Code

plugin: Dynamically populate timeseries information when querying metrics.
[sysdb.git] / src / core / plugin.c
index f581eb1..ecd84b5 100644 (file)
@@ -80,31 +80,47 @@ typedef struct {
        void *cb_callback;
        sdb_object_t *cb_user_data;
        ctx_t *cb_ctx;
-} sdb_plugin_cb_t;
-#define SDB_PLUGIN_CB_INIT { SDB_OBJECT_INIT, \
+} callback_t;
+#define CB_INIT { SDB_OBJECT_INIT, \
        /* callback = */ NULL, /* user_data = */ NULL, \
        SDB_PLUGIN_CTX_INIT }
-#define SDB_PLUGIN_CB(obj) ((sdb_plugin_cb_t *)(obj))
-#define SDB_CONST_PLUGIN_CB(obj) ((const sdb_plugin_cb_t *)(obj))
+#define CB(obj) ((callback_t *)(obj))
+#define CONST_CB(obj) ((const callback_t *)(obj))
 
 typedef struct {
-       sdb_plugin_cb_t super;
+       callback_t super;
 #define ccb_callback super.cb_callback
 #define ccb_user_data super.cb_user_data
 #define ccb_ctx super.cb_ctx
        sdb_time_t ccb_interval;
        sdb_time_t ccb_next_update;
-} sdb_plugin_collector_cb_t;
-#define SDB_PLUGIN_CCB(obj) ((sdb_plugin_collector_cb_t *)(obj))
-#define SDB_CONST_PLUGIN_CCB(obj) ((const sdb_plugin_collector_cb_t *)(obj))
+} collector_t;
+#define CCB(obj) ((collector_t *)(obj))
+#define CONST_CCB(obj) ((const collector_t *)(obj))
 
 typedef struct {
-       sdb_plugin_cb_t super; /* cb_callback will always be NULL */
+       callback_t super; /* cb_callback will always be NULL */
 #define w_user_data super.cb_user_data
 #define w_ctx super.cb_ctx
        sdb_store_writer_t impl;
-} sdb_plugin_writer_t;
-#define SDB_PLUGIN_WRITER(obj) ((sdb_plugin_writer_t *)(obj))
+} writer_t;
+#define WRITER(obj) ((writer_t *)(obj))
+
+typedef struct {
+       callback_t super; /* cb_callback will always be NULL */
+#define r_user_data super.cb_user_data
+#define r_ctx super.cb_ctx
+       sdb_store_reader_t impl;
+} reader_t;
+#define READER(obj) ((reader_t *)(obj))
+
+typedef struct {
+       callback_t super; /* cb_callback will always be NULL */
+#define ts_user_data super.cb_user_data
+#define ts_ctx super.cb_ctx
+       sdb_timeseries_fetcher_t impl;
+} ts_fetcher_t;
+#define TS_FETCHER(obj) ((ts_fetcher_t *)(obj))
 
 /*
  * private variables
@@ -125,8 +141,9 @@ static sdb_llist_t      *collector_list = NULL;
 static sdb_llist_t      *cname_list = NULL;
 static sdb_llist_t      *shutdown_list = NULL;
 static sdb_llist_t      *log_list = NULL;
-static sdb_llist_t      *ts_fetcher_list = NULL;
+static sdb_llist_t      *timeseries_fetcher_list = NULL;
 static sdb_llist_t      *writer_list = NULL;
+static sdb_llist_t      *reader_list = NULL;
 
 static struct {
        const char   *type;
@@ -138,8 +155,9 @@ static struct {
        { "cname",              &cname_list },
        { "shutdown",           &shutdown_list },
        { "log",                &log_list },
-       { "timeseries fetcher", &ts_fetcher_list },
+       { "timeseries fetcher", &timeseries_fetcher_list },
        { "store writer",       &writer_list },
+       { "store reader",       &reader_list },
 };
 
 /*
@@ -181,10 +199,8 @@ ctx_key_init(void)
 static int
 plugin_cmp_next_update(const sdb_object_t *a, const sdb_object_t *b)
 {
-       const sdb_plugin_collector_cb_t *ccb1
-               = (const sdb_plugin_collector_cb_t *)a;
-       const sdb_plugin_collector_cb_t *ccb2
-               = (const sdb_plugin_collector_cb_t *)b;
+       const collector_t *ccb1 = (const collector_t *)a;
+       const collector_t *ccb2 = (const collector_t *)b;
 
        assert(ccb1 && ccb2);
 
@@ -196,7 +212,7 @@ plugin_cmp_next_update(const sdb_object_t *a, const sdb_object_t *b)
 static int
 plugin_lookup_by_name(const sdb_object_t *obj, const void *id)
 {
-       const sdb_plugin_cb_t *cb = SDB_CONST_PLUGIN_CB(obj);
+       const callback_t *cb = CONST_CB(obj);
        const char *name = id;
 
        assert(cb && id);
@@ -225,9 +241,9 @@ plugin_unregister_by_name(const char *plugin_name)
                sdb_llist_t *list = *all_lists[i].list;
 
                while (1) {
-                       sdb_plugin_cb_t *cb;
+                       callback_t *cb;
 
-                       cb = SDB_PLUGIN_CB(sdb_llist_remove(list,
+                       cb = CB(sdb_llist_remove(list,
                                                plugin_lookup_by_name, plugin_name));
                        if (! cb)
                                break;
@@ -251,6 +267,73 @@ plugin_unregister_by_name(const char *plugin_name)
        /* else: other callbacks still reference it */
 } /* plugin_unregister_by_name */
 
+/*
+ * store writer wrapper for performing database queries:
+ * It wraps another store writer, adding extra logic as needed.
+ */
+
+typedef struct {
+       sdb_object_t super;
+       sdb_store_writer_t *w;
+       sdb_object_t *ud;
+} query_writer_t;
+#define QUERY_WRITER_INIT(w, ud) { SDB_OBJECT_INIT, (w), (ud) }
+#define QUERY_WRITER(obj) ((query_writer_t *)(obj))
+
+static int
+query_store_host(sdb_store_host_t *host, sdb_object_t *user_data)
+{
+       query_writer_t *qw = QUERY_WRITER(user_data);
+       return qw->w->store_host(host, qw->ud);
+} /* query_store_host */
+
+static int
+query_store_service(sdb_store_service_t *service, sdb_object_t *user_data)
+{
+       query_writer_t *qw = QUERY_WRITER(user_data);
+       return qw->w->store_service(service, qw->ud);
+} /* query_store_service */
+
+static int
+query_store_metric(sdb_store_metric_t *metric, sdb_object_t *user_data)
+{
+       query_writer_t *qw = QUERY_WRITER(user_data);
+       sdb_timeseries_info_t *infos[metric->stores_num];
+       sdb_metric_store_t stores[metric->stores_num];
+
+       const sdb_metric_store_t *orig_stores = metric->stores;
+       int status;
+       size_t i;
+
+       for (i = 0; i < metric->stores_num; i++) {
+               /* TODO: Make this optional using query options. */
+               sdb_metric_store_t *s = stores + i;
+               *s = metric->stores[i];
+               infos[i] = sdb_plugin_describe_timeseries(s->type, s->id);
+               s->info = infos[i];
+       }
+
+       metric->stores = stores;
+       status = qw->w->store_metric(metric, qw->ud);
+       metric->stores = orig_stores;
+
+       for (i = 0; i < metric->stores_num; i++)
+               sdb_timeseries_info_destroy(infos[i]);
+       return status;
+} /* query_store_metric */
+
+static int
+query_store_attribute(sdb_store_attribute_t *attr, sdb_object_t *user_data)
+{
+       query_writer_t *qw = QUERY_WRITER(user_data);
+       return qw->w->store_attribute(attr, qw->ud);
+} /* query_store_attribute */
+
+static sdb_store_writer_t query_writer = {
+       query_store_host, query_store_service,
+       query_store_metric, query_store_attribute,
+};
+
 /*
  * private types
  */
@@ -337,33 +420,48 @@ ctx_create(const char *name)
        return ctx;
 } /* ctx_create */
 
-static int
-plugin_cb_init(sdb_object_t *obj, va_list ap)
+/*
+ * plugin_init_ok:
+ * Checks whether the registration of a new plugin identified by 'obj' is
+ * okay. It consumes the first two arguments of 'ap'.
+ */
+static bool
+plugin_init_ok(sdb_object_t *obj, va_list ap)
 {
        sdb_llist_t **list = va_arg(ap, sdb_llist_t **);
-       const char   *type = va_arg(ap, const char *);
-       void     *callback = va_arg(ap, void *);
-       sdb_object_t   *ud = va_arg(ap, sdb_object_t *);
+       const char *type = va_arg(ap, const char *);
 
-       assert(list);
-       assert(type);
-       assert(obj);
+       assert(list); assert(type);
 
        if (sdb_llist_search_by_name(*list, obj->name)) {
                sdb_log(SDB_LOG_WARNING, "core: %s callback '%s' "
                                "has already been registered. Ignoring newly "
                                "registered version.", type, obj->name);
-               return -1;
+               return 0;
        }
+       return 1;
+} /* plugin_init_ok */
+
+static int
+plugin_cb_init(sdb_object_t *obj, va_list ap)
+{
+       void *callback;
+       sdb_object_t *ud;
+
+       if (! plugin_init_ok(obj, ap))
+               return -1;
+
+       callback = va_arg(ap, void *);
+       ud = va_arg(ap, sdb_object_t *);
 
        /* cb_ctx may be NULL if the plugin was not registered by a plugin */
 
-       SDB_PLUGIN_CB(obj)->cb_callback = callback;
-       SDB_PLUGIN_CB(obj)->cb_ctx      = ctx_get();
-       sdb_object_ref(SDB_OBJ(SDB_PLUGIN_CB(obj)->cb_ctx));
+       CB(obj)->cb_callback = callback;
+       CB(obj)->cb_ctx      = ctx_get();
+       sdb_object_ref(SDB_OBJ(CB(obj)->cb_ctx));
 
        sdb_object_ref(ud);
-       SDB_PLUGIN_CB(obj)->cb_user_data = ud;
+       CB(obj)->cb_user_data = ud;
        return 0;
 } /* plugin_cb_init */
 
@@ -371,19 +469,19 @@ static void
 plugin_cb_destroy(sdb_object_t *obj)
 {
        assert(obj);
-       sdb_object_deref(SDB_PLUGIN_CB(obj)->cb_user_data);
-       sdb_object_deref(SDB_OBJ(SDB_PLUGIN_CB(obj)->cb_ctx));
+       sdb_object_deref(CB(obj)->cb_user_data);
+       sdb_object_deref(SDB_OBJ(CB(obj)->cb_ctx));
 } /* plugin_cb_destroy */
 
-static sdb_type_t sdb_plugin_cb_type = {
-       sizeof(sdb_plugin_cb_t),
+static sdb_type_t callback_type = {
+       sizeof(callback_t),
 
        plugin_cb_init,
        plugin_cb_destroy
 };
 
-static sdb_type_t sdb_plugin_collector_cb_type = {
-       sizeof(sdb_plugin_collector_cb_t),
+static sdb_type_t collector_type = {
+       sizeof(collector_t),
 
        plugin_cb_init,
        plugin_cb_destroy
@@ -392,34 +490,32 @@ static sdb_type_t sdb_plugin_collector_cb_type = {
 static int
 plugin_writer_init(sdb_object_t *obj, va_list ap)
 {
-       sdb_store_writer_t *impl = va_arg(ap, sdb_store_writer_t *);
-       sdb_object_t       *ud   = va_arg(ap, sdb_object_t *);
+       sdb_store_writer_t *impl;
+       sdb_object_t *ud;
 
+       if (! plugin_init_ok(obj, ap))
+               return -1;
+
+       impl = va_arg(ap, sdb_store_writer_t *);
+       ud = va_arg(ap, sdb_object_t *);
        assert(impl);
 
        if ((! impl->store_host) || (! impl->store_service)
-                       || (! impl->store_metric) || (! impl->store_attribute)
-                       || (! impl->store_service_attr) || (! impl->store_metric_attr)) {
+                       || (! impl->store_metric) || (! impl->store_attribute)) {
                sdb_log(SDB_LOG_ERR, "core: store writer callback '%s' "
                                "does not fully implement the writer interface.",
                                obj->name);
                return -1;
        }
-       if (sdb_llist_search_by_name(writer_list, obj->name)) {
-               sdb_log(SDB_LOG_WARNING, "core: store writer callback '%s' "
-                               "has already been registered. Ignoring newly "
-                               "registered version.", obj->name);
-               return -1;
-       }
 
-       /* ctx may be NULL if the plugin was not registered by a plugin */
+       /* ctx may be NULL if the callback was not registered by a plugin */
 
-       SDB_PLUGIN_WRITER(obj)->impl = *impl;
-       SDB_PLUGIN_WRITER(obj)->w_ctx  = ctx_get();
-       sdb_object_ref(SDB_OBJ(SDB_PLUGIN_WRITER(obj)->w_ctx));
+       WRITER(obj)->impl = *impl;
+       WRITER(obj)->w_ctx  = ctx_get();
+       sdb_object_ref(SDB_OBJ(WRITER(obj)->w_ctx));
 
        sdb_object_ref(ud);
-       SDB_PLUGIN_WRITER(obj)->w_user_data = ud;
+       WRITER(obj)->w_user_data = ud;
        return 0;
 } /* plugin_writer_init */
 
@@ -427,17 +523,109 @@ static void
 plugin_writer_destroy(sdb_object_t *obj)
 {
        assert(obj);
-       sdb_object_deref(SDB_PLUGIN_WRITER(obj)->w_user_data);
-       sdb_object_deref(SDB_OBJ(SDB_PLUGIN_WRITER(obj)->w_ctx));
+       sdb_object_deref(WRITER(obj)->w_user_data);
+       sdb_object_deref(SDB_OBJ(WRITER(obj)->w_ctx));
 } /* plugin_writer_destroy */
 
-static sdb_type_t sdb_plugin_writer_type = {
-       sizeof(sdb_plugin_writer_t),
+static sdb_type_t writer_type = {
+       sizeof(writer_t),
 
        plugin_writer_init,
        plugin_writer_destroy
 };
 
+static int
+plugin_reader_init(sdb_object_t *obj, va_list ap)
+{
+       sdb_store_reader_t *impl;
+       sdb_object_t *ud;
+
+       if (! plugin_init_ok(obj, ap))
+               return -1;
+
+       impl = va_arg(ap, sdb_store_reader_t *);
+       ud = va_arg(ap, sdb_object_t *);
+       assert(impl);
+
+       if ((! impl->prepare_query) || (! impl->execute_query)) {
+               sdb_log(SDB_LOG_ERR, "core: store reader callback '%s' "
+                               "does not fully implement the reader interface.",
+                               obj->name);
+               return -1;
+       }
+
+       /* ctx may be NULL if the callback was not registered by a plugin */
+
+       READER(obj)->impl = *impl;
+       READER(obj)->r_ctx  = ctx_get();
+       sdb_object_ref(SDB_OBJ(READER(obj)->r_ctx));
+
+       sdb_object_ref(ud);
+       READER(obj)->r_user_data = ud;
+       return 0;
+} /* plugin_reader_init */
+
+static void
+plugin_reader_destroy(sdb_object_t *obj)
+{
+       assert(obj);
+       sdb_object_deref(READER(obj)->r_user_data);
+       sdb_object_deref(SDB_OBJ(READER(obj)->r_ctx));
+} /* plugin_reader_destroy */
+
+static sdb_type_t reader_type = {
+       sizeof(reader_t),
+
+       plugin_reader_init,
+       plugin_reader_destroy
+};
+
+static int
+plugin_ts_fetcher_init(sdb_object_t *obj, va_list ap)
+{
+       sdb_timeseries_fetcher_t *impl;
+       sdb_object_t *ud;
+
+       if (! plugin_init_ok(obj, ap))
+               return -1;
+
+       impl = va_arg(ap, sdb_timeseries_fetcher_t *);
+       ud = va_arg(ap, sdb_object_t *);
+       assert(impl);
+
+       if ((! impl->describe) || (! impl->fetch)) {
+               sdb_log(SDB_LOG_ERR, "core: timeseries fetcher callback '%s' "
+                               "does not fully implement the interface.",
+                               obj->name);
+               return -1;
+       }
+
+       /* ctx may be NULL if the callback was not registered by a plugin */
+
+       TS_FETCHER(obj)->impl = *impl;
+       TS_FETCHER(obj)->ts_ctx  = ctx_get();
+       sdb_object_ref(SDB_OBJ(TS_FETCHER(obj)->ts_ctx));
+
+       sdb_object_ref(ud);
+       TS_FETCHER(obj)->ts_user_data = ud;
+       return 0;
+} /* plugin_ts_fetcher_init */
+
+static void
+plugin_ts_fetcher_destroy(sdb_object_t *obj)
+{
+       assert(obj);
+       sdb_object_deref(TS_FETCHER(obj)->ts_user_data);
+       sdb_object_deref(SDB_OBJ(TS_FETCHER(obj)->ts_ctx));
+} /* plugin_ts_fetcher_destroy */
+
+static sdb_type_t ts_fetcher_type = {
+       sizeof(ts_fetcher_t),
+
+       plugin_ts_fetcher_init,
+       plugin_ts_fetcher_destroy
+};
+
 static int
 module_init(const char *name, lt_dlhandle lh, sdb_plugin_info_t *info)
 {
@@ -574,12 +762,12 @@ plugin_get_name(const char *name, char *buf, size_t bufsize)
 } /* plugin_get_name */
 
 static int
-plugin_add_callback(sdb_llist_t **list, const char *type,
-               const char *name, void *callback, sdb_object_t *user_data)
+plugin_add_impl(sdb_llist_t **list, sdb_type_t T, const char *type,
+               const char *name, void *impl, sdb_object_t *user_data)
 {
        sdb_object_t *obj;
 
-       if ((! name) || (! callback))
+       if ((! name) || (! impl))
                return -1;
 
        assert(list);
@@ -589,8 +777,7 @@ plugin_add_callback(sdb_llist_t **list, const char *type,
        if (! *list)
                return -1;
 
-       obj = sdb_object_create(name, sdb_plugin_cb_type,
-                       list, type, callback, user_data);
+       obj = sdb_object_create(name, T, list, type, impl, user_data);
        if (! obj)
                return -1;
 
@@ -605,7 +792,127 @@ plugin_add_callback(sdb_llist_t **list, const char *type,
        sdb_log(SDB_LOG_INFO, "core: Registered %s callback '%s'.",
                        type, name);
        return 0;
-} /* plugin_add_callback */
+} /* plugin_add_impl */
+
+/*
+ * object meta-data
+ */
+
+typedef struct {
+       int obj_type;
+       sdb_time_t last_update;
+       sdb_time_t interval;
+} interval_fetcher_t;
+
+static int
+interval_fetcher_host(sdb_store_host_t *host, sdb_object_t *user_data)
+{
+       interval_fetcher_t *lu = SDB_OBJ_WRAPPER(user_data)->data;
+       lu->obj_type = SDB_HOST;
+       lu->last_update = host->last_update;
+       return 0;
+} /* interval_fetcher_host */
+
+static int
+interval_fetcher_service(sdb_store_service_t *svc, sdb_object_t *user_data)
+{
+       interval_fetcher_t *lu = SDB_OBJ_WRAPPER(user_data)->data;
+       lu->obj_type = SDB_SERVICE;
+       lu->last_update = svc->last_update;
+       return 0;
+} /* interval_fetcher_service */
+
+static int
+interval_fetcher_metric(sdb_store_metric_t *metric, sdb_object_t *user_data)
+{
+       interval_fetcher_t *lu = SDB_OBJ_WRAPPER(user_data)->data;
+       lu->obj_type = SDB_METRIC;
+       lu->last_update = metric->last_update;
+       return 0;
+} /* interval_fetcher_metric */
+
+static int
+interval_fetcher_attr(sdb_store_attribute_t *attr, sdb_object_t *user_data)
+{
+       interval_fetcher_t *lu = SDB_OBJ_WRAPPER(user_data)->data;
+       lu->obj_type = SDB_ATTRIBUTE;
+       lu->last_update = attr->last_update;
+       return 0;
+} /* interval_fetcher_attr */
+
+static sdb_store_writer_t interval_fetcher = {
+       interval_fetcher_host, interval_fetcher_service,
+       interval_fetcher_metric, interval_fetcher_attr,
+};
+
+static int
+get_interval(int obj_type, const char *hostname,
+               int parent_type, const char *parent, const char *name,
+               sdb_time_t last_update, sdb_time_t *interval_out)
+{
+       sdb_ast_fetch_t fetch = SDB_AST_FETCH_INIT;
+       char hn[hostname ? strlen(hostname) + 1 : 1];
+       char pn[parent ? strlen(parent) + 1 : 1];
+       char n[strlen(name) + 1];
+       int status;
+
+       interval_fetcher_t lu = { 0, 0, 0 };
+       sdb_object_wrapper_t obj = SDB_OBJECT_WRAPPER_STATIC(&lu);
+       sdb_time_t interval;
+
+       assert(name);
+
+       if (hostname)
+               strncpy(hn, hostname, sizeof(hn));
+       if (parent)
+               strncpy(pn, parent, sizeof(pn));
+       strncpy(n, name, sizeof(n));
+
+       fetch.obj_type = obj_type;
+       fetch.hostname = hostname ? hn : NULL;
+       fetch.parent_type = parent_type;
+       fetch.parent = parent ? pn : NULL;
+       fetch.name = n;
+
+       status = sdb_plugin_query(SDB_AST_NODE(&fetch),
+                       &interval_fetcher, SDB_OBJ(&obj), NULL);
+       if ((status < 0) || (lu.obj_type != obj_type) || (lu.last_update == 0)) {
+               *interval_out = 0;
+               return 0;
+       }
+
+       if (lu.last_update >= last_update) {
+               if (lu.last_update > last_update)
+                       sdb_log(SDB_LOG_DEBUG, "memstore: Cannot update %s '%s' - "
+                                       "value too old (%"PRIsdbTIME" < %"PRIsdbTIME")",
+                                       SDB_STORE_TYPE_TO_NAME(obj_type), name,
+                                       lu.last_update, last_update);
+               *interval_out = lu.interval;
+               return 1;
+       }
+
+       interval = last_update - lu.last_update;
+       if (lu.interval && interval)
+               interval = (sdb_time_t)((0.9 * (double)lu.interval)
+                               + (0.1 * (double)interval));
+       *interval_out = interval;
+       return 0;
+} /* get_interval */
+
+static void
+get_backend(char **backends, size_t *backends_num)
+{
+       const sdb_plugin_info_t *info;
+
+       info = sdb_plugin_current();
+       if ((! info) || (! info->plugin_name) || (! *info->plugin_name)) {
+               *backends_num = 0;
+               return;
+       }
+
+       backends[0] = info->plugin_name;
+       *backends_num = 1;
+} /* get_backend */
 
 /*
  * public API
@@ -722,8 +1029,8 @@ sdb_plugin_register_config(sdb_plugin_config_cb callback)
                                "config callback from outside a plugin");
                return -1;
        }
-       return plugin_add_callback(&config_list, "config", ctx->info.plugin_name,
-                       (void *)callback, NULL);
+       return plugin_add_impl(&config_list, callback_type, "config",
+                       ctx->info.plugin_name, (void *)callback, NULL);
 } /* sdb_plugin_register_config */
 
 int
@@ -731,7 +1038,7 @@ sdb_plugin_register_init(const char *name, sdb_plugin_init_cb callback,
                sdb_object_t *user_data)
 {
        char cb_name[1024];
-       return plugin_add_callback(&init_list, "init",
+       return plugin_add_impl(&init_list, callback_type, "init",
                        plugin_get_name(name, cb_name, sizeof(cb_name)),
                        (void *)callback, user_data);
 } /* sdb_plugin_register_init */
@@ -741,7 +1048,7 @@ sdb_plugin_register_shutdown(const char *name, sdb_plugin_shutdown_cb callback,
                sdb_object_t *user_data)
 {
        char cb_name[1024];
-       return plugin_add_callback(&shutdown_list, "shutdown",
+       return plugin_add_impl(&shutdown_list, callback_type, "shutdown",
                        plugin_get_name(name, cb_name, sizeof(cb_name)),
                        (void *)callback, user_data);
 } /* sdb_plugin_register_shutdown */
@@ -751,7 +1058,7 @@ sdb_plugin_register_log(const char *name, sdb_plugin_log_cb callback,
                sdb_object_t *user_data)
 {
        char cb_name[1024];
-       return plugin_add_callback(&log_list, "log",
+       return plugin_add_impl(&log_list, callback_type, "log",
                        plugin_get_name(name, cb_name, sizeof(cb_name)),
                        callback, user_data);
 } /* sdb_plugin_register_log */
@@ -761,7 +1068,7 @@ sdb_plugin_register_cname(const char *name, sdb_plugin_cname_cb callback,
                sdb_object_t *user_data)
 {
        char cb_name[1024];
-       return plugin_add_callback(&cname_list, "cname",
+       return plugin_add_impl(&cname_list, callback_type, "cname",
                        plugin_get_name(name, cb_name, sizeof(cb_name)),
                        callback, user_data);
 } /* sdb_plugin_register_cname */
@@ -783,13 +1090,13 @@ sdb_plugin_register_collector(const char *name, sdb_plugin_collector_cb callback
 
        plugin_get_name(name, cb_name, sizeof(cb_name));
 
-       obj = sdb_object_create(cb_name, sdb_plugin_collector_cb_type,
+       obj = sdb_object_create(cb_name, collector_type,
                        &collector_list, "collector", callback, user_data);
        if (! obj)
                return -1;
 
        if (interval)
-               SDB_PLUGIN_CCB(obj)->ccb_interval = *interval;
+               CCB(obj)->ccb_interval = *interval;
        else {
                ctx_t *ctx = ctx_get();
 
@@ -800,10 +1107,10 @@ sdb_plugin_register_collector(const char *name, sdb_plugin_collector_cb callback
                        return -1;
                }
 
-               SDB_PLUGIN_CCB(obj)->ccb_interval = ctx->public.interval;
+               CCB(obj)->ccb_interval = ctx->public.interval;
        }
 
-       if (! (SDB_PLUGIN_CCB(obj)->ccb_next_update = sdb_gettime())) {
+       if (! (CCB(obj)->ccb_next_update = sdb_gettime())) {
                char errbuf[1024];
                sdb_log(SDB_LOG_ERR, "core: Failed to determine current "
                                "time: %s", sdb_strerror(errno, errbuf, sizeof(errbuf)));
@@ -822,53 +1129,38 @@ sdb_plugin_register_collector(const char *name, sdb_plugin_collector_cb callback
 
        sdb_log(SDB_LOG_INFO, "core: Registered collector callback '%s' "
                        "(interval = %.3fs).", cb_name,
-                       SDB_TIME_TO_DOUBLE(SDB_PLUGIN_CCB(obj)->ccb_interval));
+                       SDB_TIME_TO_DOUBLE(CCB(obj)->ccb_interval));
        return 0;
 } /* sdb_plugin_register_collector */
 
 int
-sdb_plugin_register_ts_fetcher(const char *name,
-               sdb_plugin_fetch_ts_cb callback, sdb_object_t *user_data)
+sdb_plugin_register_timeseries_fetcher(const char *name,
+               sdb_timeseries_fetcher_t *fetcher, sdb_object_t *user_data)
 {
-       return plugin_add_callback(&ts_fetcher_list, "time-series fetcher",
-                       name, callback, user_data);
-} /* sdb_plugin_register_ts_fetcher */
+       return plugin_add_impl(&timeseries_fetcher_list, ts_fetcher_type, "time-series fetcher",
+                       name, fetcher, user_data);
+} /* sdb_plugin_register_timeseries_fetcher */
 
 int
 sdb_plugin_register_writer(const char *name,
                sdb_store_writer_t *writer, sdb_object_t *user_data)
 {
        char cb_name[1024];
-       sdb_object_t *obj;
-
-       if ((! name) || (! writer))
-               return -1;
-
-       if (! writer_list)
-               writer_list = sdb_llist_create();
-       if (! writer_list)
-               return -1;
-
-       plugin_get_name(name, cb_name, sizeof(cb_name));
-
-       obj = sdb_object_create(cb_name, sdb_plugin_writer_type,
+       return plugin_add_impl(&writer_list, writer_type, "store writer",
+                       plugin_get_name(name, cb_name, sizeof(cb_name)),
                        writer, user_data);
-       if (! obj)
-               return -1;
-
-       if (sdb_llist_append(writer_list, obj)) {
-               sdb_object_deref(obj);
-               return -1;
-       }
-
-       /* pass control to the list */
-       sdb_object_deref(obj);
-
-       sdb_log(SDB_LOG_INFO, "core: Registered store writer callback '%s'.",
-                       cb_name);
-       return 0;
 } /* sdb_store_register_writer */
 
+int
+sdb_plugin_register_reader(const char *name,
+               sdb_store_reader_t *reader, sdb_object_t *user_data)
+{
+       char cb_name[1024];
+       return plugin_add_impl(&reader_list, reader_type, "store reader",
+                       plugin_get_name(name, cb_name, sizeof(cb_name)),
+                       reader, user_data);
+} /* sdb_plugin_register_reader */
+
 void
 sdb_plugin_unregister_all(void)
 {
@@ -934,7 +1226,7 @@ sdb_plugin_current(void)
 int
 sdb_plugin_configure(const char *name, oconfig_item_t *ci)
 {
-       sdb_plugin_cb_t *plugin;
+       callback_t *plugin;
        sdb_plugin_config_cb callback;
 
        ctx_t *old_ctx;
@@ -944,7 +1236,7 @@ sdb_plugin_configure(const char *name, oconfig_item_t *ci)
        if ((! name) || (! ci))
                return -1;
 
-       plugin = SDB_PLUGIN_CB(sdb_llist_search_by_name(config_list, name));
+       plugin = CB(sdb_llist_search_by_name(config_list, name));
        if (! plugin) {
                ctx_t *ctx = CTX(sdb_llist_search_by_name(all_plugins, name));
                if (! ctx)
@@ -976,11 +1268,11 @@ sdb_plugin_reconfigure_init(void)
 
        /* deconfigure all plugins */
        while (sdb_llist_iter_has_next(iter)) {
-               sdb_plugin_cb_t *plugin;
+               callback_t *plugin;
                sdb_plugin_config_cb callback;
                ctx_t *old_ctx;
 
-               plugin = SDB_PLUGIN_CB(sdb_llist_iter_get_next(iter));
+               plugin = CB(sdb_llist_iter_get_next(iter));
                old_ctx = ctx_set(plugin->cb_ctx);
                callback = (sdb_plugin_config_cb)plugin->cb_callback;
                callback(NULL);
@@ -1033,13 +1325,13 @@ sdb_plugin_init_all(void)
 
        iter = sdb_llist_get_iter(init_list);
        while (sdb_llist_iter_has_next(iter)) {
-               sdb_plugin_cb_t *cb;
+               callback_t *cb;
                sdb_plugin_init_cb callback;
                ctx_t *old_ctx;
 
                sdb_object_t *obj = sdb_llist_iter_get_next(iter);
                assert(obj);
-               cb = SDB_PLUGIN_CB(obj);
+               cb = CB(obj);
 
                callback = (sdb_plugin_init_cb)cb->cb_callback;
 
@@ -1066,13 +1358,13 @@ sdb_plugin_shutdown_all(void)
 
        iter = sdb_llist_get_iter(shutdown_list);
        while (sdb_llist_iter_has_next(iter)) {
-               sdb_plugin_cb_t *cb;
+               callback_t *cb;
                sdb_plugin_shutdown_cb callback;
                ctx_t *old_ctx;
 
                sdb_object_t *obj = sdb_llist_iter_get_next(iter);
                assert(obj);
-               cb = SDB_PLUGIN_CB(obj);
+               cb = CB(obj);
 
                callback = (sdb_plugin_shutdown_cb)cb->cb_callback;
 
@@ -1110,18 +1402,18 @@ sdb_plugin_collector_loop(sdb_plugin_loop_t *loop)
                if (! obj)
                        return -1;
 
-               callback = (sdb_plugin_collector_cb)SDB_PLUGIN_CCB(obj)->ccb_callback;
+               callback = (sdb_plugin_collector_cb)CCB(obj)->ccb_callback;
 
                if (! (now = sdb_gettime())) {
                        char errbuf[1024];
                        sdb_log(SDB_LOG_ERR, "core: Failed to determine current "
                                        "time in collector main loop: %s",
                                        sdb_strerror(errno, errbuf, sizeof(errbuf)));
-                       now = SDB_PLUGIN_CCB(obj)->ccb_next_update;
+                       now = CCB(obj)->ccb_next_update;
                }
 
-               if (now < SDB_PLUGIN_CCB(obj)->ccb_next_update) {
-                       interval = SDB_PLUGIN_CCB(obj)->ccb_next_update - now;
+               if (now < CCB(obj)->ccb_next_update) {
+                       interval = CCB(obj)->ccb_next_update - now;
 
                        errno = 0;
                        while (loop->do_loop && sdb_sleep(interval, &interval)) {
@@ -1147,13 +1439,13 @@ sdb_plugin_collector_loop(sdb_plugin_loop_t *loop)
                        }
                }
 
-               old_ctx = ctx_set(SDB_PLUGIN_CCB(obj)->ccb_ctx);
-               if (callback(SDB_PLUGIN_CCB(obj)->ccb_user_data)) {
+               old_ctx = ctx_set(CCB(obj)->ccb_ctx);
+               if (callback(CCB(obj)->ccb_user_data)) {
                        /* XXX */
                }
                ctx_set(old_ctx);
 
-               interval = SDB_PLUGIN_CCB(obj)->ccb_interval;
+               interval = CCB(obj)->ccb_interval;
                if (! interval)
                        interval = loop->default_interval;
                if (! interval) {
@@ -1164,21 +1456,21 @@ sdb_plugin_collector_loop(sdb_plugin_loop_t *loop)
                        continue;
                }
 
-               SDB_PLUGIN_CCB(obj)->ccb_next_update += interval;
+               CCB(obj)->ccb_next_update += interval;
 
                if (! (now = sdb_gettime())) {
                        char errbuf[1024];
                        sdb_log(SDB_LOG_ERR, "core: Failed to determine current "
                                        "time in collector main loop: %s",
                                        sdb_strerror(errno, errbuf, sizeof(errbuf)));
-                       now = SDB_PLUGIN_CCB(obj)->ccb_next_update;
+                       now = CCB(obj)->ccb_next_update;
                }
 
-               if (now > SDB_PLUGIN_CCB(obj)->ccb_next_update) {
+               if (now > CCB(obj)->ccb_next_update) {
                        sdb_log(SDB_LOG_WARNING, "core: Plugin '%s' took too "
                                        "long; skipping iterations to keep up.",
                                        obj->name);
-                       SDB_PLUGIN_CCB(obj)->ccb_next_update = now;
+                       CCB(obj)->ccb_next_update = now;
                }
 
                if (sdb_llist_insert_sorted(collector_list, obj,
@@ -1216,8 +1508,8 @@ sdb_plugin_cname(char *hostname)
                sdb_object_t *obj = sdb_llist_iter_get_next(iter);
                assert(obj);
 
-               callback = (sdb_plugin_cname_cb)SDB_PLUGIN_CB(obj)->cb_callback;
-               cname = callback(hostname, SDB_PLUGIN_CB(obj)->cb_user_data);
+               callback = (sdb_plugin_cname_cb)CB(obj)->cb_callback;
+               cname = callback(hostname, CB(obj)->cb_user_data);
                if (cname) {
                        free(hostname);
                        hostname = cname;
@@ -1247,12 +1539,12 @@ sdb_plugin_log(int prio, const char *msg)
                sdb_object_t *obj = sdb_llist_iter_get_next(iter);
                assert(obj);
 
-               callback = (sdb_plugin_log_cb)SDB_PLUGIN_CB(obj)->cb_callback;
-               tmp = callback(prio, msg, SDB_PLUGIN_CB(obj)->cb_user_data);
+               callback = (sdb_plugin_log_cb)CB(obj)->cb_callback;
+               tmp = callback(prio, msg, CB(obj)->cb_user_data);
                if (tmp > ret)
                        ret = tmp;
 
-               if (SDB_PLUGIN_CB(obj)->cb_ctx)
+               if (CB(obj)->cb_ctx)
                        logged = 1;
                /* else: this is an internally registered callback */
        }
@@ -1308,8 +1600,7 @@ sdb_timeseries_t *
 sdb_plugin_fetch_timeseries(const char *type, const char *id,
                sdb_timeseries_opts_t *opts)
 {
-       sdb_plugin_cb_t *plugin;
-       sdb_plugin_fetch_ts_cb callback;
+       ts_fetcher_t *fetcher;
        sdb_timeseries_t *ts;
 
        ctx_t *old_ctx;
@@ -1317,39 +1608,139 @@ sdb_plugin_fetch_timeseries(const char *type, const char *id,
        if ((! type) || (! id) || (! opts))
                return NULL;
 
-       plugin = SDB_PLUGIN_CB(sdb_llist_search_by_name(ts_fetcher_list, type));
-       if (! plugin) {
+       fetcher = TS_FETCHER(sdb_llist_search_by_name(timeseries_fetcher_list, type));
+       if (! fetcher) {
                sdb_log(SDB_LOG_ERR, "core: Cannot fetch time-series of type %s: "
                                "no such plugin loaded", type);
                errno = ENOENT;
                return NULL;
        }
 
-       old_ctx = ctx_set(plugin->cb_ctx);
-       callback = (sdb_plugin_fetch_ts_cb)plugin->cb_callback;
-       ts = callback(id, opts, plugin->cb_user_data);
+       old_ctx = ctx_set(fetcher->ts_ctx);
+       ts = fetcher->impl.fetch(id, opts, fetcher->ts_user_data);
        ctx_set(old_ctx);
        return ts;
 } /* sdb_plugin_fetch_timeseries */
 
+sdb_timeseries_info_t *
+sdb_plugin_describe_timeseries(const char *type, const char *id)
+{
+       ts_fetcher_t *fetcher;
+       sdb_timeseries_info_t *ts_info;
+
+       ctx_t *old_ctx;
+
+       if ((! type) || (! id))
+               return NULL;
+
+       fetcher = TS_FETCHER(sdb_llist_search_by_name(timeseries_fetcher_list, type));
+       if (! fetcher) {
+               sdb_log(SDB_LOG_ERR, "core: Cannot describe time-series of type %s: "
+                               "no such plugin loaded", type);
+               errno = ENOENT;
+               return NULL;
+       }
+
+       old_ctx = ctx_set(fetcher->ts_ctx);
+       ts_info = fetcher->impl.describe(id, fetcher->ts_user_data);
+       ctx_set(old_ctx);
+       return ts_info;
+} /* sdb_plugin_describe_timeseries */
+
+int
+sdb_plugin_query(sdb_ast_node_t *ast,
+               sdb_store_writer_t *w, sdb_object_t *wd, sdb_strbuf_t *errbuf)
+{
+       query_writer_t qw = QUERY_WRITER_INIT(w, wd);
+       reader_t *reader;
+       sdb_object_t *q;
+
+       size_t n = sdb_llist_len(reader_list);
+       int status = 0;
+
+       if (! ast)
+               return 0;
+
+       if ((ast->type != SDB_AST_TYPE_FETCH)
+                       && (ast->type != SDB_AST_TYPE_LIST)
+                       && (ast->type != SDB_AST_TYPE_LOOKUP)) {
+               sdb_log(SDB_LOG_ERR, "core: Cannot execute query of type %s",
+                               SDB_AST_TYPE_TO_STRING(ast));
+               sdb_strbuf_sprintf(errbuf, "Cannot execute query of type %s",
+                               SDB_AST_TYPE_TO_STRING(ast));
+               return -1;
+       }
+
+       if (n != 1) {
+               char *msg = (n > 0)
+                       ? "Cannot execute query: multiple readers not supported"
+                       : "Cannot execute query: no readers registered";
+               sdb_strbuf_sprintf(errbuf, "%s", msg);
+               sdb_log(SDB_LOG_ERR, "core: %s", msg);
+               return -1;
+       }
+
+       reader = READER(sdb_llist_get(reader_list, 0));
+       assert(reader);
+
+       q = reader->impl.prepare_query(ast, errbuf, reader->r_user_data);
+       if (q)
+               status = reader->impl.execute_query(q, &query_writer, SDB_OBJ(&qw),
+                               errbuf, reader->r_user_data);
+       else
+               status = -1;
+
+       sdb_object_deref(SDB_OBJ(q));
+       sdb_object_deref(SDB_OBJ(reader));
+       return status;
+} /* sdb_plugin_query */
+
 int
 sdb_plugin_store_host(const char *name, sdb_time_t last_update)
 {
+       sdb_store_host_t host = SDB_STORE_HOST_INIT;
+       char *backends[1];
+       char *cname;
+
        sdb_llist_iter_t *iter;
        int status = 0;
 
        if (! name)
                return -1;
 
+       if (! sdb_llist_len(writer_list)) {
+               sdb_log(SDB_LOG_ERR, "core: Cannot store host: "
+                               "no writers registered");
+               return -1;
+       }
+
+       cname = sdb_plugin_cname(strdup(name));
+       if (! cname) {
+               sdb_log(SDB_LOG_ERR, "core: strdup failed");
+               return -1;
+       }
+
+       host.name = cname;
+       host.last_update = last_update ? last_update : sdb_gettime();
+       if (get_interval(SDB_HOST, NULL, -1, NULL, cname,
+                               host.last_update, &host.interval)) {
+               free(cname);
+               return 1;
+       }
+       host.backends = (const char * const *)backends;
+       get_backend(backends, &host.backends_num);
+
        iter = sdb_llist_get_iter(writer_list);
        while (sdb_llist_iter_has_next(iter)) {
-               sdb_plugin_writer_t *writer;
-               writer = SDB_PLUGIN_WRITER(sdb_llist_iter_get_next(iter));
+               writer_t *writer = WRITER(sdb_llist_iter_get_next(iter));
+               int s;
                assert(writer);
-               if (writer->impl.store_host(name, last_update, writer->w_user_data))
-                       status = -1;
+               s = writer->impl.store_host(&host, writer->w_user_data);
+               if (((s > 0) && (status >= 0)) || (s < 0))
+                       status = s;
        }
        sdb_llist_iter_destroy(iter);
+       free(cname);
        return status;
 } /* sdb_plugin_store_host */
 
@@ -1357,22 +1748,62 @@ int
 sdb_plugin_store_service(const char *hostname, const char *name,
                sdb_time_t last_update)
 {
+       sdb_store_service_t service = SDB_STORE_SERVICE_INIT;
+       char *backends[1];
+       char *cname;
+
        sdb_llist_iter_t *iter;
+       sdb_data_t d;
+
        int status = 0;
 
        if ((! hostname) || (! name))
                return -1;
 
+       if (! sdb_llist_len(writer_list)) {
+               sdb_log(SDB_LOG_ERR, "core: Cannot store service: "
+                               "no writers registered");
+               return -1;
+       }
+
+       cname = sdb_plugin_cname(strdup(hostname));
+       if (! cname) {
+               sdb_log(SDB_LOG_ERR, "core: strdup failed");
+               return -1;
+       }
+
+       service.hostname = cname;
+       service.name = name;
+       service.last_update = last_update ? last_update : sdb_gettime();
+       if (get_interval(SDB_SERVICE, cname, -1, NULL, name,
+                               service.last_update, &service.interval)) {
+               free(cname);
+               return 1;
+       }
+       service.backends = (const char * const *)backends;
+       get_backend(backends, &service.backends_num);
+
        iter = sdb_llist_get_iter(writer_list);
        while (sdb_llist_iter_has_next(iter)) {
-               sdb_plugin_writer_t *writer;
-               writer = SDB_PLUGIN_WRITER(sdb_llist_iter_get_next(iter));
+               writer_t *writer = WRITER(sdb_llist_iter_get_next(iter));
+               int s;
                assert(writer);
-               if (writer->impl.store_service(hostname, name, last_update,
-                                       writer->w_user_data))
-                       status = -1;
+               s = writer->impl.store_service(&service, writer->w_user_data);
+               if (((s > 0) && (status >= 0)) || (s < 0))
+                       status = s;
        }
        sdb_llist_iter_destroy(iter);
+
+       if (! status) {
+               /* record the hostname as an attribute */
+               d.type = SDB_TYPE_STRING;
+               d.data.string = cname;
+               if (sdb_plugin_store_service_attribute(cname, name,
+                                       "hostname", &d, service.last_update))
+                       status = -1;
+       }
+
+       free(cname);
        return status;
 } /* sdb_plugin_store_service */
 
@@ -1380,25 +1811,71 @@ int
 sdb_plugin_store_metric(const char *hostname, const char *name,
                sdb_metric_store_t *store, sdb_time_t last_update)
 {
+       sdb_store_metric_t metric = SDB_STORE_METRIC_INIT;
+       char *backends[1];
+       char *cname;
+
        sdb_llist_iter_t *iter;
+       sdb_data_t d;
+
        int status = 0;
 
        if ((! hostname) || (! name))
                return -1;
 
+       if (! sdb_llist_len(writer_list)) {
+               sdb_log(SDB_LOG_ERR, "core: Cannot store metric: "
+                               "no writers registered");
+               return -1;
+       }
+
+       cname = sdb_plugin_cname(strdup(hostname));
+       if (! cname) {
+               sdb_log(SDB_LOG_ERR, "core: strdup failed");
+               return -1;
+       }
+
        if (store && ((! store->type) || (! store->id)))
                store = NULL;
 
+       metric.hostname = cname;
+       metric.name = name;
+       if (store) {
+               if (store->last_update < last_update)
+                       store->last_update = last_update;
+               metric.stores = store;
+               metric.stores_num = 1;
+       }
+       metric.last_update = last_update ? last_update : sdb_gettime();
+       if (get_interval(SDB_METRIC, cname, -1, NULL, name,
+                               metric.last_update, &metric.interval)) {
+               free(cname);
+               return 1;
+       }
+       metric.backends = (const char * const *)backends;
+       get_backend(backends, &metric.backends_num);
+
        iter = sdb_llist_get_iter(writer_list);
        while (sdb_llist_iter_has_next(iter)) {
-               sdb_plugin_writer_t *writer;
-               writer = SDB_PLUGIN_WRITER(sdb_llist_iter_get_next(iter));
+               writer_t *writer = WRITER(sdb_llist_iter_get_next(iter));
+               int s;
                assert(writer);
-               if (writer->impl.store_metric(hostname, name, store, last_update,
-                                       writer->w_user_data))
-                       status = -1;
+               s = writer->impl.store_metric(&metric, writer->w_user_data);
+               if (((s > 0) && (status >= 0)) || (s < 0))
+                       status = s;
        }
        sdb_llist_iter_destroy(iter);
+
+       if (! status) {
+               /* record the hostname as an attribute */
+               d.type = SDB_TYPE_STRING;
+               d.data.string = cname;
+               if (sdb_plugin_store_metric_attribute(cname, name,
+                                       "hostname", &d, metric.last_update))
+                       status = -1;
+       }
+
+       free(cname);
        return status;
 } /* sdb_plugin_store_metric */
 
@@ -1406,22 +1883,52 @@ int
 sdb_plugin_store_attribute(const char *hostname, const char *key,
                const sdb_data_t *value, sdb_time_t last_update)
 {
+       sdb_store_attribute_t attr = SDB_STORE_ATTRIBUTE_INIT;
+       char *backends[1];
+       char *cname;
+
        sdb_llist_iter_t *iter;
        int status = 0;
 
        if ((! hostname) || (! key) || (! value))
                return -1;
 
+       if (! sdb_llist_len(writer_list)) {
+               sdb_log(SDB_LOG_ERR, "core: Cannot store attribute: "
+                               "no writers registered");
+               return -1;
+       }
+
+       cname = sdb_plugin_cname(strdup(hostname));
+       if (! cname) {
+               sdb_log(SDB_LOG_ERR, "core: strdup failed");
+               return -1;
+       }
+
+       attr.parent_type = SDB_HOST;
+       attr.parent = cname;
+       attr.key = key;
+       attr.value = *value;
+       attr.last_update = last_update ? last_update : sdb_gettime();
+       if (get_interval(SDB_ATTRIBUTE, cname, -1, NULL, key,
+                               attr.last_update, &attr.interval)) {
+               free(cname);
+               return 1;
+       }
+       attr.backends = (const char * const *)backends;
+       get_backend(backends, &attr.backends_num);
+
        iter = sdb_llist_get_iter(writer_list);
        while (sdb_llist_iter_has_next(iter)) {
-               sdb_plugin_writer_t *writer;
-               writer = SDB_PLUGIN_WRITER(sdb_llist_iter_get_next(iter));
+               writer_t *writer = WRITER(sdb_llist_iter_get_next(iter));
+               int s;
                assert(writer);
-               if (writer->impl.store_attribute(hostname, key, value, last_update,
-                                       writer->w_user_data))
-                       status = -1;
+               s = writer->impl.store_attribute(&attr, writer->w_user_data);
+               if (((s > 0) && (status >= 0)) || (s < 0))
+                       status = s;
        }
        sdb_llist_iter_destroy(iter);
+       free(cname);
        return status;
 } /* sdb_plugin_store_attribute */
 
@@ -1429,22 +1936,53 @@ int
 sdb_plugin_store_service_attribute(const char *hostname, const char *service,
                const char *key, const sdb_data_t *value, sdb_time_t last_update)
 {
+       sdb_store_attribute_t attr = SDB_STORE_ATTRIBUTE_INIT;
+       char *backends[1];
+       char *cname;
+
        sdb_llist_iter_t *iter;
        int status = 0;
 
        if ((! hostname) || (! service) || (! key) || (! value))
                return -1;
 
+       if (! sdb_llist_len(writer_list)) {
+               sdb_log(SDB_LOG_ERR, "core: Cannot store service attribute: "
+                               "no writers registered");
+               return -1;
+       }
+
+       cname = sdb_plugin_cname(strdup(hostname));
+       if (! cname) {
+               sdb_log(SDB_LOG_ERR, "core: strdup failed");
+               return -1;
+       }
+
+       attr.hostname = cname;
+       attr.parent_type = SDB_SERVICE;
+       attr.parent = service;
+       attr.key = key;
+       attr.value = *value;
+       attr.last_update = last_update ? last_update : sdb_gettime();
+       if (get_interval(SDB_ATTRIBUTE, cname, SDB_SERVICE, service, key,
+                               attr.last_update, &attr.interval)) {
+               free(cname);
+               return 1;
+       }
+       attr.backends = (const char * const *)backends;
+       get_backend(backends, &attr.backends_num);
+
        iter = sdb_llist_get_iter(writer_list);
        while (sdb_llist_iter_has_next(iter)) {
-               sdb_plugin_writer_t *writer;
-               writer = SDB_PLUGIN_WRITER(sdb_llist_iter_get_next(iter));
+               writer_t *writer = WRITER(sdb_llist_iter_get_next(iter));
+               int s;
                assert(writer);
-               if (writer->impl.store_service_attr(hostname, service,
-                                       key, value, last_update, writer->w_user_data))
-                       status = -1;
+               s = writer->impl.store_attribute(&attr, writer->w_user_data);
+               if (((s > 0) && (status >= 0)) || (s < 0))
+                       status = s;
        }
        sdb_llist_iter_destroy(iter);
+       free(cname);
        return status;
 } /* sdb_plugin_store_service_attribute */
 
@@ -1452,22 +1990,53 @@ int
 sdb_plugin_store_metric_attribute(const char *hostname, const char *metric,
                const char *key, const sdb_data_t *value, sdb_time_t last_update)
 {
+       sdb_store_attribute_t attr = SDB_STORE_ATTRIBUTE_INIT;
+       char *backends[1];
+       char *cname;
+
        sdb_llist_iter_t *iter;
        int status = 0;
 
        if ((! hostname) || (! metric) || (! key) || (! value))
                return -1;
 
+       if (! sdb_llist_len(writer_list)) {
+               sdb_log(SDB_LOG_ERR, "core: Cannot store metric attribute: "
+                               "no writers registered");
+               return -1;
+       }
+
+       cname = sdb_plugin_cname(strdup(hostname));
+       if (! cname) {
+               sdb_log(SDB_LOG_ERR, "core: strdup failed");
+               return -1;
+       }
+
+       attr.hostname = cname;
+       attr.parent_type = SDB_METRIC;
+       attr.parent = metric;
+       attr.key = key;
+       attr.value = *value;
+       attr.last_update = last_update ? last_update : sdb_gettime();
+       if (get_interval(SDB_ATTRIBUTE, cname, SDB_METRIC, metric, key,
+                               attr.last_update, &attr.interval)) {
+               free(cname);
+               return 1;
+       }
+       attr.backends = (const char * const *)backends;
+       get_backend(backends, &attr.backends_num);
+
        iter = sdb_llist_get_iter(writer_list);
        while (sdb_llist_iter_has_next(iter)) {
-               sdb_plugin_writer_t *writer;
-               writer = SDB_PLUGIN_WRITER(sdb_llist_iter_get_next(iter));
+               writer_t *writer = WRITER(sdb_llist_iter_get_next(iter));
+               int s;
                assert(writer);
-               if (writer->impl.store_metric_attr(hostname, metric,
-                                       key, value, last_update, writer->w_user_data))
-                       status = -1;
+               s = writer->impl.store_attribute(&attr, writer->w_user_data);
+               if (((s > 0) && (status >= 0)) || (s < 0))
+                       status = s;
        }
        sdb_llist_iter_destroy(iter);
+       free(cname);
        return status;
 } /* sdb_plugin_store_metric_attribute */