Metabase crashes without any explanation in the logs

Once or twice a day, there is a huge spike in CPU utilization for about a hour (from around 2-4% to 95-99%) and metabase crashes after that.

The database is a very small mongoDB with a about 200-400 documents.
Metabase is running on a t2.micro instance with 1GB ram and 1vCPU.

I could not find any pattern as to what causes a crash. Here are some instances of logs just before metabase crashes.

2020-11-17 05:48:22,481 INFO task.send-pulses :: Sending scheduled pulses...
2020-11-17 05:50:52,276 ERROR metabot.websocket :: Error connecting websocket:
clojure.lang.ExceptionInfo: slack.com: Temporary failure in name resolution
	at metabase.integrations.slack$do_slack_request.invokeStatic(slack.clj:65) ~[metabase.jar:?]
	at metabase.integrations.slack$do_slack_request.invoke(slack.clj:47) ~[metabase.jar:?]
	at metabase.integrations.slack$GET.invokeStatic(slack.clj:70) ~[metabase.jar:?]
	at metabase.integrations.slack$GET.doInvoke(slack.clj:67) ~[metabase.jar:?]
	at clojure.lang.RestFn.invoke(RestFn.java:410) ~[metabase.jar:?]
	at clojure.core$partial$fn__5839.invoke(core.clj:2623) ~[metabase.jar:?]
	at clojure.core$comp$fn__5807.invoke(core.clj:2568) ~[metabase.jar:?]
	at metabase.metabot.websocket$connect_websocket_BANG_.invokeStatic(websocket.clj:30) ~[metabase.jar:?]
	at metabase.metabot.websocket$connect_websocket_BANG_.invoke(websocket.clj:29) ~[metabase.jar:?]
	at metabase.metabot.websocket$reopen_websocket_connection_if_needed_BANG_.invokeStatic(websocket.clj:101) [metabase.jar:?]
	at metabase.metabot.websocket$reopen_websocket_connection_if_needed_BANG_.invoke(websocket.clj:91) [metabase.jar:?]
	at metabase.metabot.websocket$start_websocket_monitor_BANG_$fn__69913.invoke(websocket.clj:116) [metabase.jar:?]
	at clojure.core$binding_conveyor_fn$fn__5754.invoke(core.clj:2030) [metabase.jar:?]
	at clojure.lang.AFn.call(AFn.java:18) [metabase.jar:?]
	at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
	at java.lang.Thread.run(Thread.java:834) [?:?]
Caused by: java.net.UnknownHostException: slack.com: Temporary failure in name resolution
	at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) ~[?:?]
	at java.net.InetAddress$PlatformNameService.lookupAllHostAddr(InetAddress.java:929) ~[?:?]
	at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1515) ~[?:?]
	at java.net.InetAddress$NameServiceAddresses.get(InetAddress.java:848) ~[?:?]
	at java.net.InetAddress.getAllByName0(InetAddress.java:1505) ~[?:?]
	at java.net.InetAddress.getAllByName(InetAddress.java:1364) ~[?:?]
	at java.net.InetAddress.getAllByName(InetAddress.java:1298) ~[?:?]
	at org.apache.http.impl.conn.SystemDefaultDnsResolver.resolve(SystemDefaultDnsResolver.java:45) ~[metabase.jar:?]
	at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:112) ~[metabase.jar:?]
	at org.apache.http.impl.conn.BasicHttpClientConnectionManager.connect(BasicHttpClientConnectionManager.java:313) ~[metabase.jar:?]
	at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:393) ~[metabase.jar:?]
	at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:236) ~[metabase.jar:?]
	at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186) ~[metabase.jar:?]
	at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89) ~[metabase.jar:?]
	at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110) ~[metabase.jar:?]
	at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185) ~[metabase.jar:?]
	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83) ~[metabase.jar:?]
	at clj_http.core$request.invokeStatic(core.clj:643) ~[metabase.jar:?]
	at clj_http.core$request.invoke(core.clj:568) ~[metabase.jar:?]
	at clj_http.core$request.invokeStatic(core.clj:569) ~[metabase.jar:?]
	at clj_http.core$request.invoke(core.clj:568) ~[metabase.jar:?]
	at clojure.lang.Var.invoke(Var.java:384) ~[metabase.jar:?]
	at clj_http.client$wrap_request_timing$fn__23813.invoke(client.clj:1077) ~[metabase.jar:?]
	at clj_http.headers$wrap_header_map$fn__22947.invoke(headers.clj:152) ~[metabase.jar:?]
	at clj_http.client$wrap_query_params$fn__23703.invoke(client.clj:811) ~[metabase.jar:?]
	at clj_http.client$wrap_basic_auth$fn__23709.invoke(client.clj:834) ~[metabase.jar:?]
	at clj_http.client$wrap_oauth$fn__23714.invoke(client.clj:851) ~[metabase.jar:?]
	at clj_http.client$wrap_user_info$fn__23723.invoke(client.clj:871) ~[metabase.jar:?]
	at clj_http.client$wrap_url$fn__23795.invoke(client.clj:1029) ~[metabase.jar:?]
	at clj_http.client$wrap_decompression$fn__23504.invoke(client.clj:418) ~[metabase.jar:?]
	at clj_http.client$wrap_input_coercion$fn__23627.invoke(client.clj:631) ~[metabase.jar:?]
	at clj_http.client$wrap_additional_header_parsing$fn__23652.invoke(client.clj:686) ~[metabase.jar:?]
	at clj_http.client$wrap_output_coercion$fn__23614.invoke(client.clj:575) ~[metabase.jar:?]
	at clj_http.client$wrap_exceptions$fn__23456.invoke(client.clj:252) ~[metabase.jar:?]
	at clj_http.client$wrap_accept$fn__23667.invoke(client.clj:729) ~[metabase.jar:?]
	at clj_http.client$wrap_accept_encoding$fn__23674.invoke(client.clj:751) ~[metabase.jar:?]
	at clj_http.client$wrap_content_type$fn__23661.invoke(client.clj:712) ~[metabase.jar:?]
	at clj_http.client$wrap_form_params$fn__23760.invoke(client.clj:953) ~[metabase.jar:?]
	at clj_http.client$wrap_nested_params$fn__23781.invoke(client.clj:987) ~[metabase.jar:?]
	at clj_http.client$wrap_flatten_nested_params$fn__23790.invoke(client.clj:1011) ~[metabase.jar:?]
	at clj_http.client$wrap_method$fn__23728.invoke(client.clj:887) ~[metabase.jar:?]
	at clj_http.cookies$wrap_cookies$fn__22859.invoke(cookies.clj:131) ~[metabase.jar:?]
	at clj_http.links$wrap_links$fn__23283.invoke(links.clj:63) ~[metabase.jar:?]
	at clj_http.client$wrap_unknown_host$fn__23798.invoke(client.clj:1040) ~[metabase.jar:?]
	at clj_http.client$request_STAR_.invokeStatic(client.clj:1168) ~[metabase.jar:?]
	at clj_http.client$request_STAR_.invoke(client.clj:1161) ~[metabase.jar:?]
	at clj_http.client$get.invokeStatic(client.clj:1174) ~[metabase.jar:?]
	at clj_http.client$get.doInvoke(client.clj:1170) ~[metabase.jar:?]
	at clojure.lang.RestFn.invoke(RestFn.java:423) ~[metabase.jar:?]
	at metabase.integrations.slack$do_slack_request.invokeStatic(slack.clj:63) ~[metabase.jar:?]
	... 17 more
2020-11-15 09:11:26,807 DEBUG middleware.log :: e[32mPOST /api/dataset 202 [ASYNC: completed] 212.8 ms (23 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (100 total active threads) Queries in flight: 0 (0 queued)e[0m
2020-11-15 09:11:36,511 ERROR middleware.log :: e[31mPOST /api/dataset 500 2.1 ms (0 DB calls) 
{:via [{:type java.lang.Exception, :message "`database` is required for all queries whose type is not `internal`.", :at [metabase.api.dataset$fn__52570 invokeStatic "dataset.clj" 49]}],
 :trace
 [[metabase.api.dataset$fn__52570 invokeStatic "dataset.clj" 49]
  [metabase.api.dataset$fn__52570 invoke "dataset.clj" 40]
  [compojure.core$wrap_response$fn__1993 invoke "core.clj" 160]
  [compojure.core$wrap_route_middleware$fn__1977 invoke "core.clj" 132]
  [compojure.core$wrap_route_info$fn__1982 invoke "core.clj" 139]
  [compojure.core$wrap_route_matches$fn__1986 invoke "core.clj" 151]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$wrap_route_matches$fn__1986 invoke "core.clj" 152]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005 invoke "core.clj" 200]
  [metabase.middleware.auth$enforce_authentication$fn__72857 invoke "auth.clj" 14]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005 invoke "core.clj" 200]
  [compojure.core$make_context$handler__2033 invoke "core.clj" 287]
  [compojure.core$make_context$fn__2035 invoke "core.clj" 296]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$make_context$fn__2035 invoke "core.clj" 297]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$make_context$fn__2035 invoke "core.clj" 297]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$make_context$fn__2035 invoke "core.clj" 297]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$make_context$fn__2035 invoke "core.clj" 297]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$make_context$fn__2035 invoke "core.clj" 297]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$make_context$fn__2035 invoke "core.clj" 297]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$make_context$fn__2035 invoke "core.clj" 297]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [metabase.api.routes$fn__72978$fn__72980 invoke "routes.clj" 73]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005 invoke "core.clj" 200]
  [clojure.lang.AFn applyToHelper "AFn.java" 160]
  [clojure.lang.AFn applyTo "AFn.java" 144]
  [clojure.core$apply invokeStatic "core.clj" 665]
  [clojure.core$apply invoke "core.clj" 660]
  [metabase.routes$fn__74306$fn__74307 doInvoke "routes.clj" 60]
  [clojure.lang.RestFn invoke "RestFn.java" 436]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005 invoke "core.clj" 200]
  [compojure.core$make_context$handler__2033 invoke "core.clj" 287]
  [compojure.core$make_context$fn__2035 invoke "core.clj" 296]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$wrap_route_matches$fn__1986 invoke "core.clj" 153]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$wrap_route_matches$fn__1986 invoke "core.clj" 153]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [compojure.core$wrap_route_matches$fn__1986 invoke "core.clj" 153]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005$f__2006$respond_SINGLEQUOTE___2007 invoke "core.clj" 197]
  [metabase.routes$fn__74294$fn__74296 invoke "routes.clj" 44]
  [compojure.core$routes$fn__2005$f__2006 invoke "core.clj" 198]
  [compojure.core$routes$fn__2005 invoke "core.clj" 200]
  [metabase.middleware.exceptions$catch_uncaught_exceptions$fn__72969 invoke "exceptions.clj" 96]
  [metabase.middleware.exceptions$catch_api_exceptions$fn__72966 invoke "exceptions.clj" 84]
  [metabase.middleware.log$log_api_call$fn__74754$fn__74755 invoke "log.clj" 197]
  [toucan.db$_do_with_call_counting invokeStatic "db.clj" 216]
  [toucan.db$_do_with_call_counting invoke "db.clj" 209]
  [metabase.middleware.log$log_api_call$fn__74754 invoke "log.clj" 191]
  [metabase.middleware.security$add_security_headers$fn__72932 invoke "security.clj" 143]
  [metabase.middleware.json$wrap_json_body$fn__74457 invoke "json.clj" 64]
  [metabase.middleware.json$wrap_streamed_json_response$fn__74475 invoke "json.clj" 100]
  [ring.middleware.keyword_params$wrap_keyword_params$fn__75020 invoke "keyword_params.clj" 55]
  [ring.middleware.params$wrap_params$fn__75036 invoke "params.clj" 69]
  [metabase.middleware.misc$maybe_set_site_url$fn__37860 invoke "misc.clj" 59]
  [metabase.middleware.session$bind_current_user$fn__69411$fn__69412 invoke "session.clj" 278]
  [metabase.middleware.session$do_with_current_user invokeStatic "session.clj" 260]
  [metabase.middleware.session$do_with_current_user invoke "session.clj" 252]
  [metabase.middleware.session$bind_current_user$fn__69411 invoke "session.clj" 277]
  [metabase.middleware.session$wrap_current_user_info$fn__69398 invoke "session.clj" 238]
  [metabase.middleware.session$wrap_session_id$fn__69384 invoke "session.clj" 184]
  [metabase.middleware.auth$wrap_api_key$fn__72865 invoke "auth.clj" 27]
  [ring.middleware.cookies$wrap_cookies$fn__74940 invoke "cookies.clj" 216]
  [metabase.middleware.misc$add_content_type$fn__37845 invoke "misc.clj" 28]
  [metabase.middleware.misc$disable_streaming_buffering$fn__37868 invoke "misc.clj" 76]
  [ring.middleware.gzip$wrap_gzip$fn__74982 invoke "gzip.clj" 86]
  [metabase.middleware.misc$bind_request$fn__37871 invoke "misc.clj" 93]
  [metabase.middleware.ssl$redirect_to_https_middleware$fn__74771 invoke "ssl.clj" 39]
  [metabase.server$async_proxy_handler$fn__74532 invoke "server.clj" 72]
  [metabase.server.proxy$org.eclipse.jetty.server.handler.AbstractHandler$ff19274a handle nil -1]
  [org.eclipse.jetty.server.handler.HandlerWrapper handle "HandlerWrapper.java" 127]
  [org.eclipse.jetty.server.Server handle "Server.java" 516]
  [org.eclipse.jetty.server.HttpChannel lambda$handle$1 "HttpChannel.java" 383]
  [org.eclipse.jetty.server.HttpChannel dispatch "HttpChannel.java" 556]
  [org.eclipse.jetty.server.HttpChannel handle "HttpChannel.java" 375]
  [org.eclipse.jetty.server.HttpConnection onFillable "HttpConnection.java" 273]
  [org.eclipse.jetty.io.AbstractConnection$ReadCallback succeeded "AbstractConnection.java" 311]
  [org.eclipse.jetty.io.FillInterest fillable "FillInterest.java" 105]
  [org.eclipse.jetty.io.ChannelEndPoint$1 run "ChannelEndPoint.java" 104]
  [org.eclipse.jetty.util.thread.strategy.EatWhatYouKill runTask "EatWhatYouKill.java" 336]
  [org.eclipse.jetty.util.thread.strategy.EatWhatYouKill doProduce "EatWhatYouKill.java" 313]
  [org.eclipse.jetty.util.thread.strategy.EatWhatYouKill tryProduce "EatWhatYouKill.java" 171]
  [org.eclipse.jetty.util.thread.strategy.EatWhatYouKill run "EatWhatYouKill.java" 129]
  [org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread run "ReservedThreadExecutor.java" 375]
  [org.eclipse.jetty.util.thread.QueuedThreadPool runJob "QueuedThreadPool.java" 773]
  [org.eclipse.jetty.util.thread.QueuedThreadPool$Runner run "QueuedThreadPool.java" 905]
  [java.lang.Thread run "Thread.java" 834]],
 :cause "`database` is required for all queries whose type is not `internal`.",
 :message "`database` is required for all queries whose type is not `internal`.",
 :type java.lang.Exception}
e[0m
2020-11-15 09:11:38,737 DEBUG middleware.log :: e[32mPOST /api/dataset 202 [ASYNC: completed] 183.5 ms (42 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (101 total active threads) Queries in flight: 0 (0 queued)e[0m
2020-11-15 09:11:57,887 ERROR middleware.catch-exceptions :: Error processing query: null
{:database_id 2,
 :started_at #t "2020-11-15T09:11:57.601372+05:30[Asia/Kolkata]",
 :error_type :unsupported-feature,
 :json_query
 {:type "query",
  :query {:source-table 13, :aggregation [["count"]], :breakout [["fk->" ["field-id" 406] ["field-id" 48]]]},
  :database 2,
  :parameters [],
  :middleware {:js-int-to-string? true, :add-default-userland-constraints? true}},
 :native nil,
 :status :failed,
 :class clojure.lang.ExceptionInfo,
 :stacktrace
 ["--> query_processor.middleware.add_implicit_joins$add_implicit_joins_STAR_.invokeStatic(add_implicit_joins.clj:240)"
  "query_processor.middleware.add_implicit_joins$add_implicit_joins_STAR_.invoke(add_implicit_joins.clj:236)"
  "query_processor.middleware.add_implicit_joins$add_implicit_joins$fn__40987.invoke(add_implicit_joins.clj:254)"
  "query_processor.middleware.large_int_id$convert_id_to_string$fn__47385.invoke(large_int_id.clj:44)"
  "query_processor.middleware.limit$limit$fn__47410.invoke(limit.clj:38)"
  "query_processor.middleware.format_rows$format_rows$fn__47365.invoke(format_rows.clj:84)"
  "query_processor.middleware.desugar$desugar$fn__46838.invoke(desugar.clj:22)"
  "query_processor.middleware.binning$update_binning_strategy$fn__45859.invoke(binning.clj:229)"
  "query_processor.middleware.resolve_fields$resolve_fields$fn__46376.invoke(resolve_fields.clj:24)"
  "query_processor.middleware.add_dimension_projections$add_remapping$fn__40531.invoke(add_dimension_projections.clj:318)"
  "query_processor.middleware.add_implicit_clauses$add_implicit_clauses$fn__40738.invoke(add_implicit_clauses.clj:141)"
  "query_processor.middleware.add_source_metadata$add_source_metadata_for_source_queries$fn__41136.invoke(add_source_metadata.clj:105)"
  "query_processor.middleware.reconcile_breakout_and_order_by_bucketing$reconcile_breakout_and_order_by_bucketing$fn__48304.invoke(reconcile_breakout_and_order_by_bucketing.clj:98)"
  "query_processor.middleware.auto_bucket_datetimes$auto_bucket_datetimes$fn__45447.invoke(auto_bucket_datetimes.clj:125)"
  "query_processor.middleware.resolve_source_table$resolve_source_tables$fn__46423.invoke(resolve_source_table.clj:46)"
  "query_processor.middleware.parameters$substitute_parameters$fn__48089.invoke(parameters.clj:114)"
  "query_processor.middleware.resolve_referenced$resolve_referenced_card_resources$fn__46475.invoke(resolve_referenced.clj:80)"
  "query_processor.middleware.expand_macros$expand_macros$fn__47094.invoke(expand_macros.clj:158)"
  "query_processor.middleware.add_timezone_info$add_timezone_info$fn__41167.invoke(add_timezone_info.clj:15)"
  "query_processor.middleware.splice_params_in_response$splice_params_in_response$fn__49025.invoke(splice_params_in_response.clj:32)"
  "query_processor.middleware.resolve_database_and_driver$resolve_database_and_driver$fn__48315$fn__48319.invoke(resolve_database_and_driver.clj:33)"
  "driver$do_with_driver.invokeStatic(driver.clj:61)"
  "driver$do_with_driver.invoke(driver.clj:57)"
  "query_processor.middleware.resolve_database_and_driver$resolve_database_and_driver$fn__48315.invoke(resolve_database_and_driver.clj:27)"
  "query_processor.middleware.fetch_source_query$resolve_card_id_source_tables$fn__47312.invoke(fetch_source_query.clj:267)"
  "query_processor.middleware.store$initialize_store$fn__49034$fn__49035.invoke(store.clj:11)"
  "query_processor.store$do_with_store.invokeStatic(store.clj:46)"
  "query_processor.store$do_with_store.invoke(store.clj:40)"
  "query_processor.middleware.store$initialize_store$fn__49034.invoke(store.clj:10)"
  "query_processor.middleware.cache$maybe_return_cached_results$fn__46352.invoke(cache.clj:214)"
  "query_processor.middleware.validate$validate_query$fn__49043.invoke(validate.clj:10)"
  "query_processor.middleware.normalize_query$normalize$fn__47437.invoke(normalize_query.clj:22)"
  "query_processor.middleware.add_rows_truncated$add_rows_truncated$fn__41005.invoke(add_rows_truncated.clj:36)"
  "query_processor.middleware.results_metadata$record_and_return_metadata_BANG_$fn__49010.invoke(results_metadata.clj:147)"
  "query_processor.middleware.constraints$add_default_userland_constraints$fn__46715.invoke(constraints.clj:42)"
  "query_processor.middleware.process_userland_query$process_userland_query$fn__48178.invoke(process_userland_query.clj:136)"
  "query_processor.middleware.catch_exceptions$catch_exceptions$fn__46658.invoke(catch_exceptions.clj:174)"
  "query_processor.reducible$async_qp$qp_STAR___39794$thunk__39795.invoke(reducible.clj:103)"
  "query_processor.reducible$async_qp$qp_STAR___39794.invoke(reducible.clj:109)"
  "query_processor.reducible$sync_qp$qp_STAR___39803$fn__39806.invoke(reducible.clj:135)"
  "query_processor.reducible$sync_qp$qp_STAR___39803.invoke(reducible.clj:134)"
  "query_processor$process_userland_query.invokeStatic(query_processor.clj:237)"
  "query_processor$process_userland_query.doInvoke(query_processor.clj:233)"
  "query_processor$fn__49201$process_query_and_save_execution_BANG___49210$fn__49213.invoke(query_processor.clj:249)"
  "query_processor$fn__49201$process_query_and_save_execution_BANG___49210.invoke(query_processor.clj:241)"
  "query_processor$fn__49245$process_query_and_save_with_max_results_constraints_BANG___49254$fn__49257.invoke(query_processor.clj:261)"
  "query_processor$fn__49245$process_query_and_save_with_max_results_constraints_BANG___49254.invoke(query_processor.clj:254)"
  "api.dataset$fn__52570$fn__52573.invoke(dataset.clj:59)"
  "query_processor.streaming$streaming_response_STAR_$fn__37098$fn__37099.invoke(streaming.clj:73)"
  "query_processor.streaming$streaming_response_STAR_$fn__37098.invoke(streaming.clj:72)"
  "async.streaming_response$do_f_STAR_.invokeStatic(streaming_response.clj:66)"
  "async.streaming_response$do_f_STAR_.invoke(streaming_response.clj:64)"
  "async.streaming_response$do_f_async$fn__24643.invoke(streaming_response.clj:85)"],
 :context :ad-hoc,
 :error ":mongo driver does not support foreign keys.",
 :row_count 0,
 :running_time 0,
 :preprocessed nil,
 :ex-data {:driver :mongo, :type :unsupported-feature},
 :data {:rows [], :cols []}}

2020-11-15 09:11:57,894 DEBUG middleware.log :: e[32mPOST /api/dataset 202 [ASYNC: completed] 300.7 ms (6 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (101 total active threads) Queries in flight: 1 (0 queued)e[0m
2020-11-15 09:12:12,616 DEBUG middleware.log :: e[32mPOST /api/dataset 202 [ASYNC: completed] 121.4 ms (12 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (101 total active threads) Queries in flight: 0 (0 queued)e[0m
2020-11-15 09:12:26,153 DEBUG middleware.log :: e[32mPOST /api/dataset 202 [ASYNC: completed] 182.9 ms (42 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (101 total active threads) Queries in flight: 0 (0 queued)e[0m
2020-11-15 09:13:21,663 DEBUG middleware.log :: e[32mPOST /api/dataset 202 [ASYNC: completed] 148.2 ms (31 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (100 total active threads) Queries in flight: 1 (0 queued)e[0m
2020-11-15 10:00:00,002 INFO task.send-pulses :: Sending scheduled pulses...
2020-11-15 10:17:31,379 DEBUG middleware.log :: e[31mGET /api/user/current 401 194.5 µs (0 DB calls) 
"Unauthenticated"
e[0m
2020-11-15 10:17:31,385 DEBUG middleware.log :: e[32mGET /api/session/properties 200 5.4 ms (0 DB calls) App DB connections: 0/15 Jetty threads: 4/50 (3 idle, 0 queued) (103 total active threads) Queries in flight: 0 (0 queued)e[0m
2020-11-15 10:51:30,658 WARN middleware.log :: e[31mPOST /api/jsonws/invoke 404 474.4 µs (0 DB calls) 
"API endpoint does not exist."
e[0m
2020-11-15 11:00:00,007 INFO task.send-pulses :: Sending scheduled pulses...
2020-11-15 12:00:00,074 INFO task.send-pulses :: Sending scheduled pulses...
2020-11-15 12:00:00,067 ERROR core.JobRunShell :: Job DEFAULT.metabase.task.abandonment-emails.job threw an unhandled Exception: 
clojure.lang.ExceptionInfo: Input to should-send-abandoment-email? does not match schema: 

	 e[0;33m  [nil (named (not (instance? java.time.temporal.Temporal a-metabase.models.user.UserInstance)) last-user) (named (not (instance? java.time.temporal.Temporal a-metabase.models.activity.ActivityInstance)) last-activity) (named (not (instance? java.time.temporal.Temporal a-metabase.models.view_log.ViewLogInstance)) last-view)] e[0m 


	at metabase.task.follow_up_emails$fn__78531$should_send_abandoment_email_QMARK___78540.invoke(follow_up_emails.clj:95) ~[metabase.jar:?]
	at metabase.task.follow_up_emails$fn__78531$should_send_abandoment_email_QMARK___78540$fn__78541.invoke(follow_up_emails.clj:97) ~[metabase.jar:?]
	at metabase.task.follow_up_emails$fn__78531$should_send_abandoment_email_QMARK___78540.invoke(follow_up_emails.clj:95) ~[metabase.jar:?]
	at metabase.task.follow_up_emails$send_abandoment_email_if_needed_BANG_.invokeStatic(follow_up_emails.clj:119) ~[metabase.jar:?]
	at metabase.task.follow_up_emails$send_abandoment_email_if_needed_BANG_.invoke(follow_up_emails.clj:114) ~[metabase.jar:?]
	at metabase.task.follow_up_emails.AbandonmentEmail.execute(follow_up_emails.clj:135) ~[metabase.jar:?]
	at org.quartz.core.JobRunShell.run(JobRunShell.java:213) [metabase.jar:?]
	at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:557) [metabase.jar:?]
2020-11-15 12:00:00,148 ERROR core.ErrorLogger :: Job (DEFAULT.metabase.task.abandonment-emails.job threw an exception.
org.quartz.SchedulerException: Job threw an unhandled exception.
	at org.quartz.core.JobRunShell.run(JobRunShell.java:224) [metabase.jar:?]
	at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:557) [metabase.jar:?]
Caused by: clojure.lang.ExceptionInfo: Input to should-send-abandoment-email? does not match schema: 

	 e[0;33m  [nil (named (not (instance? java.time.temporal.Temporal a-metabase.models.user.UserInstance)) last-user) (named (not (instance? java.time.temporal.Temporal a-metabase.models.activity.ActivityInstance)) last-activity) (named (not (instance? java.time.temporal.Temporal a-metabase.models.view_log.ViewLogInstance)) last-view)] e[0m 


	at metabase.task.follow_up_emails$fn__78531$should_send_abandoment_email_QMARK___78540.invoke(follow_up_emails.clj:95) ~[metabase.jar:?]
	at metabase.task.follow_up_emails$fn__78531$should_send_abandoment_email_QMARK___78540$fn__78541.invoke(follow_up_emails.clj:97) ~[metabase.jar:?]
	at metabase.task.follow_up_emails$fn__78531$should_send_abandoment_email_QMARK___78540.invoke(follow_up_emails.clj:95) ~[metabase.jar:?]
	at metabase.task.follow_up_emails$send_abandoment_email_if_needed_BANG_.invokeStatic(follow_up_emails.clj:119) ~[metabase.jar:?]
	at metabase.task.follow_up_emails$send_abandoment_email_if_needed_BANG_.invoke(follow_up_emails.clj:114) ~[metabase.jar:?]
	at metabase.task.follow_up_emails.AbandonmentEmail.execute(follow_up_emails.clj:135) ~[metabase.jar:?]
	at org.quartz.core.JobRunShell.run(JobRunShell.java:213) ~[metabase.jar:?]
	... 1 more
2020-11-15 12:27:21,337 DEBUG middleware.log :: e[32mGET /api/dashboard/1 200 14.7 ms (15 DB calls) App DB connections: 0/15 Jetty threads: 3/50 (4 idle, 0 queued) (100 total active threads) Queries in flight: 0 (0 queued)e[0m
2020-11-15 12:27:22,004 DEBUG middleware.log :: e[32mPOST /api/card/2/query 202 [ASYNC: completed] 518.0 ms (5 DB calls) App DB connections: 1/15 Jetty threads: 2/50 (5 idle, 0 queued) (129 total active threads) Queries in flight: 5 (0 queued)e[0m
2020-11-15 12:27:22,156 DEBUG middleware.log :: e[32mPOST /api/card/4/query 202 [ASYNC: completed] 494.4 ms (11 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (126 total active threads) Queries in flight: 5 (0 queued)e[0m
2020-11-15 12:27:22,232 DEBUG middleware.log :: e[32mPOST /api/card/98/query 202 [ASYNC: completed] 573.3 ms (12 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (130 total active threads) Queries in flight: 5 (0 queued)e[0m
2020-11-15 12:27:22,315 DEBUG middleware.log :: e[32mPOST /api/card/1/query 202 [ASYNC: completed] 658.0 ms (10 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (128 total active threads) Queries in flight: 5 (0 queued)e[0m
2020-11-15 12:27:22,407 DEBUG middleware.log :: e[32mPOST /api/card/5/query 202 [ASYNC: completed] 748.2 ms (20 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (127 total active threads) Queries in flight: 4 (0 queued)e[0m
2020-11-15 12:27:22,523 DEBUG middleware.log :: e[32mPOST /api/card/3/query 202 [ASYNC: completed] 884.4 ms (21 DB calls) App DB connections: 1/15 Jetty threads: 2/50 (5 idle, 0 queued) (127 total active threads) Queries in flight: 5 (0 queued)e[0m
2020-11-15 12:27:22,905 DEBUG middleware.log :: e[32mPOST /api/card/99/query 202 [ASYNC: completed] 781.9 ms (11 DB calls) App DB connections: 0/15 Jetty threads: 2/50 (5 idle, 0 queued) (131 total active threads) Queries in flight: 5 (0 queued)e[0m
2020-11-15 00:00:02,623 INFO sync.util :: e[35mFINISHED: Sync metadata for mongo Database 2 '****-prod' (2.6 s)e[0m
2020-11-13 13:31:08,218 DEBUG middleware.log :: e[32mPOST /api/card/99/query 202 [ASYNC: completed] 263.7 ms (11 DB calls) App DB connections: 0/13 Jetty threads: 2/50 (5 idle, 0 queued) (111 total active threads) Queries in flight: 0 (0 queued)e[0m
2020-11-13 14:00:00,002 INFO task.send-pulses :: Sending scheduled pulses...

Diagnostic info

{
  "browser-info": {
    "language": "en-US",
    "platform": "Linux x86_64",
    "userAgent": "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:82.0) Gecko/20100101 Firefox/82.0",
    "vendor": ""
  },
  "system-info": {
    "file.encoding": "UTF-8",
    "java.runtime.name": "OpenJDK Runtime Environment",
    "java.runtime.version": "11.0.9.1+1-Ubuntu-0ubuntu1.20.04",
    "java.vendor": "Ubuntu",
    "java.vendor.url": "https://ubuntu.com/",
    "java.version": "11.0.9.1",
    "java.vm.name": "OpenJDK 64-Bit Server VM",
    "java.vm.version": "11.0.9.1+1-Ubuntu-0ubuntu1.20.04",
    "os.name": "Linux",
    "os.version": "5.4.0-1029-aws",
    "user.language": "en",
    "user.timezone": "Asia/Kolkata"
  },
  "metabase-info": {
    "databases": [
      "mongo"
    ],
    "hosting-env": "unknown",
    "application-database": "h2",
    "application-database-details": {
      "database": {
        "name": "H2",
        "version": "1.4.197 (2018-03-18)"
      },
      "jdbc-driver": {
        "name": "H2 JDBC Driver",
        "version": "1.4.197 (2018-03-18)"
      }
    },
    "run-mode": "prod",
    "version": {
      "date": "2020-10-26",
      "tag": "v0.37.0.2",
      "branch": "release-x.37.x",
      "hash": "ba7be09"
    },
    "settings": {
      "report-timezone": "Asia/Calcutta"
    }
  }
}

Any pointers on what could cause this and how we can fix this would be really appreciated. Thanks!

Hi @bharatkalluri

Upgrade to 0.37.2, which has several fixes for the sync/scan process, which I’m pretty sure you’re hitting.

The first log looks to be DNS issues on the server running Metabase. Or perhaps “just” regular network problems.

Second log seems to be various different problems, but seems unrelated to the crash.

You should be able to find logs from the crash, but I don’t know if you’re running Metabase as a service - if not, then you should do that: https://www.metabase.com/docs/latest/operations-guide/running-metabase-on-debian.html

And then you should migrate away from H2:
https://www.metabase.com/docs/latest/operations-guide/migrating-from-h2.html