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From "Sunil Govindan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SUBMARINE-47) Provide an implementation to parse configuration values from a YAML file
Date Tue, 02 Apr 2019 05:11:00 GMT

    [ https://issues.apache.org/jira/browse/SUBMARINE-47?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16807408#comment-16807408
] 

Sunil Govindan commented on SUBMARINE-47:
-----------------------------------------

Thanks [~snemeth]

Few more comments.
 # Since u made some typos corrected, pls change this as well "pre-destributed" ==> "pre-distributed"
in RunJobCli.java
 # In {{createParametersHolder}}, what if "-f job.yaml" is given with some more cli params.
If we are not doing fail-fast (I think thats my thought), it is better to print a line in
the console stating all CLI params will be skipped as we consider only file.
 # In YamlParseException, mostly it is using super methods to print the cause. Since submarine
is CLI driven, how bulky these exceptions traces will look like in console if any failure
happens in parsing. Lets me try to cover some cases.
 ## If file doesn't exist, a simple cleaner message in console is enough to state that the
file is not present or invalid file.
 ## If file contents are empty or in not a parsable format, we should show some more exception
details.
 ## Now coming to some parsing error due to some sections are not correctly indented or wrongly
given, will we show the line number in exception stating that this line has some issues in
parsing.?
 # initGenericConfigs doesnt needs last param yamlConfig.getConfigs() as yamlConfig itself
is passed as first param.
 # In methods line initTensorBoard, initSecurity and etc, an initial null check is done
to see whether section exists. What is the value is not configured in sub sections such as TENSORBOARD_DOCKER_IMAGE
is empty or PRINCIPAL is empty etc. Are we putting "null" as value to each of these key values
in the final map now ?
 ## If this is the case, we need to ensure methods like convertToEnvsList  doesnt throw NPE.
 ## And some more test cases are also needed, where one param in each subsection is not configured
if its not already added as a test case in this patch.
 # Please add javadoc for public methods like hasOption etc.
 # All LOG.debug need to be wrapped with LOG.isDebugEnabled. For ex: ParametersHolder.java:269

> Provide an implementation to parse configuration values from a YAML file
> ------------------------------------------------------------------------
>
>                 Key: SUBMARINE-47
>                 URL: https://issues.apache.org/jira/browse/SUBMARINE-47
>             Project: Hadoop Submarine
>          Issue Type: New Feature
>            Reporter: Szilard Nemeth
>            Assignee: Szilard Nemeth
>            Priority: Major
>         Attachments: SUBMARINE-47.001.patch, SUBMARINE-47.002.patch, SUBMARINE-47.002.patch,
SUBMARINE-47.003.patch, SUBMARINE-47.003.patch, SUBMARINE-47.004.patch, SUBMARINE-47.005.patch,
valid-config.yaml
>
>
> In the Submarine design doc ([https://docs.google.com/document/d/199J4pB3blqgV9SCNvBbTqkEoQdjoyGMjESV4MktCo0k/edit#heading=h.klmv5hrbgx9l]),
under section "Job commands" (submarine job run), the document talks about the need to implement
a YAML parser as an alternative configuration source of Submarine.
>  This jira provides an implementation of this YAML configuration parser.
> *Some details on the implementation:*
> *Data model and YAML library:* 
>  SnakeYAML was the library of choice, as we already include it in other Hadoop maven
modules.
>  SnakeYAML requires data classes to parse the YAML structure into Java classes, this
is very similar to parsing JSON data.
>  The data classes are under this package: org.apache.hadoop.yarn.submarine.client.cli.param.yaml
>  The data model is the following: 
>  1. On the root level, we have the class YamlConfigFile. This class has fields for configs,
roles, scheduling, etc.
>  2. Class Configs is a class that stores various config values.
>  3. We have the class Roles, that stores the role configurations, currently we only have
Worker and Ps (ParameterServer).
>  4. There's a base class for Roles, called Role. For some reasons, SnakeYAML did not
like this class as an abstract class, but it's not that important to have it like that, so
I stopped caring.
> There are several other data classes, please note that all of these classes are trying
to "mirror" the example YAML file from the design doc, so you can check that for more details.
> *Testing:* 
>  Added a new class called TestRunJobCliParsingYaml that exclusively verifies the correctness
of YAML parsing.
>  I tried to define the names of the testcases as descriptive and easy to understand as
possible.
>  Covering some edge cases was also a quite important factor, like checking how parsing
handles non-existing files, empty files, etc.
> *ParameterHolder:*
> In order to minimize changes in RunJobParameters, I introduced a ParameterHolder class
that is passed RunJobParameters#updateParametersByParsedCommandline instead of the parsed
CLI object we had before. This way, I could use the ParameterHolder to store the parsed CLI
values along with parsed YAML values, so it's a single source of configuration. This class
can act as a "decision point" about future needs on value precedences: For example, if we
want to have precedence for some configs coming from the CLI over the same configs coming
from the YAML file (or vica-versa), it is easily doable with the current implementation.
>  Currently, all values coming from the YAML config are in precedence.
> *What CLI options are covered by YAML:*
> Every CLI option have it's YAML counterpart, so the coverage is 100%.
>  See this method for all the available options: RunJobCli#generateOptions.
>  However, the design doc contains 2 fields (called reservation and placement) under the
'scheduling' section that are not added to the YAML data classes. The reason for this is that
I haven't found any implementation for these properties with the original CLI parser, either.
> *Questions:* 
>  1. Do we want to allow mixing of CLI configs and YAML configs? We could either fail-fast
if a config is defined twice. With my current implementation, the values coming from YAML
always have precedence over CLI values, so defining a config twice is not an error case yet.
>  2. What types of roles should we allow? Is there any additional apart from Worker and
Ps?
>  



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