promtail: change to use viper

[daixiang0]

Signed-off-by: Xiang Dai 764524258@qq.com

Which issue(s) this PR fixes:
Fixes #520

[cyriltovena]

Thank you it's great but just like this it doesn't improve or help though it brings a lot of new dependencies.

I think if you want to take care of this we should also set default using viper, parse flag and file and merge everything together.

[daixiang0]

@Kuqd hi, i delete unrelated dependencies, now it support parse flags with default value and then read config, what do you mean about merge? looks like issue in #638?

[daixiang0]

@Kuqd met a confused issue, viper get config but can not pack them into config sturct:

Aliases:
map[string]string{}
Override:
map[string]interface {}{}
PFlags:
map[string]viper.FlagValue{"client.batch-size-bytes":viper.pflagValue{flag:(*pflag.Flag)(0xc000196c80)}, "client.batch-wait":viper.pflagValue{flag:(*pflag.Flag)(0xc000196d20)}, "client.external-labels":viper.pflagValue{flag:(*pflag.Flag)(0xc000196dc0)}, "client.max-backoff":viper.pflagValue{flag:(*pflag.Flag)(0xc000196f00)}, "client.max-retries":viper.pflagValue{flag:(*pflag.Flag)(0xc000196fa0)}, "client.min-backoff":viper.pflagValue{flag:(*pflag.Flag)(0xc000197040)}, "client.timeout":viper.pflagValue{flag:(*pflag.Flag)(0xc0001970e0)}, "client.url":viper.pflagValue{flag:(*pflag.Flag)(0xc000197180)}, "config.file":viper.pflagValue{flag:(*pflag.Flag)(0xc000197220)}, "log.level":viper.pflagValue{flag:(*pflag.Flag)(0xc0001972c0)}, "positions.file":viper.pflagValue{flag:(*pflag.Flag)(0xc000197360)}, "positions.sync-period":viper.pflagValue{flag:(*pflag.Flag)(0xc000197400)}, "server.graceful-shutdown-timeout":viper.pflagValue{flag:(*pflag.Flag)(0xc0001974a0)}, "server.grpc-listen-host":viper.pflagValue{flag:(*pflag.Flag)(0xc000197540)}, "server.grpc-listen-port":viper.pflagValue{flag:(*pflag.Flag)(0xc0001975e0)}, "server.grpc-max-concurrent-streams":viper.pflagValue{flag:(*pflag.Flag)(0xc000197680)}, "server.grpc-max-recv-msg-size-bytes":viper.pflagValue{flag:(*pflag.Flag)(0xc000197720)}, "server.grpc-max-send-msg-size-bytes":viper.pflagValue{flag:(*pflag.Flag)(0xc0001977c0)}, "server.http-idle-timeout":viper.pflagValue{flag:(*pflag.Flag)(0xc000197860)}, "server.http-listen-host":viper.pflagValue{flag:(*pflag.Flag)(0xc000197900)}, "server.http-listen-port":viper.pflagValue{flag:(*pflag.Flag)(0xc0001979a0)}, "server.http-read-timeout":viper.pflagValue{flag:(*pflag.Flag)(0xc000197a40)}, "server.http-write-timeout":viper.pflagValue{flag:(*pflag.Flag)(0xc000197ae0)}, "server.path-prefix":viper.pflagValue{flag:(*pflag.Flag)(0xc000197b80)}, "server.register-instrumentation":viper.pflagValue{flag:(*pflag.Flag)(0xc000197c20)}, "target.sync-period":viper.pflagValue{flag:(*pflag.Flag)(0xc000197cc0)}}
Env:
map[string]string{}
Key/Value Store:
map[string]interface {}{}
Config:
map[string]interface {}{"clients":[]interface {}{map[interface {}]interface {}{"url":"http://loki:3100/api/prom/push"}}, "positions":map[string]interface {}{"filename":"/tmp/positions.yaml"}, "scrape_configs":[]interface {}{map[interface {}]interface {}{"job_name":"system", "static_configs":[]interface {}{map[interface {}]interface {}{"labels":map[interface {}]interface {}{"__path__":"/var/log/*log", "job":"varlogs"}, "targets":[]interface {}{"localhost"}}}}}, "server":map[string]interface {}{"grpc_listen_port":0, "http_listen_port":9080}}
Defaults:
map[string]interface {}{}
level=error ts=2019-06-21T06:39:16.968629307Z caller=main.go:62 msg="error creating promtail" error="at least one client config should be provided"

[daixiang0]

file issue to viper

[daixiang0]

If use viper, since viper use mapstructure, so all config like "yaml: inline" shoulc convert to mapstructure: inline, or need to overvide default tagName as below:

viper.Unmarshal(&config, func(decoderConfig *mapstructure.DecoderConfig) {
		decoderConfig.TagName = "yaml"
	})

On the other hand, all UnmarshalYAML func would become useless since mapstructure do not cal it.

[sh0rez]

Closing this in favor of #980 which implements correct configuration source precedence (defaults < yaml < flag).

Thanks for your contribution!