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From "Di Li" <>
Subject Re: Review Request 38269: AMBARI-12949: Downgrade fails with err: 500 status code received on POST method for API: /api/vi/clusters/mycluster/upgrades
Date Wed, 16 Sep 2015 17:14:12 GMT

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(Updated Sept. 16, 2015, 5:14 p.m.)

Review request for Ambari, Alejandro Fernandez, Jonathan Hurley, and Nate Cole.


used {} placeholders in the LOG output.

Bugs: AMBARI-12949

Repository: ambari


This seems to be an issue that happens when the "latest" configuration stored in the "clusterconfig"
table is for a conf group instead of the default configurations. The named query "ClusterConfigEntity.findLatestConfigsByStack"
returns the latest configuration to be set with "selected = 1" in the clusterconfigmapping
table. When the "latest" config is for a conf group, this record will not have a corresponding
entry in the clusterconfigmapping table. So the clusterconfigmapping table is left with a
type that does not have the selected column set to 1.

My proposed fix is the new named query "ClusterConfigEntity.findLatestConfigsOfClusterConfigMappingEntriesByStack"
in, which searches the clusterconfig table for the latest version
of a type_name and version_tag specified in the clusterconfigmapping table. This is different
from the current "ClusterConfigEntity.findLatestConfigsByStack" query, which simply pulls
the latest config of a type_name from the clusterconfig table regardless whether the corresponding
version_tag is in the clusterconfigmapping table or not.


I used Oozie for debugging.

When a user clicks the Downgrade button from the Finalize page. The request eventually hits
ClusterImpl.applyLatestConfigurations method where the Ambari server updates the database
to reverse back to the "latest" configuration of each type for the older stack (HDP 2.2)

The workflow goes as
1. Set ALL entries in clusterconfigmapping table to have selected value set to 0
2. Ambari server uses ClusterImpl.applyLatestConfigurations method to get the "latest" configuration
of each type for the older stack (HDP 2.2)
3. Loop through all the entries in the clusterconfigmapping table, and set the selected to
1 if this entry also happens to be in the "latest" configuration returned in step 2.

The ClusterImpl.applyLatestConfigurations method calls getLatestConfigurations
to get the latest configuration for each type for the older stack. The DAO class simply runs
the following SQL query (cluster id and stack id are the parameters) and passes the results

SELECT clusterConfig1 FROM clusterconfig clusterConfig1 WHERE clusterConfig1.cluster_id='2'
AND clusterConfig1.create_timestamp = (SELECT MAX(clusterConfig2.create_timestamp) FROM clusterconfig
clusterConfig2 WHERE clusterConfig2.cluster_id='2' AND clusterConfig2.stack_id= '3' AND clusterConfig2.type_name
= clusterConfig1.type_name);

For downgrade, in our particular use case, the oozie-env configuration stored in the clusterconfig
table, when the stack id is the HDP 2.2 version, only contains TWO conf, the original version1
and the one for the config group.

The query above will return the entry corresponding to the oozie config group, as it was the
last configuration entry added to the clusterconfig table for oozie-site with stack id = 3.
However, because the config group entry is NEVER stored into the clusterconfigmapping table,
the logic in ClusterImpl.applyLatestConfigurations method to re-select a version for a type
in the clusterconfigmapping will not be able to update the clusterconfigmapping table. Thus
no oozie-site is set with selected = 1 in the clusterconfigmapping table.

for( ClusterConfigEntity clusterConfigToMakeSelected : clusterConfigsToMakeSelected ){"Checking " + clusterConfigToMakeSelected.getType() + " with tag " + clusterConfigToMakeSelected.getTag());
for (ClusterConfigMappingEntity configMappingEntity : configMappingEntities) {
String tag = configMappingEntity.getTag();
String type = configMappingEntity.getType();

if (clusterConfigToMakeSelected.getTag().equals(tag)
&& clusterConfigToMakeSelected.getType().equals(type))
{ + " with tag " + tag + " is selected"); configMappingEntity.setSelected(1);


Diffs (updated)

  ambari-server/src/main/java/org/apache/ambari/server/orm/dao/ 6e55128 
  ambari-server/src/main/java/org/apache/ambari/server/state/cluster/ a48fb54

  ambari-server/src/test/java/org/apache/ambari/server/orm/dao/ 4c186b5



unit test: added more test cases to ambari-server code
test on a rolling upgrade then downgrade.


Di Li

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