Code

store: Record each object's parent.
[sysdb.git] / src / core / store.c
index bb6cb96a45bb4b91d934705324e06b179b4742b4..52328f8cf4ad6aa89b8039e0e7b2372babaa2a40 100644 (file)
@@ -58,6 +58,7 @@ static pthread_rwlock_t host_lock = PTHREAD_RWLOCK_INITIALIZER;
 
 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 int
@@ -87,8 +88,10 @@ store_obj_destroy(sdb_object_t *obj)
        sobj->backends = NULL;
        sobj->backends_num = 0;
 
-       if (sobj->parent)
-               sdb_object_deref(SDB_OBJ(sobj->parent));
+       // We don't currently keep an extra reference for parent objects to
+       // avoid circular self-references which are not handled correctly by
+       // the ref-count base management layer.
+       //sdb_object_deref(SDB_OBJ(sobj->parent));
 } /* store_obj_destroy */
 
 static int
@@ -105,6 +108,9 @@ sdb_host_init(sdb_object_t *obj, va_list ap)
        sobj->services = sdb_avltree_create();
        if (! sobj->services)
                return -1;
+       sobj->metrics = sdb_avltree_create();
+       if (! sobj->metrics)
+               return -1;
        sobj->attributes = sdb_avltree_create();
        if (! sobj->attributes)
                return -1;
@@ -121,6 +127,8 @@ sdb_host_destroy(sdb_object_t *obj)
 
        if (sobj->services)
                sdb_avltree_destroy(sobj->services);
+       if (sobj->metrics)
+               sdb_avltree_destroy(sobj->metrics);
        if (sobj->attributes)
                sdb_avltree_destroy(sobj->attributes);
 } /* sdb_host_destroy */
@@ -154,6 +162,42 @@ sdb_service_destroy(sdb_object_t *obj)
                sdb_avltree_destroy(sobj->attributes);
 } /* sdb_service_destroy */
 
+static int
+sdb_metric_init(sdb_object_t *obj, va_list ap)
+{
+       sdb_metric_t *sobj = METRIC(obj);
+       int ret;
+
+       /* this will consume the first argument (type) of ap */
+       ret = store_obj_init(obj, ap);
+       if (ret)
+               return ret;
+
+       sobj->attributes = sdb_avltree_create();
+       if (! sobj->attributes)
+               return -1;
+
+       sobj->store.type = sobj->store.id = NULL;
+       return 0;
+} /* sdb_metric_init */
+
+static void
+sdb_metric_destroy(sdb_object_t *obj)
+{
+       sdb_metric_t *sobj = METRIC(obj);
+       assert(obj);
+
+       store_obj_destroy(obj);
+
+       if (sobj->attributes)
+               sdb_avltree_destroy(sobj->attributes);
+
+       if (sobj->store.type)
+               free(sobj->store.type);
+       if (sobj->store.id)
+               free(sobj->store.id);
+} /* sdb_metric_destroy */
+
 static int
 sdb_attr_init(sdb_object_t *obj, va_list ap)
 {
@@ -194,6 +238,12 @@ static sdb_type_t sdb_service_type = {
        sdb_service_destroy
 };
 
+static sdb_type_t sdb_metric_type = {
+       sizeof(sdb_metric_t),
+       sdb_metric_init,
+       sdb_metric_destroy
+};
+
 static sdb_type_t sdb_attribute_type = {
        sizeof(sdb_attribute_t),
        sdb_attr_init,
@@ -205,9 +255,25 @@ static sdb_type_t sdb_attribute_type = {
  */
 
 static sdb_host_t *
-lookup_host(const char *name)
+lookup_host(const char *name, _Bool canonicalize)
 {
-       return HOST(sdb_avltree_lookup(hosts, name));
+       sdb_host_t *host;
+       char *cname;
+
+       assert(name);
+       if (! canonicalize)
+               return HOST(sdb_avltree_lookup(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
@@ -240,8 +306,9 @@ record_backend(sdb_store_obj_t *obj)
 } /* record_backend */
 
 static int
-store_obj(sdb_avltree_t *parent_tree, int type, const char *name,
-               sdb_time_t last_update, sdb_store_obj_t **updated_obj)
+store_obj(sdb_store_obj_t *parent, sdb_avltree_t *parent_tree,
+               int type, const char *name, sdb_time_t last_update,
+               sdb_store_obj_t **updated_obj)
 {
        sdb_store_obj_t *old, *new;
        int status = 0;
@@ -255,7 +322,7 @@ store_obj(sdb_avltree_t *parent_tree, int type, const char *name,
        if (old) {
                if (old->last_update > last_update) {
                        sdb_log(SDB_LOG_DEBUG, "store: Cannot update %s '%s' - "
-                                       "value too old (%"PRIscTIME" < %"PRIscTIME")",
+                                       "value too old (%"PRIsdbTIME" < %"PRIsdbTIME")",
                                        SDB_STORE_TYPE_TO_NAME(type), name,
                                        last_update, old->last_update);
                        /* don't report an error; the object may be updated by multiple
@@ -290,7 +357,11 @@ store_obj(sdb_avltree_t *parent_tree, int type, const char *name,
                }
                else {
                        sdb_type_t t;
-                       t = type == SDB_HOST ? sdb_host_type : sdb_service_type;
+                       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));
                }
 
@@ -313,6 +384,14 @@ store_obj(sdb_avltree_t *parent_tree, int type, const char *name,
                return status;
        assert(new);
 
+       if (new->parent != parent) {
+               // Avoid circular self-references which are not handled
+               // correctly by the ref-count based management layer.
+               //sdb_object_deref(SDB_OBJ(new->parent));
+               //sdb_object_ref(SDB_OBJ(parent));
+               new->parent = parent;
+       }
+
        if (updated_obj)
                *updated_obj = new;
 
@@ -322,13 +401,14 @@ store_obj(sdb_avltree_t *parent_tree, int type, const char *name,
 } /* store_obj */
 
 static int
-store_attr(sdb_avltree_t *attributes, const char *key, const sdb_data_t *value,
-               sdb_time_t last_update)
+store_attr(sdb_store_obj_t *parent, sdb_avltree_t *attributes,
+               const char *key, const sdb_data_t *value, sdb_time_t last_update)
 {
        sdb_store_obj_t *attr = NULL;
        int status;
 
-       status = store_obj(attributes, SDB_ATTRIBUTE, key, last_update, &attr);
+       status = store_obj(parent, attributes, SDB_ATTRIBUTE,
+                       key, last_update, &attr);
        if (status)
                return status;
 
@@ -344,31 +424,18 @@ store_attr(sdb_avltree_t *attributes, const char *key, const sdb_data_t *value,
 
 /* The host_lock has to be acquired before calling this function. */
 static sdb_avltree_t *
-get_host_children(const char *hostname, int type)
+get_host_children(sdb_host_t *host, int type)
 {
-       char *cname = NULL;
-       sdb_host_t *host;
-
-       assert(hostname);
-       assert((type == SDB_SERVICE) || (type == SDB_ATTRIBUTE));
-
-       if (! hosts)
-               return NULL;
+       assert((type == SDB_SERVICE) || (type == SDB_METRIC)
+                       || (type == SDB_ATTRIBUTE));
 
-       cname = sdb_plugin_cname(strdup(hostname));
-       if (! cname) {
-               sdb_log(SDB_LOG_ERR, "store: strdup failed");
-               return NULL;
-       }
-
-       host = lookup_host(cname);
-       free(cname);
        if (! host)
                return NULL;
 
-       sdb_object_deref(SDB_OBJ(host));
        if (type == SDB_ATTRIBUTE)
                return host->attributes;
+       else if (type == SDB_METRIC)
+               return host->metrics;
        else
                return host->services;
 } /* get_host_children */
@@ -386,6 +453,7 @@ store_common_tojson(sdb_store_obj_t *obj, sdb_strbuf_t *buf)
        char interval_str[64];
        size_t i;
 
+       /* TODO: make time and interval formats configurable */
        if (! sdb_strftime(time_str, sizeof(time_str),
                                "%F %T %z", obj->last_update))
                snprintf(time_str, sizeof(time_str), "<error>");
@@ -409,7 +477,7 @@ store_common_tojson(sdb_store_obj_t *obj, sdb_strbuf_t *buf)
 } /* store_common_tojson */
 
 /*
- * store_obj_tojson serializes attribute / service objects to JSON.
+ * store_obj_tojson serializes attribute / metric / service objects to JSON.
  *
  * The function never returns an error. Rather, an error message will be part
  * of the serialized data.
@@ -420,7 +488,9 @@ store_obj_tojson(sdb_avltree_t *tree, int type, sdb_strbuf_t *buf,
 {
        sdb_avltree_iter_t *iter;
 
-       assert((type == SDB_ATTRIBUTE) || (type == SDB_SERVICE));
+       assert((type == SDB_ATTRIBUTE)
+                       || (type == SDB_METRIC)
+                       || (type == SDB_SERVICE));
 
        sdb_strbuf_append(buf, "[");
        iter = sdb_avltree_get_iter(tree);
@@ -457,6 +527,12 @@ store_obj_tojson(sdb_avltree_t *tree, int type, sdb_strbuf_t *buf,
                        store_obj_tojson(SVC(sobj)->attributes, SDB_ATTRIBUTE,
                                        buf, filter, flags);
                }
+               else if ((sobj->type == SDB_METRIC)
+                               && (! (flags & SDB_SKIP_ATTRIBUTES))) {
+                       sdb_strbuf_append(buf, ", \"attributes\": ");
+                       store_obj_tojson(METRIC(sobj)->attributes, SDB_ATTRIBUTE,
+                                       buf, filter, flags);
+               }
                sdb_strbuf_append(buf, "}");
 
                if (sdb_avltree_iter_has_next(iter))
@@ -467,6 +543,60 @@ store_obj_tojson(sdb_avltree_t *tree, int type, sdb_strbuf_t *buf,
        sdb_strbuf_append(buf, "]");
 } /* store_obj_tojson */
 
+/*
+ * ts_tojson serializes a time-series to JSON.
+ *
+ * The function never returns an error. Rather, an error message will be part
+ * of the serialized data.
+ */
+static void
+ts_tojson(sdb_timeseries_t *ts, sdb_strbuf_t *buf)
+{
+       char start_str[64];
+       char end_str[64];
+
+       size_t i;
+
+       /* TODO: make time format configurable */
+       if (! sdb_strftime(start_str, sizeof(start_str),
+                               "%F %T %z", 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))
+               snprintf(end_str, sizeof(end_str), "<error>");
+       end_str[sizeof(end_str) - 1] = '\0';
+
+       sdb_strbuf_append(buf, "{\"start\": \"%s\", \"end\": \"%s\", \"data\": {",
+                       start_str, end_str);
+
+       for (i = 0; i < ts->data_names_len; ++i) {
+               size_t j;
+               sdb_strbuf_append(buf, "\"%s\": [", ts->data_names[i]);
+
+               for (j = 0; j < ts->data_len; ++j) {
+                       char time_str[64];
+
+                       if (! sdb_strftime(time_str, sizeof(time_str),
+                                               "%F %T %z", 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);
+
+                       if (j < ts->data_len - 1)
+                               sdb_strbuf_append(buf, ",");
+               }
+
+               if (i < ts->data_names_len - 1)
+                       sdb_strbuf_append(buf, "],");
+               else
+                       sdb_strbuf_append(buf, "]");
+       }
+       sdb_strbuf_append(buf, "}}");
+} /* ts_tojson */
+
 /*
  * public API
  */
@@ -499,7 +629,7 @@ sdb_store_host(const char *name, sdb_time_t last_update)
                        status = -1;
 
        if (! status)
-               status = store_obj(hosts, SDB_HOST, cname, last_update, NULL);
+               status = store_obj(NULL, hosts, SDB_HOST, cname, last_update, NULL);
        pthread_rwlock_unlock(&host_lock);
 
        free(cname);
@@ -514,7 +644,8 @@ sdb_store_has_host(const char *name)
        if (! name)
                return NULL;
 
-       host = lookup_host(name);
+       host = lookup_host(name, /* canonicalize = */ 0);
+       sdb_object_deref(SDB_OBJ(host));
        return host != NULL;
 } /* sdb_store_has_host */
 
@@ -526,7 +657,7 @@ sdb_store_get_host(const char *name)
        if (! name)
                return NULL;
 
-       host = lookup_host(name);
+       host = lookup_host(name, /* canonicalize = */ 0);
        if (! host)
                return NULL;
 
@@ -538,6 +669,7 @@ sdb_store_attribute(const char *hostname,
                const char *key, const sdb_data_t *value,
                sdb_time_t last_update)
 {
+       sdb_host_t *host;
        sdb_avltree_t *attrs;
        int status = 0;
 
@@ -545,7 +677,8 @@ sdb_store_attribute(const char *hostname,
                return -1;
 
        pthread_rwlock_wrlock(&host_lock);
-       attrs = get_host_children(hostname, SDB_ATTRIBUTE);
+       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);
@@ -553,8 +686,9 @@ sdb_store_attribute(const char *hostname,
        }
 
        if (! status)
-               status = store_attr(attrs, key, value, last_update);
+               status = store_attr(STORE_OBJ(host), attrs, key, value, last_update);
 
+       sdb_object_deref(SDB_OBJ(host));
        pthread_rwlock_unlock(&host_lock);
        return status;
 } /* sdb_store_attribute */
@@ -563,6 +697,7 @@ int
 sdb_store_service(const char *hostname, const char *name,
                sdb_time_t last_update)
 {
+       sdb_host_t *host;
        sdb_avltree_t *services;
 
        int status = 0;
@@ -571,7 +706,8 @@ sdb_store_service(const char *hostname, const char *name,
                return -1;
 
        pthread_rwlock_wrlock(&host_lock);
-       services = get_host_children(hostname, SDB_SERVICE);
+       host = lookup_host(hostname, /* canonicalize = */ 1);
+       services = get_host_children(host, SDB_SERVICE);
        if (! services) {
                sdb_log(SDB_LOG_ERR, "store: Failed to store service '%s' - "
                                "host '%s' not found", name, hostname);
@@ -579,7 +715,10 @@ sdb_store_service(const char *hostname, const char *name,
        }
 
        if (! status)
-               status = store_obj(services, SDB_SERVICE, name, last_update, NULL);
+               status = store_obj(STORE_OBJ(host), services, SDB_SERVICE,
+                               name, last_update, NULL);
+
+       sdb_object_deref(SDB_OBJ(host));
        pthread_rwlock_unlock(&host_lock);
        return status;
 } /* sdb_store_service */
@@ -588,15 +727,18 @@ int
 sdb_store_service_attr(const char *hostname, const char *service,
                const char *key, const sdb_data_t *value, sdb_time_t last_update)
 {
-       sdb_avltree_t *services;
+       sdb_host_t *host;
        sdb_service_t *svc;
+       sdb_avltree_t *services;
        int status = 0;
 
        if ((! hostname) || (! service) || (! key))
                return -1;
 
        pthread_rwlock_wrlock(&host_lock);
-       services = get_host_children(hostname, SDB_SERVICE);
+       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",
@@ -613,13 +755,258 @@ sdb_store_service_attr(const char *hostname, const char *service,
        }
 
        if (! status)
-               status = store_attr(svc->attributes, key, value, last_update);
+               status = store_attr(STORE_OBJ(svc), svc->attributes,
+                               key, value, last_update);
 
        sdb_object_deref(SDB_OBJ(svc));
        pthread_rwlock_unlock(&host_lock);
        return status;
 } /* sdb_store_service_attr */
 
+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;
+
+       sdb_avltree_t *metrics;
+
+       int status = 0;
+
+       if ((! hostname) || (! name))
+               return -1;
+       if (store && ((! store->type) || (! store->id)))
+               return -1;
+
+       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;
+       }
+
+       if (! status)
+               status = store_obj(STORE_OBJ(host), metrics, SDB_METRIC,
+                               name, last_update, &obj);
+       sdb_object_deref(SDB_OBJ(host));
+
+       if (status || (! store)) {
+               pthread_rwlock_unlock(&host_lock);
+               return status;
+       }
+
+       assert(obj);
+       metric = METRIC(obj);
+
+       if ((! metric->store.type) || strcasecmp(metric->store.type, store->type)) {
+               if (metric->store.type)
+                       free(metric->store.type);
+               metric->store.type = strdup(store->type);
+       }
+       if ((! metric->store.id) || strcasecmp(metric->store.id, store->id)) {
+               if (metric->store.id)
+                       free(metric->store.id);
+               metric->store.id = strdup(store->id);
+       }
+
+       if ((! 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;
+       }
+       pthread_rwlock_unlock(&host_lock);
+       return status;
+} /* sdb_store_metric */
+
+int
+sdb_store_metric_attr(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;
+       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;
+       }
+
+       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;
+       }
+
+       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 */
+
+int
+sdb_store_fetch_timeseries(const char *hostname, const char *metric,
+               sdb_timeseries_opts_t *opts, sdb_strbuf_t *buf)
+{
+       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;
+       }
+
+       m = METRIC(sdb_avltree_lookup(metrics, metric));
+       if (! m) {
+               sdb_log(SDB_LOG_ERR, "store: Failed to fetch time-series '%s/%s' "
+                               "- metric '%s' not found", hostname, metric, metric);
+               pthread_rwlock_unlock(&host_lock);
+               return -1;
+       }
+
+       if ((! 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;
+       }
+
+       {
+               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(&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);
+                       return -1;
+               }
+       }
+
+       ts_tojson(ts, buf);
+       sdb_timeseries_destroy(ts);
+       return 0;
+} /* sdb_store_fetch_timeseries */
+
+int
+sdb_store_get_field(sdb_store_obj_t *obj, int field, sdb_data_t *res)
+{
+       sdb_data_t tmp;
+
+       if (! obj)
+               return -1;
+
+       switch (field) {
+               case SDB_FIELD_NAME:
+                       tmp.type = SDB_TYPE_STRING;
+                       tmp.data.string = strdup(SDB_OBJ(obj)->name);
+                       if (! tmp.data.string)
+                               return -1;
+                       break;
+               case SDB_FIELD_LAST_UPDATE:
+                       tmp.type = SDB_TYPE_DATETIME;
+                       tmp.data.datetime = obj->last_update;
+                       break;
+               case SDB_FIELD_AGE:
+                       tmp.type = SDB_TYPE_DATETIME;
+                       tmp.data.datetime = sdb_gettime() - obj->last_update;
+                       break;
+               case SDB_FIELD_INTERVAL:
+                       tmp.type = SDB_TYPE_DATETIME;
+                       tmp.data.datetime = obj->interval;
+                       break;
+               case SDB_FIELD_BACKEND:
+               {
+                       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;
+               }
+               default:
+                       return -1;
+       }
+       if (res)
+               *res = tmp;
+       else
+               sdb_data_free_datum(&tmp);
+       return 0;
+} /* sdb_store_get_field */
+
+int
+sdb_store_get_attr(sdb_store_obj_t *obj, const char *name, sdb_data_t *res,
+               sdb_store_matcher_t *filter)
+{
+       sdb_avltree_t *tree = NULL;
+       sdb_store_obj_t *attr;
+
+       if ((! obj) || (! name))
+               return -1;
+
+       if (obj->type == SDB_HOST)
+               tree = HOST(obj)->attributes;
+       else if (obj->type == SDB_SERVICE)
+               tree = SVC(obj)->attributes;
+       else if (obj->type == SDB_METRIC)
+               tree = METRIC(obj)->attributes;
+
+       if (! tree)
+               return -1;
+
+       attr = STORE_OBJ(sdb_avltree_lookup(tree, name));
+       if (! attr)
+               return -1;
+       if (filter && (! sdb_store_matcher_matches(filter, attr, NULL))) {
+               sdb_object_deref(SDB_OBJ(attr));
+               return -1;
+       }
+
+       assert(STORE_OBJ(attr)->type == SDB_ATTRIBUTE);
+       if (res)
+               sdb_data_copy(res, &ATTR(attr)->value);
+       sdb_object_deref(SDB_OBJ(attr));
+       return 0;
+} /* sdb_store_get_attr */
+
 int
 sdb_store_host_tojson(sdb_store_obj_t *h, sdb_strbuf_t *buf,
                sdb_store_matcher_t *filter, int flags)
@@ -629,8 +1016,9 @@ sdb_store_host_tojson(sdb_store_obj_t *h, sdb_strbuf_t *buf,
        if ((! h) || (h->type != SDB_HOST) || (! buf))
                return -1;
 
-       if (filter && (! sdb_store_matcher_matches(filter, h, NULL)))
-               return 0;
+       /* This function ignores SKIP_EMPTY flags given that the current
+        * implementation sucks and it's nut currently used when calling this
+        * function directly. */
 
        sdb_strbuf_append(buf, "{\"name\": \"%s\", ", SDB_OBJ(host)->name);
        store_common_tojson(h, buf);
@@ -640,6 +1028,11 @@ sdb_store_host_tojson(sdb_store_obj_t *h, sdb_strbuf_t *buf,
                store_obj_tojson(host->attributes, SDB_ATTRIBUTE, buf, filter, flags);
        }
 
+       if (! (flags & SDB_SKIP_METRICS)) {
+               sdb_strbuf_append(buf, ", \"metrics\": ");
+               store_obj_tojson(host->metrics, SDB_METRIC, buf, filter, flags);
+       }
+
        if (! (flags & SDB_SKIP_SERVICES)) {
                sdb_strbuf_append(buf, ", \"services\": ");
                store_obj_tojson(host->services, SDB_SERVICE, buf, filter, flags);
@@ -649,10 +1042,31 @@ sdb_store_host_tojson(sdb_store_obj_t *h, sdb_strbuf_t *buf,
        return 0;
 } /* sdb_store_host_tojson */
 
+static _Bool
+has_children(sdb_avltree_t *tree, sdb_store_matcher_t *filter)
+{
+       sdb_avltree_iter_t *iter;
+
+       if (! filter)
+               return sdb_avltree_size(tree) > 0;
+
+       iter = sdb_avltree_get_iter(tree);
+       while (sdb_avltree_iter_has_next(iter)) {
+               sdb_store_obj_t *sobj = STORE_OBJ(sdb_avltree_iter_get_next(iter));
+               if (sdb_store_matcher_matches(filter, sobj, NULL)) {
+                       sdb_avltree_iter_destroy(iter);
+                       return 1;
+               }
+       }
+       sdb_avltree_iter_destroy(iter);
+       return 0;
+} /* has_children */
+
 int
 sdb_store_tojson(sdb_strbuf_t *buf, sdb_store_matcher_t *filter, int flags)
 {
        sdb_avltree_iter_t *host_iter;
+       size_t len;
 
        if (! buf)
                return -1;
@@ -665,38 +1079,61 @@ sdb_store_tojson(sdb_strbuf_t *buf, sdb_store_matcher_t *filter, int flags)
                return -1;
        }
 
-       sdb_strbuf_append(buf, "{\"hosts\":[");
+       sdb_strbuf_append(buf, "[");
 
+       len = sdb_strbuf_len(buf);
        while (sdb_avltree_iter_has_next(host_iter)) {
                sdb_store_obj_t *host;
-               size_t len = sdb_strbuf_len(buf);
 
                host = STORE_OBJ(sdb_avltree_iter_get_next(host_iter));
                assert(host);
 
-               if (sdb_store_host_tojson(host, buf, filter, flags))
-                       return -1;
+               if (filter && (! sdb_store_matcher_matches(filter, host, NULL)))
+                       continue;
+
+               /*
+                * XXX: This approach sucks but it's the best we can do at the moment.
+                * In the future, all store lookups should be split into multiple
+                * steps instead: first, retrieve all relevant objects and apply all
+                * pre-processing operations and then format it for the wire.
+                */
+               if ((flags & SDB_SKIP_EMPTY_SERVICES)
+                               && (! has_children(HOST(host)->services, filter)))
+                       continue;
+               if ((flags & SDB_SKIP_EMPTY_METRICS)
+                               && (! has_children(HOST(host)->metrics, filter)))
+                       continue;
 
-               /* sdb_store_host_tojson may leave the buffer unmodified */
-               if ((sdb_avltree_iter_has_next(host_iter))
-                               && (sdb_strbuf_len(buf) != len))
+               if (sdb_strbuf_len(buf) > len)
                        sdb_strbuf_append(buf, ",");
+               len = sdb_strbuf_len(buf);
+
+               if (sdb_store_host_tojson(host, buf, filter, flags))
+                       return -1;
        }
 
-       sdb_strbuf_append(buf, "]}");
+       sdb_strbuf_append(buf, "]");
 
        sdb_avltree_iter_destroy(host_iter);
        pthread_rwlock_unlock(&host_lock);
        return 0;
 } /* sdb_store_tojson */
 
-/* TODO: actually support hierarchical data */
 int
-sdb_store_iterate(sdb_store_iter_cb cb, void *user_data)
+sdb_store_scan(int type, sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
+               sdb_store_lookup_cb cb, void *user_data)
 {
        sdb_avltree_iter_t *host_iter;
        int status = 0;
 
+       if (! cb)
+               return -1;
+
+       if ((type != SDB_HOST) && (type != SDB_SERVICE) && (type != SDB_METRIC)) {
+               sdb_log(SDB_LOG_ERR, "store: Cannot scan objects of type %d", type);
+               return -1;
+       }
+
        pthread_rwlock_rdlock(&host_lock);
 
        host_iter = sdb_avltree_get_iter(hosts);
@@ -706,20 +1143,52 @@ sdb_store_iterate(sdb_store_iter_cb cb, void *user_data)
        /* has_next returns false if the iterator is NULL */
        while (sdb_avltree_iter_has_next(host_iter)) {
                sdb_store_obj_t *host;
+               sdb_avltree_iter_t *iter = NULL;
 
                host = STORE_OBJ(sdb_avltree_iter_get_next(host_iter));
                assert(host);
 
-               if (cb(host, user_data)) {
-                       status = -1;
-                       break;
+               if (! sdb_store_matcher_matches(filter, host, NULL))
+                       continue;
+
+               if (type == SDB_SERVICE)
+                       iter = sdb_avltree_get_iter(HOST(host)->services);
+               else if (type == SDB_METRIC)
+                       iter = sdb_avltree_get_iter(HOST(host)->metrics);
+
+               if (iter) {
+                       while (sdb_avltree_iter_has_next(iter)) {
+                               sdb_store_obj_t *obj;
+                               obj = STORE_OBJ(sdb_avltree_iter_get_next(iter));
+                               assert(obj);
+
+                               if (sdb_store_matcher_matches(m, obj, filter)) {
+                                       if (cb(obj, filter, user_data)) {
+                                               sdb_log(SDB_LOG_ERR, "store: Callback returned "
+                                                               "an error while scanning");
+                                               status = -1;
+                                               break;
+                                       }
+                               }
+                       }
                }
+               else if (sdb_store_matcher_matches(m, host, filter)) {
+                       if (cb(host, filter, user_data)) {
+                               sdb_log(SDB_LOG_ERR, "store: Callback returned "
+                                               "an error while scanning");
+                               status = -1;
+                       }
+               }
+
+               sdb_avltree_iter_destroy(iter);
+               if (status)
+                       break;
        }
 
        sdb_avltree_iter_destroy(host_iter);
        pthread_rwlock_unlock(&host_lock);
        return status;
-} /* sdb_store_iterate */
+} /* sdb_store_scan */
 
 /* vim: set tw=78 sw=4 ts=4 noexpandtab : */