Fix CRC and I/O error handling in dbengine so that netdata is not halted and relevant error messages are printed and alarms are raised (#6452)

configs.signatures

@@ -381,7 +381,7 @@ declare -A configs_signatures=(
   ['7deb236ec68a512b9bdd18e6a51d76f7']='python.d/mysql.conf'
   ['7e5fc1644aa7a54f9dbb1bd102521b09']='health.d/memcached.conf'
   ['7f13631183fbdf79c21c8e5a171e9b34']='health.d/zfs.conf'
-  ['ce285c90747428ee5da4efb547418dda']='health.d/dbengine.conf'
+  ['93674f3206872ae9c43ecbc54988413b']='health.d/dbengine.conf'
   ['7fb8184d56a27040e73261ed9c6fc76f']='health_alarm_notify.conf'
   ['80266bddd3df374923c750a6de91d120']='health.d/apache.conf'
   ['803a7f9dcb942eeac0fd764b9e3e38ca']='fping.conf'

database/engine/journalfile.c

@@ -3,13 +3,18 @@
 
 static void flush_transaction_buffer_cb(uv_fs_t* req)
 {
-    struct generic_io_descriptor *io_descr;
+    struct generic_io_descriptor *io_descr = req->data;
+    struct rrdengine_worker_config* wc = req->loop->data;
+    struct rrdengine_instance *ctx = wc->ctx;
 
     debug(D_RRDENGINE, "%s: Journal block was written to disk.", __func__);
     if (req->result < 0) {
-        fatal("%s: uv_fs_write: %s", __func__, uv_strerror((int)req->result));
+        ++ctx->stats.io_errors;
+        rrd_stat_atomic_add(&global_io_errors, 1);
+        error("%s: uv_fs_write: %s", __func__, uv_strerror((int)req->result));
+    } else {
+        debug(D_RRDENGINE, "%s: Journal block was written to disk.", __func__);
     }
-    io_descr = req->data;
 
     uv_fs_req_cleanup(req);
     free(io_descr->buf);
@@ -348,6 +353,7 @@ static unsigned replay_transaction(struct rrdengine_instance *ctx, struct rrdeng
     ret = crc32cmp(jf_trailer->checksum, crc);
     debug(D_RRDENGINE, "Transaction %"PRIu64" was read from disk. CRC32 check: %s", *id, ret ? "FAILED" : "SUCCEEDED");
     if (unlikely(ret)) {
+        error("Transaction %"PRIu64" was read from disk. CRC32 check: FAILED", *id);
         return size_bytes;
     }
     switch (jf_header->type) {

database/engine/rrdengine.c

@@ -37,24 +37,29 @@ void read_extent_cb(uv_fs_t* req)
     unsigned i, j, count;
     void *page, *uncompressed_buf = NULL;
     uint32_t payload_length, payload_offset, page_offset, uncompressed_payload_length;
+    uint8_t have_read_error = 0;
     /* persistent structures */
     struct rrdeng_df_extent_header *header;
     struct rrdeng_df_extent_trailer *trailer;
     uLong crc;
 
     xt_io_descr = req->data;
-    if (req->result < 0) {
-        error("%s: uv_fs_read: %s", __func__, uv_strerror((int)req->result));
-        goto cleanup;
-    }
-
     header = xt_io_descr->buf;
     payload_length = header->payload_length;
     count = header->number_of_pages;
-
     payload_offset = sizeof(*header) + sizeof(header->descr[0]) * count;
-
     trailer = xt_io_descr->buf + xt_io_descr->bytes - sizeof(*trailer);
+
+    if (req->result < 0) {
+        struct rrdengine_datafile *datafile = xt_io_descr->descr_array[0]->extent->datafile;
+
+        ++ctx->stats.io_errors;
+        rrd_stat_atomic_add(&global_io_errors, 1);
+        have_read_error = 1;
+        error("%s: uv_fs_read - %s - extent at offset %"PRIu64"(%u) in datafile %u-%u.", __func__,
+              uv_strerror((int)req->result), xt_io_descr->pos, xt_io_descr->bytes, datafile->tier, datafile->fileno);
+        goto after_crc_check;
+    }
     crc = crc32(0L, Z_NULL, 0);
     crc = crc32(crc, xt_io_descr->buf, xt_io_descr->bytes - sizeof(*trailer));
     ret = crc32cmp(trailer->checksum, crc);
@@ -66,12 +71,17 @@ void read_extent_cb(uv_fs_t* req)
     }
 #endif
     if (unlikely(ret)) {
-        /* TODO: handle errors */
-        exit(UV_EIO);
-        goto cleanup;
+        struct rrdengine_datafile *datafile = xt_io_descr->descr_array[0]->extent->datafile;
+
+        ++ctx->stats.io_errors;
+        rrd_stat_atomic_add(&global_io_errors, 1);
+        have_read_error = 1;
+        error("%s: Extent at offset %"PRIu64"(%u) was read from datafile %u-%u. CRC32 check: FAILED", __func__,
+              xt_io_descr->pos, xt_io_descr->bytes, datafile->tier, datafile->fileno);
     }
 
-    if (RRD_NO_COMPRESSION != header->compression_algorithm) {
+after_crc_check:
+    if (!have_read_error && RRD_NO_COMPRESSION != header->compression_algorithm) {
         uncompressed_payload_length = 0;
         for (i = 0 ; i < count ; ++i) {
             uncompressed_payload_length += header->descr[i].page_length;
@@ -99,7 +109,10 @@ void read_extent_cb(uv_fs_t* req)
             page_offset += header->descr[j].page_length;
         }
         /* care, we don't hold the descriptor mutex */
-        if (RRD_NO_COMPRESSION == header->compression_algorithm) {
+        if (have_read_error) {
+            /* Applications should make sure NULL values match 0 as does SN_EMPTY_SLOT */
+            memset(page, 0, descr->page_length);
+        } else if (RRD_NO_COMPRESSION == header->compression_algorithm) {
             (void) memcpy(page, xt_io_descr->buf + payload_offset + page_offset, descr->page_length);
         } else {
             (void) memcpy(page, uncompressed_buf + page_offset, descr->page_length);
@@ -118,12 +131,11 @@ void read_extent_cb(uv_fs_t* req)
         }
         rrdeng_page_descr_mutex_unlock(ctx, descr);
     }
-    if (RRD_NO_COMPRESSION != header->compression_algorithm) {
+    if (!have_read_error && RRD_NO_COMPRESSION != header->compression_algorithm) {
         freez(uncompressed_buf);
     }
     if (xt_io_descr->completion)
         complete(xt_io_descr->completion);
-cleanup:
     uv_fs_req_cleanup(req);
     free(xt_io_descr->buf);
     freez(xt_io_descr);
@@ -246,8 +258,9 @@ void flush_pages_cb(uv_fs_t* req)
 
     xt_io_descr = req->data;
     if (req->result < 0) {
+        ++ctx->stats.io_errors;
+        rrd_stat_atomic_add(&global_io_errors, 1);
         error("%s: uv_fs_write: %s", __func__, uv_strerror((int)req->result));
-        goto cleanup;
     }
 #ifdef NETDATA_INTERNAL_CHECKS
     {
@@ -279,7 +292,6 @@ void flush_pages_cb(uv_fs_t* req)
     }
     if (xt_io_descr->completion)
         complete(xt_io_descr->completion);
-cleanup:
     uv_fs_req_cleanup(req);
     free(xt_io_descr->buf);
     freez(xt_io_descr);

health/health.d/dbengine.conf

@@ -22,5 +22,5 @@
    every: 10s
     crit: $this > 0
    delay: down 1h multiplier 1.5 max 3h
-    info: number of IO errors dbengine came across the last 10 minutes (out of space, bad disk etc)
+    info: number of IO errors dbengine came across the last 10 minutes (CRC errors, out of space, bad disk etc)
       to: sysadmin