Migrate elasticsearch rollover to go

[rubenvp8510]

Part of the work for migrate away from curator #3179

Which problem is this PR solving?

• This is a first PR of the work to migrate the rollover to golang

Short description of the changes

• Extend the index client created on the index cleaner PR, added functionality to rollover, and alias handling.
• Implemented the three actions of the original rollover python script: init, rollover, lookback
• Added unit tests

Future PRs:

• add docker build and include this in ES integration tests
• remove old python implementation

[pavolloffay]

Good progress.

We should fix the PR to pass the CI and add tests.

[pavolloffay]

how are the common flags initialized?

[codecov]

Codecov Report

Merging #3242 (8778c27) into master (8427e01) will decrease coverage by 0.14%.
The diff coverage is 95.71%.

@@            Coverage Diff             @@
##           master    #3242      +/-   ##
==========================================
- Coverage   95.99%   95.85%   -0.15%     
==========================================
  Files         242      259      +17     
  Lines       14815    15398     +583     
==========================================
+ Hits        14221    14759     +538     
- Misses        514      550      +36     
- Partials       80       89       +9     

Impacted Files	Coverage Δ
cmd/collector/app/handler/grpc_handler.go	85.71% <ø> (ø)
pkg/es/client/client.go	87.03% <87.03%> (ø)
pkg/es/client/index_client.go	92.71% <92.71%> (ø)
cmd/es-rollover/app/init/action.go	93.75% <93.75%> (ø)
cmd/es-index-cleaner/app/index_filter.go	100.00% <100.00%> (ø)
cmd/es-rollover/app/actions.go	100.00% <100.00%> (ø)
cmd/es-rollover/app/flags.go	100.00% <100.00%> (ø)
cmd/es-rollover/app/index_options.go	100.00% <100.00%> (ø)
cmd/es-rollover/app/init/flags.go	100.00% <100.00%> (ø)
cmd/es-rollover/app/lookback/action.go	100.00% <100.00%> (ø)
... and 48 more

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[pavolloffay]

Looks good to me, now we should increase the test coverage.

[pavolloffay]

nit: I would rename this to align with cobra terminology - persistent flags and the function could have the same signature as config.AddFlags.

[pavolloffay]

I think it would be better if the action config structs called added flags on the genetric config and do the same for the init viper.

// AddFlags adds flags for TLS to the FlagSet.
func (c *Config) AddFlags(flags *flag.FlagSet) {
	flags.String(unit, defaultUnit, "used with lookback to remove indices from read alias e.g, days, weeks, months, years")
	flags.Int(unitCount, defaultUnitCount, "count of UNITs")
	c.Config.AddFlags(flags)
}

// InitFromViper initializes config from viper.Viper.
func (c *Config) InitFromViper(v *viper.Viper) {
	c.Unit = v.GetString(unit)
	c.UnitCount = v.GetInt(unitCount)
	c.InitFromViper(v)
}

this way caller can be sure that the object is initalized property.

[rubenvp8510]

I tried in this way and for some reason the repeated flags binds to different commands are not recognized, I was able to pass the flag, but wasn't able to recovery the value. So I leave as it is, using root persistent flags.

[rubenvp8510]

I renamed the function and changed a little bit the signature, but still use persistent flags, so I add global flags to root, and call AddFlags for other subcommands config.