Hello All,
I would like to discuss the method we use to manage default options. I believe
it can be significantly simplified.
Please read though and comment.
Thank you,
Alon Bar-Lev
---
CURRENT STATE
Most options are located in three different locations.
Let's explain by example... The FenceQuietTimeBetweenOperationsInSec option.
---
ConfigValues.java
---
public enum ConfigValues {
<snip>
@Reloadable
@TypeConverterAttribute(Integer.class)
@DefaultValueAttribute("180")
FenceQuietTimeBetweenOperationsInSec(30),
<snip>
}
---
---
0000_config.sql
---
<snip>
select
fn_db_add_config_value('FenceQuietTimeBetweenOperationsInSec','180','general');
<snip>
---
---
engine-config.properties
---
<snip>
FenceQuietTimeBetweenOperationsInSec.type=Integer
FenceQuietTimeBetweenOperationsInSec.validValues=60..600
FenceQuietTimeBetweenOperationsInSec.description="Fence quiet time between
operations (in seconds)"
FenceQuietTimeBetweenOperationsInSec.alternateKey=Fence_Quiet_Time
<snip>
---
ConfigValues.java is the base, it defines all options and appropriate metadata
as annotations. It defines the option name, type, default value, and if
reloadable.
0000_config.sql adds all parameters into the database using their default
value, we actually duplicate the parameter name and default value into the sql
script. Please note that even if we do not add the parameter to the database
the engine infrastructure will use the default value specify at ConfigValues.
engine-config.properties is used as an interface to engine-config utility, a
command-line utility that can manipulate engine options. engine-config manages
only options that are specified in this property files. Property files
specifies user friendly description, valid values, alias, but duplicate the
option name and type that already specified in ConfigValues. engine-config will
only manage options that exists in database.
QUESTIONS
1. Why do we store default values in database?
>From what I managed to gather, we store default values in database under the
>assumption that we need to keep defaults when we upgrade from one version to
>another.
However, in most cases when upgrading an application the new defaults should
apply as long as they were not overridden by user. Keeping old default as a new
value is an exception that can be taken care of during the upgrade process for
selected options.
2. Why do we keep properties file?
In practice we could specify the metadata within the property files as
annotations in ConfigValues.java. So why do we actually need the properties
file?
>From what I managed to gather, we use the property file as an interface to
>support personal, to allow adding/removing options exposed to the
>engine-config utility. An addition of option to the property file exposes it.
SUGGESTED STATE
Establish a single place to manage options.
Do not store default values in database.
Provide alternate method of exposing internal options to engine-config utility.
---
ConfigValues.java
---
public enum ConfigValues {
<snip>
@Reloadable
@Public
@TypeConverterAttribute(Integer.class)
@Restriction.IntegerRange(60, 600)
@DefaultValueAttribute("180")
@Description("Fence quiet time between operations (in seconds)")
FenceQuietTimeBetweenOperationsInSec(30),
<snip>
}
---
BENEFITS
No duplication of option name, type, default value, etc... between multiple
files. One place to role them all.
Simpler upgrade sequence, in most cases as we do want the new defaults to apply.
METHOD
1. Add @Public annotation for ConfigValues, to expose options to engine-config
instead of the properties file.
2. Add @Restrict annotation for ConfigValues, instead of validValues of
properties file.
3. Add @Description annotation for ConfigValues, instead of description of
properties file.
4. Add engine-config --internal parameter to allow get/set/list of none @Public
option, instead of the need to update the properties file.
5. Modify enigne-config [set] to add option if does not exist in database and
does not match default value.
6. Modify engine-config [set] to delete option if value matches default value.
7. Modify engine-config [get] to retrieve default from ConfigValues if value is
missing from database.
8. Create upgrade script which deletes all options with value that matches the
default from the database.
IMPLICATIONS
The option alias is removed. Can be added at later time if required using own
@Alias annotation. Not sure it is actually required.
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