(sdb_object_t *obj)
 {
 	sdb_metric_t *sobj = METRIC(obj);
 	assert(obj);
@@ -194,10 +235,10 @@ sdb_metric_destroy(sdb_object_t *obj)
 		free(sobj->store.type);
 	if (sobj->store.id)
 		free(sobj->store.id);
-} /* sdb_metric_destroy */
+} /* metric_destroy */
 
 static int
-sdb_attr_init(sdb_object_t *obj, va_list ap)
+attr_init(sdb_object_t *obj, va_list ap)
 {
 	const sdb_data_t *value;
 	int ret;
@@ -213,39 +254,45 @@ sdb_attr_init(sdb_object_t *obj, va_list ap)
 		if (sdb_data_copy(&ATTR(obj)->value, value))
 			return -1;
 	return 0;
-} /* sdb_attr_init */
+} /* attr_init */
 
 static void
-sdb_attr_destroy(sdb_object_t *obj)
+attr_destroy(sdb_object_t *obj)
 {
 	assert(obj);
 
 	store_obj_destroy(obj);
 	sdb_data_free_datum(&ATTR(obj)->value);
-} /* sdb_attr_destroy */
+} /* attr_destroy */
+
+static sdb_type_t store_type = {
+	/* size = */ sizeof(sdb_store_t),
+	/* init = */ store_init,
+	/* destroy = */ store_destroy,
+};
 
-static sdb_type_t sdb_host_type = {
-	sizeof(sdb_host_t),
-	sdb_host_init,
-	sdb_host_destroy
+static sdb_type_t host_type = {
+	/* size = */ sizeof(sdb_host_t),
+	/* init = */ host_init,
+	/* destroy = */ host_destroy
 };
 
-static sdb_type_t sdb_service_type = {
-	sizeof(sdb_service_t),
-	sdb_service_init,
-	sdb_service_destroy
+static sdb_type_t service_type = {
+	/* size = */ sizeof(sdb_service_t),
+	/* init = */ service_init,
+	/* destroy = */ service_destroy
 };
 
-static sdb_type_t sdb_metric_type = {
-	sizeof(sdb_metric_t),
-	sdb_metric_init,
-	sdb_metric_destroy
+static sdb_type_t metric_type = {
+	/* size = */ sizeof(sdb_metric_t),
+	/* init = */ metric_init,
+	/* destroy = */ metric_destroy
 };
 
-static sdb_type_t sdb_attribute_type = {
-	sizeof(sdb_attribute_t),
-	sdb_attr_init,
-	sdb_attr_destroy
+static sdb_type_t attribute_type = {
+	/* size = */ sizeof(sdb_attribute_t),
+	/* init = */ attr_init,
+	/* destroy = */ attr_destroy
 };
 
 /*
@@ -253,9 +300,25 @@ static sdb_type_t sdb_attribute_type = {
  */
 
 static sdb_host_t *
-lookup_host(const char *name)
+lookup_host(sdb_store_t *st, const char *name, bool canonicalize)
 {
-	return HOST(sdb_avltree_lookup(hosts, name));
+	sdb_host_t *host;
+	char *cname;
+
+	assert(name);
+	if (! canonicalize)
+		return HOST(sdb_avltree_lookup(st->hosts, name));
+
+	cname = strdup(name);
+	cname = sdb_plugin_cname(cname);
+	if (! cname) {
+		sdb_log(SDB_LOG_ERR, "store: strdup failed");
+		return NULL;
+	}
+
+	host = HOST(sdb_avltree_lookup(st->hosts, cname));
+	free(cname);
+	return host;
 } /* lookup_host */
 
 static int
@@ -288,8 +351,9 @@ record_backend(sdb_store_obj_t *obj)
 } /* record_backend */
 
 static int
-store_obj(sdb_avltree_t *parent_tree, int type, const char *name,
-		sdb_time_t last_update, sdb_store_obj_t **updated_obj)
+store_obj(sdb_store_obj_t *parent, sdb_avltree_t *parent_tree,
+		int type, const char *name, sdb_time_t last_update,
+		sdb_store_obj_t **updated_obj)
 {
 	sdb_store_obj_t *old, *new;
 	int status = 0;
@@ -333,16 +397,16 @@ store_obj(sdb_avltree_t *parent_tree, int type, const char *name,
 	else {
 		if (type == SDB_ATTRIBUTE) {
 			/* the value will be updated by the caller */
-			new = STORE_OBJ(sdb_object_create(name, sdb_attribute_type,
+			new = STORE_OBJ(sdb_object_create(name, attribute_type,
 						type, last_update, NULL));
 		}
 		else {
 			sdb_type_t t;
 			t = type == SDB_HOST
-				? sdb_host_type
+				? host_type
 				: type == SDB_SERVICE
-					? sdb_service_type
-					: sdb_metric_type;
+					? service_type
+					: metric_type;
 			new = STORE_OBJ(sdb_object_create(name, t, type, last_update));
 		}
 
@@ -365,6 +429,14 @@ store_obj(sdb_avltree_t *parent_tree, int type, const char *name,
 		return status;
 	assert(new);
 
+	if (new->parent != parent) {
+		// Avoid circular self-references which are not handled
+		// correctly by the ref-count based management layer.
+		//sdb_object_deref(SDB_OBJ(new->parent));
+		//sdb_object_ref(SDB_OBJ(parent));
+		new->parent = parent;
+	}
+
 	if (updated_obj)
 		*updated_obj = new;
 
@@ -374,13 +446,14 @@ store_obj(sdb_avltree_t *parent_tree, int type, const char *name,
 } /* store_obj */
 
 static int
-store_attr(sdb_avltree_t *attributes, const char *key, const sdb_data_t *value,
-		sdb_time_t last_update)
+store_attr(sdb_store_obj_t *parent, sdb_avltree_t *attributes,
+		const char *key, const sdb_data_t *value, sdb_time_t last_update)
 {
 	sdb_store_obj_t *attr = NULL;
 	int status;
 
-	status = store_obj(attributes, SDB_ATTRIBUTE, key, last_update, &attr);
+	status = store_obj(parent, attributes, SDB_ATTRIBUTE,
+			key, last_update, &attr);
 	if (status)
 		return status;
 
@@ -394,32 +467,48 @@ store_attr(sdb_avltree_t *attributes, const char *key, const sdb_data_t *value,
 	return status;
 } /* store_attr */
 
-/* The host_lock has to be acquired before calling this function. */
-static sdb_avltree_t *
-get_host_children(const char *hostname, int type)
+static int
+store_metric_store(sdb_metric_t *metric, sdb_metric_store_t *store)
 {
-	char *cname = NULL;
-	sdb_host_t *host;
+	char *type = metric->store.type;
+	char *id = metric->store.id;
 
-	assert(hostname);
-	assert((type == SDB_SERVICE) || (type == SDB_METRIC)
-			|| (type == SDB_ATTRIBUTE));
+	if ((! metric->store.type) || strcasecmp(metric->store.type, store->type)) {
+		if (! (type = strdup(store->type)))
+			return -1;
+	}
+	if ((! metric->store.id) || strcasecmp(metric->store.id, store->id)) {
+		if (! (id = strdup(store->id))) {
+			if (type != metric->store.type)
+				free(type);
+			return -1;
+		}
+	}
 
-	if (! hosts)
-		return NULL;
+	if (type != metric->store.type) {
+		if (metric->store.type)
+			free(metric->store.type);
+		metric->store.type = type;
+	}
+	if (id != metric->store.id) {
+		if (metric->store.id)
+			free(metric->store.id);
+		metric->store.id = id;
+	}
+	return 0;
+} /* store_metric_store */
 
-	cname = sdb_plugin_cname(strdup(hostname));
-	if (! cname) {
-		sdb_log(SDB_LOG_ERR, "store: strdup failed");
+/* The store's host_lock has to be acquired before calling this function. */
+static sdb_avltree_t *
+get_host_children(sdb_host_t *host, int type)
+{
+	if ((type != SDB_SERVICE) && (type != SDB_METRIC)
+			&& (type != SDB_ATTRIBUTE))
 		return NULL;
-	}
 
-	host = lookup_host(cname);
-	free(cname);
 	if (! host)
 		return NULL;
 
-	sdb_object_deref(SDB_OBJ(host));
 	if (type == SDB_ATTRIBUTE)
 		return host->attributes;
 	else if (type == SDB_METRIC)
@@ -428,109 +517,6 @@ get_host_children(const char *hostname, int type)
 		return host->services;
 } /* get_host_children */
 
-/*
- * store_common_tojson serializes common object attributes to JSON.
- *
- * The function never returns an error. Rather, an error message will be part
- * of the serialized data.
- */
-static void
-store_common_tojson(sdb_store_obj_t *obj, sdb_strbuf_t *buf)
-{
-	char time_str[64];
-	char interval_str[64];
-	size_t i;
-
-	/* TODO: make time and interval formats configurable */
-	if (! sdb_strftime(time_str, sizeof(time_str),
-				"%F %T %z", obj->last_update))
-		snprintf(time_str, sizeof(time_str), "<error>");
-	time_str[sizeof(time_str) - 1] = '\0';
-
-	if (! sdb_strfinterval(interval_str, sizeof(interval_str),
-				obj->interval))
-		snprintf(interval_str, sizeof(interval_str), "<error>");
-	interval_str[sizeof(interval_str) - 1] = '\0';
-
-	sdb_strbuf_append(buf, "\"last_update\": \"%s\", "
-			"\"update_interval\": \"%s\", \"backends\": [",
-			time_str, interval_str);
-
-	for (i = 0; i < obj->backends_num; ++i) {
-		sdb_strbuf_append(buf, "\"%s\"", obj->backends[i]);
-		if (i < obj->backends_num - 1)
-			sdb_strbuf_append(buf, ",");
-	}
-	sdb_strbuf_append(buf, "]");
-} /* store_common_tojson */
-
-/*
- * store_obj_tojson serializes attribute / metric / service objects to JSON.
- *
- * The function never returns an error. Rather, an error message will be part
- * of the serialized data.
- */
-static void
-store_obj_tojson(sdb_avltree_t *tree, int type, sdb_strbuf_t *buf,
-		sdb_store_matcher_t *filter, int flags)
-{
-	sdb_avltree_iter_t *iter;
-
-	assert((type == SDB_ATTRIBUTE)
-			|| (type == SDB_METRIC)
-			|| (type == SDB_SERVICE));
-
-	sdb_strbuf_append(buf, "[");
-	iter = sdb_avltree_get_iter(tree);
-	if (! iter) {
-		char errbuf[1024];
-		sdb_log(SDB_LOG_ERR, "store: Failed to retrieve %ss: %s\n",
-				SDB_STORE_TYPE_TO_NAME(type),
-				sdb_strerror(errno, errbuf, sizeof(errbuf)));
-		sdb_strbuf_append(buf, "{\"error\": \"failed to retrieve %ss: %s\"}",
-				SDB_STORE_TYPE_TO_NAME(type), errbuf);
-	}
-
-	/* has_next returns false if the iterator is NULL */
-	while (sdb_avltree_iter_has_next(iter)) {
-		sdb_store_obj_t *sobj = STORE_OBJ(sdb_avltree_iter_get_next(iter));
-		assert(sobj);
-		assert(sobj->type == type);
-
-		if (filter && (! sdb_store_matcher_matches(filter, sobj, NULL)))
-			continue;
-
-		sdb_strbuf_append(buf, "{\"name\": \"%s\", ", SDB_OBJ(sobj)->name);
-		if (sobj->type == SDB_ATTRIBUTE) {
-			char tmp[sdb_data_strlen(&ATTR(sobj)->value) + 1];
-			sdb_data_format(&ATTR(sobj)->value, tmp, sizeof(tmp),
-					SDB_DOUBLE_QUOTED);
-			sdb_strbuf_append(buf, "\"value\": %s, ", tmp);
-		}
-		store_common_tojson(sobj, buf);
-
-		if ((sobj->type == SDB_SERVICE)
-				&& (! (flags & SDB_SKIP_ATTRIBUTES))) {
-			sdb_strbuf_append(buf, ", \"attributes\": ");
-			store_obj_tojson(SVC(sobj)->attributes, SDB_ATTRIBUTE,
-					buf, filter, flags);
-		}
-		else if ((sobj->type == SDB_METRIC)
-				&& (! (flags & SDB_SKIP_ATTRIBUTES))) {
-			sdb_strbuf_append(buf, ", \"attributes\": ");
-			store_obj_tojson(METRIC(sobj)->attributes, SDB_ATTRIBUTE,
-					buf, filter, flags);
-		}
-		sdb_strbuf_append(buf, "}");
-
-		if (sdb_avltree_iter_has_next(iter))
-			sdb_strbuf_append(buf, ",");
-	}
-
-	sdb_avltree_iter_destroy(iter);
-	sdb_strbuf_append(buf, "]");
-} /* store_obj_tojson */
-
 /*
  * ts_tojson serializes a time-series to JSON.
  *
@@ -546,12 +532,10 @@ ts_tojson(sdb_timeseries_t *ts, sdb_strbuf_t *buf)
 	size_t i;
 
 	/* TODO: make time format configurable */
-	if (! sdb_strftime(start_str, sizeof(start_str),
-				"%F %T %z", ts->start))
+	if (! sdb_strftime(start_str, sizeof(start_str), ts->start))
 		snprintf(start_str, sizeof(start_str), "<error>");
 	start_str[sizeof(start_str) - 1] = '\0';
-	if (! sdb_strftime(end_str, sizeof(end_str),
-				"%F %T %z", ts->end))
+	if (! sdb_strftime(end_str, sizeof(end_str), ts->end))
 		snprintf(end_str, sizeof(end_str), "<error>");
 	end_str[sizeof(end_str) - 1] = '\0';
 
@@ -565,13 +549,17 @@ ts_tojson(sdb_timeseries_t *ts, sdb_strbuf_t *buf)
 		for (j = 0; j < ts->data_len; ++j) {
 			char time_str[64];
 
-			if (! sdb_strftime(time_str, sizeof(time_str),
-						"%F %T %z", ts->data[i][j].timestamp))
+			if (! sdb_strftime(time_str, sizeof(time_str), ts->data[i][j].timestamp))
 				snprintf(time_str, sizeof(time_str), "<error>");
 			time_str[sizeof(time_str) - 1] = '\0';
 
-			sdb_strbuf_append(buf, "{\"timestamp\": \"%s\", "
-					"\"value\": \"%f\"}", time_str, ts->data[i][j].value);
+			/* Some GNU libc versions may print '-nan' which we dont' want */
+			if (isnan(ts->data[i][j].value))
+				sdb_strbuf_append(buf, "{\"timestamp\": \"%s\", "
+						"\"value\": \"nan\"}", time_str);
+			else
+				sdb_strbuf_append(buf, "{\"timestamp\": \"%s\", "
+						"\"value\": \"%f\"}", time_str, ts->data[i][j].value);
 
 			if (j < ts->data_len - 1)
 				sdb_strbuf_append(buf, ",");
@@ -586,84 +574,26 @@ ts_tojson(sdb_timeseries_t *ts, sdb_strbuf_t *buf)
 } /* ts_tojson */
 
 /*
- * public API
+ * store writer API
  */
 
-void
-sdb_store_clear(void)
-{
-	sdb_avltree_destroy(hosts);
-	hosts = NULL;
-} /* sdb_store_clear */
-
-int
-sdb_store_host(const char *name, sdb_time_t last_update)
-{
-	char *cname = NULL;
-	int status = 0;
-
-	if (! name)
-		return -1;
-
-	cname = sdb_plugin_cname(strdup(name));
-	if (! cname) {
-		sdb_log(SDB_LOG_ERR, "store: strdup failed");
-		return -1;
-	}
-
-	pthread_rwlock_wrlock(&host_lock);
-	if (! hosts)
-		if (! (hosts = sdb_avltree_create()))
-			status = -1;
-
-	if (! status)
-		status = store_obj(hosts, SDB_HOST, cname, last_update, NULL);
-	pthread_rwlock_unlock(&host_lock);
-
-	free(cname);
-	return status;
-} /* sdb_store_host */
-
-_Bool
-sdb_store_has_host(const char *name)
+static int
+store_attribute(const char *hostname,
+		const char *key, const sdb_data_t *value,
+		sdb_time_t last_update, sdb_object_t *user_data)
 {
-	sdb_host_t *host;
-
-	if (! name)
-		return NULL;
-
-	host = lookup_host(name);
-	return host != NULL;
-} /* sdb_store_has_host */
+	sdb_store_t *st = ST(user_data);
 
-sdb_store_obj_t *
-sdb_store_get_host(const char *name)
-{
 	sdb_host_t *host;
-
-	if (! name)
-		return NULL;
-
-	host = lookup_host(name);
-	if (! host)
-		return NULL;
-
-	return STORE_OBJ(host);
-} /* sdb_store_get_host */
-
-int
-sdb_store_attribute(const char *hostname,
-		const char *key, const sdb_data_t *value,
-		sdb_time_t last_update)
-{
 	sdb_avltree_t *attrs;
 	int status = 0;
 
 	if ((! hostname) || (! key))
 		return -1;
 
-	pthread_rwlock_wrlock(&host_lock);
-	attrs = get_host_children(hostname, SDB_ATTRIBUTE);
+	pthread_rwlock_wrlock(&st->host_lock);
+	host = lookup_host(st, hostname, /* canonicalize = */ 1);
+	attrs = get_host_children(host, SDB_ATTRIBUTE);
 	if (! attrs) {
 		sdb_log(SDB_LOG_ERR, "store: Failed to store attribute '%s' - "
 				"host '%s' not found", key, hostname);
@@ -671,55 +601,64 @@ sdb_store_attribute(const char *hostname,
 	}
 
 	if (! status)
-		status = store_attr(attrs, key, value, last_update);
+		status = store_attr(STORE_OBJ(host), attrs, key, value, last_update);
+
+	sdb_object_deref(SDB_OBJ(host));
+	pthread_rwlock_unlock(&st->host_lock);
 
-	pthread_rwlock_unlock(&host_lock);
 	return status;
-} /* sdb_store_attribute */
+} /* store_attribute */
 
-int
-sdb_store_service(const char *hostname, const char *name,
-		sdb_time_t last_update)
+static int
+store_host(const char *name, sdb_time_t last_update, sdb_object_t *user_data)
 {
-	sdb_avltree_t *services;
+	sdb_store_t *st = ST(user_data);
 
+	char *cname = NULL;
 	int status = 0;
 
-	if ((! hostname) || (! name))
+	if (! name)
 		return -1;
 
-	pthread_rwlock_wrlock(&host_lock);
-	services = get_host_children(hostname, SDB_SERVICE);
-	if (! services) {
-		sdb_log(SDB_LOG_ERR, "store: Failed to store service '%s' - "
-				"host '%s' not found", name, hostname);
-		status = -1;
+	cname = sdb_plugin_cname(strdup(name));
+	if (! cname) {
+		sdb_log(SDB_LOG_ERR, "store: strdup failed");
+		return -1;
 	}
 
-	if (! status)
-		status = store_obj(services, SDB_SERVICE, name, last_update, NULL);
-	pthread_rwlock_unlock(&host_lock);
+	pthread_rwlock_wrlock(&st->host_lock);
+	status = store_obj(NULL, st->hosts,
+			SDB_HOST, cname, last_update, NULL);
+	pthread_rwlock_unlock(&st->host_lock);
+
+	free(cname);
 	return status;
-} /* sdb_store_service */
+} /* store_host */
 
-int
-sdb_store_service_attr(const char *hostname, const char *service,
-		const char *key, const sdb_data_t *value, sdb_time_t last_update)
+static int
+store_service_attr(const char *hostname, const char *service,
+		const char *key, const sdb_data_t *value, sdb_time_t last_update,
+		sdb_object_t *user_data)
 {
-	sdb_avltree_t *services;
+	sdb_store_t *st = ST(user_data);
+
+	sdb_host_t *host;
 	sdb_service_t *svc;
+	sdb_avltree_t *services;
 	int status = 0;
 
 	if ((! hostname) || (! service) || (! key))
 		return -1;
 
-	pthread_rwlock_wrlock(&host_lock);
-	services = get_host_children(hostname, SDB_SERVICE);
+	pthread_rwlock_wrlock(&st->host_lock);
+	host = lookup_host(st, hostname, /* canonicalize = */ 1);
+	services = get_host_children(host, SDB_SERVICE);
+	sdb_object_deref(SDB_OBJ(host));
 	if (! services) {
 		sdb_log(SDB_LOG_ERR, "store: Failed to store attribute '%s' "
 				"for service '%s' - host '%ss' not found",
 				key, service, hostname);
-		pthread_rwlock_unlock(&host_lock);
+		pthread_rwlock_unlock(&st->host_lock);
 		return -1;
 	}
 
@@ -731,89 +670,81 @@ sdb_store_service_attr(const char *hostname, const char *service,
 	}
 
 	if (! status)
-		status = store_attr(svc->attributes, key, value, last_update);
+		status = store_attr(STORE_OBJ(svc), svc->attributes,
+				key, value, last_update);
 
 	sdb_object_deref(SDB_OBJ(svc));
-	pthread_rwlock_unlock(&host_lock);
+	pthread_rwlock_unlock(&st->host_lock);
+
 	return status;
-} /* sdb_store_service_attr */
+} /* store_service_attr */
 
-int
-sdb_store_metric(const char *hostname, const char *name,
-		sdb_metric_store_t *store, sdb_time_t last_update)
+static int
+store_service(const char *hostname, const char *name,
+		sdb_time_t last_update, sdb_object_t *user_data)
 {
-	sdb_store_obj_t *obj = NULL;
-	sdb_metric_t *metric;
+	sdb_store_t *st = ST(user_data);
 
-	sdb_avltree_t *metrics;
+	sdb_host_t *host;
+	sdb_avltree_t *services;
+	sdb_data_t d;
 
 	int status = 0;
 
 	if ((! hostname) || (! name))
 		return -1;
-	if (store && ((! store->type) || (! store->id)))
-		return -1;
 
-	pthread_rwlock_wrlock(&host_lock);
-	metrics = get_host_children(hostname, SDB_METRIC);
-	if (! metrics) {
-		sdb_log(SDB_LOG_ERR, "store: Failed to store metric '%s' - "
+	pthread_rwlock_wrlock(&st->host_lock);
+	host = lookup_host(st, hostname, /* canonicalize = */ 1);
+	services = get_host_children(host, SDB_SERVICE);
+	if (! services) {
+		sdb_log(SDB_LOG_ERR, "store: Failed to store service '%s' - "
 				"host '%s' not found", name, hostname);
 		status = -1;
 	}
 
 	if (! status)
-		status = store_obj(metrics, SDB_METRIC, name, last_update, &obj);
-
-	if (status || (! store)) {
-		pthread_rwlock_unlock(&host_lock);
-		return status;
-	}
+		status = store_obj(STORE_OBJ(host), services, SDB_SERVICE,
+				name, last_update, NULL);
 
-	assert(obj);
-	metric = METRIC(obj);
+	sdb_object_deref(SDB_OBJ(host));
+	pthread_rwlock_unlock(&st->host_lock);
 
-	if ((! metric->store.type) || strcasecmp(metric->store.type, store->type)) {
-		if (metric->store.type)
-			free(metric->store.type);
-		metric->store.type = strdup(store->type);
-	}
-	if ((! metric->store.id) || strcasecmp(metric->store.id, store->id)) {
-		if (metric->store.id)
-			free(metric->store.id);
-		metric->store.id = strdup(store->id);
-	}
+	if (status)
+		return status;
 
-	if ((! metric->store.type) || (! metric->store.id)) {
-		if (metric->store.type)
-			free(metric->store.type);
-		if (metric->store.id)
-			free(metric->store.id);
-		metric->store.type = metric->store.id = NULL;
+	/* record the hostname as an attribute */
+	d.type = SDB_TYPE_STRING;
+	d.data.string = SDB_OBJ(host)->name;
+	if (store_service_attr(hostname, name, "hostname", &d, last_update, user_data))
 		status = -1;
-	}
-	pthread_rwlock_unlock(&host_lock);
 	return status;
-} /* sdb_store_metric */
+} /* store_service */
 
-int
-sdb_store_metric_attr(const char *hostname, const char *metric,
-		const char *key, const sdb_data_t *value, sdb_time_t last_update)
+static int
+store_metric_attr(const char *hostname, const char *metric,
+		const char *key, const sdb_data_t *value, sdb_time_t last_update,
+		sdb_object_t *user_data)
 {
+	sdb_store_t *st = ST(user_data);
+
 	sdb_avltree_t *metrics;
+	sdb_host_t *host;
 	sdb_metric_t *m;
 	int status = 0;
 
 	if ((! hostname) || (! metric) || (! key))
 		return -1;
 
-	pthread_rwlock_wrlock(&host_lock);
-	metrics = get_host_children(hostname, SDB_METRIC);
+	pthread_rwlock_wrlock(&st->host_lock);
+	host = lookup_host(st, hostname, /* canonicalize = */ 1);
+	metrics = get_host_children(host, SDB_METRIC);
+	sdb_object_deref(SDB_OBJ(host));
 	if (! metrics) {
 		sdb_log(SDB_LOG_ERR, "store: Failed to store attribute '%s' "
 				"for metric '%s' - host '%s' not found",
 				key, metric, hostname);
-		pthread_rwlock_unlock(&host_lock);
+		pthread_rwlock_unlock(&st->host_lock);
 		return -1;
 	}
 
@@ -825,71 +756,164 @@ sdb_store_metric_attr(const char *hostname, const char *metric,
 	}
 
 	if (! status)
-		status = store_attr(m->attributes, key, value, last_update);
+		status = store_attr(STORE_OBJ(m), m->attributes,
+				key, value, last_update);
 
 	sdb_object_deref(SDB_OBJ(m));
-	pthread_rwlock_unlock(&host_lock);
+	pthread_rwlock_unlock(&st->host_lock);
+
 	return status;
-} /* sdb_store_metric_attr */
+} /* store_metric_attr */
 
-int
-sdb_store_fetch_timeseries(const char *hostname, const char *metric,
-		sdb_timeseries_opts_t *opts, sdb_strbuf_t *buf)
+static int
+store_metric(const char *hostname, const char *name,
+		sdb_metric_store_t *store, sdb_time_t last_update,
+		sdb_object_t *user_data)
 {
+	sdb_store_t *st = ST(user_data);
+
+	sdb_store_obj_t *obj = NULL;
+	sdb_host_t *host;
+	sdb_metric_t *metric;
+	sdb_data_t d;
+
 	sdb_avltree_t *metrics;
-	sdb_metric_t *m;
 
-	sdb_timeseries_t *ts;
+	int status = 0;
 
-	if ((! hostname) || (! metric) || (! opts) || (! buf))
+	if ((! hostname) || (! name))
 		return -1;
 
-	pthread_rwlock_rdlock(&host_lock);
-	metrics = get_host_children(hostname, SDB_METRIC);
+	if (store) {
+		if ((store->type != NULL) != (store->id != NULL))
+			return -1;
+		else if (! store->type)
+			store = NULL;
+	}
+
+	pthread_rwlock_wrlock(&st->host_lock);
+	host = lookup_host(st, hostname, /* canonicalize = */ 1);
+	metrics = get_host_children(host, SDB_METRIC);
 	if (! metrics) {
-		sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
-				"- host '%s' not found", hostname, metric, hostname);
-		pthread_rwlock_unlock(&host_lock);
-		return -1;
+		sdb_log(SDB_LOG_ERR, "store: Failed to store metric '%s' - "
+				"host '%s' not found", name, hostname);
+		status = -1;
 	}
 
-	m = METRIC(sdb_avltree_lookup(metrics, metric));
-	if (! m) {
-		sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
-				"- metric '%s' not found", hostname, metric, metric);
-		pthread_rwlock_unlock(&host_lock);
-		return -1;
+	if (! status)
+		status = store_obj(STORE_OBJ(host), metrics, SDB_METRIC,
+				name, last_update, &obj);
+	sdb_object_deref(SDB_OBJ(host));
+
+	if (status) {
+		pthread_rwlock_unlock(&st->host_lock);
+		return status;
 	}
 
-	if ((! m->store.type) || (! m->store.id)) {
-		sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
-				"- no data-store configured for the stored metric",
-				hostname, metric);
-		pthread_rwlock_unlock(&host_lock);
+	assert(obj);
+	metric = METRIC(obj);
+
+	if (store)
+		if (store_metric_store(metric, store))
+			status = -1;
+	pthread_rwlock_unlock(&st->host_lock);
+
+	/* record the hostname as an attribute */
+	d.type = SDB_TYPE_STRING;
+	d.data.string = SDB_OBJ(host)->name;
+	if (store_metric_attr(hostname, name, "hostname", &d, last_update, user_data))
+		status = -1;
+	return status;
+} /* store_metric */
+
+static sdb_store_writer_t store_writer = {
+	store_host, store_service, store_metric,
+	store_attribute, store_service_attr, store_metric_attr,
+};
+
+/*
+ * TODO: let prepare and execute accept a store object as their user_data
+ * object
+ */
+
+static sdb_object_t *
+prepare_query(sdb_ast_node_t *ast,
+		sdb_strbuf_t __attribute__((unused)) *errbuf,
+		sdb_object_t __attribute__((unused)) *user_data)
+{
+	return SDB_OBJ(sdb_store_query_prepare(ast));
+} /* prepare_query */
+
+static int
+execute_query(sdb_object_t *q,
+		sdb_strbuf_t *buf, sdb_strbuf_t *errbuf,
+		sdb_object_t __attribute__((unused)) *user_data)
+{
+	return sdb_store_query_execute(QUERY(q), buf, errbuf);
+} /* execute_query */
+
+static sdb_store_reader_t store_reader = {
+	prepare_query, execute_query,
+};
+
+/*
+ * public API
+ */
+
+int
+sdb_store_init(void)
+{
+	if (global_store)
+		return 0;
+
+	global_store = ST(sdb_object_create("store", store_type));
+	if (! global_store) {
+		sdb_log(SDB_LOG_ERR, "store: Failed to allocate store");
 		return -1;
 	}
+	if (sdb_plugin_register_writer("memstore",
+				&store_writer, SDB_OBJ(global_store)))
+		return -1;
+	return sdb_plugin_register_reader("memstore",
+			&store_reader, SDB_OBJ(global_store));
+} /* sdb_store_init */
 
-	{
-		char type[strlen(m->store.type) + 1];
-		char id[strlen(m->store.id) + 1];
+void
+sdb_store_clear(void)
+{
+	if (! global_store)
+		return;
+	sdb_avltree_clear(global_store->hosts);
+} /* sdb_store_clear */
 
-		strncpy(type, m->store.type, sizeof(type));
-		strncpy(id, m->store.id, sizeof(id));
-		pthread_rwlock_unlock(&host_lock);
+sdb_store_obj_t *
+sdb_store_get_host(const char *name)
+{
+	sdb_host_t *host;
 
-		ts = sdb_plugin_fetch_timeseries(type, id, opts);
-		if (! ts) {
-			sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
-					"- %s fetcher callback returned no data for '%s'",
-					hostname, metric, type, id);
-			return -1;
-		}
-	}
+	if ((! global_store) || (! name))
+		return NULL;
 
-	ts_tojson(ts, buf);
-	sdb_timeseries_destroy(ts);
-	return 0;
-} /* sdb_store_fetch_timeseries */
+	host = lookup_host(global_store, name, /* canonicalize = */ 0);
+	if (! host)
+		return NULL;
+
+	return STORE_OBJ(host);
+} /* sdb_store_get_host */
+
+sdb_store_obj_t *
+sdb_store_get_child(sdb_store_obj_t *host, int type, const char *name)
+{
+	sdb_avltree_t *children;
+
+	if ((! host) || (host->type != SDB_HOST) || (! name))
+		return NULL;
+
+	children = get_host_children(HOST(host), type);
+	if (! children)
+		return NULL;
+	return STORE_OBJ(sdb_avltree_lookup(children, name));
+} /* sdb_store_get_child */
 
 int
 sdb_store_get_field(sdb_store_obj_t *obj, int field, sdb_data_t *res)
@@ -919,13 +943,23 @@ sdb_store_get_field(sdb_store_obj_t *obj, int field, sdb_data_t *res)
 			tmp.data.datetime = obj->interval;
 			break;
 		case SDB_FIELD_BACKEND:
-		{
+			if (! res)
+				return 0;
 			tmp.type = SDB_TYPE_ARRAY | SDB_TYPE_STRING;
 			tmp.data.array.length = obj->backends_num;
 			tmp.data.array.values = obj->backends;
 			return sdb_data_copy(res, &tmp);
-			break;
-		}
+		case SDB_FIELD_VALUE:
+			if (obj->type != SDB_ATTRIBUTE)
+				return -1;
+			if (! res)
+				return 0;
+			return sdb_data_copy(res, &ATTR(obj)->value);
+		case SDB_FIELD_TIMESERIES:
+			if (obj->type != SDB_METRIC)
+				return -1;
+			tmp.type = SDB_TYPE_BOOLEAN;
+			tmp.data.boolean = METRIC(obj)->store.type != NULL;
 		default:
 			return -1;
 	}
@@ -971,126 +1005,82 @@ sdb_store_get_attr(sdb_store_obj_t *obj, const char *name, sdb_data_t *res,
 	return 0;
 } /* sdb_store_get_attr */
 
+/* TODO: sdb_store_fetch_timeseries should move into the plugin module */
+
 int
-sdb_store_host_tojson(sdb_store_obj_t *h, sdb_strbuf_t *buf,
-		sdb_store_matcher_t *filter, int flags)
+sdb_store_fetch_timeseries(const char *hostname, const char *metric,
+		sdb_timeseries_opts_t *opts, sdb_strbuf_t *buf)
 {
-	sdb_host_t *host = HOST(h);
-
-	if ((! h) || (h->type != SDB_HOST) || (! buf))
-		return -1;
-
-	/* This function ignores SKIP_EMPTY flags given that the current
-	 * implementation sucks and it's nut currently used when calling this
-	 * function directly. */
+	sdb_avltree_t *metrics;
+	sdb_host_t *host;
+	sdb_metric_t *m;
 
-	sdb_strbuf_append(buf, "{\"name\": \"%s\", ", SDB_OBJ(host)->name);
-	store_common_tojson(h, buf);
+	sdb_timeseries_t *ts;
 
-	if (! (flags & SDB_SKIP_ATTRIBUTES)) {
-		sdb_strbuf_append(buf, ", \"attributes\": ");
-		store_obj_tojson(host->attributes, SDB_ATTRIBUTE, buf, filter, flags);
-	}
+	int status = 0;
 
-	if (! (flags & SDB_SKIP_METRICS)) {
-		sdb_strbuf_append(buf, ", \"metrics\": ");
-		store_obj_tojson(host->metrics, SDB_METRIC, buf, filter, flags);
-	}
+	if ((! global_store) || (! hostname) || (! metric) || (! opts) || (! buf))
+		return -1;
 
-	if (! (flags & SDB_SKIP_SERVICES)) {
-		sdb_strbuf_append(buf, ", \"services\": ");
-		store_obj_tojson(host->services, SDB_SERVICE, buf, filter, flags);
+	pthread_rwlock_rdlock(&global_store->host_lock);
+	host = lookup_host(global_store, hostname, /* canonicalize = */ 1);
+	metrics = get_host_children(host, SDB_METRIC);
+	sdb_object_deref(SDB_OBJ(host));
+	if (! metrics) {
+		sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
+				"- host '%s' not found", hostname, metric, hostname);
+		pthread_rwlock_unlock(&global_store->host_lock);
+		return -1;
 	}
 
-	sdb_strbuf_append(buf, "}");
-	return 0;
-} /* sdb_store_host_tojson */
-
-static _Bool
-has_children(sdb_avltree_t *tree, sdb_store_matcher_t *filter)
-{
-	sdb_avltree_iter_t *iter;
-
-	if (! filter)
-		return sdb_avltree_size(tree) > 0;
-
-	iter = sdb_avltree_get_iter(tree);
-	while (sdb_avltree_iter_has_next(iter)) {
-		sdb_store_obj_t *sobj = STORE_OBJ(sdb_avltree_iter_get_next(iter));
-		if (sdb_store_matcher_matches(filter, sobj, NULL)) {
-			sdb_avltree_iter_destroy(iter);
-			return 1;
-		}
-	}
-	sdb_avltree_iter_destroy(iter);
-	return 0;
-} /* has_children */
-
-int
-sdb_store_tojson(sdb_strbuf_t *buf, sdb_store_matcher_t *filter, int flags)
-{
-	sdb_avltree_iter_t *host_iter;
-	size_t len;
-
-	if (! buf)
+	m = METRIC(sdb_avltree_lookup(metrics, metric));
+	if (! m) {
+		sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
+				"- metric '%s' not found", hostname, metric, metric);
+		pthread_rwlock_unlock(&global_store->host_lock);
 		return -1;
+	}
 
-	pthread_rwlock_rdlock(&host_lock);
-
-	host_iter = sdb_avltree_get_iter(hosts);
-	if (! host_iter) {
-		pthread_rwlock_unlock(&host_lock);
+	if ((! m->store.type) || (! m->store.id)) {
+		sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
+				"- no data-store configured for the stored metric",
+				hostname, metric);
+		sdb_object_deref(SDB_OBJ(m));
+		pthread_rwlock_unlock(&global_store->host_lock);
 		return -1;
 	}
 
-	sdb_strbuf_append(buf, "[");
-
-	len = sdb_strbuf_len(buf);
-	while (sdb_avltree_iter_has_next(host_iter)) {
-		sdb_store_obj_t *host;
-
-		host = STORE_OBJ(sdb_avltree_iter_get_next(host_iter));
-		assert(host);
-
-		if (filter && (! sdb_store_matcher_matches(filter, host, NULL)))
-			continue;
-
-		/*
-		 * XXX: This approach sucks but it's the best we can do at the moment.
-		 * In the future, all store lookups should be split into multiple
-		 * steps instead: first, retrieve all relevant objects and apply all
-		 * pre-processing operations and then format it for the wire.
-		 */
-		if ((flags & SDB_SKIP_EMPTY_SERVICES)
-				&& (! has_children(HOST(host)->services, filter)))
-			continue;
-		if ((flags & SDB_SKIP_EMPTY_METRICS)
-				&& (! has_children(HOST(host)->metrics, filter)))
-			continue;
+	{
+		char type[strlen(m->store.type) + 1];
+		char id[strlen(m->store.id) + 1];
 
-		if (sdb_strbuf_len(buf) > len)
-			sdb_strbuf_append(buf, ",");
-		len = sdb_strbuf_len(buf);
+		strncpy(type, m->store.type, sizeof(type));
+		strncpy(id, m->store.id, sizeof(id));
+		pthread_rwlock_unlock(&global_store->host_lock);
 
-		if (sdb_store_host_tojson(host, buf, filter, flags))
-			return -1;
+		ts = sdb_plugin_fetch_timeseries(type, id, opts);
+		if (! ts) {
+			sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
+					"- %s fetcher callback returned no data for '%s'",
+					hostname, metric, type, id);
+			status = -1;
+		}
 	}
 
-	sdb_strbuf_append(buf, "]");
-
-	sdb_avltree_iter_destroy(host_iter);
-	pthread_rwlock_unlock(&host_lock);
-	return 0;
-} /* sdb_store_tojson */
+	ts_tojson(ts, buf);
+	sdb_object_deref(SDB_OBJ(m));
+	sdb_timeseries_destroy(ts);
+	return status;
+} /* sdb_store_fetch_timeseries */
 
 int
 sdb_store_scan(int type, sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
 		sdb_store_lookup_cb cb, void *user_data)
 {
-	sdb_avltree_iter_t *host_iter;
+	sdb_avltree_iter_t *host_iter = NULL;
 	int status = 0;
 
-	if (! cb)
+	if ((! global_store) || (! cb))
 		return -1;
 
 	if ((type != SDB_HOST) && (type != SDB_SERVICE) && (type != SDB_METRIC)) {
@@ -1098,9 +1088,8 @@ sdb_store_scan(int type, sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
 		return -1;
 	}
 
-	pthread_rwlock_rdlock(&host_lock);
-
-	host_iter = sdb_avltree_get_iter(hosts);
+	pthread_rwlock_rdlock(&global_store->host_lock);
+	host_iter = sdb_avltree_get_iter(global_store->hosts);
 	if (! host_iter)
 		status = -1;
 
@@ -1150,7 +1139,7 @@ sdb_store_scan(int type, sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
 	}
 
 	sdb_avltree_iter_destroy(host_iter);
-	pthread_rwlock_unlock(&host_lock);
+	pthread_rwlock_unlock(&global_store->host_lock);
 	return status;
 } /* sdb_store_scan */