98 lines
2.6 KiB
Markdown
98 lines
2.6 KiB
Markdown
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# ADR 013: Observability
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## Changelog
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- 20-01-2020: Initial Draft
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## Status
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Proposed
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## Context
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There has been discussion around exposing more metrics to users and node operators about the application. Currently there is only a way to expose metrics from Tendermint and not the application itself. To bring more visibility into applications, I would like to propose reporting of metrics through [Prometheus](https://prometheus.io/).
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Extending `AppModuleBasic` to support registering of metrics would enable developers to see more information about individual modules.
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```go
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type AppModuleBasic interface {
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Name() string
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RegisterCodec(*codec.Codec)
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RegisterMetrics(namespace string, labelsAndValues... string) *Metrics
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// genesis
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DefaultGenesis() json.RawMessage
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ValidateGenesis(json.RawMessage) error
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// client functionality
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RegisterRESTRoutes(context.CLIContext, *mux.Router)
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GetTxCmd(*codec.Codec) *cobra.Command
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GetQueryCmd(*codec.Codec) *cobra.Command
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}
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// .....
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func (bm BasicManager) RegisterMetrics(appName string, labelsAndValues... string) MetricsProvider {
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for _, b := range bm {
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b.CreateMetrics(appName, labelsAndValues)
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}
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}
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```
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Each module can define its own `Metrics` type and`CreateMetrics` function in the x/<module>/observability/metrics.go file:
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```go
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type Metrics struct {
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Size metrics.Guage
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Transactions metrics.Counter
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}
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func CreateMetrics(namespace string, labelsAndValues... string) *Metrics {
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labels := make([]string, len(labelsAndValues/2))
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for i := 0; i < len(labelsAndValues); i += 2 {
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labels[i/2] = labelsAndValues[i]
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}
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return &Metrics{
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Size: prometheus.NewGaugeFrom(stdprometheus.GaugeOpts{
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Namespace: namespace,
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Subsystem: "subsystem",
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Name: "size",
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Help: "Size of the custom metric",
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}, labels).With(labelsAndValues...),
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Transactions: prometheus.NewCounterFrom(stdprometheus.CounterOpts{
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Namespace: namespace,
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Subsystem: "subsystem",
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Name: "transactions",
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Help: "Number of transactions processed",
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}, labels).With(labelsAndValues...),
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}
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```
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To get the correct namespace for the modules changing `BasicManager` to consist of the app name is needed.
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```go
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type BasicManager struct {
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appName string
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modules map[string]AppModuleBasic
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}
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```
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## Decision
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- Use Prometheus for metric gathering.
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- Add a method to register metrics to the `AppModuleBasic` interface
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- Modules create a observability/metrics.go that defines the metrics and create the metrics object.
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## Consequences
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### Positive
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- Add more visibility into SDK based application and modules
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### Negative
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### Neutral
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## References
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