X-Git-Url: https://git.tokkee.org/?p=sysdb.git;a=blobdiff_plain;f=src%2Fcore%2Fstore.c;h=e643f457a7e6ba564242e369f8ad7bf64b0ebbd2;hp=2522233112a8d125024d9853710ff90565f768d4;hb=82f8f7dbf1dcfb18f74f1ca8b58ed823a1225404;hpb=c9ed4d2a7a92ef589809a7df9b04c061afa4ef64

diff --git a/src/core/store.c b/src/core/store.c
index 2522233..e643f45 100644
--- a/src/core/store.c
+++ b/src/core/store.c
@@ -25,11 +25,15 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#if HAVE_CONFIG_H
+#	include "config.h"
+#endif /* HAVE_CONFIG_H */
+
 #include "sysdb.h"
-#include "core/store.h"
+#include "core/store-private.h"
 #include "core/plugin.h"
+#include "utils/avltree.h"
 #include "utils/error.h"
-#include "utils/llist.h"
 
 #include <assert.h>
 
@@ -39,557 +43,1034 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <math.h>
 #include <pthread.h>
 
 /*
  * private variables
  */
 
-static sdb_llist_t *obj_list = NULL;
-static pthread_rwlock_t obj_lock = PTHREAD_RWLOCK_INITIALIZER;
+struct sdb_store {
+	sdb_object_t super;
+
+	/* hosts are the top-level entries and
+	 * reference everything else */
+	sdb_avltree_t *hosts;
+	pthread_rwlock_t host_lock;
+};
 
 /*
  * private types
  */
 
-static sdb_type_t sdb_store_obj_type;
-static sdb_type_t sdb_attribute_type;
-
-struct sdb_store_base {
-	sdb_object_t super;
-
-	/* object type */
-	int 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;
 
-	/* common meta information */
-	sdb_time_t last_update;
-	sdb_store_base_t *parent;
-};
-#define STORE_BASE(obj) ((sdb_store_base_t *)(obj))
-#define STORE_CONST_BASE(obj) ((const sdb_store_base_t *)(obj))
-
-typedef struct {
-	sdb_store_base_t super;
-
-	sdb_data_t value;
-} sdb_attribute_t;
-#define SDB_ATTR(obj) ((sdb_attribute_t *)(obj))
-#define SDB_CONST_ATTR(obj) ((const sdb_attribute_t *)(obj))
-
-typedef struct {
-	sdb_store_base_t super;
-
-	sdb_llist_t *children;
-	sdb_llist_t *attributes;
-} sdb_store_obj_t;
-#define SDB_STORE_OBJ(obj) ((sdb_store_obj_t *)(obj))
-#define SDB_CONST_STORE_OBJ(obj) ((const sdb_store_obj_t *)(obj))
-
-enum {
-	SDB_HOST = 1,
-	SDB_SERVICE,
-	SDB_ATTRIBUTE,
-};
-#define TYPE_TO_NAME(t) \
-	(((t) == SDB_HOST) ? "host" \
-		: ((t) == SDB_SERVICE) ? "service" \
-		: ((t) == SDB_ATTRIBUTE) ? "attribute" : "unknown")
+static int
+store_init(sdb_object_t *obj, va_list __attribute__((unused)) ap)
+{
+	int err;
+	if (! (SDB_STORE(obj)->hosts = sdb_avltree_create()))
+		return -1;
+	if ((err = pthread_rwlock_init(&SDB_STORE(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 */
 
-/* shortcuts for accessing the sdb_store_obj_t attributes
- * of inheriting objects */
-#define _last_update super.last_update
+static void
+store_destroy(sdb_object_t *obj)
+{
+	int err;
+	if ((err = pthread_rwlock_destroy(&SDB_STORE(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(SDB_STORE(obj)->hosts);
+	SDB_STORE(obj)->hosts = NULL;
+} /* store_destroy */
 
 static int
-store_base_init(sdb_object_t *obj, va_list ap)
+store_obj_init(sdb_object_t *obj, va_list ap)
 {
-	sdb_store_base_t *sobj = STORE_BASE(obj);
+	sdb_store_obj_t *sobj = STORE_OBJ(obj);
 
 	sobj->type = va_arg(ap, int);
 
 	sobj->last_update = va_arg(ap, sdb_time_t);
+	sobj->interval = 0;
+	sobj->backends = NULL;
+	sobj->backends_num = 0;
 	sobj->parent = NULL;
 	return 0;
-} /* store_base_init */
+} /* store_obj_init */
 
 static void
-store_base_destroy(sdb_object_t *obj)
+store_obj_destroy(sdb_object_t *obj)
 {
-	const sdb_store_base_t *sobj = STORE_CONST_BASE(obj);
+	sdb_store_obj_t *sobj = STORE_OBJ(obj);
+	size_t i;
+
+	for (i = 0; i < sobj->backends_num; ++i)
+		free(sobj->backends[i]);
+	free(sobj->backends);
+	sobj->backends = NULL;
+	sobj->backends_num = 0;
 
-	if (sobj->parent)
-		sdb_object_deref(SDB_OBJ(sobj->parent));
-} /* store_base_destroy */
+	// 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_store_obj_init(sdb_object_t *obj, va_list ap)
+host_init(sdb_object_t *obj, va_list ap)
 {
-	sdb_store_obj_t *sobj = SDB_STORE_OBJ(obj);
+	host_t *sobj = HOST(obj);
 	int ret;
 
 	/* this will consume the first argument (type) of ap */
-	ret = store_base_init(obj, ap);
+	ret = store_obj_init(obj, ap);
 	if (ret)
 		return ret;
 
-	sobj->children = sdb_llist_create();
-	if (! sobj->children)
+	sobj->services = sdb_avltree_create();
+	if (! sobj->services)
 		return -1;
-	sobj->attributes = sdb_llist_create();
+	sobj->metrics = sdb_avltree_create();
+	if (! sobj->metrics)
+		return -1;
+	sobj->attributes = sdb_avltree_create();
+	if (! sobj->attributes)
+		return -1;
+	return 0;
+} /* host_init */
+
+static void
+host_destroy(sdb_object_t *obj)
+{
+	host_t *sobj = HOST(obj);
+	assert(obj);
+
+	store_obj_destroy(obj);
+
+	if (sobj->services)
+		sdb_avltree_destroy(sobj->services);
+	if (sobj->metrics)
+		sdb_avltree_destroy(sobj->metrics);
+	if (sobj->attributes)
+		sdb_avltree_destroy(sobj->attributes);
+} /* host_destroy */
+
+static int
+service_init(sdb_object_t *obj, va_list ap)
+{
+	service_t *sobj = SVC(obj);
+	int ret;
+
+	/* this will consume the first argument (type) of ap */
+	ret = store_obj_init(obj, ap);
+	if (ret)
+		return ret;
+
+	sobj->attributes = sdb_avltree_create();
 	if (! sobj->attributes)
 		return -1;
 	return 0;
-} /* sdb_store_obj_init */
+} /* service_init */
 
 static void
-sdb_store_obj_destroy(sdb_object_t *obj)
+service_destroy(sdb_object_t *obj)
+{
+	service_t *sobj = SVC(obj);
+	assert(obj);
+
+	store_obj_destroy(obj);
+
+	if (sobj->attributes)
+		sdb_avltree_destroy(sobj->attributes);
+} /* service_destroy */
+
+static int
+metric_init(sdb_object_t *obj, va_list ap)
 {
-	sdb_store_obj_t *sobj = SDB_STORE_OBJ(obj);
+	sdb_metric_t *sobj = METRIC(obj);
+	int ret;
+
+	/* this will consume the first argument (type) of ap */
+	ret = store_obj_init(obj, ap);
+	if (ret)
+		return ret;
+
+	sobj->attributes = sdb_avltree_create();
+	if (! sobj->attributes)
+		return -1;
+
+	sobj->store.type = sobj->store.id = NULL;
+	return 0;
+} /* metric_init */
 
+static void
+metric_destroy(sdb_object_t *obj)
+{
+	sdb_metric_t *sobj = METRIC(obj);
 	assert(obj);
 
-	store_base_destroy(obj);
+	store_obj_destroy(obj);
 
-	if (sobj->children)
-		sdb_llist_destroy(sobj->children);
 	if (sobj->attributes)
-		sdb_llist_destroy(sobj->attributes);
-} /* sdb_store_obj_destroy */
+		sdb_avltree_destroy(sobj->attributes);
+
+	if (sobj->store.type)
+		free(sobj->store.type);
+	if (sobj->store.id)
+		free(sobj->store.id);
+} /* 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;
 
 	/* this will consume the first two arguments
 	 * (type and last_update) of ap */
-	ret = store_base_init(obj, ap);
+	ret = store_obj_init(obj, ap);
 	if (ret)
 		return ret;
 	value = va_arg(ap, const sdb_data_t *);
 
 	if (value)
-		if (sdb_data_copy(&SDB_ATTR(obj)->value, value))
+		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_base_destroy(obj);
-	sdb_data_free_datum(&SDB_ATTR(obj)->value);
-} /* sdb_attr_destroy */
+	store_obj_destroy(obj);
+	sdb_data_free_datum(&ATTR(obj)->value);
+} /* attr_destroy */
 
-static sdb_type_t sdb_store_obj_type = {
-	sizeof(sdb_store_obj_t),
+static sdb_type_t store_type = {
+	/* size = */ sizeof(sdb_store_t),
+	/* init = */ store_init,
+	/* destroy = */ store_destroy,
+};
 
-	sdb_store_obj_init,
-	sdb_store_obj_destroy
+static sdb_type_t host_type = {
+	/* size = */ sizeof(host_t),
+	/* init = */ host_init,
+	/* destroy = */ host_destroy
 };
 
-static sdb_type_t sdb_attribute_type = {
-	sizeof(sdb_attribute_t),
+static sdb_type_t service_type = {
+	/* size = */ sizeof(service_t),
+	/* init = */ service_init,
+	/* destroy = */ service_destroy
+};
 
-	sdb_attr_init,
-	sdb_attr_destroy
+static sdb_type_t metric_type = {
+	/* size = */ sizeof(sdb_metric_t),
+	/* init = */ metric_init,
+	/* destroy = */ metric_destroy
+};
+
+static sdb_type_t attribute_type = {
+	/* size = */ sizeof(attr_t),
+	/* init = */ attr_init,
+	/* destroy = */ attr_destroy
 };
 
 /*
  * private helper functions
  */
 
-static sdb_store_obj_t *
-sdb_store_lookup_in_list(sdb_llist_t *l, int type, const char *name)
+static int
+record_backend(sdb_store_obj_t *obj)
 {
-	sdb_llist_iter_t *iter;
-
-	if (! l)
-		return NULL;
+	const sdb_plugin_info_t *info;
+	char **tmp;
+	size_t i;
 
-	iter = sdb_llist_get_iter(l);
-	if (! iter)
-		return NULL;
+	info = sdb_plugin_current();
+	if (! info)
+		return 0;
 
-	while (sdb_llist_iter_has_next(iter)) {
-		sdb_store_obj_t *sobj = SDB_STORE_OBJ(sdb_llist_iter_get_next(iter));
-		assert(sobj);
+	for (i = 0; i < obj->backends_num; ++i)
+		if (!strcasecmp(obj->backends[i], info->plugin_name))
+			return 0;
 
-		if ((STORE_BASE(sobj)->type == type)
-				&& (! strcasecmp(SDB_OBJ(sobj)->name, name))) {
-			sdb_llist_iter_destroy(iter);
-			return sobj;
-		}
-
-		/* don't lookups non-host types from hierarchical hosts */
-		if ((type != SDB_HOST) && (STORE_BASE(sobj)->type == SDB_HOST))
-			continue;
+	tmp = realloc(obj->backends,
+			(obj->backends_num + 1) * sizeof(*obj->backends));
+	if (! tmp)
+		return -1;
 
-		sobj = sdb_store_lookup_in_list(sobj->children, type, name);
-		if (sobj) {
-			sdb_llist_iter_destroy(iter);
-			return sobj;
-		}
-	}
-	sdb_llist_iter_destroy(iter);
-	return NULL;
-} /* sdb_store_lookup_in_list */
+	obj->backends = tmp;
+	obj->backends[obj->backends_num] = strdup(info->plugin_name);
+	if (! obj->backends[obj->backends_num])
+		return -1;
 
-static sdb_store_obj_t *
-sdb_store_lookup(int type, const char *name)
-{
-	return sdb_store_lookup_in_list(obj_list, type, name);
-} /* sdb_store_lookup */
+	++obj->backends_num;
+	return 0;
+} /* record_backend */
 
-/* The obj_lock has to be acquired before calling this function. */
 static int
-store_obj(int parent_type, const char *parent_name,
+store_obj(sdb_store_obj_t *parent, sdb_avltree_t *parent_tree,
 		int type, const char *name, sdb_time_t last_update,
-		sdb_store_base_t **updated_obj)
+		sdb_store_obj_t **updated_obj)
 {
-	char *parent_cname = NULL, *cname = NULL;
-
-	sdb_llist_t *parent_list;
-	sdb_store_base_t *old;
+	sdb_store_obj_t *old, *new;
 	int status = 0;
 
+	assert(parent_tree);
+
 	if (last_update <= 0)
 		last_update = sdb_gettime();
 
-	assert((parent_type == 0)
-			|| (parent_type == SDB_HOST)
-			|| (parent_type == SDB_SERVICE));
-	assert((type == 0)
-			|| (type == SDB_HOST)
-			|| (type == SDB_SERVICE)
-			|| (type == SDB_ATTRIBUTE));
-
-	if (parent_type == SDB_HOST) {
-		parent_cname = sdb_plugin_cname(strdup(parent_name));
-		if (! parent_cname) {
-			sdb_log(SDB_LOG_ERR, "store: strdup failed");
-			return -1;
-		}
-		parent_name = parent_cname;
-	}
-	if (type == SDB_HOST) {
-		cname = sdb_plugin_cname(strdup(name));
-		if (! cname) {
-			sdb_log(SDB_LOG_ERR, "store: strdup failed");
-			return -1;
-		}
-		name = cname;
-	}
-
-	if (! obj_list) {
-		if (! (obj_list = sdb_llist_create())) {
-			free(parent_cname);
-			free(cname);
-			return -1;
-		}
-	}
-	parent_list = obj_list;
-
-	if (parent_type && parent_name) {
-		sdb_store_obj_t *parent;
-
-		parent = sdb_store_lookup(parent_type, parent_name);
-		if (! parent) {
-			sdb_log(SDB_LOG_ERR, "store: Failed to store %s '%s' - "
-					"parent %s '%s' not found", TYPE_TO_NAME(type), name,
-					TYPE_TO_NAME(parent_type), parent_name);
-			free(parent_cname);
-			free(cname);
-			return -1;
-		}
-
-		if (type == SDB_ATTRIBUTE)
-			parent_list = parent->attributes;
-		else
-			parent_list = parent->children;
-	}
-
-	if (type == SDB_HOST)
-		/* make sure that each host is unique */
-		old = STORE_BASE(sdb_store_lookup_in_list(obj_list, type, name));
-	else if (type == SDB_ATTRIBUTE)
-		/* look into attributes of this host */
-		old = STORE_BASE(sdb_llist_search_by_name(parent_list, name));
-	else
-		/* look into services assigned to this host (sdb_store_lookup_in_list
-		 * does not look up services from hierarchical hosts) */
-		old = STORE_BASE(sdb_store_lookup_in_list(parent_list, type, name));
-
+	old = STORE_OBJ(sdb_avltree_lookup(parent_tree, name));
 	if (old) {
 		if (old->last_update > last_update) {
 			sdb_log(SDB_LOG_DEBUG, "store: Cannot update %s '%s' - "
-					"value too old (%"PRIscTIME" < %"PRIscTIME")",
-					TYPE_TO_NAME(type), name, last_update, old->last_update);
+					"value too old (%"PRIsdbTIME" < %"PRIsdbTIME")",
+					SDB_STORE_TYPE_TO_NAME(type), name,
+					last_update, old->last_update);
 			/* don't report an error; the object may be updated by multiple
 			 * backends */
 			status = 1;
 		}
+		else if (old->last_update == last_update) {
+			/* don't report an error and also don't even log this to avoid
+			 * excessive noise on high sampling frequencies */
+			status = 1;
+		}
 		else {
+			sdb_time_t interval = last_update - old->last_update;
 			old->last_update = last_update;
+			if (interval) {
+				if (old->interval)
+					old->interval = (sdb_time_t)((0.9 * (double)old->interval)
+							+ (0.1 * (double)interval));
+				else
+					old->interval = interval;
+			}
 		}
 
-		if (updated_obj)
-			*updated_obj = old;
+		new = old;
+		sdb_object_deref(SDB_OBJ(old));
 	}
 	else {
-		sdb_store_base_t *new;
-
-		if (type == SDB_ATTRIBUTE)
+		if (type == SDB_ATTRIBUTE) {
 			/* the value will be updated by the caller */
-			new = STORE_BASE(sdb_object_create(name, sdb_attribute_type,
+			new = STORE_OBJ(sdb_object_create(name, attribute_type,
 						type, last_update, NULL));
-		else
-			new = STORE_BASE(sdb_object_create(name, sdb_store_obj_type,
-						type, last_update));
+		}
+		else {
+			sdb_type_t t;
+			t = type == SDB_HOST
+				? host_type
+				: type == SDB_SERVICE
+					? service_type
+					: metric_type;
+			new = STORE_OBJ(sdb_object_create(name, t, type, last_update));
+		}
+
+		if (new) {
+			status = sdb_avltree_insert(parent_tree, SDB_OBJ(new));
 
-		if (! new) {
+			/* pass control to the tree or destroy in case of an error */
+			sdb_object_deref(SDB_OBJ(new));
+		}
+		else {
 			char errbuf[1024];
 			sdb_log(SDB_LOG_ERR, "store: Failed to create %s '%s': %s",
-					TYPE_TO_NAME(type), name,
+					SDB_STORE_TYPE_TO_NAME(type), name,
 					sdb_strerror(errno, errbuf, sizeof(errbuf)));
-			free(parent_cname);
-			free(cname);
-			return -1;
+			status = -1;
 		}
+	}
 
-		/* TODO: insert type-aware; the current version works as long as we
-		 * don't support to store hierarchical data */
-		status = sdb_llist_insert_sorted(parent_list, SDB_OBJ(new),
-				sdb_object_cmp_by_name);
-
-		/* pass control to the list or destroy in case of an error */
-		sdb_object_deref(SDB_OBJ(new));
+	if (status < 0)
+		return status;
+	assert(new);
 
-		if (updated_obj)
-			*updated_obj = 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;
 	}
-	free(parent_cname);
-	free(cname);
+
+	if (updated_obj)
+		*updated_obj = new;
+
+	if (record_backend(new))
+		return -1;
 	return status;
 } /* store_obj */
 
+static int
+store_metric_store(sdb_metric_t *metric, sdb_store_metric_t *m)
+{
+	char *type = metric->store.type;
+	char *id = metric->store.id;
+
+	if ((! metric->store.type) || strcasecmp(metric->store.type, m->store.type)) {
+		if (! (type = strdup(m->store.type)))
+			return -1;
+	}
+	if ((! metric->store.id) || strcasecmp(metric->store.id, m->store.id)) {
+		if (! (id = strdup(m->store.id))) {
+			if (type != metric->store.type)
+				free(type);
+			return -1;
+		}
+	}
+
+	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 */
+
+/* The store's host_lock has to be acquired before calling this function. */
+static sdb_avltree_t *
+get_host_children(host_t *host, int type)
+{
+	if ((type != SDB_SERVICE) && (type != SDB_METRIC)
+			&& (type != SDB_ATTRIBUTE))
+		return NULL;
+
+	if (! host)
+		return NULL;
+
+	if (type == SDB_ATTRIBUTE)
+		return host->attributes;
+	else if (type == SDB_METRIC)
+		return host->metrics;
+	else
+		return host->services;
+} /* get_host_children */
+
 /*
- * store_obj_tojson serializes attribute / service objects to JSON.
+ * ts_tojson serializes a time-series 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_llist_t *list, int type, sdb_strbuf_t *buf)
+ts_tojson(sdb_timeseries_t *ts, sdb_strbuf_t *buf)
 {
-	sdb_llist_iter_t *iter;
-	char time_str[64];
+	char start_str[64];
+	char end_str[64];
+
+	size_t i;
+
+	/* TODO: make time format configurable */
+	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), ts->end))
+		snprintf(end_str, sizeof(end_str), "<error>");
+	end_str[sizeof(end_str) - 1] = '\0';
+
+	sdb_strbuf_append(buf, "{\"start\": \"%s\", \"end\": \"%s\", \"data\": {",
+			start_str, end_str);
+
+	for (i = 0; i < ts->data_names_len; ++i) {
+		size_t j;
+		sdb_strbuf_append(buf, "\"%s\": [", ts->data_names[i]);
+
+		for (j = 0; j < ts->data_len; ++j) {
+			char time_str[64];
+
+			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';
+
+			/* 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, ",");
+		}
 
-	assert((type == SDB_ATTRIBUTE) || (type == SDB_SERVICE));
+		if (i < ts->data_names_len - 1)
+			sdb_strbuf_append(buf, "],");
+		else
+			sdb_strbuf_append(buf, "]");
+	}
+	sdb_strbuf_append(buf, "}}");
+} /* ts_tojson */
 
-	sdb_strbuf_append(buf, "[");
+/*
+ * store writer API
+ */
 
-	iter = sdb_llist_get_iter(list);
-	if (! iter) {
-		char errbuf[1024];
-		sdb_log(SDB_LOG_ERR, "store: Failed to retrieve %ss: %s\n",
-				TYPE_TO_NAME(type),
-				sdb_strerror(errno, errbuf, sizeof(errbuf)));
-		sdb_strbuf_append(buf, "{\"error\": \"failed to retrieve %ss: %s\"}",
-				TYPE_TO_NAME(type), errbuf);
+static int
+store_attribute(sdb_store_attribute_t *attr, sdb_object_t *user_data)
+{
+	sdb_store_t *st = SDB_STORE(user_data);
+	sdb_store_obj_t *parent = NULL;
+	sdb_store_obj_t *new = NULL;
+	const char *hostname;
+	host_t *host;
+
+	sdb_avltree_t *children = NULL;
+	sdb_avltree_t *attributes;
+	int status = 0;
+
+	if ((! attr) || (! attr->parent) || (! attr->key))
+		return -1;
+
+	hostname = attr->hostname;
+	if (attr->parent_type == SDB_HOST)
+		hostname = attr->parent;
+	if (! hostname)
+		return -1;
+
+	pthread_rwlock_wrlock(&st->host_lock);
+	host = HOST(sdb_avltree_lookup(st->hosts, hostname));
+	if (! host) {
+		sdb_log(SDB_LOG_ERR, "store: Failed to store attribute '%s' - "
+				"host '%s' not found", attr->key, hostname);
+		status = -1;
 	}
 
-	/* has_next returns false if the iterator is NULL */
-	while (sdb_llist_iter_has_next(iter)) {
-		sdb_store_base_t *sobj = STORE_BASE(sdb_llist_iter_get_next(iter));
-		assert(sobj);
-
-		if (! sdb_strftime(time_str, sizeof(time_str),
-					"%F %T %z", sobj->last_update))
-			snprintf(time_str, sizeof(time_str), "<error>");
-		time_str[sizeof(time_str) - 1] = '\0';
-
-		sdb_strbuf_append(buf, "{\"name\": \"%s\", ", SDB_OBJ(sobj)->name);
-		if (type == SDB_ATTRIBUTE)
-			/* XXX: this needs to be type-dependent */
-			sdb_strbuf_append(buf, "\"value\": \"%s\", ",
-					SDB_ATTR(sobj)->value.data.string);
-		sdb_strbuf_append(buf, "\"last_update\": \"%s\"}", time_str);
-
-		if (sdb_llist_iter_has_next(iter))
-			sdb_strbuf_append(buf, ",");
+	switch (attr->parent_type) {
+	case SDB_HOST:
+		parent = STORE_OBJ(host);
+		attributes = get_host_children(host, SDB_ATTRIBUTE);
+		break;
+	case SDB_SERVICE:
+		children = get_host_children(host, SDB_SERVICE);
+		break;
+	case SDB_METRIC:
+		children = get_host_children(host, SDB_METRIC);
+		break;
+	default:
+		status = -1;
+		break;
+	}
+
+	if (children) {
+		parent = STORE_OBJ(sdb_avltree_lookup(children, attr->parent));
+		if (! parent) {
+			sdb_log(SDB_LOG_ERR, "store: Failed to store attribute '%s' - "
+					"%s '%s/%s' not found", attr->key,
+					SDB_STORE_TYPE_TO_NAME(attr->parent_type),
+					attr->hostname, attr->parent);
+			status = -1;
+		}
+		else
+			attributes = attr->parent_type == SDB_SERVICE
+				? SVC(parent)->attributes
+				: METRIC(parent)->attributes;
 	}
 
-	sdb_llist_iter_destroy(iter);
-	sdb_strbuf_append(buf, "]");
-} /* store_obj_tojson */
+	if (! status)
+		status = store_obj(parent, attributes, SDB_ATTRIBUTE,
+				attr->key, attr->last_update, &new);
+
+	if (! status) {
+		assert(new);
+		/* update the value if it changed */
+		if (sdb_data_cmp(&ATTR(new)->value, &attr->value))
+			if (sdb_data_copy(&ATTR(new)->value, &attr->value))
+				status = -1;
+	}
+
+	if (parent != STORE_OBJ(host))
+		sdb_object_deref(SDB_OBJ(parent));
+	sdb_object_deref(SDB_OBJ(host));
+	pthread_rwlock_unlock(&st->host_lock);
+
+	return status;
+} /* store_attribute */
+
+static int
+store_host(sdb_store_host_t *host, sdb_object_t *user_data)
+{
+	sdb_store_t *st = SDB_STORE(user_data);
+	int status = 0;
+
+	if ((! host) || (! host->name))
+		return -1;
+
+	pthread_rwlock_wrlock(&st->host_lock);
+	status = store_obj(NULL, st->hosts,
+			SDB_HOST, host->name, host->last_update, NULL);
+	pthread_rwlock_unlock(&st->host_lock);
+
+	return status;
+} /* store_host */
+
+static int
+store_service(sdb_store_service_t *service, sdb_object_t *user_data)
+{
+	sdb_store_t *st = SDB_STORE(user_data);
+
+	host_t *host;
+	sdb_avltree_t *services;
+
+	int status = 0;
+
+	if ((! service) || (! service->hostname) || (! service->name))
+		return -1;
+
+	pthread_rwlock_wrlock(&st->host_lock);
+	host = HOST(sdb_avltree_lookup(st->hosts, service->hostname));
+	services = get_host_children(host, SDB_SERVICE);
+	if (! services) {
+		sdb_log(SDB_LOG_ERR, "store: Failed to store service '%s' - "
+				"host '%s' not found", service->name, service->hostname);
+		status = -1;
+	}
+
+	if (! status)
+		status = store_obj(STORE_OBJ(host), services, SDB_SERVICE,
+				service->name, service->last_update, NULL);
+
+	sdb_object_deref(SDB_OBJ(host));
+	pthread_rwlock_unlock(&st->host_lock);
+	return status;
+} /* store_service */
+
+static int
+store_metric(sdb_store_metric_t *metric, sdb_object_t *user_data)
+{
+	sdb_store_t *st = SDB_STORE(user_data);
+
+	sdb_store_obj_t *obj = NULL;
+	sdb_avltree_t *metrics;
+	host_t *host;
+
+	int status = 0;
+
+	if ((! metric) || (! metric->hostname) || (! metric->name))
+		return -1;
+
+	if ((metric->store.type != NULL) != (metric->store.id != NULL))
+		return -1;
+
+	pthread_rwlock_wrlock(&st->host_lock);
+	host = HOST(sdb_avltree_lookup(st->hosts, metric->hostname));
+	metrics = get_host_children(host, SDB_METRIC);
+	if (! metrics) {
+		sdb_log(SDB_LOG_ERR, "store: Failed to store metric '%s' - "
+				"host '%s' not found", metric->name, metric->hostname);
+		status = -1;
+	}
+
+	if (! status)
+		status = store_obj(STORE_OBJ(host), metrics, SDB_METRIC,
+				metric->name, metric->last_update, &obj);
+	sdb_object_deref(SDB_OBJ(host));
+
+	if (status) {
+		pthread_rwlock_unlock(&st->host_lock);
+		return status;
+	}
+
+	assert(obj);
+	if (metric->store.type && metric->store.id)
+		if (store_metric_store(METRIC(obj), metric))
+			status = -1;
+	pthread_rwlock_unlock(&st->host_lock);
+	return status;
+} /* store_metric */
+
+sdb_store_writer_t sdb_store_writer = {
+	store_host, store_service, store_metric, store_attribute,
+};
+
+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 *user_data)
+{
+	return sdb_store_query_execute(SDB_STORE(user_data),
+			QUERY(q), buf, errbuf);
+} /* execute_query */
+
+sdb_store_reader_t sdb_store_reader = {
+	prepare_query, execute_query,
+};
 
 /*
  * public API
  */
 
+sdb_store_t *
+sdb_store_create(void)
+{
+	return SDB_STORE(sdb_object_create("store", store_type));
+} /* sdb_store_create */
+
 int
-sdb_store_host(const char *name, sdb_time_t last_update)
+sdb_store_host(sdb_store_t *store, const char *name, sdb_time_t last_update)
 {
-	int status;
+	sdb_store_host_t host = {
+		name, last_update, 0, NULL, 0,
+	};
+	return store_host(&host, SDB_OBJ(store));
+} /* sdb_store_host */
 
-	if (! name)
-		return -1;
+int
+sdb_store_service(sdb_store_t *store, const char *hostname, const char *name,
+		sdb_time_t last_update)
+{
+	sdb_store_service_t service = {
+		hostname, name, last_update, 0, NULL, 0,
+	};
+	return store_service(&service, SDB_OBJ(store));
+} /* sdb_store_service */
 
-	pthread_rwlock_wrlock(&obj_lock);
-	status = store_obj(/* parent = */ 0, NULL,
-			/* stored object = */ SDB_HOST, name, last_update,
-			/* updated_obj = */ NULL);
-	pthread_rwlock_unlock(&obj_lock);
-	return status;
-} /* sdb_store_host */
+int
+sdb_store_metric(sdb_store_t *store, const char *hostname, const char *name,
+		sdb_metric_store_t *metric_store, sdb_time_t last_update)
+{
+	sdb_store_metric_t metric = {
+		hostname, name, { NULL, NULL }, last_update, 0, NULL, 0,
+	};
+	if (metric_store) {
+		metric.store.type = metric_store->type;
+		metric.store.id = metric_store->id;
+	}
+	return store_metric(&metric, SDB_OBJ(store));
+} /* sdb_store_metric */
 
-_Bool
-sdb_store_has_host(const char *name)
+int
+sdb_store_attribute(sdb_store_t *store, const char *hostname,
+		const char *key, const sdb_data_t *value, sdb_time_t last_update)
 {
-	sdb_store_obj_t *host;
+	sdb_store_attribute_t attr = {
+		NULL, SDB_HOST, hostname, key, SDB_DATA_INIT, last_update, 0, NULL, 0,
+	};
+	if (value) {
+		attr.value = *value;
+	}
+	return store_attribute(&attr, SDB_OBJ(store));
+} /* sdb_store_attribute */
 
-	if (! name)
-		return NULL;
+int
+sdb_store_service_attr(sdb_store_t *store, const char *hostname,
+		const char *service, const char *key, const sdb_data_t *value,
+		sdb_time_t last_update)
+{
+	sdb_store_attribute_t attr = {
+		hostname, SDB_SERVICE, service, key, SDB_DATA_INIT, last_update, 0, NULL, 0,
+	};
+	if (value) {
+		attr.value = *value;
+	}
+	return store_attribute(&attr, SDB_OBJ(store));
+} /* sdb_store_service_attr */
 
-	host = sdb_store_lookup(SDB_HOST, name);
-	return host != NULL;
-} /* sdb_store_has_host */
+int
+sdb_store_metric_attr(sdb_store_t *store, const char *hostname,
+		const char *metric, const char *key, const sdb_data_t *value,
+		sdb_time_t last_update)
+{
+	sdb_store_attribute_t attr = {
+		hostname, SDB_METRIC, metric, key, SDB_DATA_INIT, last_update, 0, NULL, 0,
+	};
+	if (value) {
+		attr.value = *value;
+	}
+	return store_attribute(&attr, SDB_OBJ(store));
+} /* sdb_store_metric_attr */
 
-sdb_store_base_t *
-sdb_store_get_host(const char *name)
+sdb_store_obj_t *
+sdb_store_get_host(sdb_store_t *store, const char *name)
 {
-	sdb_store_obj_t *host;
+	host_t *host;
 
-	if (! name)
+	if ((! store) || (! name))
 		return NULL;
 
-	host = sdb_store_lookup(SDB_HOST, name);
+	host = HOST(sdb_avltree_lookup(store->hosts, name));
 	if (! host)
 		return NULL;
 
-	sdb_object_ref(SDB_OBJ(host));
-	return STORE_BASE(host);
+	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_store_obj_t *
+sdb_store_get_child(sdb_store_obj_t *host, int type, const char *name)
 {
-	int status;
+	sdb_avltree_t *children;
 
-	sdb_store_base_t *updated_attr = NULL;
+	if ((! host) || (host->type != SDB_HOST) || (! name))
+		return NULL;
 
-	if ((! hostname) || (! key))
-		return -1;
+	children = get_host_children(HOST(host), type);
+	if (! children)
+		return NULL;
+	return STORE_OBJ(sdb_avltree_lookup(children, name));
+} /* sdb_store_get_child */
 
-	pthread_rwlock_wrlock(&obj_lock);
-	status = store_obj(/* parent = */ SDB_HOST, hostname,
-			/* stored object = */ SDB_ATTRIBUTE, key, last_update,
-			&updated_attr);
+int
+sdb_store_get_field(sdb_store_obj_t *obj, int field, sdb_data_t *res)
+{
+	sdb_data_t tmp;
 
-	if (status >= 0) {
-		assert(updated_attr);
-		if (sdb_data_copy(&SDB_ATTR(updated_attr)->value, value)) {
-			sdb_object_deref(SDB_OBJ(updated_attr));
-			status = -1;
-		}
-	}
+	if (! obj)
+		return -1;
 
-	pthread_rwlock_unlock(&obj_lock);
-	return status;
-} /* sdb_store_attribute */
+	switch (field) {
+		case SDB_FIELD_NAME:
+			tmp.type = SDB_TYPE_STRING;
+			tmp.data.string = strdup(SDB_OBJ(obj)->name);
+			if (! tmp.data.string)
+				return -1;
+			break;
+		case SDB_FIELD_LAST_UPDATE:
+			tmp.type = SDB_TYPE_DATETIME;
+			tmp.data.datetime = obj->last_update;
+			break;
+		case SDB_FIELD_AGE:
+			tmp.type = SDB_TYPE_DATETIME;
+			tmp.data.datetime = sdb_gettime() - obj->last_update;
+			break;
+		case SDB_FIELD_INTERVAL:
+			tmp.type = SDB_TYPE_DATETIME;
+			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);
+		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;
+	}
+	if (res)
+		*res = tmp;
+	else
+		sdb_data_free_datum(&tmp);
+	return 0;
+} /* sdb_store_get_field */
 
 int
-sdb_store_service(const char *hostname, const char *name,
-		sdb_time_t last_update)
+sdb_store_get_attr(sdb_store_obj_t *obj, const char *name, sdb_data_t *res,
+		sdb_store_matcher_t *filter)
 {
-	int status;
+	sdb_avltree_t *tree = NULL;
+	sdb_store_obj_t *attr;
 
-	if ((! hostname) || (! name))
+	if ((! obj) || (! name))
 		return -1;
 
-	pthread_rwlock_wrlock(&obj_lock);
-	status = store_obj(/* parent = */ SDB_HOST, hostname,
-			/* stored object = */ SDB_SERVICE, name, last_update,
-			/* updated obj = */ NULL);
-	pthread_rwlock_unlock(&obj_lock);
-	return status;
-} /* sdb_store_service */
+	if (obj->type == SDB_HOST)
+		tree = HOST(obj)->attributes;
+	else if (obj->type == SDB_SERVICE)
+		tree = SVC(obj)->attributes;
+	else if (obj->type == SDB_METRIC)
+		tree = METRIC(obj)->attributes;
+
+	if (! tree)
+		return -1;
+
+	attr = STORE_OBJ(sdb_avltree_lookup(tree, name));
+	if (! attr)
+		return -1;
+	if (filter && (! sdb_store_matcher_matches(filter, attr, NULL))) {
+		sdb_object_deref(SDB_OBJ(attr));
+		return -1;
+	}
+
+	assert(STORE_OBJ(attr)->type == SDB_ATTRIBUTE);
+	if (res)
+		sdb_data_copy(res, &ATTR(attr)->value);
+	sdb_object_deref(SDB_OBJ(attr));
+	return 0;
+} /* sdb_store_get_attr */
+
+/* TODO: sdb_store_fetch_timeseries should move into the plugin module */
 
 int
-sdb_store_host_tojson(sdb_store_base_t *h, sdb_strbuf_t *buf, int flags)
+sdb_store_fetch_timeseries(sdb_store_t *store,
+		const char *hostname, const char *metric,
+		sdb_timeseries_opts_t *opts, sdb_strbuf_t *buf)
 {
-	sdb_store_obj_t *host;
-	char time_str[64];
+	sdb_avltree_t *metrics;
+	host_t *host;
+	sdb_metric_t *m;
 
-	if ((! h) || (h->type != SDB_HOST) || (! buf))
-		return -1;
+	sdb_timeseries_t *ts;
 
-	host = SDB_STORE_OBJ(h);
+	int status = 0;
 
-	if (! sdb_strftime(time_str, sizeof(time_str),
-				"%F %T %z", host->_last_update))
-		snprintf(time_str, sizeof(time_str), "<error>");
-	time_str[sizeof(time_str) - 1] = '\0';
+	if ((! store) || (! hostname) || (! metric) || (! opts) || (! buf))
+		return -1;
 
-	sdb_strbuf_append(buf, "{\"name\": \"%s\", "
-			"\"last_update\": \"%s\"",
-			SDB_OBJ(host)->name, time_str);
+	pthread_rwlock_rdlock(&store->host_lock);
+	host = HOST(sdb_avltree_lookup(store->hosts, hostname));
+	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(&store->host_lock);
+		return -1;
+	}
 
-	if (! (flags & SDB_SKIP_ATTRIBUTES)) {
-		sdb_strbuf_append(buf, ", \"attributes\": ");
-		store_obj_tojson(host->attributes, SDB_ATTRIBUTE, 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(&store->host_lock);
+		return -1;
 	}
 
-	if (! (flags & SDB_SKIP_SERVICES)) {
-		sdb_strbuf_append(buf, ", \"services\": ");
-		store_obj_tojson(host->children, SDB_SERVICE, buf);
+	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(&store->host_lock);
+		return -1;
 	}
 
-	sdb_strbuf_append(buf, "}");
-	return 0;
-} /* sdb_store_host_tojson */
+	{
+		char type[strlen(m->store.type) + 1];
+		char id[strlen(m->store.id) + 1];
+
+		strncpy(type, m->store.type, sizeof(type));
+		strncpy(id, m->store.id, sizeof(id));
+		pthread_rwlock_unlock(&store->host_lock);
+
+		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;
+		}
+	}
+
+	ts_tojson(ts, buf);
+	sdb_object_deref(SDB_OBJ(m));
+	sdb_timeseries_destroy(ts);
+	return status;
+} /* sdb_store_fetch_timeseries */
 
-/* TODO: actually support hierarchical data */
 int
-sdb_store_tojson(sdb_strbuf_t *buf, int flags)
+sdb_store_scan(sdb_store_t *store, int type,
+		sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
+		sdb_store_lookup_cb cb, void *user_data)
 {
-	sdb_llist_iter_t *host_iter;
+	sdb_avltree_iter_t *host_iter = NULL;
+	int status = 0;
 
-	if (! buf)
+	if ((! store) || (! cb))
 		return -1;
 
-	pthread_rwlock_rdlock(&obj_lock);
-
-	host_iter = sdb_llist_get_iter(obj_list);
-	if (! host_iter) {
-		pthread_rwlock_unlock(&obj_lock);
+	if ((type != SDB_HOST) && (type != SDB_SERVICE) && (type != SDB_METRIC)) {
+		sdb_log(SDB_LOG_ERR, "store: Cannot scan objects of type %d", type);
 		return -1;
 	}
 
-	sdb_strbuf_append(buf, "{\"hosts\":[");
+	pthread_rwlock_rdlock(&store->host_lock);
+	host_iter = sdb_avltree_get_iter(store->hosts);
+	if (! host_iter)
+		status = -1;
+
+	/* has_next returns false if the iterator is NULL */
+	while (sdb_avltree_iter_has_next(host_iter)) {
+		sdb_store_obj_t *host;
+		sdb_avltree_iter_t *iter = NULL;
 
-	while (sdb_llist_iter_has_next(host_iter)) {
-		sdb_store_base_t *host = STORE_BASE(sdb_llist_iter_get_next(host_iter));
+		host = STORE_OBJ(sdb_avltree_iter_get_next(host_iter));
 		assert(host);
 
-		if (sdb_store_host_tojson(host, buf, flags))
-			return -1;
+		if (! sdb_store_matcher_matches(filter, host, NULL))
+			continue;
 
-		if (sdb_llist_iter_has_next(host_iter))
-			sdb_strbuf_append(buf, ",");
-	}
+		if (type == SDB_SERVICE)
+			iter = sdb_avltree_get_iter(HOST(host)->services);
+		else if (type == SDB_METRIC)
+			iter = sdb_avltree_get_iter(HOST(host)->metrics);
+
+		if (iter) {
+			while (sdb_avltree_iter_has_next(iter)) {
+				sdb_store_obj_t *obj;
+				obj = STORE_OBJ(sdb_avltree_iter_get_next(iter));
+				assert(obj);
+
+				if (sdb_store_matcher_matches(m, obj, filter)) {
+					if (cb(obj, filter, user_data)) {
+						sdb_log(SDB_LOG_ERR, "store: Callback returned "
+								"an error while scanning");
+						status = -1;
+						break;
+					}
+				}
+			}
+		}
+		else if (sdb_store_matcher_matches(m, host, filter)) {
+			if (cb(host, filter, user_data)) {
+				sdb_log(SDB_LOG_ERR, "store: Callback returned "
+						"an error while scanning");
+				status = -1;
+			}
+		}
 
-	sdb_strbuf_append(buf, "]}");
+		sdb_avltree_iter_destroy(iter);
+		if (status)
+			break;
+	}
 
-	sdb_llist_iter_destroy(host_iter);
-	pthread_rwlock_unlock(&obj_lock);
-	return 0;
-} /* sdb_store_tojson */
+	sdb_avltree_iter_destroy(host_iter);
+	pthread_rwlock_unlock(&store->host_lock);
+	return status;
+} /* sdb_store_scan */
 
 /* vim: set tw=78 sw=4 ts=4 noexpandtab : */