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From "Di Li" <d...@ca.ibm.com>
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 Thu, 17 Sep 2015 17:07:42 GMT


> On Sept. 16, 2015, 3:41 p.m., Jonathan Hurley wrote:
> > ambari-server/src/main/java/org/apache/ambari/server/orm/entities/ClusterConfigEntity.java,
line 54
> > <https://reviews.apache.org/r/38269/diff/3/?file=1074459#file1074459line54>
> >
> >     Instead of double a triple nested SELECT, would it instead make sense to just
iterate over the clusterocnfigmapping listings and take the latest of each? So instead of
using the clusterconfig table, we're using the clusterconfigmapping table to "apply" the latest
configs?
> 
> Di Li wrote:
>     I guess the alternative approach suggested here is the Java way of what that named
query is trying to get from the database. Actually, I thought about iterating the clusterconfigmapping
table initially. But I opted to updating the named query as I think changing the query introduces
fewer changes to the code base while achieving the same result.
>     
>     Please correct me if I am wrong, still new and learning...
> 
> Jonathan Hurley wrote:
>     Your solution will work - it's just that when you have 2 nested select statements
then there might be a better way to accomplish what you're trying to do. In this case, we
need to find the latest applicable configuration for a given stack - not the latest configuration.
Since the config group change is a new entry in clusterconfig but it's the mapping in clusterconfigmapping
we're after, we probably don't want to do all of the SELECT filtering on clusterconfig.
>     
>     I think in this case, it's probably best to introduce a new named query that gets
you the data you want directly from the clusterconfigmapping table and then use the tags from
that list to mark the appropirate entities as "selected".

Hello Jonathan,

Please find the latest patch uploaded as my attempt to use entities from the clusterconfigmapping
table and iterate thru them in Java in order to set the selected to 1 for the latest config
of a give type of a given stack id.

Thanks.


- Di


-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/38269/#review99227
-----------------------------------------------------------


On Sept. 16, 2015, 5:14 p.m., Di Li wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/38269/
> -----------------------------------------------------------
> 
> (Updated Sept. 16, 2015, 5:14 p.m.)
> 
> 
> Review request for Ambari, Alejandro Fernandez, Jonathan Hurley, and Nate Cole.
> 
> 
> Bugs: AMBARI-12949
>     https://issues.apache.org/jira/browse/AMBARI-12949
> 
> 
> Repository: ambari
> 
> 
> Description
> -------
> 
> 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 ClusterConfigEntity.java, 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.
> 
> 
> Investigation:
> 
> 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 ClusterDAO.java 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
back.
> 
> 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 ){
> LOG.info("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))
> { LOG.info(type + " with tag " + tag + " is selected"); configMappingEntity.setSelected(1);
}
> 
> }
> }
> 
> 
> Diffs
> -----
> 
>   ambari-server/src/main/java/org/apache/ambari/server/orm/dao/ClusterDAO.java 6e55128

>   ambari-server/src/main/java/org/apache/ambari/server/orm/entities/ClusterConfigEntity.java
899ffe8 
>   ambari-server/src/main/java/org/apache/ambari/server/state/cluster/ClusterImpl.java
a48fb54 
>   ambari-server/src/test/java/org/apache/ambari/server/orm/dao/ServiceConfigDAOTest.java
4c186b5 
> 
> Diff: https://reviews.apache.org/r/38269/diff/
> 
> 
> Testing
> -------
> 
> unit test: added more test cases to ambari-server code
> test on a rolling upgrade then downgrade.
> 
> 
> Thanks,
> 
> Di Li
> 
>


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