Merging upstream version 1.29.0.

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

1 files changed, 257 insertions, 96 deletions

diff --git a/database/engine/rrdengineapi.c b/database/engine/rrdengineapi.c
index baf4a9973..7b2ff5b72 100644..100755
--- a/database/engine/rrdengineapi.c
+++ b/database/engine/rrdengineapi.c
@@ -2,65 +2,148 @@
 #include "rrdengine.h"
 
 /* Default global database instance */
-static struct rrdengine_instance default_global_ctx;
+struct rrdengine_instance multidb_ctx;
 
 int default_rrdeng_page_cache_mb = 32;
-int default_rrdeng_disk_quota_mb = RRDENG_MIN_DISK_SPACE_MB;
+int default_rrdeng_disk_quota_mb = 256;
+int default_multidb_disk_quota_mb = 256;
+/* Default behaviour is to unblock data collection if the page cache is full of dirty pages by dropping metrics */
+uint8_t rrdeng_drop_metrics_under_page_cache_pressure = 1;
 
-/*
- * Gets a handle for storing metrics to the database.
- * The handle must be released with rrdeng_store_metric_final().
- */
-void rrdeng_store_metric_init(RRDDIM *rd)
+static inline struct rrdengine_instance *get_rrdeng_ctx_from_host(RRDHOST *host)
+{
+    return host->rrdeng_ctx;
+}
+
+/* This UUID is not unique across hosts */
+void rrdeng_generate_legacy_uuid(const char *dim_id, char *chart_id, uuid_t *ret_uuid)
 {
-    struct rrdeng_collect_handle *handle;
-    struct page_cache *pg_cache;
-    struct rrdengine_instance *ctx;
-    uuid_t temp_id;
-    Pvoid_t *PValue;
-    struct pg_cache_page_index *page_index;
     EVP_MD_CTX *evpctx;
     unsigned char hash_value[EVP_MAX_MD_SIZE];
     unsigned int hash_len;
 
-    //&default_global_ctx; TODO: test this use case or remove it?
+    evpctx = EVP_MD_CTX_create();
+    EVP_DigestInit_ex(evpctx, EVP_sha256(), NULL);
+    EVP_DigestUpdate(evpctx, dim_id, strlen(dim_id));
+    EVP_DigestUpdate(evpctx, chart_id, strlen(chart_id));
+    EVP_DigestFinal_ex(evpctx, hash_value, &hash_len);
+    EVP_MD_CTX_destroy(evpctx);
+    fatal_assert(hash_len > sizeof(uuid_t));
+    memcpy(ret_uuid, hash_value, sizeof(uuid_t));
+}
 
-    ctx = rd->rrdset->rrdhost->rrdeng_ctx;
-    pg_cache = &ctx->pg_cache;
-    handle = &rd->state->handle.rrdeng;
-    handle->ctx = ctx;
+/* Transform legacy UUID to be unique across hosts deterministacally */
+void rrdeng_convert_legacy_uuid_to_multihost(char machine_guid[GUID_LEN + 1], uuid_t *legacy_uuid, uuid_t *ret_uuid)
+{
+    EVP_MD_CTX *evpctx;
+    unsigned char hash_value[EVP_MAX_MD_SIZE];
+    unsigned int hash_len;
 
     evpctx = EVP_MD_CTX_create();
     EVP_DigestInit_ex(evpctx, EVP_sha256(), NULL);
-    EVP_DigestUpdate(evpctx, rd->id, strlen(rd->id));
-    EVP_DigestUpdate(evpctx, rd->rrdset->id, strlen(rd->rrdset->id));
+    EVP_DigestUpdate(evpctx, machine_guid, GUID_LEN);
+    EVP_DigestUpdate(evpctx, *legacy_uuid, sizeof(uuid_t));
     EVP_DigestFinal_ex(evpctx, hash_value, &hash_len);
     EVP_MD_CTX_destroy(evpctx);
-    assert(hash_len > sizeof(temp_id));
-    memcpy(&temp_id, hash_value, sizeof(temp_id));
+    fatal_assert(hash_len > sizeof(uuid_t));
+    memcpy(ret_uuid, hash_value, sizeof(uuid_t));
+}
 
-    handle->descr = NULL;
-    handle->prev_descr = NULL;
-    handle->unaligned_page = 0;
+void rrdeng_metric_init(RRDDIM *rd, uuid_t *dim_uuid)
+{
+    struct page_cache *pg_cache;
+    struct rrdengine_instance *ctx;
+    uuid_t legacy_uuid;
+    uuid_t multihost_legacy_uuid;
+    Pvoid_t *PValue;
+    struct pg_cache_page_index *page_index = NULL;
+    int is_multihost_child = 0;
+    RRDHOST *host = rd->rrdset->rrdhost;
+
+    ctx = get_rrdeng_ctx_from_host(rd->rrdset->rrdhost);
+    if (unlikely(!ctx)) {
+        error("Failed to fetch multidb context");
+        return;
+    }
+    pg_cache = &ctx->pg_cache;
+
+    rrdeng_generate_legacy_uuid(rd->id, rd->rrdset->id, &legacy_uuid);
+    rd->state->metric_uuid = dim_uuid;
+    if (host != localhost && host->rrdeng_ctx == &multidb_ctx)
+        is_multihost_child = 1;
 
     uv_rwlock_rdlock(&pg_cache->metrics_index.lock);
-    PValue = JudyHSGet(pg_cache->metrics_index.JudyHS_array, &temp_id, sizeof(uuid_t));
+    PValue = JudyHSGet(pg_cache->metrics_index.JudyHS_array, &legacy_uuid, sizeof(uuid_t));
     if (likely(NULL != PValue)) {
         page_index = *PValue;
     }
     uv_rwlock_rdunlock(&pg_cache->metrics_index.lock);
-    if (NULL == PValue) {
-        /* First time we see the UUID */
-        uv_rwlock_wrlock(&pg_cache->metrics_index.lock);
-        PValue = JudyHSIns(&pg_cache->metrics_index.JudyHS_array, &temp_id, sizeof(uuid_t), PJE0);
-        assert(NULL == *PValue); /* TODO: figure out concurrency model */
-        *PValue = page_index = create_page_index(&temp_id);
-        page_index->prev = pg_cache->metrics_index.last_page_index;
-        pg_cache->metrics_index.last_page_index = page_index;
-        uv_rwlock_wrunlock(&pg_cache->metrics_index.lock);
+    if (is_multihost_child || NULL == PValue) {
+        /* First time we see the legacy UUID or metric belongs to child host in multi-host DB.
+         * Drop legacy support, normal path */
+
+        if (unlikely(!rd->state->metric_uuid))
+            rd->state->metric_uuid = create_dimension_uuid(rd->rrdset, rd);
+
+        uv_rwlock_rdlock(&pg_cache->metrics_index.lock);
+        PValue = JudyHSGet(pg_cache->metrics_index.JudyHS_array, rd->state->metric_uuid, sizeof(uuid_t));
+        if (likely(NULL != PValue)) {
+            page_index = *PValue;
+        }
+        uv_rwlock_rdunlock(&pg_cache->metrics_index.lock);
+        if (NULL == PValue) {
+            uv_rwlock_wrlock(&pg_cache->metrics_index.lock);
+            PValue = JudyHSIns(&pg_cache->metrics_index.JudyHS_array, rd->state->metric_uuid, sizeof(uuid_t), PJE0);
+            fatal_assert(NULL == *PValue); /* TODO: figure out concurrency model */
+            *PValue = page_index = create_page_index(rd->state->metric_uuid);
+            page_index->prev = pg_cache->metrics_index.last_page_index;
+            pg_cache->metrics_index.last_page_index = page_index;
+            uv_rwlock_wrunlock(&pg_cache->metrics_index.lock);
+        }
+    } else {
+        /* There are legacy UUIDs in the database, implement backward compatibility */
+
+        rrdeng_convert_legacy_uuid_to_multihost(rd->rrdset->rrdhost->machine_guid, &legacy_uuid,
+                                                &multihost_legacy_uuid);
+
+        if (unlikely(!rd->state->metric_uuid))
+            rd->state->metric_uuid = mallocz(sizeof(uuid_t));
+
+        int need_to_store = (dim_uuid == NULL || uuid_compare(*rd->state->metric_uuid, multihost_legacy_uuid));
+
+        uuid_copy(*rd->state->metric_uuid, multihost_legacy_uuid);
+
+        if (unlikely(need_to_store))
+            (void)sql_store_dimension(rd->state->metric_uuid, rd->rrdset->chart_uuid, rd->id, rd->name, rd->multiplier, rd->divisor,
+                rd->algorithm);
+
     }
     rd->state->rrdeng_uuid = &page_index->id;
-    handle->page_index = page_index;
+    rd->state->page_index = page_index;
+}
+
+/*
+ * Gets a handle for storing metrics to the database.
+ * The handle must be released with rrdeng_store_metric_final().
+ */
+void rrdeng_store_metric_init(RRDDIM *rd)
+{
+    struct rrdeng_collect_handle *handle;
+    struct rrdengine_instance *ctx;
+    struct pg_cache_page_index *page_index;
+
+    ctx = get_rrdeng_ctx_from_host(rd->rrdset->rrdhost);
+    handle = &rd->state->handle.rrdeng;
+    handle->ctx = ctx;
+
+    handle->descr = NULL;
+    handle->prev_descr = NULL;
+    handle->unaligned_page = 0;
+
+    page_index = rd->state->page_index;
+    uv_rwlock_wrlock(&page_index->lock);
+    ++page_index->writers;
+    uv_rwlock_wrunlock(&page_index->lock);
 }
 
 /* The page must be populated and referenced */
@@ -88,12 +171,14 @@ void rrdeng_store_metric_flush_current_page(RRDDIM *rd)
 
     handle = &rd->state->handle.rrdeng;
     ctx = handle->ctx;
+    if (unlikely(!ctx))
+        return;
     descr = handle->descr;
     if (unlikely(NULL == descr)) {
         return;
     }
     if (likely(descr->page_length)) {
-        int ret, page_is_empty;
+        int page_is_empty;
 
         rrd_stat_atomic_add(&ctx->stats.metric_API_producers, -1);
 
@@ -107,17 +192,21 @@ void rrdeng_store_metric_flush_current_page(RRDDIM *rd)
             if (unlikely(debug_flags & D_RRDENGINE))
                 print_page_cache_descr(descr);
             pg_cache_put(ctx, descr);
-            pg_cache_punch_hole(ctx, descr, 1);
+            pg_cache_punch_hole(ctx, descr, 1, 0, NULL);
             handle->prev_descr = NULL;
         } else {
+            /*
+             * Disable pinning for now as it leads to deadlocks. When a collector stops collecting the extra pinned page
+             * eventually gets rotated but it cannot be destroyed due to the extra reference.
+             */
             /* added 1 extra reference to keep 2 dirty pages pinned per metric, expected refcnt = 2 */
-            rrdeng_page_descr_mutex_lock(ctx, descr);
+/*          rrdeng_page_descr_mutex_lock(ctx, descr);
             ret = pg_cache_try_get_unsafe(descr, 0);
             rrdeng_page_descr_mutex_unlock(ctx, descr);
-            assert (1 == ret);
+            fatal_assert(1 == ret);*/
 
             rrdeng_commit_page(ctx, descr, handle->page_correlation_id);
-            handle->prev_descr = descr;
+            /* handle->prev_descr = descr;*/
         }
     } else {
         freez(descr->pg_cache_descr->page);
@@ -168,14 +257,12 @@ void rrdeng_store_metric_next(RRDDIM *rd, usec_t point_in_time, storage_number n
                  must_flush_unaligned_page)) {
         rrdeng_store_metric_flush_current_page(rd);
 
-        page = rrdeng_create_page(ctx, &handle->page_index->id, &descr);
-        assert(page);
+        page = rrdeng_create_page(ctx, &rd->state->page_index->id, &descr);
+        fatal_assert(page);
 
         handle->descr = descr;
 
-        uv_rwlock_wrlock(&pg_cache->committed_page_index.lock);
-        handle->page_correlation_id = pg_cache->committed_page_index.latest_corr_id++;
-        uv_rwlock_wrunlock(&pg_cache->committed_page_index.lock);
+        handle->page_correlation_id = rrd_atomic_fetch_add(&pg_cache->committed_page_index.latest_corr_id, 1);
 
         if (0 == rd->rrdset->rrddim_page_alignment) {
             /* this is the leading dimension that defines chart alignment */
@@ -189,30 +276,53 @@ void rrdeng_store_metric_next(RRDDIM *rd, usec_t point_in_time, storage_number n
     if (perfect_page_alignment)
         rd->rrdset->rrddim_page_alignment = descr->page_length;
     if (unlikely(INVALID_TIME == descr->start_time)) {
+        unsigned long new_metric_API_producers, old_metric_API_max_producers, ret_metric_API_max_producers;
         descr->start_time = point_in_time;
 
-        rrd_stat_atomic_add(&ctx->stats.metric_API_producers, 1);
-        pg_cache_insert(ctx, handle->page_index, descr);
+        new_metric_API_producers = rrd_atomic_add_fetch(&ctx->stats.metric_API_producers, 1);
+        while (unlikely(new_metric_API_producers > (old_metric_API_max_producers = ctx->metric_API_max_producers))) {
+            /* Increase ctx->metric_API_max_producers */
+            ret_metric_API_max_producers = ulong_compare_and_swap(&ctx->metric_API_max_producers,
+                                                                  old_metric_API_max_producers,
+                                                                  new_metric_API_producers);
+            if (old_metric_API_max_producers == ret_metric_API_max_producers) {
+                /* success */
+                break;
+            }
+        }
+
+        pg_cache_insert(ctx, rd->state->page_index, descr);
     } else {
-        pg_cache_add_new_metric_time(handle->page_index, descr);
+        pg_cache_add_new_metric_time(rd->state->page_index, descr);
     }
 }
 
 /*
  * Releases the database reference from the handle for storing metrics.
+ * Returns 1 if it's safe to delete the dimension.
  */
-void rrdeng_store_metric_finalize(RRDDIM *rd)
+int rrdeng_store_metric_finalize(RRDDIM *rd)
 {
     struct rrdeng_collect_handle *handle;
     struct rrdengine_instance *ctx;
+    struct pg_cache_page_index *page_index;
+    uint8_t can_delete_metric = 0;
 
     handle = &rd->state->handle.rrdeng;
     ctx = handle->ctx;
+    page_index = rd->state->page_index;
     rrdeng_store_metric_flush_current_page(rd);
     if (handle->prev_descr) {
         /* unpin old second page */
         pg_cache_put(ctx, handle->prev_descr);
     }
+    uv_rwlock_wrlock(&page_index->lock);
+    if (!--page_index->writers && !page_index->page_count) {
+        can_delete_metric = 1;
+    }
+    uv_rwlock_wrunlock(&page_index->lock);
+
+   return can_delete_metric;
 }
 
 /* Returns 1 if the data collection interval is well defined, 0 otherwise */
@@ -253,7 +363,7 @@ static inline uint32_t *pginfo_to_points(struct rrdeng_page_info *page_info)
  * @return number of regions with different data collection intervals.
  */
 unsigned rrdeng_variable_step_boundaries(RRDSET *st, time_t start_time, time_t end_time,
-                                         struct rrdeng_region_info **region_info_arrayp, unsigned *max_intervalp)
+                                         struct rrdeng_region_info **region_info_arrayp, unsigned *max_intervalp, struct context_param *context_param_list)
 {
     struct pg_cache_page_index *page_index;
     struct rrdengine_instance *ctx;
@@ -266,15 +376,16 @@ unsigned rrdeng_variable_step_boundaries(RRDSET *st, time_t start_time, time_t e
     struct rrdeng_region_info *region_info_array;
     uint8_t is_first_region_initialized;
 
-    ctx = st->rrdhost->rrdeng_ctx;
+    ctx = get_rrdeng_ctx_from_host(st->rrdhost);
     regions = 1;
     *max_intervalp = max_interval = 0;
     region_info_array = NULL;
     *region_info_arrayp = NULL;
     page_info_array = NULL;
 
+    RRDDIM *temp_rd = context_param_list ? context_param_list->rd : NULL;
     rrdset_rdlock(st);
-    for(rd_iter = st->dimensions, rd = NULL, min_time = (usec_t)-1 ; rd_iter ; rd_iter = rd_iter->next) {
+    for(rd_iter = temp_rd?temp_rd:st->dimensions, rd = NULL, min_time = (usec_t)-1 ; rd_iter ; rd_iter = rd_iter->next) {
         /*
          * Choose oldest dimension as reference. This is not equivalent to the union of all dimensions
          * but it is a best effort approximation with a bias towards older metrics in a chart. It
@@ -316,7 +427,7 @@ unsigned rrdeng_variable_step_boundaries(RRDSET *st, time_t start_time, time_t e
             continue;
         }
         page_entries = curr->page_length / sizeof(storage_number);
-        assert(0 != page_entries);
+        fatal_assert(0 != page_entries);
         if (likely(1 != page_entries)) {
             dt = (curr->end_time - curr->start_time) / (page_entries - 1);
             *pginfo_to_dt(curr) = ROUND_USEC_TO_SEC(dt);
@@ -352,7 +463,7 @@ unsigned rrdeng_variable_step_boundaries(RRDSET *st, time_t start_time, time_t e
             if (1 == page_points)
                 first_valid_time_in_page = current_position_time;
             if (unlikely(!is_first_region_initialized)) {
-                assert(1 == regions);
+                fatal_assert(1 == regions);
                 /* this is the first region */
                 region_info_array[0].start_time = current_position_time;
                 is_first_region_initialized = 1;
@@ -365,7 +476,7 @@ unsigned rrdeng_variable_step_boundaries(RRDSET *st, time_t start_time, time_t e
         }
 
         if (unlikely(0 == *pginfo_to_dt(curr))) { /* unknown data collection interval */
-            assert(1 == page_points);
+            fatal_assert(1 == page_points);
 
             if (likely(NULL != prev)) { /* get interval from previous page */
                 *pginfo_to_dt(curr) = *pginfo_to_dt(prev);
@@ -428,7 +539,7 @@ void rrdeng_load_metric_init(RRDDIM *rd, struct rrddim_query_handle *rrdimm_hand
     struct rrdengine_instance *ctx;
     unsigned pages_nr;
 
-    ctx = rd->rrdset->rrdhost->rrdeng_ctx;
+    ctx = get_rrdeng_ctx_from_host(rd->rrdset->rrdhost);
     rrdimm_handle->start_time = start_time;
     rrdimm_handle->end_time = end_time;
     handle = &rrdimm_handle->rrdeng;
@@ -452,7 +563,7 @@ storage_number rrdeng_load_metric_next(struct rrddim_query_handle *rrdimm_handle
     struct rrdeng_page_descr *descr;
     storage_number *page, ret;
     unsigned position, entries;
-    usec_t next_page_time, current_position_time, page_end_time;
+    usec_t next_page_time = 0, current_position_time, page_end_time = 0;
     uint32_t page_length;
 
     handle = &rrdimm_handle->rrdeng;
@@ -473,17 +584,18 @@ storage_number rrdeng_load_metric_next(struct rrddim_query_handle *rrdimm_handle
         /* We need to get a new page */
         if (descr) {
             /* Drop old page's reference */
-            handle->next_page_time = (page_end_time / USEC_PER_SEC) + 1;
-            if (unlikely(handle->next_page_time > rrdimm_handle->end_time)) {
-                goto no_more_metrics;
-            }
-            next_page_time = handle->next_page_time * USEC_PER_SEC;
 #ifdef NETDATA_INTERNAL_CHECKS
             rrd_stat_atomic_add(&ctx->stats.metric_API_consumers, -1);
 #endif
             pg_cache_put(ctx, descr);
             handle->descr = NULL;
+            handle->next_page_time = (page_end_time / USEC_PER_SEC) + 1;
+            if (unlikely(handle->next_page_time > rrdimm_handle->end_time)) {
+                goto no_more_metrics;
+            }
+            next_page_time = handle->next_page_time * USEC_PER_SEC;
         }
+
         descr = pg_cache_lookup_next(ctx, handle->page_index, &handle->page_index->id,
                                      next_page_time, rrdimm_handle->end_time * USEC_PER_SEC);
         if (NULL == descr) {
@@ -520,7 +632,7 @@ storage_number rrdeng_load_metric_next(struct rrddim_query_handle *rrdimm_handle
     }
     handle->position = position;
     handle->now = current_position_time / USEC_PER_SEC;
-/*  assert(handle->now >= rrdimm_handle->start_time && handle->now <= rrdimm_handle->end_time);
+/*  fatal_assert(handle->now >= rrdimm_handle->start_time && handle->now <= rrdimm_handle->end_time);
     The above assertion is an approximation and needs to take update_every into account */
     if (unlikely(handle->now >= rrdimm_handle->end_time)) {
         /* next calls will not load any more metrics */
@@ -564,21 +676,17 @@ void rrdeng_load_metric_finalize(struct rrddim_query_handle *rrdimm_handle)
 
 time_t rrdeng_metric_latest_time(RRDDIM *rd)
 {
-    struct rrdeng_collect_handle *handle;
     struct pg_cache_page_index *page_index;
 
-    handle = &rd->state->handle.rrdeng;
-    page_index = handle->page_index;
+    page_index = rd->state->page_index;
 
     return page_index->latest_time / USEC_PER_SEC;
 }
 time_t rrdeng_metric_oldest_time(RRDDIM *rd)
 {
-    struct rrdeng_collect_handle *handle;
     struct pg_cache_page_index *page_index;
 
-    handle = &rd->state->handle.rrdeng;
-    page_index = handle->page_index;
+    page_index = rd->state->page_index;
 
     return page_index->oldest_time / USEC_PER_SEC;
 }
@@ -620,7 +728,7 @@ void rrdeng_commit_page(struct rrdengine_instance *ctx, struct rrdeng_page_descr
         debug(D_RRDENGINE, "%s: page descriptor is NULL, page has already been force-committed.", __func__);
         return;
     }
-    assert(descr->page_length);
+    fatal_assert(descr->page_length);
 
     uv_rwlock_wrlock(&pg_cache->committed_page_index.lock);
     PValue = JudyLIns(&pg_cache->committed_page_index.JudyL_array, page_correlation_id, PJE0);
@@ -628,16 +736,27 @@ void rrdeng_commit_page(struct rrdengine_instance *ctx, struct rrdeng_page_descr
     nr_committed_pages = ++pg_cache->committed_page_index.nr_committed_pages;
     uv_rwlock_wrunlock(&pg_cache->committed_page_index.lock);
 
-    if (nr_committed_pages >= (pg_cache_hard_limit(ctx) - (unsigned long)ctx->stats.metric_API_producers) / 2) {
-        /* 50% of pages have not been committed yet */
-        if (0 == (unsigned long)ctx->stats.flushing_errors) {
-            /* only print the first time */
-            error("Failed to flush quickly enough in dbengine instance \"%s\""
-                  ". Metric data will not be stored in the database"
-                  ", please reduce disk load or use a faster disk.", ctx->dbfiles_path);
+    if (nr_committed_pages >= pg_cache_hard_limit(ctx) / 2) {
+        /* over 50% of pages have not been committed yet */
+
+        if (ctx->drop_metrics_under_page_cache_pressure &&
+            nr_committed_pages >= pg_cache_committed_hard_limit(ctx)) {
+            /* 100% of pages are dirty */
+            struct rrdeng_cmd cmd;
+
+            cmd.opcode = RRDENG_INVALIDATE_OLDEST_MEMORY_PAGE;
+            rrdeng_enq_cmd(&ctx->worker_config, &cmd);
+        } else {
+            if (0 == (unsigned long) ctx->stats.pg_cache_over_half_dirty_events) {
+                /* only print the first time */
+                errno = 0;
+                error("Failed to flush dirty buffers quickly enough in dbengine instance \"%s\". "
+                      "Metric data at risk of not being stored in the database, "
+                      "please reduce disk load or use a faster disk.", ctx->dbfiles_path);
+            }
+            rrd_stat_atomic_add(&ctx->stats.pg_cache_over_half_dirty_events, 1);
+            rrd_stat_atomic_add(&global_pg_cache_over_half_dirty_events, 1);
         }
-        rrd_stat_atomic_add(&ctx->stats.flushing_errors, 1);
-        rrd_stat_atomic_add(&global_flushing_errors, 1);
     }
 
     pg_cache_put(ctx, descr);
@@ -687,8 +806,11 @@ void *rrdeng_get_page(struct rrdengine_instance *ctx, uuid_t *id, usec_t point_i
  * You must not change the indices of the statistics or user code will break.
  * You must not exceed RRDENG_NR_STATS or it will crash.
  */
-void rrdeng_get_35_statistics(struct rrdengine_instance *ctx, unsigned long long *array)
+void rrdeng_get_37_statistics(struct rrdengine_instance *ctx, unsigned long long *array)
 {
+    if (ctx == NULL)
+        return;
+
     struct page_cache *pg_cache = &ctx->pg_cache;
 
     array[0] = (uint64_t)ctx->stats.metric_API_producers;
@@ -724,9 +846,11 @@ void rrdeng_get_35_statistics(struct rrdengine_instance *ctx, unsigned long long
     array[30] = (uint64_t)global_io_errors;
     array[31] = (uint64_t)global_fs_errors;
     array[32] = (uint64_t)rrdeng_reserved_file_descriptors;
-    array[33] = (uint64_t)ctx->stats.flushing_errors;
-    array[34] = (uint64_t)global_flushing_errors;
-    assert(RRDENG_NR_STATS == 35);
+    array[33] = (uint64_t)ctx->stats.pg_cache_over_half_dirty_events;
+    array[34] = (uint64_t)global_pg_cache_over_half_dirty_events;
+    array[35] = (uint64_t)ctx->stats.flushing_pressure_page_deletions;
+    array[36] = (uint64_t)global_flushing_pressure_page_deletions;
+    fatal_assert(RRDENG_NR_STATS == 37);
 }
 
 /* Releases reference to page */
@@ -739,21 +863,21 @@ void rrdeng_put_page(struct rrdengine_instance *ctx, void *handle)
 /*
  * Returns 0 on success, negative on error
  */
-int rrdeng_init(struct rrdengine_instance **ctxp, char *dbfiles_path, unsigned page_cache_mb, unsigned disk_space_mb)
+int rrdeng_init(RRDHOST *host, struct rrdengine_instance **ctxp, char *dbfiles_path, unsigned page_cache_mb,
+                unsigned disk_space_mb)
 {
     struct rrdengine_instance *ctx;
     int error;
     uint32_t max_open_files;
 
-    sanity_check();
-
     max_open_files = rlimit_nofile.rlim_cur / 4;
 
     /* reserve RRDENG_FD_BUDGET_PER_INSTANCE file descriptors for this instance */
     rrd_stat_atomic_add(&rrdeng_reserved_file_descriptors, RRDENG_FD_BUDGET_PER_INSTANCE);
     if (rrdeng_reserved_file_descriptors > max_open_files) {
-        error("Exceeded the budget of available file descriptors (%u/%u), cannot create new dbengine instance.",
-              (unsigned)rrdeng_reserved_file_descriptors, (unsigned)max_open_files);
+        error(
+            "Exceeded the budget of available file descriptors (%u/%u), cannot create new dbengine instance.",
+            (unsigned)rrdeng_reserved_file_descriptors, (unsigned)max_open_files);
 
         rrd_stat_atomic_add(&global_fs_errors, 1);
         rrd_stat_atomic_add(&rrdeng_reserved_file_descriptors, -RRDENG_FD_BUDGET_PER_INSTANCE);
@@ -761,8 +885,7 @@ int rrdeng_init(struct rrdengine_instance **ctxp, char *dbfiles_path, unsigned p
     }
 
     if (NULL == ctxp) {
-        /* for testing */
-        ctx = &default_global_ctx;
+        ctx = &multidb_ctx;
         memset(ctx, 0, sizeof(*ctx));
     } else {
         *ctxp = ctx = callocz(1, sizeof(*ctx));
@@ -778,6 +901,16 @@ int rrdeng_init(struct rrdengine_instance **ctxp, char *dbfiles_path, unsigned p
     ctx->max_disk_space = disk_space_mb * 1048576LLU;
     strncpyz(ctx->dbfiles_path, dbfiles_path, sizeof(ctx->dbfiles_path) - 1);
     ctx->dbfiles_path[sizeof(ctx->dbfiles_path) - 1] = '\0';
+    if (NULL == host)
+        strncpyz(ctx->machine_guid, registry_get_this_machine_guid(), GUID_LEN);
+    else
+        strncpyz(ctx->machine_guid, host->machine_guid, GUID_LEN);
+
+    ctx->drop_metrics_under_page_cache_pressure = rrdeng_drop_metrics_under_page_cache_pressure;
+    ctx->metric_API_max_producers = 0;
+    ctx->quiesce = NO_QUIESCE;
+    ctx->metalog_ctx = NULL; /* only set this after the metadata log has finished initializing */
+    ctx->host = host;
 
     memset(&ctx->worker_config, 0, sizeof(ctx->worker_config));
     ctx->worker_config.ctx = ctx;
@@ -789,20 +922,27 @@ int rrdeng_init(struct rrdengine_instance **ctxp, char *dbfiles_path, unsigned p
     }
 
     init_completion(&ctx->rrdengine_completion);
-    assert(0 == uv_thread_create(&ctx->worker_config.thread, rrdeng_worker, &ctx->worker_config));
+    fatal_assert(0 == uv_thread_create(&ctx->worker_config.thread, rrdeng_worker, &ctx->worker_config));
     /* wait for worker thread to initialize */
     wait_for_completion(&ctx->rrdengine_completion);
     destroy_completion(&ctx->rrdengine_completion);
+    uv_thread_set_name_np(ctx->worker_config.thread, "DBENGINE");
     if (ctx->worker_config.error) {
         goto error_after_rrdeng_worker;
     }
+    error = metalog_init(ctx);
+    if (error) {
+        error("Failed to initialize metadata log file event loop.");
+        goto error_after_rrdeng_worker;
+    }
+
     return 0;
 
 error_after_rrdeng_worker:
     finalize_rrd_files(ctx);
 error_after_init_rrd_files:
     free_page_cache(ctx);
-    if (ctx != &default_global_ctx) {
+    if (ctx != &multidb_ctx) {
         freez(ctx);
         *ctxp = NULL;
     }
@@ -825,14 +965,35 @@ int rrdeng_exit(struct rrdengine_instance *ctx)
     cmd.opcode = RRDENG_SHUTDOWN;
     rrdeng_enq_cmd(&ctx->worker_config, &cmd);
 
-    assert(0 == uv_thread_join(&ctx->worker_config.thread));
+    fatal_assert(0 == uv_thread_join(&ctx->worker_config.thread));
 
     finalize_rrd_files(ctx);
+    //metalog_exit(ctx->metalog_ctx);
     free_page_cache(ctx);
 
-    if (ctx != &default_global_ctx) {
+    if (ctx != &multidb_ctx) {
         freez(ctx);
     }
     rrd_stat_atomic_add(&rrdeng_reserved_file_descriptors, -RRDENG_FD_BUDGET_PER_INSTANCE);
     return 0;
-}
\ No newline at end of file
+}
+
+void rrdeng_prepare_exit(struct rrdengine_instance *ctx)
+{
+    struct rrdeng_cmd cmd;
+
+    if (NULL == ctx) {
+        return;
+    }
+
+    init_completion(&ctx->rrdengine_completion);
+    cmd.opcode = RRDENG_QUIESCE;
+    rrdeng_enq_cmd(&ctx->worker_config, &cmd);
+
+    /* wait for dbengine to quiesce */
+    wait_for_completion(&ctx->rrdengine_completion);
+    destroy_completion(&ctx->rrdengine_completion);
+
+    //metalog_prepare_exit(ctx->metalog_ctx);
+}
+