Merging upstream version 1.37.1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

13 files changed, 115 insertions, 84 deletions

diff --git a/database/engine/pagecache.c b/database/engine/pagecache.c
index d65cb35a5..4f5da7084 100644
--- a/database/engine/pagecache.c
+++ b/database/engine/pagecache.c
@@ -524,6 +524,14 @@ uint8_t pg_cache_punch_hole(struct rrdengine_instance *ctx, struct rrdeng_page_d
     }
     rrdeng_page_descr_mutex_unlock(ctx, descr);
 
+    while (unlikely(pg_cache_descr->flags & RRD_PAGE_READ_PENDING)) {
+        error_limit_static_global_var(erl, 1, 0);
+        error_limit(&erl, "%s: Found page with READ PENDING, waiting for read to complete", __func__);
+        if (unlikely(debug_flags & D_RRDENGINE))
+            print_page_cache_descr(descr, "", true);
+        pg_cache_wait_event_unsafe(descr);
+    }
+
     if (pg_cache_descr->flags & RRD_PAGE_POPULATED) {
         /* only after locking can it be safely deleted from LRU */
         pg_cache_replaceQ_delete(ctx, descr);
@@ -1196,7 +1204,6 @@ struct pg_cache_page_index *create_page_index(uuid_t *id, struct rrdengine_insta
     page_index->refcount = 0;
     page_index->writers = 0;
     page_index->ctx = ctx;
-    page_index->alignment = NULL;
     page_index->latest_update_every_s = default_rrd_update_every;
 
     return page_index;
diff --git a/database/engine/pagecache.h b/database/engine/pagecache.h
index 2f4d6b332..635b02123 100644
--- a/database/engine/pagecache.h
+++ b/database/engine/pagecache.h
@@ -112,7 +112,6 @@ struct pg_cache_page_index {
     usec_t latest_time_ut;
 
     struct rrdengine_instance *ctx;
-    struct pg_alignment *alignment;
     uint32_t latest_update_every_s;
 
     struct pg_cache_page_index *prev;
diff --git a/database/engine/rrdengine.c b/database/engine/rrdengine.c
index e4cd37e98..a6840f38c 100644
--- a/database/engine/rrdengine.c
+++ b/database/engine/rrdengine.c
@@ -272,9 +272,19 @@ static void fill_page_with_nulls(void *page, uint32_t page_length, uint8_t type)
     }
 }
 
+struct rrdeng_page_descr *get_descriptor(struct pg_cache_page_index *page_index, time_t start_time_s)
+{
+    uv_rwlock_rdlock(&page_index->lock);
+    Pvoid_t *PValue = JudyLGet(page_index->JudyL_array, start_time_s, PJE0);
+    struct rrdeng_page_descr *descr = unlikely(NULL == PValue) ? NULL : *PValue;
+    uv_rwlock_rdunlock(&page_index->lock);
+    return descr;
+};
+
 static void do_extent_processing (struct rrdengine_worker_config *wc, struct extent_io_descriptor *xt_io_descr, bool read_failed)
 {
     struct rrdengine_instance *ctx = wc->ctx;
+    struct page_cache *pg_cache = &ctx->pg_cache;
     struct rrdeng_page_descr *descr;
     struct page_cache_descr *pg_cache_descr;
     int ret;
@@ -365,19 +375,30 @@ after_crc_check:
         }
     }
 
+    uv_rwlock_rdlock(&pg_cache->metrics_index.lock);
+    Pvoid_t *PValue = JudyHSGet(pg_cache->metrics_index.JudyHS_array, xt_io_descr->descr_array[0]->id, sizeof(uuid_t));
+    struct pg_cache_page_index *page_index = likely( NULL != PValue) ? *PValue : NULL;
+    uv_rwlock_rdunlock(&pg_cache->metrics_index.lock);
+
+
     for (i = 0, page_offset = 0; i < count; page_offset += header->descr[i++].page_length) {
         uint8_t is_prefetched_page;
         descr = NULL;
         for (j = 0 ; j < xt_io_descr->descr_count; ++j) {
-            struct rrdeng_page_descr *descrj;
+            struct rrdeng_page_descr descrj;
 
-            descrj = xt_io_descr->descr_array[j];
+            descrj = xt_io_descr->descr_read_array[j];
             /* care, we don't hold the descriptor mutex */
-            if (!uuid_compare(*(uuid_t *) header->descr[i].uuid, *descrj->id) &&
-                header->descr[i].page_length == descrj->page_length &&
-                header->descr[i].start_time_ut == descrj->start_time_ut &&
-                header->descr[i].end_time_ut == descrj->end_time_ut) {
-                descr = descrj;
+            if (!uuid_compare(*(uuid_t *) header->descr[i].uuid, *descrj.id) &&
+                header->descr[i].page_length == descrj.page_length &&
+                header->descr[i].start_time_ut == descrj.start_time_ut &&
+                header->descr[i].end_time_ut == descrj.end_time_ut) {
+                //descr = descrj;
+                descr = get_descriptor(page_index, (time_t) (descrj.start_time_ut / USEC_PER_SEC));
+                if (unlikely(!descr)) {
+                    error_limit_static_thread_var(erl, 1, 0);
+                    error_limit(&erl, "%s: Required descriptor is not in the page index anymore", __FUNCTION__);
+                }
                 break;
             }
         }
@@ -506,6 +527,7 @@ static void do_read_extent(struct rrdengine_worker_config* wc,
         pg_cache_descr->flags |= RRD_PAGE_READ_PENDING;
         rrdeng_page_descr_mutex_unlock(ctx, descr[i]);
         xt_io_descr->descr_array[i] = descr[i];
+        xt_io_descr->descr_read_array[i] = *(descr[i]);
     }
     xt_io_descr->descr_count = count;
     xt_io_descr->file = datafile->file;
diff --git a/database/engine/rrdengine.h b/database/engine/rrdengine.h
index fedadbe86..521d2521a 100644
--- a/database/engine/rrdengine.h
+++ b/database/engine/rrdengine.h
@@ -41,6 +41,7 @@ struct rrdeng_collect_handle {
     unsigned long page_correlation_id;
     // set to 1 when this dimension is not page aligned with the other dimensions in the chart
     uint8_t unaligned_page;
+    struct pg_alignment *alignment;
 };
 
 struct rrdeng_query_handle {
@@ -117,6 +118,7 @@ struct extent_io_descriptor {
     unsigned descr_count;
     int release_descr;
     struct rrdeng_page_descr *descr_array[MAX_PAGES_PER_EXTENT];
+    struct rrdeng_page_descr descr_read_array[MAX_PAGES_PER_EXTENT];
     Word_t descr_commit_idx_array[MAX_PAGES_PER_EXTENT];
     struct extent_io_descriptor *next; /* multiple requests to be served by the same cached extent */
 };
diff --git a/database/engine/rrdengineapi.c b/database/engine/rrdengineapi.c
index 27503baee..4525b041f 100755
--- a/database/engine/rrdengineapi.c
+++ b/database/engine/rrdengineapi.c
@@ -39,21 +39,35 @@ uint8_t rrdeng_drop_metrics_under_page_cache_pressure = 1;
 // ----------------------------------------------------------------------------
 // metrics groups
 
+static inline void rrdeng_page_alignment_acquire(struct pg_alignment *pa) {
+    if(unlikely(!pa)) return;
+    __atomic_add_fetch(&pa->refcount, 1, __ATOMIC_SEQ_CST);
+}
+
+static inline bool rrdeng_page_alignment_release(struct pg_alignment *pa) {
+    if(unlikely(!pa)) return true;
+
+    if(__atomic_sub_fetch(&pa->refcount, 1, __ATOMIC_SEQ_CST) == 0) {
+        freez(pa);
+        return true;
+    }
+
+    return false;
+}
+
+// charts call this
 STORAGE_METRICS_GROUP *rrdeng_metrics_group_get(STORAGE_INSTANCE *db_instance __maybe_unused, uuid_t *uuid __maybe_unused) {
-    return callocz(1, sizeof(struct pg_alignment));
+    struct pg_alignment *pa = callocz(1, sizeof(struct pg_alignment));
+    rrdeng_page_alignment_acquire(pa);
+    return (STORAGE_METRICS_GROUP *)pa;
 }
 
-void rrdeng_metrics_group_release(STORAGE_INSTANCE *db_instance, STORAGE_METRICS_GROUP *smg) {
-    if(!smg) return;
+// charts call this
+void rrdeng_metrics_group_release(STORAGE_INSTANCE *db_instance __maybe_unused, STORAGE_METRICS_GROUP *smg) {
+    if(unlikely(!smg)) return;
 
-    struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
     struct pg_alignment *pa = (struct pg_alignment *)smg;
-    struct page_cache *pg_cache = &ctx->pg_cache;
-
-    uv_rwlock_rdlock(&pg_cache->metrics_index.lock);
-    if(pa->refcount == 0)
-        freez(pa);
-    uv_rwlock_rdunlock(&pg_cache->metrics_index.lock);
+    rrdeng_page_alignment_release(pa);
 }
 
 // ----------------------------------------------------------------------------
@@ -93,10 +107,10 @@ void rrdeng_convert_legacy_uuid_to_multihost(char machine_guid[GUID_LEN + 1], uu
     memcpy(ret_uuid, hash_value, sizeof(uuid_t));
 }
 
-STORAGE_METRIC_HANDLE *rrdeng_metric_get_legacy(STORAGE_INSTANCE *db_instance, const char *rd_id, const char *st_id, STORAGE_METRICS_GROUP *smg) {
+STORAGE_METRIC_HANDLE *rrdeng_metric_get_legacy(STORAGE_INSTANCE *db_instance, const char *rd_id, const char *st_id) {
     uuid_t legacy_uuid;
     rrdeng_generate_legacy_uuid(rd_id, st_id, &legacy_uuid);
-    return rrdeng_metric_get(db_instance, &legacy_uuid, smg);
+    return rrdeng_metric_get(db_instance, &legacy_uuid);
 }
 
 // ----------------------------------------------------------------------------
@@ -105,11 +119,7 @@ STORAGE_METRIC_HANDLE *rrdeng_metric_get_legacy(STORAGE_INSTANCE *db_instance, c
 void rrdeng_metric_release(STORAGE_METRIC_HANDLE *db_metric_handle) {
     struct pg_cache_page_index *page_index = (struct pg_cache_page_index *)db_metric_handle;
 
-    unsigned short refcount = __atomic_sub_fetch(&page_index->refcount, 1, __ATOMIC_SEQ_CST);
-    if(refcount == 0 && page_index->alignment) {
-        __atomic_sub_fetch(&page_index->alignment->refcount, 1, __ATOMIC_SEQ_CST);
-        page_index->alignment = NULL;
-    }
+    __atomic_sub_fetch(&page_index->refcount, 1, __ATOMIC_SEQ_CST);
 }
 
 STORAGE_METRIC_HANDLE *rrdeng_metric_dup(STORAGE_METRIC_HANDLE *db_metric_handle) {
@@ -118,9 +128,8 @@ STORAGE_METRIC_HANDLE *rrdeng_metric_dup(STORAGE_METRIC_HANDLE *db_metric_handle
     return db_metric_handle;
 }
 
-STORAGE_METRIC_HANDLE *rrdeng_metric_get(STORAGE_INSTANCE *db_instance, uuid_t *uuid, STORAGE_METRICS_GROUP *smg) {
+STORAGE_METRIC_HANDLE *rrdeng_metric_get(STORAGE_INSTANCE *db_instance, uuid_t *uuid) {
     struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    struct pg_alignment *pa = (struct pg_alignment *)smg;
     struct page_cache *pg_cache = &ctx->pg_cache;
     struct pg_cache_page_index *page_index = NULL;
 
@@ -130,27 +139,16 @@ STORAGE_METRIC_HANDLE *rrdeng_metric_get(STORAGE_INSTANCE *db_instance, uuid_t *
         page_index = *PValue;
     uv_rwlock_rdunlock(&pg_cache->metrics_index.lock);
 
-    if (likely(page_index)) {
+    if (likely(page_index))
         __atomic_add_fetch(&page_index->refcount, 1, __ATOMIC_SEQ_CST);
 
-        if(pa) {
-            if(page_index->alignment && page_index->alignment != pa && page_index->writers > 0)
-                fatal("DBENGINE: page_index has a different alignment (page_index refcount is %u, writers is %u).",
-                        page_index->refcount, page_index->writers);
-
-            page_index->alignment = pa;
-            __atomic_add_fetch(&pa->refcount, 1, __ATOMIC_SEQ_CST);
-        }
-    }
-
     return (STORAGE_METRIC_HANDLE *)page_index;
 }
 
-STORAGE_METRIC_HANDLE *rrdeng_metric_create(STORAGE_INSTANCE *db_instance, uuid_t *uuid, STORAGE_METRICS_GROUP *smg) {
+STORAGE_METRIC_HANDLE *rrdeng_metric_create(STORAGE_INSTANCE *db_instance, uuid_t *uuid) {
     internal_fatal(!db_instance, "DBENGINE: db_instance is NULL");
 
     struct rrdengine_instance *ctx = (struct rrdengine_instance *)db_instance;
-    struct pg_alignment *pa = (struct pg_alignment *)smg;
     struct pg_cache_page_index *page_index;
     struct page_cache *pg_cache = &ctx->pg_cache;
 
@@ -160,28 +158,25 @@ STORAGE_METRIC_HANDLE *rrdeng_metric_create(STORAGE_INSTANCE *db_instance, uuid_
     *PValue = page_index = create_page_index(uuid, ctx);
     page_index->prev = pg_cache->metrics_index.last_page_index;
     pg_cache->metrics_index.last_page_index = page_index;
-    page_index->alignment = pa;
     page_index->refcount = 1;
-    if(pa)
-        pa->refcount++;
     uv_rwlock_wrunlock(&pg_cache->metrics_index.lock);
 
     return (STORAGE_METRIC_HANDLE *)page_index;
 }
 
-STORAGE_METRIC_HANDLE *rrdeng_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance, STORAGE_METRICS_GROUP *smg) {
+STORAGE_METRIC_HANDLE *rrdeng_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance) {
     STORAGE_METRIC_HANDLE *db_metric_handle;
 
-    db_metric_handle = rrdeng_metric_get(db_instance, &rd->metric_uuid, smg);
+    db_metric_handle = rrdeng_metric_get(db_instance, &rd->metric_uuid);
     if(!db_metric_handle) {
-        db_metric_handle = rrdeng_metric_get_legacy(db_instance, rrddim_id(rd), rrdset_id(rd->rrdset), smg);
+        db_metric_handle = rrdeng_metric_get_legacy(db_instance, rrddim_id(rd), rrdset_id(rd->rrdset));
         if(db_metric_handle) {
             struct pg_cache_page_index *page_index = (struct pg_cache_page_index *)db_metric_handle;
             uuid_copy(rd->metric_uuid, page_index->id);
         }
     }
     if(!db_metric_handle)
-        db_metric_handle = rrdeng_metric_create(db_instance, &rd->metric_uuid, smg);
+        db_metric_handle = rrdeng_metric_create(db_instance, &rd->metric_uuid);
 
 #ifdef NETDATA_INTERNAL_CHECKS
     struct pg_cache_page_index *page_index = (struct pg_cache_page_index *)db_metric_handle;
@@ -210,19 +205,19 @@ STORAGE_METRIC_HANDLE *rrdeng_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE
  * Gets a handle for storing metrics to the database.
  * The handle must be released with rrdeng_store_metric_final().
  */
-STORAGE_COLLECT_HANDLE *rrdeng_store_metric_init(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every) {
+STORAGE_COLLECT_HANDLE *rrdeng_store_metric_init(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every, STORAGE_METRICS_GROUP *smg) {
     struct pg_cache_page_index *page_index = (struct pg_cache_page_index *)db_metric_handle;
     struct rrdeng_collect_handle *handle;
 
-    if(!page_index->alignment)
-        fatal("DBENGINE: metric group is required for collect operations");
-
     handle = callocz(1, sizeof(struct rrdeng_collect_handle));
     handle->page_index = page_index;
     handle->descr = NULL;
     handle->unaligned_page = 0;
     page_index->latest_update_every_s = update_every;
 
+    handle->alignment = (struct pg_alignment *)smg;
+    rrdeng_page_alignment_acquire(handle->alignment);
+
     uv_rwlock_wrlock(&page_index->lock);
     ++page_index->writers;
     uv_rwlock_wrunlock(&page_index->lock);
@@ -331,18 +326,18 @@ static void rrdeng_store_metric_next_internal(STORAGE_COLLECT_HANDLE *collection
         }
 #endif
 
-        if (descr->page_length == page_index->alignment->page_length) {
+        if (descr->page_length == handle->alignment->page_length) {
             /* this is the leading dimension that defines chart alignment */
             perfect_page_alignment = 1;
         }
         /* is the metric far enough out of alignment with the others? */
-        if (unlikely(descr->page_length + PAGE_POINT_SIZE_BYTES(descr) < page_index->alignment->page_length)) {
+        if (unlikely(descr->page_length + PAGE_POINT_SIZE_BYTES(descr) < handle->alignment->page_length)) {
             handle->unaligned_page = 1;
             print_page_cache_descr(descr, "Metric page is not aligned with chart", true);
         }
         if (unlikely(handle->unaligned_page &&
                      /* did the other metrics change page? */
-                     page_index->alignment->page_length <= PAGE_POINT_SIZE_BYTES(descr))) {
+                     handle->alignment->page_length <= PAGE_POINT_SIZE_BYTES(descr))) {
             print_page_cache_descr(descr, "must_flush_unaligned_page = 1", true);
             must_flush_unaligned_page = 1;
             handle->unaligned_page = 0;
@@ -365,7 +360,7 @@ static void rrdeng_store_metric_next_internal(STORAGE_COLLECT_HANDLE *collection
 
         handle->page_correlation_id = rrd_atomic_fetch_add(&pg_cache->committed_page_index.latest_corr_id, 1);
 
-        if (0 == page_index->alignment->page_length) {
+        if (0 == handle->alignment->page_length) {
             /* this is the leading dimension that defines chart alignment */
             perfect_page_alignment = 1;
         }
@@ -403,7 +398,7 @@ static void rrdeng_store_metric_next_internal(STORAGE_COLLECT_HANDLE *collection
     pg_cache_atomic_set_pg_info(descr, point_in_time_ut, descr->page_length + PAGE_POINT_SIZE_BYTES(descr));
 
     if (perfect_page_alignment)
-        page_index->alignment->page_length = descr->page_length;
+        handle->alignment->page_length = descr->page_length;
     if (unlikely(INVALID_TIME == descr->start_time_ut)) {
         unsigned long new_metric_API_producers, old_metric_API_max_producers, ret_metric_API_max_producers;
         descr->start_time_ut = point_in_time_ut;
@@ -530,10 +525,13 @@ int rrdeng_store_metric_finalize(STORAGE_COLLECT_HANDLE *collection_handle) {
 
     rrdeng_store_metric_flush_current_page(collection_handle);
     uv_rwlock_wrlock(&page_index->lock);
-    if (!--page_index->writers && !page_index->page_count) {
+
+    if (!--page_index->writers && !page_index->page_count)
         can_delete_metric = 1;
-    }
+
     uv_rwlock_wrunlock(&page_index->lock);
+
+    rrdeng_page_alignment_release(handle->alignment);
     freez(handle);
 
     return can_delete_metric;
diff --git a/database/engine/rrdengineapi.h b/database/engine/rrdengineapi.h
index 85375044f..3acee4ec6 100644
--- a/database/engine/rrdengineapi.h
+++ b/database/engine/rrdengineapi.h
@@ -42,14 +42,14 @@ void rrdeng_convert_legacy_uuid_to_multihost(char machine_guid[GUID_LEN + 1], uu
                                                     uuid_t *ret_uuid);
 
 
-STORAGE_METRIC_HANDLE *rrdeng_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance, STORAGE_METRICS_GROUP *smg);
-STORAGE_METRIC_HANDLE *rrdeng_metric_get(STORAGE_INSTANCE *db_instance, uuid_t *uuid, STORAGE_METRICS_GROUP *smg);
-STORAGE_METRIC_HANDLE *rrdeng_metric_create(STORAGE_INSTANCE *db_instance, uuid_t *uuid, STORAGE_METRICS_GROUP *smg);
-STORAGE_METRIC_HANDLE *rrdeng_metric_get_legacy(STORAGE_INSTANCE *db_instance, const char *rd_id, const char *st_id, STORAGE_METRICS_GROUP *smg);
+STORAGE_METRIC_HANDLE *rrdeng_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance);
+STORAGE_METRIC_HANDLE *rrdeng_metric_get(STORAGE_INSTANCE *db_instance, uuid_t *uuid);
+STORAGE_METRIC_HANDLE *rrdeng_metric_create(STORAGE_INSTANCE *db_instance, uuid_t *uuid);
+STORAGE_METRIC_HANDLE *rrdeng_metric_get_legacy(STORAGE_INSTANCE *db_instance, const char *rd_id, const char *st_id);
 void rrdeng_metric_release(STORAGE_METRIC_HANDLE *db_metric_handle);
 STORAGE_METRIC_HANDLE *rrdeng_metric_dup(STORAGE_METRIC_HANDLE *db_metric_handle);
 
-STORAGE_COLLECT_HANDLE *rrdeng_store_metric_init(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every);
+STORAGE_COLLECT_HANDLE *rrdeng_store_metric_init(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every, STORAGE_METRICS_GROUP *smg);
 void rrdeng_store_metric_flush_current_page(STORAGE_COLLECT_HANDLE *collection_handle);
 void rrdeng_store_metric_change_collection_frequency(STORAGE_COLLECT_HANDLE *collection_handle, int update_every);
 void rrdeng_store_metric_next(STORAGE_COLLECT_HANDLE *collection_handle, usec_t point_in_time_ut, NETDATA_DOUBLE n,
diff --git a/database/ram/rrddim_mem.c b/database/ram/rrddim_mem.c
index 43f32350b..299b6557a 100644
--- a/database/ram/rrddim_mem.c
+++ b/database/ram/rrddim_mem.c
@@ -22,8 +22,8 @@ void rrddim_metrics_group_release(STORAGE_INSTANCE *db_instance __maybe_unused,
 // RRDDIM legacy data collection functions
 
 STORAGE_METRIC_HANDLE *
-rrddim_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance __maybe_unused, STORAGE_METRICS_GROUP *smg __maybe_unused) {
-    STORAGE_METRIC_HANDLE *t = rrddim_metric_get(db_instance, &rd->metric_uuid, smg);
+rrddim_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance __maybe_unused) {
+    STORAGE_METRIC_HANDLE *t = rrddim_metric_get(db_instance, &rd->metric_uuid);
     if(!t) {
         netdata_rwlock_wrlock(&rrddim_JudyHS_rwlock);
         Pvoid_t *PValue = JudyHSIns(&rrddim_JudyHS_array, &rd->metric_uuid, sizeof(uuid_t), PJE0);
@@ -40,7 +40,7 @@ rrddim_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance __maybe_un
 }
 
 STORAGE_METRIC_HANDLE *
-rrddim_metric_get(STORAGE_INSTANCE *db_instance __maybe_unused, uuid_t *uuid, STORAGE_METRICS_GROUP *smg __maybe_unused) {
+rrddim_metric_get(STORAGE_INSTANCE *db_instance __maybe_unused, uuid_t *uuid) {
     RRDDIM *rd = NULL;
     netdata_rwlock_rdlock(&rrddim_JudyHS_rwlock);
     Pvoid_t *PValue = JudyHSGet(rrddim_JudyHS_array, uuid, sizeof(uuid_t));
@@ -67,7 +67,7 @@ void rrddim_store_metric_change_collection_frequency(STORAGE_COLLECT_HANDLE *col
     rrddim_store_metric_flush(collection_handle);
 }
 
-STORAGE_COLLECT_HANDLE *rrddim_collect_init(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every __maybe_unused) {
+STORAGE_COLLECT_HANDLE *rrddim_collect_init(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every __maybe_unused, STORAGE_METRICS_GROUP *smg __maybe_unused) {
     RRDDIM *rd = (RRDDIM *)db_metric_handle;
     rd->db[rd->rrdset->current_entry] = pack_storage_number(NAN, SN_FLAG_NONE);
     struct mem_collect_handle *ch = callocz(1, sizeof(struct mem_collect_handle));
diff --git a/database/ram/rrddim_mem.h b/database/ram/rrddim_mem.h
index 297388f51..79c59f110 100644
--- a/database/ram/rrddim_mem.h
+++ b/database/ram/rrddim_mem.h
@@ -20,15 +20,15 @@ struct mem_query_handle {
     size_t last_slot;
 };
 
-STORAGE_METRIC_HANDLE *rrddim_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance, STORAGE_METRICS_GROUP *smg);
-STORAGE_METRIC_HANDLE *rrddim_metric_get(STORAGE_INSTANCE *db_instance, uuid_t *uuid, STORAGE_METRICS_GROUP *smg);
+STORAGE_METRIC_HANDLE *rrddim_metric_get_or_create(RRDDIM *rd, STORAGE_INSTANCE *db_instance);
+STORAGE_METRIC_HANDLE *rrddim_metric_get(STORAGE_INSTANCE *db_instance, uuid_t *uuid);
 STORAGE_METRIC_HANDLE *rrddim_metric_dup(STORAGE_METRIC_HANDLE *db_metric_handle);
 void rrddim_metric_release(STORAGE_METRIC_HANDLE *db_metric_handle);
 
 STORAGE_METRICS_GROUP *rrddim_metrics_group_get(STORAGE_INSTANCE *db_instance, uuid_t *uuid);
 void rrddim_metrics_group_release(STORAGE_INSTANCE *db_instance, STORAGE_METRICS_GROUP *smg);
 
-STORAGE_COLLECT_HANDLE *rrddim_collect_init(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every);
+STORAGE_COLLECT_HANDLE *rrddim_collect_init(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every, STORAGE_METRICS_GROUP *smg);
 void rrddim_store_metric_change_collection_frequency(STORAGE_COLLECT_HANDLE *collection_handle, int update_every);
 void rrddim_collect_store_metric(STORAGE_COLLECT_HANDLE *collection_handle, usec_t point_in_time, NETDATA_DOUBLE number,
                                  NETDATA_DOUBLE min_value,
diff --git a/database/rrd.h b/database/rrd.h
index f071ee254..0796ff901 100644
--- a/database/rrd.h
+++ b/database/rrd.h
@@ -409,7 +409,7 @@ typedef struct storage_query_handle STORAGE_QUERY_HANDLE;
 // function pointers that handle data collection
 struct storage_engine_collect_ops {
     // an initialization function to run before starting collection
-    STORAGE_COLLECT_HANDLE *(*init)(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every);
+    STORAGE_COLLECT_HANDLE *(*init)(STORAGE_METRIC_HANDLE *db_metric_handle, uint32_t update_every, STORAGE_METRICS_GROUP *smg);
 
     // run this to store each metric into the database
     void (*store_metric)(STORAGE_COLLECT_HANDLE *collection_handle, usec_t point_in_time, NETDATA_DOUBLE number, NETDATA_DOUBLE min_value,
@@ -464,8 +464,8 @@ typedef struct storage_engine STORAGE_ENGINE;
 // function pointers for all APIs provided by a storage engine
 typedef struct storage_engine_api {
     // metric management
-    STORAGE_METRIC_HANDLE *(*metric_get)(STORAGE_INSTANCE *instance, uuid_t *uuid, STORAGE_METRICS_GROUP *smg);
-    STORAGE_METRIC_HANDLE *(*metric_get_or_create)(RRDDIM *rd, STORAGE_INSTANCE *instance, STORAGE_METRICS_GROUP *smg);
+    STORAGE_METRIC_HANDLE *(*metric_get)(STORAGE_INSTANCE *instance, uuid_t *uuid);
+    STORAGE_METRIC_HANDLE *(*metric_get_or_create)(RRDDIM *rd, STORAGE_INSTANCE *instance);
     void (*metric_release)(STORAGE_METRIC_HANDLE *);
     STORAGE_METRIC_HANDLE *(*metric_dup)(STORAGE_METRIC_HANDLE *);
 
diff --git a/database/rrdcontext.c b/database/rrdcontext.c
index cfa8af3e0..3413d1ea8 100644
--- a/database/rrdcontext.c
+++ b/database/rrdcontext.c
@@ -29,7 +29,7 @@
 #define WORKER_JOB_PP_QUEUE_SIZE   13
 
 
-typedef enum {
+typedef enum __attribute__ ((__packed__)) {
     RRD_FLAG_NONE           = 0,
     RRD_FLAG_DELETED        = (1 << 0), // this is a deleted object (metrics, instances, contexts)
     RRD_FLAG_COLLECTED      = (1 << 1), // this object is currently being collected
@@ -115,6 +115,7 @@ typedef enum {
 static inline void
 rrd_flag_add_remove_atomic(RRD_FLAGS *flags, RRD_FLAGS check, RRD_FLAGS conditionally_add, RRD_FLAGS always_remove) {
     RRD_FLAGS expected, desired;
+
     do {
         expected = *flags;
 
@@ -2435,7 +2436,7 @@ static void query_target_add_metric(QUERY_TARGET_LOCALS *qtl, RRDMETRIC_ACQUIRED
         if(rm->rrddim && rm->rrddim->tiers[tier] && rm->rrddim->tiers[tier]->db_metric_handle)
             tier_retention[tier].db_metric_handle = eng->api.metric_dup(rm->rrddim->tiers[tier]->db_metric_handle);
         else
-            tier_retention[tier].db_metric_handle = eng->api.metric_get(qtl->host->db[tier].instance, &rm->uuid, NULL);
+            tier_retention[tier].db_metric_handle = eng->api.metric_get(qtl->host->db[tier].instance, &rm->uuid);
 
         if(tier_retention[tier].db_metric_handle) {
             tier_retention[tier].db_first_time_t = tier_retention[tier].eng->api.query_ops.oldest_time(tier_retention[tier].db_metric_handle);
@@ -3253,8 +3254,6 @@ static void rrdcontext_garbage_collect_single_host(RRDHOST *host, bool worker_jo
                     "RRDCONTEXT: context '%s' of host '%s', deleted from rrdmetrics dictionary.",
                     string2str(rc->id),
                     rrdhost_hostname(host));
-
-            fprintf(stderr, "RRDCONTEXT: deleted context '%s'", string2str(rc->id));
         }
 
         // the item is referenced in the dictionary
diff --git a/database/rrddim.c b/database/rrddim.c
index 1b3d9952c..2d909a701 100644
--- a/database/rrddim.c
+++ b/database/rrddim.c
@@ -112,7 +112,7 @@ static void rrddim_insert_callback(const DICTIONARY_ITEM *item __maybe_unused, v
             rd->tiers[tier]->tier_grouping = host->db[tier].tier_grouping;
             rd->tiers[tier]->collect_ops = &eng->api.collect_ops;
             rd->tiers[tier]->query_ops = &eng->api.query_ops;
-            rd->tiers[tier]->db_metric_handle = eng->api.metric_get_or_create(rd, host->db[tier].instance, rd->rrdset->storage_metrics_groups[tier]);
+            rd->tiers[tier]->db_metric_handle = eng->api.metric_get_or_create(rd, host->db[tier].instance);
             storage_point_unset(rd->tiers[tier]->virtual_point);
             initialized++;
 
@@ -131,7 +131,7 @@ static void rrddim_insert_callback(const DICTIONARY_ITEM *item __maybe_unused, v
         size_t initialized = 0;
         for (size_t tier = 0; tier < storage_tiers; tier++) {
             if (rd->tiers[tier]) {
-                rd->tiers[tier]->db_collection_handle = rd->tiers[tier]->collect_ops->init(rd->tiers[tier]->db_metric_handle, st->rrdhost->db[tier].tier_grouping * st->update_every);
+                rd->tiers[tier]->db_collection_handle = rd->tiers[tier]->collect_ops->init(rd->tiers[tier]->db_metric_handle, st->rrdhost->db[tier].tier_grouping * st->update_every, rd->rrdset->storage_metrics_groups[tier]);
                 initialized++;
             }
         }
@@ -195,19 +195,19 @@ static void rrddim_delete_callback(const DICTIONARY_ITEM *item __maybe_unused, v
 
     debug(D_RRD_CALLS, "rrddim_free() %s.%s", rrdset_name(st), rrddim_name(rd));
 
-    size_t tiers_available = 0, tiers_said_yes = 0;
+    size_t tiers_available = 0, tiers_said_no_retention = 0;
     for(size_t tier = 0; tier < storage_tiers ;tier++) {
         if(rd->tiers[tier] && rd->tiers[tier]->db_collection_handle) {
             tiers_available++;
 
             if(rd->tiers[tier]->collect_ops->finalize(rd->tiers[tier]->db_collection_handle))
-                tiers_said_yes++;
+                tiers_said_no_retention++;
 
             rd->tiers[tier]->db_collection_handle = NULL;
         }
     }
 
-    if (tiers_available == tiers_said_yes && tiers_said_yes && rd->rrd_memory_mode == RRD_MEMORY_MODE_DBENGINE) {
+    if (tiers_available == tiers_said_no_retention && tiers_said_no_retention && rd->rrd_memory_mode == RRD_MEMORY_MODE_DBENGINE) {
         /* This metric has no data and no references */
         metaqueue_delete_dimension_uuid(&rd->metric_uuid);
     }
@@ -261,7 +261,7 @@ static bool rrddim_conflict_callback(const DICTIONARY_ITEM *item __maybe_unused,
     for(size_t tier = 0; tier < storage_tiers ;tier++) {
         if (rd->tiers[tier] && !rd->tiers[tier]->db_collection_handle)
             rd->tiers[tier]->db_collection_handle =
-                rd->tiers[tier]->collect_ops->init(rd->tiers[tier]->db_metric_handle, st->rrdhost->db[tier].tier_grouping * st->update_every);
+                rd->tiers[tier]->collect_ops->init(rd->tiers[tier]->db_metric_handle, st->rrdhost->db[tier].tier_grouping * st->update_every, rd->rrdset->storage_metrics_groups[tier]);
     }
 
     if(rrddim_flag_check(rd, RRDDIM_FLAG_ARCHIVED)) {
diff --git a/database/sqlite/sqlite_context.c b/database/sqlite/sqlite_context.c
index 9c7a61c6e..deca84584 100644
--- a/database/sqlite/sqlite_context.c
+++ b/database/sqlite/sqlite_context.c
@@ -449,7 +449,9 @@ skip_delete:
 int sql_context_cache_stats(int op)
 {
     int count, dummy;
+    netdata_thread_disable_cancelability();
     sqlite3_db_status(db_context_meta, op, &count, &dummy, 0);
+    netdata_thread_enable_cancelability();
     return count;
 }
 
diff --git a/database/sqlite/sqlite_functions.c b/database/sqlite/sqlite_functions.c
index eeb3c3822..ce5487fbf 100644
--- a/database/sqlite/sqlite_functions.c
+++ b/database/sqlite/sqlite_functions.c
@@ -1263,7 +1263,9 @@ int bind_text_null(sqlite3_stmt *res, int position, const char *text, bool can_b
 int sql_metadata_cache_stats(int op)
 {
     int count, dummy;
+    netdata_thread_disable_cancelability();
     sqlite3_db_status(db_meta, op, &count, &dummy, 0);
+    netdata_thread_enable_cancelability();
     return count;
 }