feat: refactor using cache for GitHub (#19)

* feat: refactor using cache for GitHub

* chore: fixed linting

.golangci.yml

@@ -47,3 +47,4 @@ linters:
     - nosnakecase
     - ifshort
     - gci
+    - depguard

pkg/config/config.go

@@ -11,23 +11,23 @@ import (
 )
 
 type LogConfig struct {
-	LogLevel   string    `toml:"level" default:"info"`
-	JSONOutput null.Bool `toml:"json" default:"false"`
+	LogLevel   string    `default:"info"  toml:"level"`
+	JSONOutput null.Bool `default:"false" toml:"json"`
 }
 
 type TendermintConfig struct {
-	Enabled       null.Bool `toml:"enabled" default:"true"`
-	Address       string    `toml:"address" default:"http://localhost:26657"`
-	QueryUpgrades null.Bool `toml:"query-upgrades" default:"true"`
+	Enabled       null.Bool `default:"true"                   toml:"enabled"`
+	Address       string    `default:"http://localhost:26657" toml:"address"`
+	QueryUpgrades null.Bool `default:"true"                   toml:"query-upgrades"`
 }
 
 type GithubConfig struct {
-	Repository string `toml:"repository" default:""`
+	Repository string `default:""   toml:"repository"`
 	Token      string `toml:"token"`
 }
 
 type CosmovisorConfig struct {
-	Enabled         null.Bool `toml:"enabled" default:"true"`
+	Enabled         null.Bool `default:"true"           toml:"enabled"`
 	ChainBinaryName string    `toml:"chain-binary-name"`
 	ChainFolder     string    `toml:"chain-folder"`
 	CosmovisorPath  string    `toml:"cosmovisor-path"`
@@ -38,7 +38,7 @@ type Config struct {
 	TendermintConfig TendermintConfig `toml:"tendermint"`
 	CosmovisorConfig CosmovisorConfig `toml:"cosmovisor"`
 	GithubConfig     GithubConfig     `toml:"github"`
-	ListenAddress    string           `toml:"listen-address" default:":9500"`
+	ListenAddress    string           `default:":9500"   toml:"listen-address"`
 }
 
 func (c *GithubConfig) Validate() error {

pkg/constants/constants.go

@@ -1,9 +1,13 @@
 package constants
 
-import "regexp"
+import (
+	"regexp"
+	"time"
+)
 
 const (
-	MetricsPrefix = "cosmos_node_exporter_"
+	MetricsPrefix           = "cosmos_node_exporter_"
+	UncachedGithubQueryTime = time.Hour
 )
 
 var (

pkg/github/github.go

@@ -33,6 +33,18 @@ func NewGithub(config *config.Config, logger *zerolog.Logger) *Github {
 	}
 }
 
+func (g *Github) UseCache() bool {
+	// If the last result is not present - do not use cache, for the first query.
+	if g.LastResult == nil {
+		return false
+	}
+
+	// We need to make uncached requests once in a while, to make sure everything is ok
+	// (for example, if we messed up caching itself).
+	diff := time.Since(g.LastModified)
+	return diff < constants.UncachedGithubQueryTime
+}
+
 func (g *Github) GetLatestRelease() (types.ReleaseInfo, error) {
 	latestReleaseUrl := fmt.Sprintf(
 		"https://api.github.com/repos/%s/%s/releases/latest",
@@ -49,7 +61,15 @@ func (g *Github) GetLatestRelease() (types.ReleaseInfo, error) {
 		return types.ReleaseInfo{}, err
 	}
 
-	if g.LastResult != nil {
+	useCache := g.UseCache()
+
+	g.Logger.Trace().
+		Str("url", latestReleaseUrl).
+		Bool("cached", useCache).
+		Str("time-since-latest", time.Since(g.LastModified).String()).
+		Msg("Querying GitHub")
+
+	if useCache {
 		req.Header.Set("If-Modified-Since", g.LastModified.Format(http.TimeFormat))
 	}
 
@@ -77,7 +97,7 @@ func (g *Github) GetLatestRelease() (types.ReleaseInfo, error) {
 		return releaseInfo, err
 	}
 
-	// Github returned error, probably rate-limiting
+	// GitHub returned error, probably rate-limiting
 	if releaseInfo.Message != "" {
 		return releaseInfo, fmt.Errorf("got error from Github: %s", releaseInfo.Message)
 	}