feat: introduce print-config command (#886)

Author: Proximyst

cmd/printconfig/cmd.go

@@ -0,0 +1,26 @@
+package printconfig
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/davecgh/go-spew/spew"
+	"github.com/grafana/grafana-image-renderer/cmd/server"
+	"github.com/urfave/cli/v3"
+)
+
+func NewCmd() *cli.Command {
+	return &cli.Command{
+		Name:  "print-config",
+		Usage: "Parse and print the current configuration. Replace 'server' with 'print-config' in the command line.",
+		Flags: server.NewCmd().Flags,
+		Action: func(ctx context.Context, c *cli.Command) error {
+			cfg, err := server.ParseConfig(c)
+			if err != nil {
+				return fmt.Errorf("failed to parse config: %w", err)
+			}
+			spew.Dump(cfg)
+			return nil
+		},
+	}
+}

cmd/root.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 
 	"github.com/grafana/grafana-image-renderer/cmd/healthcheck"
+	"github.com/grafana/grafana-image-renderer/cmd/printconfig"
 	"github.com/grafana/grafana-image-renderer/cmd/sandbox"
 	"github.com/grafana/grafana-image-renderer/cmd/server"
 	"github.com/grafana/grafana-image-renderer/pkg/config"
@@ -41,6 +42,7 @@ func NewRootCmd() *cli.Command {
 			healthcheck.NewCmd(),
 			server.NewCmd(),
 			sandbox.NewCmd(),
+			printconfig.NewCmd(),
 		},
 	}
 }

cmd/server/cmd.go

@@ -26,33 +26,53 @@ func NewCmd() *cli.Command {
 	}
 }
 
-func run(ctx context.Context, c *cli.Command) error {
-	_, err := maxprocs.Set(
-		// We use maxprocs over automaxprocs because we need a new minimum value.
-		// 2 is the absolute minimum we can handle, because we use multiple goroutines many places for timeouts.
-		maxprocs.Min(2),
-		maxprocs.Logger(maxProcsLog))
-	if err != nil {
-		slog.Info("failed to set GOMAXPROCS", "err", err)
-	}
+type Cfg struct {
+	server    config.ServerConfig
+	browser   config.BrowserConfig
+	tracing   config.TracingConfig
+	rateLimit config.RateLimitConfig
+}
 
+func ParseConfig(c *cli.Command) (*Cfg, error) {
 	serverConfig, err := config.ServerConfigFromCommand(c)
 	if err != nil {
-		return fmt.Errorf("failed to parse server config: %w", err)
+		return nil, fmt.Errorf("failed to parse server config: %w", err)
 	}
 	browserConfig, err := config.BrowserConfigFromCommand(c)
 	if err != nil {
-		return fmt.Errorf("failed to parse browser config: %w", err)
+		return nil, fmt.Errorf("failed to parse browser config: %w", err)
 	}
 	tracingConfig, err := config.TracingConfigFromCommand(c)
 	if err != nil {
-		return fmt.Errorf("failed to parse tracing config: %w", err)
+		return nil, fmt.Errorf("failed to parse tracing config: %w", err)
 	}
 	rateLimitConfig, err := config.RateLimitConfigFromCommand(c)
 	if err != nil {
-		return fmt.Errorf("failed to parse process tracker config: %w", err)
+		return nil, fmt.Errorf("failed to parse process tracker config: %w", err)
+	}
+	return &Cfg{
+		server:    serverConfig,
+		browser:   browserConfig,
+		tracing:   tracingConfig,
+		rateLimit: rateLimitConfig,
+	}, nil
+}
+
+func run(ctx context.Context, c *cli.Command) error {
+	_, err := maxprocs.Set(
+		// We use maxprocs over automaxprocs because we need a new minimum value.
+		// 2 is the absolute minimum we can handle, because we use multiple goroutines many places for timeouts.
+		maxprocs.Min(2),
+		maxprocs.Logger(maxProcsLog))
+	if err != nil {
+		slog.Info("failed to set GOMAXPROCS", "err", err)
+	}
+
+	cfg, err := ParseConfig(c)
+	if err != nil {
+		return fmt.Errorf("failed to parse config: %w", err)
 	}
-	tracerProvider, err := traces.NewTracerProvider(ctx, tracingConfig)
+	tracerProvider, err := traces.NewTracerProvider(ctx, cfg.tracing)
 	if err != nil {
 		return fmt.Errorf("failed to set up tracer: %w", err)
 	}
@@ -62,15 +82,15 @@ func run(ctx context.Context, c *cli.Command) error {
 		otel.SetTracerProvider(tracerProvider)
 		otel.SetTextMapPropagator(propagation.TraceContext{})
 	}
-	processStatService := service.NewProcessStatService(rateLimitConfig)
-	browser := service.NewBrowserService(browserConfig, processStatService)
+	processStatService := service.NewProcessStatService(cfg.rateLimit)
+	browser := service.NewBrowserService(cfg.browser, processStatService)
 	versions := service.NewVersionService()
 	metrics := metrics.NewRegistry()
-	handler, err := api.NewHandler(metrics, serverConfig, rateLimitConfig, processStatService, browser, versions)
+	handler, err := api.NewHandler(metrics, cfg.server, cfg.rateLimit, processStatService, browser, versions)
 	if err != nil {
 		return fmt.Errorf("failed to create API handler: %w", err)
 	}
-	return api.ListenAndServe(ctx, serverConfig, handler)
+	return api.ListenAndServe(ctx, cfg.server, handler)
 }
 
 func maxProcsLog(format string, args ...any) {

docs/sources/flags.md

@@ -147,3 +147,25 @@ This is a verbatim copy of the output of the `grafana-image-renderer server --he
 --tracing.trusted-certificate=<string> [${TRACING_TRUSTED_CERTIFICATE}]
     A path to a PEM-encoded certificate to use as a trusted root when connecting to the tracing endpoint over gRPC or HTTPS. [config: tracing.trusted_certificate]
 ```
+
+## Debug the configuration
+
+{{< admonition type="note" >}}
+The command recommended here prints secrets and sensitive information in
+plain text. Be careful when sharing the output or storing it in logs.
+{{< /admonition >}}
+
+When the service doesn't appear to be working as expected, it can be because the
+configuration is invalid. If the flags are invalid, the service won't start, but
+the configuration files may contain unknown keys and thus silently ignore them.
+
+To debug that the configuration is valid and what you expect, you can get a full
+dump of the Go structures representing the configuration by running the
+`print-config` command. For example:
+
+```
+docker run --rm -v ./config.json:/home/nonroot/config.json grafana/grafana-image-renderer:latest print-config
+```
+
+The command takes the exact same flags and configuration files as the `server`
+command does.

docs/sources/troubleshooting.md

@@ -381,3 +381,25 @@ To identify whether this applies to you, check whether the `newPDFRendering`
 feature flag has been explicitly set to `false` in Grafana's configuration.
 
 To solve this problem, remove the feature toggle override.
+
+## Debug the configuration
+
+{{< admonition type="note" >}}
+The command recommended here prints secrets and sensitive information in
+plain text. Be careful when sharing the output or storing it in logs.
+{{< /admonition >}}
+
+When the service doesn't appear to be working as expected, it can be because the
+configuration is invalid. If the flags are invalid, the service won't start, but
+the configuration files may contain unknown keys and thus silently ignore them.
+
+To debug that the configuration is valid and what you expect, you can get a full
+dump of the Go structures representing the configuration by running the
+`print-config` command. For example:
+
+```
+docker run --rm -v ./config.json:/home/nonroot/config.json grafana/grafana-image-renderer:latest print-config
+```
+
+The command takes the exact same flags and configuration files as the `server`
+command does.

go.mod

@@ -5,6 +5,7 @@ go 1.25.3
 require (
 	github.com/Masterminds/semver/v3 v3.4.0
 	github.com/chromedp/cdproto v0.0.0-20250803210736-d308e07a266d
+	github.com/davecgh/go-spew v1.1.1
 	github.com/docker/docker v28.3.3+incompatible
 	github.com/docker/go-connections v0.6.0
 	github.com/gen2brain/go-fitz v1.24.15
@@ -45,7 +46,6 @@ require (
 	github.com/containerd/log v0.1.0 // indirect
 	github.com/containerd/platforms v0.2.1 // indirect
 	github.com/cpuguy83/dockercfg v0.3.2 // indirect
-	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/distribution/reference v0.6.0 // indirect
 	github.com/docker/go-units v0.5.0 // indirect
 	github.com/ebitengine/purego v0.9.0 // indirect

scripts/help-documentation/help.md.tmpl

@@ -50,3 +50,25 @@ This is a verbatim copy of the output of the `grafana-image-renderer server --he
 ```
 {{.Help}}
 ```
+
+## Debug the configuration
+
+{{"{{< admonition type=\"note\" >}}"}}
+The command recommended here prints secrets and sensitive information in
+plain text. Be careful when sharing the output or storing it in logs.
+{{"{{< /admonition >}}"}}
+
+When the service doesn't appear to be working as expected, it can be because the
+configuration is invalid. If the flags are invalid, the service won't start, but
+the configuration files may contain unknown keys and thus silently ignore them.
+
+To debug that the configuration is valid and what you expect, you can get a full
+dump of the Go structures representing the configuration by running the
+`print-config` command. For example:
+
+```
+docker run --rm -v ./config.json:/home/nonroot/config.json grafana/grafana-image-renderer:latest print-config
+```
+
+The command takes the exact same flags and configuration files as the `server`
+command does.

scripts/help-documentation/main.go

@@ -6,7 +6,6 @@ import (
 	_ "embed"
 	"fmt"
 	"io"
-	"log/slog"
 	"maps"
 	"os"
 	"path/filepath"
@@ -27,7 +26,7 @@ type templateData struct {
 
 func main() {
 	if err := run(); err != nil {
-		slog.Error("failed to run", "err", err)
+		fmt.Println("application error:", err)
 		os.Exit(1)
 	}
 }
@@ -60,33 +59,32 @@ func run() error {
 		return fmt.Errorf("failed to execute template: %w", err)
 	}
 
-	gitRoot := findGitRoot()
-	if gitRoot == "" {
-		return fmt.Errorf("failed to find git root")
+	gitRoot, err := findGitRoot()
+	if err != nil {
+		return fmt.Errorf("failed to find git root: %w", err)
 	}
 
 	helpFile := filepath.Join(gitRoot, "docs", "sources", "flags.md")
 	if err := os.WriteFile(helpFile, buffer.Bytes(), 0644); err != nil {
 		return fmt.Errorf("failed to write help file to %q: %w", helpFile, err)
 	}
 
-	slog.Info("wrote help", "file", helpFile)
+	fmt.Println("Help documentation generated at", helpFile)
 	return nil
 }
 
-func findGitRoot() string {
+func findGitRoot() (string, error) {
 	dir, err := os.Getwd()
 	if err != nil {
-		slog.Error("failed to get current working directory", "err", err)
-		os.Exit(1)
+		return "", fmt.Errorf("failed to get working directory: %w", err)
 	}
 	for {
 		if _, err := os.Stat(filepath.Join(dir, ".git")); err == nil {
-			return dir
+			return dir, nil
 		}
 		dir = filepath.Dir(dir)
 		if dir == "/" {
-			return ""
+			return "", fmt.Errorf("git root not found")
 		}
 	}
 }