Code

store, plugin: Let the plugin module determine an objects backends.
[sysdb.git] / src / core / store.c
index b2062831c7447cff2feeea535e9ee325e45e70b1..c6e22df69f55591e433c2d52fee5341dea6c2d90 100644 (file)
 #include <stdlib.h>
 #include <string.h>
 
+#include <math.h>
 #include <pthread.h>
 
 /*
- * private variables
+ * private types
  */
 
-static sdb_avltree_t *hosts = NULL;
-static pthread_rwlock_t host_lock = PTHREAD_RWLOCK_INITIALIZER;
+struct sdb_store {
+       sdb_object_t super;
 
-/*
- * private types
- */
+       /* hosts are the top-level entries and
+        * reference everything else */
+       sdb_avltree_t *hosts;
+       pthread_rwlock_t host_lock;
+};
+
+/* internal representation of a to-be-stored object */
+typedef struct {
+       sdb_store_obj_t *parent;
+       sdb_avltree_t *parent_tree;
+       int type;
+       const char *name;
+       sdb_time_t last_update;
+       const char **backends;
+       size_t backends_num;
+} store_obj_t;
+#define STORE_OBJ_INIT { NULL, NULL, 0, NULL, 0, NULL, 0 }
+
+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 (! (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 */
 
-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 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_obj_init(sdb_object_t *obj, va_list ap)
@@ -95,9 +140,9 @@ store_obj_destroy(sdb_object_t *obj)
 } /* 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);
+       host_t *sobj = HOST(obj);
        int ret;
 
        /* this will consume the first argument (type) of ap */
@@ -115,12 +160,12 @@ 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);
+       host_t *sobj = HOST(obj);
        assert(obj);
 
        store_obj_destroy(obj);
@@ -131,12 +176,12 @@ 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);
+       service_t *sobj = SVC(obj);
        int ret;
 
        /* this will consume the first argument (type) of ap */
@@ -148,22 +193,22 @@ 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);
+       service_t *sobj = SVC(obj);
        assert(obj);
 
        store_obj_destroy(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;
@@ -179,10 +224,10 @@ 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);
@@ -196,10 +241,10 @@ 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;
@@ -215,128 +260,116 @@ 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(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(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(attr_t),
+       /* init = */ attr_init,
+       /* destroy = */ attr_destroy
 };
 
 /*
  * private helper functions
  */
 
-static sdb_host_t *
-lookup_host(const char *name, _Bool canonicalize)
-{
-       sdb_host_t *host;
-       char *cname;
-
-       assert(name);
-       if (! canonicalize)
-               return HOST(sdb_avltree_lookup(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(hosts, cname));
-       free(cname);
-       return host;
-} /* lookup_host */
-
 static int
-record_backend(sdb_store_obj_t *obj)
+record_backends(sdb_store_obj_t *obj,
+               const char **backends, size_t backends_num)
 {
-       const sdb_plugin_info_t *info;
        char **tmp;
        size_t i;
 
-       info = sdb_plugin_current();
-       if (! info)
-               return 0;
+       for (i = 0; i < backends_num; i++) {
+               bool found = 0;
+               size_t j;
 
-       for (i = 0; i < obj->backends_num; ++i)
-               if (!strcasecmp(obj->backends[i], info->plugin_name))
-                       return 0;
+               for (j = 0; j < obj->backends_num; ++j) {
+                       if (!strcasecmp(obj->backends[j], backends[i])) {
+                               found = 1;
+                               break;
+                       }
+               }
+               if (found)
+                       continue;
 
-       tmp = realloc(obj->backends,
-                       (obj->backends_num + 1) * sizeof(*obj->backends));
-       if (! tmp)
-               return -1;
+               tmp = realloc(obj->backends,
+                               (obj->backends_num + 1) * sizeof(*obj->backends));
+               if (! tmp)
+                       return -1;
 
-       obj->backends = tmp;
-       obj->backends[obj->backends_num] = strdup(info->plugin_name);
-       if (! obj->backends[obj->backends_num])
-               return -1;
+               obj->backends = tmp;
+               obj->backends[obj->backends_num] = strdup(backends[i]);
+               if (! obj->backends[obj->backends_num])
+                       return -1;
 
-       ++obj->backends_num;
+               ++obj->backends_num;
+       }
        return 0;
-} /* record_backend */
+} /* record_backends */
 
 static int
-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)
+store_obj(store_obj_t *obj, sdb_store_obj_t **updated_obj)
 {
        sdb_store_obj_t *old, *new;
        int status = 0;
 
-       assert(parent_tree);
+       assert(obj->parent_tree);
 
-       if (last_update <= 0)
-               last_update = sdb_gettime();
+       if (obj->last_update <= 0)
+               obj->last_update = sdb_gettime();
 
-       old = STORE_OBJ(sdb_avltree_lookup(parent_tree, name));
+       old = STORE_OBJ(sdb_avltree_lookup(obj->parent_tree, obj->name));
        if (old) {
-               if (old->last_update > last_update) {
+               if (old->last_update > obj->last_update) {
                        sdb_log(SDB_LOG_DEBUG, "store: Cannot update %s '%s' - "
                                        "value too old (%"PRIsdbTIME" < %"PRIsdbTIME")",
-                                       SDB_STORE_TYPE_TO_NAME(type), name,
-                                       last_update, old->last_update);
+                                       SDB_STORE_TYPE_TO_NAME(obj->type), obj->name,
+                                       obj->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) {
+               else if (old->last_update == obj->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;
+                       sdb_time_t interval = obj->last_update - old->last_update;
+                       old->last_update = obj->last_update;
                        if (interval) {
                                if (old->interval)
                                        old->interval = (sdb_time_t)((0.9 * (double)old->interval)
@@ -350,23 +383,24 @@ store_obj(sdb_store_obj_t *parent, sdb_avltree_t *parent_tree,
                sdb_object_deref(SDB_OBJ(old));
        }
        else {
-               if (type == SDB_ATTRIBUTE) {
+               if (obj->type == SDB_ATTRIBUTE) {
                        /* the value will be updated by the caller */
-                       new = STORE_OBJ(sdb_object_create(name, sdb_attribute_type,
-                                               type, last_update, NULL));
+                       new = STORE_OBJ(sdb_object_create(obj->name, attribute_type,
+                                               obj->type, obj->last_update, NULL));
                }
                else {
                        sdb_type_t t;
-                       t = type == SDB_HOST
-                               ? sdb_host_type
-                               : type == SDB_SERVICE
-                                       ? sdb_service_type
-                                       : sdb_metric_type;
-                       new = STORE_OBJ(sdb_object_create(name, t, type, last_update));
+                       t = obj->type == SDB_HOST
+                               ? host_type
+                               : obj->type == SDB_SERVICE
+                                       ? service_type
+                                       : metric_type;
+                       new = STORE_OBJ(sdb_object_create(obj->name, t,
+                                               obj->type, obj->last_update));
                }
 
                if (new) {
-                       status = sdb_avltree_insert(parent_tree, SDB_OBJ(new));
+                       status = sdb_avltree_insert(obj->parent_tree, SDB_OBJ(new));
 
                        /* pass control to the tree or destroy in case of an error */
                        sdb_object_deref(SDB_OBJ(new));
@@ -374,7 +408,7 @@ store_obj(sdb_store_obj_t *parent, sdb_avltree_t *parent_tree,
                else {
                        char errbuf[1024];
                        sdb_log(SDB_LOG_ERR, "store: Failed to create %s '%s': %s",
-                                       SDB_STORE_TYPE_TO_NAME(type), name,
+                                       SDB_STORE_TYPE_TO_NAME(obj->type), obj->name,
                                        sdb_strerror(errno, errbuf, sizeof(errbuf)));
                        status = -1;
                }
@@ -384,50 +418,60 @@ store_obj(sdb_store_obj_t *parent, sdb_avltree_t *parent_tree,
                return status;
        assert(new);
 
-       if (new->parent != parent) {
+       if (new->parent != obj->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;
+               //sdb_object_ref(SDB_OBJ(obj->parent));
+               new->parent = obj->parent;
        }
 
        if (updated_obj)
                *updated_obj = new;
 
-       if (record_backend(new))
+       if (record_backends(new, obj->backends, obj->backends_num))
                return -1;
        return status;
 } /* store_obj */
 
 static int
-store_attr(sdb_store_obj_t *parent, sdb_avltree_t *attributes,
-               const char *key, const sdb_data_t *value, sdb_time_t last_update)
+store_metric_store(sdb_metric_t *metric, sdb_store_metric_t *m)
 {
-       sdb_store_obj_t *attr = NULL;
-       int status;
+       char *type = metric->store.type;
+       char *id = metric->store.id;
 
-       status = store_obj(parent, attributes, SDB_ATTRIBUTE,
-                       key, last_update, &attr);
-       if (status)
-               return status;
-
-       /* don't update unchanged values */
-       if (! sdb_data_cmp(&ATTR(attr)->value, value))
-               return status;
+       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;
+               }
+       }
 
-       assert(attr);
-       if (sdb_data_copy(&ATTR(attr)->value, value))
-               return -1;
-       return status;
-} /* store_attr */
+       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 host_lock has to be acquired before calling this function. */
+/* 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)
+get_host_children(host_t *host, int type)
 {
-       assert((type == SDB_SERVICE) || (type == SDB_METRIC)
-                       || (type == SDB_ATTRIBUTE));
+       if ((type != SDB_SERVICE) && (type != SDB_METRIC)
+                       && (type != SDB_ATTRIBUTE))
+               return NULL;
 
        if (! host)
                return NULL;
@@ -455,12 +499,10 @@ 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';
 
@@ -474,13 +516,17 @@ 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, ",");
@@ -495,334 +541,334 @@ ts_tojson(sdb_timeseries_t *ts, sdb_strbuf_t *buf)
 } /* ts_tojson */
 
 /*
- * public API
+ * store writer API
  */
 
-void
-sdb_store_clear(void)
+static int
+store_attribute(sdb_store_attribute_t *attr, sdb_object_t *user_data)
 {
-       sdb_avltree_destroy(hosts);
-       hosts = NULL;
-} /* sdb_store_clear */
+       sdb_store_t *st = SDB_STORE(user_data);
+       store_obj_t obj = STORE_OBJ_INIT;
+       sdb_store_obj_t *new = NULL;
+       const char *hostname;
+       host_t *host;
 
-int
-sdb_store_host(const char *name, sdb_time_t last_update)
-{
-       char *cname = NULL;
+       sdb_avltree_t *children = NULL;
        int status = 0;
 
-       if (! name)
+       if ((! attr) || (! attr->parent) || (! attr->key))
                return -1;
 
-       cname = sdb_plugin_cname(strdup(name));
-       if (! cname) {
-               sdb_log(SDB_LOG_ERR, "store: strdup failed");
+       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;
+       }
+
+       switch (attr->parent_type) {
+       case SDB_HOST:
+               obj.parent = STORE_OBJ(host);
+               obj.parent_tree = 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;
        }
 
-       pthread_rwlock_wrlock(&host_lock);
-       if (! hosts)
-               if (! (hosts = sdb_avltree_create()))
+       if (children) {
+               obj.parent = STORE_OBJ(sdb_avltree_lookup(children, attr->parent));
+               if (! obj.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
+                       obj.parent_tree = attr->parent_type == SDB_SERVICE
+                               ? SVC(obj.parent)->attributes
+                               : METRIC(obj.parent)->attributes;
+       }
 
+       obj.type = SDB_ATTRIBUTE;
+       obj.name = attr->key;
+       obj.last_update = attr->last_update;
+       obj.backends = attr->backends;
+       obj.backends_num = attr->backends_num;
        if (! status)
-               status = store_obj(NULL, hosts, SDB_HOST, cname, last_update, NULL);
-       pthread_rwlock_unlock(&host_lock);
+               status = store_obj(&obj, &new);
 
-       free(cname);
-       return status;
-} /* sdb_store_host */
-
-_Bool
-sdb_store_has_host(const char *name)
-{
-       sdb_host_t *host;
-
-       if (! name)
-               return NULL;
+       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;
+       }
 
-       host = lookup_host(name, /* canonicalize = */ 0);
+       if (obj.parent != STORE_OBJ(host))
+               sdb_object_deref(SDB_OBJ(obj.parent));
        sdb_object_deref(SDB_OBJ(host));
-       return host != NULL;
-} /* sdb_store_has_host */
-
-sdb_store_obj_t *
-sdb_store_get_host(const char *name)
-{
-       sdb_host_t *host;
+       pthread_rwlock_unlock(&st->host_lock);
 
-       if (! name)
-               return NULL;
-
-       host = lookup_host(name, /* canonicalize = */ 0);
-       if (! host)
-               return NULL;
-
-       return STORE_OBJ(host);
-} /* sdb_store_get_host */
+       return status;
+} /* store_attribute */
 
-int
-sdb_store_attribute(const char *hostname,
-               const char *key, const sdb_data_t *value,
-               sdb_time_t last_update)
+static int
+store_host(sdb_store_host_t *host, sdb_object_t *user_data)
 {
-       sdb_host_t *host;
-       sdb_avltree_t *attrs;
+       sdb_store_t *st = SDB_STORE(user_data);
+       store_obj_t obj = { NULL, st->hosts, SDB_HOST, NULL, 0, NULL, 0 };
        int status = 0;
 
-       if ((! hostname) || (! key))
+       if ((! host) || (! host->name))
                return -1;
 
-       pthread_rwlock_wrlock(&host_lock);
-       host = lookup_host(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);
-               status = -1;
-       }
+       obj.name = host->name;
+       obj.last_update = host->last_update;
+       obj.backends = host->backends;
+       obj.backends_num = host->backends_num;
+       pthread_rwlock_wrlock(&st->host_lock);
+       status = store_obj(&obj, NULL);
+       pthread_rwlock_unlock(&st->host_lock);
 
-       if (! status)
-               status = store_attr(STORE_OBJ(host), attrs, key, value, last_update);
-
-       sdb_object_deref(SDB_OBJ(host));
-       pthread_rwlock_unlock(&host_lock);
        return status;
-} /* sdb_store_attribute */
+} /* store_host */
 
-int
-sdb_store_service(const char *hostname, const char *name,
-               sdb_time_t last_update)
+static int
+store_service(sdb_store_service_t *service, sdb_object_t *user_data)
 {
-       sdb_host_t *host;
-       sdb_avltree_t *services;
+       sdb_store_t *st = SDB_STORE(user_data);
+       store_obj_t obj = STORE_OBJ_INIT;
+       host_t *host;
 
        int status = 0;
 
-       if ((! hostname) || (! name))
+       if ((! service) || (! service->hostname) || (! service->name))
                return -1;
 
-       pthread_rwlock_wrlock(&host_lock);
-       host = lookup_host(hostname, /* canonicalize = */ 1);
-       services = get_host_children(host, SDB_SERVICE);
-       if (! services) {
+       pthread_rwlock_wrlock(&st->host_lock);
+       host = HOST(sdb_avltree_lookup(st->hosts, service->hostname));
+       obj.parent = STORE_OBJ(host);
+       obj.parent_tree = get_host_children(host, SDB_SERVICE);
+       obj.type = SDB_SERVICE;
+       if (! obj.parent_tree) {
                sdb_log(SDB_LOG_ERR, "store: Failed to store service '%s' - "
-                               "host '%s' not found", name, hostname);
+                               "host '%s' not found", service->name, service->hostname);
                status = -1;
        }
 
+       obj.name = service->name;
+       obj.last_update = service->last_update;
+       obj.backends = service->backends;
+       obj.backends_num = service->backends_num;
        if (! status)
-               status = store_obj(STORE_OBJ(host), services, SDB_SERVICE,
-                               name, last_update, NULL);
+               status = store_obj(&obj, NULL);
 
        sdb_object_deref(SDB_OBJ(host));
-       pthread_rwlock_unlock(&host_lock);
+       pthread_rwlock_unlock(&st->host_lock);
        return status;
-} /* sdb_store_service */
+} /* store_service */
 
-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_metric(sdb_store_metric_t *metric, sdb_object_t *user_data)
 {
-       sdb_host_t *host;
-       sdb_service_t *svc;
-       sdb_avltree_t *services;
+       sdb_store_t *st = SDB_STORE(user_data);
+       store_obj_t obj = STORE_OBJ_INIT;
+       sdb_store_obj_t *new = NULL;
+       host_t *host;
+
        int status = 0;
 
-       if ((! hostname) || (! service) || (! key))
+       if ((! metric) || (! metric->hostname) || (! metric->name))
                return -1;
 
-       pthread_rwlock_wrlock(&host_lock);
-       host = lookup_host(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);
+       if ((metric->store.type != NULL) != (metric->store.id != NULL))
                return -1;
-       }
 
-       svc = SVC(sdb_avltree_lookup(services, service));
-       if (! svc) {
-               sdb_log(SDB_LOG_ERR, "store: Failed to store attribute '%s' - "
-                               "service '%s/%s' not found", key, hostname, service);
+       pthread_rwlock_wrlock(&st->host_lock);
+       host = HOST(sdb_avltree_lookup(st->hosts, metric->hostname));
+       obj.parent = STORE_OBJ(host);
+       obj.parent_tree = get_host_children(host, SDB_METRIC);
+       obj.type = SDB_METRIC;
+       if (! obj.parent_tree) {
+               sdb_log(SDB_LOG_ERR, "store: Failed to store metric '%s' - "
+                               "host '%s' not found", metric->name, metric->hostname);
                status = -1;
        }
 
+       obj.name = metric->name;
+       obj.last_update = metric->last_update;
+       obj.backends = metric->backends;
+       obj.backends_num = metric->backends_num;
        if (! status)
-               status = store_attr(STORE_OBJ(svc), svc->attributes,
-                               key, value, last_update);
+               status = store_obj(&obj, &new);
+       sdb_object_deref(SDB_OBJ(host));
 
-       sdb_object_deref(SDB_OBJ(svc));
-       pthread_rwlock_unlock(&host_lock);
-       return status;
-} /* sdb_store_service_attr */
+       if (status) {
+               pthread_rwlock_unlock(&st->host_lock);
+               return status;
+       }
 
-int
-sdb_store_metric(const char *hostname, const char *name,
-               sdb_metric_store_t *store, sdb_time_t last_update)
-{
-       sdb_store_obj_t *obj = NULL;
-       sdb_host_t *host;
-       sdb_metric_t *metric;
+       assert(new);
+       if (metric->store.type && metric->store.id)
+               if (store_metric_store(METRIC(new), metric))
+                       status = -1;
+       pthread_rwlock_unlock(&st->host_lock);
+       return status;
+} /* store_metric */
 
-       sdb_avltree_t *metrics;
+sdb_store_writer_t sdb_store_writer = {
+       store_host, store_service, store_metric, store_attribute,
+};
 
-       int status = 0;
+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 */
 
-       if ((! hostname) || (! name))
-               return -1;
-       if (store && ((! store->type) || (! store->id)))
-               return -1;
+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 */
 
-       pthread_rwlock_wrlock(&host_lock);
-       host = lookup_host(hostname, /* canonicalize = */ 1);
-       metrics = get_host_children(host, SDB_METRIC);
-       if (! metrics) {
-               sdb_log(SDB_LOG_ERR, "store: Failed to store metric '%s' - "
-                               "host '%s' not found", name, hostname);
-               status = -1;
-       }
+sdb_store_reader_t sdb_store_reader = {
+       prepare_query, execute_query,
+};
 
-       if (! status)
-               status = store_obj(STORE_OBJ(host), metrics, SDB_METRIC,
-                               name, last_update, &obj);
-       sdb_object_deref(SDB_OBJ(host));
+/*
+ * public API
+ */
 
-       if (status || (! store)) {
-               pthread_rwlock_unlock(&host_lock);
-               return status;
-       }
+sdb_store_t *
+sdb_store_create(void)
+{
+       return SDB_STORE(sdb_object_create("store", store_type));
+} /* sdb_store_create */
 
-       assert(obj);
-       metric = METRIC(obj);
+int
+sdb_store_host(sdb_store_t *store, const char *name, sdb_time_t last_update)
+{
+       sdb_store_host_t host = {
+               name, last_update, 0, NULL, 0,
+       };
+       return store_host(&host, SDB_OBJ(store));
+} /* sdb_store_host */
 
-       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);
-       }
+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 */
 
-       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;
-               status = -1;
+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;
        }
-       pthread_rwlock_unlock(&host_lock);
-       return status;
+       return store_metric(&metric, SDB_OBJ(store));
 } /* sdb_store_metric */
 
 int
-sdb_store_metric_attr(const char *hostname, const char *metric,
+sdb_store_attribute(sdb_store_t *store, const char *hostname,
                const char *key, const sdb_data_t *value, sdb_time_t last_update)
 {
-       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);
-       host = lookup_host(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);
-               return -1;
+       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 */
 
-       m = METRIC(sdb_avltree_lookup(metrics, metric));
-       if (! m) {
-               sdb_log(SDB_LOG_ERR, "store: Failed to store attribute '%s' - "
-                               "metric '%s/%s' not found", key, hostname, metric);
-               status = -1;
+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;
        }
-
-       if (! status)
-               status = store_attr(STORE_OBJ(m), m->attributes,
-                               key, value, last_update);
-
-       sdb_object_deref(SDB_OBJ(m));
-       pthread_rwlock_unlock(&host_lock);
-       return status;
-} /* sdb_store_metric_attr */
+       return store_attribute(&attr, SDB_OBJ(store));
+} /* sdb_store_service_attr */
 
 int
-sdb_store_fetch_timeseries(const char *hostname, const char *metric,
-               sdb_timeseries_opts_t *opts, sdb_strbuf_t *buf)
+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_avltree_t *metrics;
-       sdb_host_t *host;
-       sdb_metric_t *m;
-
-       sdb_timeseries_t *ts;
-
-       if ((! hostname) || (! metric) || (! opts) || (! buf))
-               return -1;
-
-       pthread_rwlock_rdlock(&host_lock);
-       host = lookup_host(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(&host_lock);
-               return -1;
+       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 */
 
-       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;
-       }
+sdb_store_obj_t *
+sdb_store_get_host(sdb_store_t *store, const char *name)
+{
+       host_t *host;
 
-       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);
-               return -1;
-       }
+       if ((! store) || (! name))
+               return NULL;
 
-       {
-               char type[strlen(m->store.type) + 1];
-               char id[strlen(m->store.id) + 1];
+       host = HOST(sdb_avltree_lookup(store->hosts, name));
+       if (! host)
+               return NULL;
 
-               strncpy(type, m->store.type, sizeof(type));
-               strncpy(id, m->store.id, sizeof(id));
-               pthread_rwlock_unlock(&host_lock);
+       return STORE_OBJ(host);
+} /* sdb_store_get_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;
-               }
-       }
+sdb_store_obj_t *
+sdb_store_get_child(sdb_store_obj_t *host, int type, const char *name)
+{
+       sdb_avltree_t *children;
 
-       ts_tojson(ts, buf);
-       sdb_timeseries_destroy(ts);
-       return 0;
-} /* sdb_store_fetch_timeseries */
+       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)
@@ -852,13 +898,23 @@ 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;
        }
@@ -904,14 +960,84 @@ 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_fetch_timeseries(sdb_store_t *store,
+               const char *hostname, const char *metric,
+               sdb_timeseries_opts_t *opts, sdb_strbuf_t *buf)
+{
+       sdb_avltree_t *metrics;
+       host_t *host;
+       sdb_metric_t *m;
+
+       sdb_timeseries_t *ts;
+
+       int status = 0;
+
+       if ((! store) || (! hostname) || (! metric) || (! opts) || (! buf))
+               return -1;
+
+       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;
+       }
+
+       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 ((! 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;
+       }
+
+       {
+               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 */
+
 int
-sdb_store_scan(int type, sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
+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_avltree_iter_t *host_iter;
+       sdb_avltree_iter_t *host_iter = NULL;
        int status = 0;
 
-       if (! cb)
+       if ((! store) || (! cb))
                return -1;
 
        if ((type != SDB_HOST) && (type != SDB_SERVICE) && (type != SDB_METRIC)) {
@@ -919,9 +1045,8 @@ 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(&store->host_lock);
+       host_iter = sdb_avltree_get_iter(store->hosts);
        if (! host_iter)
                status = -1;
 
@@ -971,7 +1096,7 @@ 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(&store->host_lock);
        return status;
 } /* sdb_store_scan */