We'd need to know which version of Ambari you're using. This type of error can typically be seen in one of two scenarios:
- You're using MySQL with MyISAM as the database engine. MyISAM doesn't support transactions or foreign keys and can lead to a corrupted Ambari database. - You're using an older build of Ambari which had issues with cached JPA entities. As a result, a restart usually fixes the issue. On May 30, 2016, at 7:20 PM, Fay Wang <faywang...@yahoo.com<mailto:faywang...@yahoo.com>> wrote: Hi, We encounter this NPE when trying to logon to Ambari UI. Any help is highly appreciated.... 30 May 2016 22:55:48,883 INFO [qtp-client-57] MetricsPropertyProvider:526 - METRICS_COLLECTOR is not live. Skip populating resources with metrics. 30 May 2016 22:55:48,883 INFO [qtp-client-57] MetricsPropertyProvider:526 - METRICS_COLLECTOR is not live. Skip populating resources with metrics. 30 May 2016 22:55:48,884 INFO [qtp-client-57] MetricsPropertyProvider:526 - METRICS_COLLECTOR is not live. Skip populating resources with metrics. 30 May 2016 22:55:48,884 INFO [qtp-client-57] MetricsPropertyProvider:526 - METRICS_COLLECTOR is not live. Skip populating resources with metrics. 30 May 2016 22:55:48,885 INFO [qtp-client-57] MetricsPropertyProvider:526 - METRICS_COLLECTOR is not live. Skip populating resources with metrics. 30 May 2016 22:55:48,885 INFO [qtp-client-57] MetricsPropertyProvider:526 - METRICS_COLLECTOR is not live. Skip populating resources with metrics. 30 May 2016 22:55:52,354 ERROR [qtp-client-57] ReadHandler:91 - Caught a runtime exception executing a query java.lang.NullPointerException at org.apache.ambari.server.controller.internal.AlertResourceProvider.toResource(AlertResourceProvider.java:199) at org.apache.ambari.server.controller.internal.AlertResourceProvider.getResources(AlertResourceProvider.java:179) at org.apache.ambari.server.controller.internal.AlertResourceProvider.queryForResources(AlertResourceProvider.java:135) at org.apache.ambari.server.controller.internal.ClusterControllerImpl$ExtendedResourceProviderWrapper.queryForResources(ClusterControllerImpl.java:945) at org.apache.ambari.server.controller.internal.ClusterControllerImpl.getResources(ClusterControllerImpl.java:132) at org.apache.ambari.server.api.query.QueryImpl.doQuery(QueryImpl.java:489) at org.apache.ambari.server.api.query.QueryImpl.queryForResources(QueryImpl.java:388) at org.apache.ambari.server.api.query.QueryImpl.execute(QueryImpl.java:224)