Agent Management: Introduce support for template variables

CHANGELOG.md

@@ -10,6 +10,10 @@ internal API changes are not present.
 Main (unreleased)
 -----------------
 
+### Features
+
+- Agent Management: Introduce support for templated configuration. (@jcreixell)
+
 ### Bugfixes
 
 - Permit `X-Faro-Session-ID` header in CORS requests for the `faro.receiver`

docs/sources/static/configuration/agent-management.md

@@ -123,7 +123,6 @@ selector:
 
 > **Note:** Snippet selection is currently done in the API server. This behaviour is subject to change in the future.
 
-
 ### Example response body
 
 ```yaml
@@ -164,3 +163,9 @@ snippets:
       os: linux
       app: app1
 ```
+
+> **Note:** Base configurations and snippets can contain go's [text/template](https://pkg.go.dev/text/template) actions. If you need preserve the literal value of a template action, you can escape it using backticks. For example:
+
+```
+{{ `{{ .template_var }}` }}
+```

pkg/config/agent_management_remote_config_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 	"time"
 
+	process_exporter "github.com/grafana/agent/pkg/integrations/process_exporter"
 	"github.com/grafana/agent/pkg/metrics/instance"
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/model/labels"
@@ -182,6 +183,82 @@ integration_configs:
 		require.Equal(t, 5*time.Second, c.Integrations.ConfigV1.IntegrationRestartBackoff)
 	})
 
+	t.Run("template variables provided", func(t *testing.T) {
+		baseConfig := `
+server:
+    log_level: {{.log_level}}
+`
+		templateInsideTemplate := "`{{ .template_inside_template }}`"
+		snippet := Snippet{
+			Config: `
+integration_configs:
+  process_exporter:
+    enabled: true
+    process_names:
+      - name: "grafana-agent"
+        cmdline:
+          - 'grafana-agent'
+      - name: "{{.nonexistent.foo.bar.baz.bat}}"
+        cmdline:
+          - "{{ ` + templateInsideTemplate + ` }}"
+      # Custom process monitors
+      {{- range $key, $value := .process_exporter_processes }}
+      - name: "{{ $value.name }}"
+        cmdline:
+          - "{{ $value.cmdline }}"
+        {{if $value.exe}}
+        exe:
+          - "{{ $value.exe }}"
+        {{end}}
+      {{- end }}
+`,
+		}
+
+		rc := RemoteConfig{
+			BaseConfig: BaseConfigContent(baseConfig),
+			Snippets:   []Snippet{snippet},
+			AgentMetadata: AgentMetadata{
+				TemplateVariables: map[string]any{
+					"log_level": "debug",
+					"process_exporter_processes": []map[string]string{
+						{
+							"name":    "java_processes",
+							"cmdline": ".*/java",
+						},
+						{
+							"name":    "{{.ExeFull}}:{{.Matches.Cfgfile}}",
+							"cmdline": `-config.path\\s+(?P<Cfgfile>\\S+)`,
+							"exe":     "/usr/local/bin/process-exporter",
+						},
+					},
+				},
+			},
+		}
+
+		c, err := rc.BuildAgentConfig()
+		require.NoError(t, err)
+		require.Equal(t, 1, len(c.Integrations.ConfigV1.Integrations))
+		processExporterConfig := c.Integrations.ConfigV1.Integrations[0].Config.(*process_exporter.Config)
+
+		require.Equal(t, 4, len(processExporterConfig.ProcessExporter))
+
+		require.Equal(t, "grafana-agent", processExporterConfig.ProcessExporter[0].Name)
+		require.Equal(t, "grafana-agent", processExporterConfig.ProcessExporter[0].CmdlineRules[0])
+		require.Equal(t, 0, len(processExporterConfig.ProcessExporter[0].ExeRules))
+
+		require.Equal(t, "<no value>", processExporterConfig.ProcessExporter[1].Name)
+		require.Equal(t, "{{ .template_inside_template }}", processExporterConfig.ProcessExporter[1].CmdlineRules[0])
+		require.Equal(t, 0, len(processExporterConfig.ProcessExporter[1].ExeRules))
+
+		require.Equal(t, "java_processes", processExporterConfig.ProcessExporter[2].Name)
+		require.Equal(t, ".*/java", processExporterConfig.ProcessExporter[2].CmdlineRules[0])
+		require.Equal(t, 0, len(processExporterConfig.ProcessExporter[2].ExeRules))
+
+		require.Equal(t, "{{.ExeFull}}:{{.Matches.Cfgfile}}", processExporterConfig.ProcessExporter[3].Name)
+		require.Equal(t, `-config.path\s+(?P<Cfgfile>\S+)`, processExporterConfig.ProcessExporter[3].CmdlineRules[0])
+		require.Equal(t, "/usr/local/bin/process-exporter", processExporterConfig.ProcessExporter[3].ExeRules[0])
+	})
+
 	t.Run("no external labels provided", func(t *testing.T) {
 		rc := RemoteConfig{
 			BaseConfig: BaseConfigContent(baseConfig),

pkg/config/agentmanagement_remote_config.go

@@ -1,6 +1,9 @@
 package config
 
 import (
+	"bytes"
+	"text/template"
+
 	"github.com/grafana/agent/pkg/integrations"
 	"github.com/grafana/agent/pkg/logs"
 	"github.com/grafana/agent/pkg/metrics/instance"
@@ -28,7 +31,8 @@ type (
 	}
 
 	AgentMetadata struct {
-		ExternalLabels map[string]string `json:"external_labels,omitempty" yaml:"external_labels,omitempty"`
+		ExternalLabels    map[string]string `json:"external_labels,omitempty" yaml:"external_labels,omitempty"`
+		TemplateVariables map[string]any    `json:"template_variables,omitempty" yaml:"template_variables,omitempty"`
 	}
 
 	// SnippetContent defines the internal structure of a snippet configuration.
@@ -55,8 +59,13 @@ func NewRemoteConfig(buf []byte) (*RemoteConfig, error) {
 
 // BuildAgentConfig builds an agent configuration from a base config and a list of snippets
 func (rc *RemoteConfig) BuildAgentConfig() (*Config, error) {
+	baseConfig, err := evaluateTemplate(string(rc.BaseConfig), rc.AgentMetadata.TemplateVariables)
+	if err != nil {
+		return nil, err
+	}
+
 	c := DefaultConfig()
-	err := yaml.Unmarshal([]byte(rc.BaseConfig), &c)
+	err = yaml.Unmarshal([]byte(baseConfig), &c)
 	if err != nil {
 		return nil, err
 	}
@@ -66,15 +75,15 @@ func (rc *RemoteConfig) BuildAgentConfig() (*Config, error) {
 		return nil, err
 	}
 
-	err = appendSnippets(&c, rc.Snippets)
+	err = appendSnippets(&c, rc.Snippets, rc.AgentMetadata.TemplateVariables)
 	if err != nil {
 		return nil, err
 	}
 	appendExternalLabels(&c, rc.AgentMetadata.ExternalLabels)
 	return &c, nil
 }
 
-func appendSnippets(c *Config, snippets []Snippet) error {
+func appendSnippets(c *Config, snippets []Snippet, templateVars map[string]any) error {
 	metricsConfigs := instance.DefaultConfig
 	metricsConfigs.Name = "snippets"
 	logsConfigs := logs.InstanceConfig{
@@ -91,8 +100,13 @@ func appendSnippets(c *Config, snippets []Snippet) error {
 	}
 
 	for _, snippet := range snippets {
+		snippetConfig, err := evaluateTemplate(snippet.Config, templateVars)
+		if err != nil {
+			return err
+		}
+
 		var snippetContent SnippetContent
-		err := yaml.Unmarshal([]byte(snippet.Config), &snippetContent)
+		err = yaml.Unmarshal([]byte(snippetConfig), &snippetContent)
 		if err != nil {
 			return err
 		}
@@ -148,3 +162,18 @@ func appendExternalLabels(c *Config, externalLabels map[string]string) {
 		c.Logs.Global.ClientConfigs[i].ExternalLabels.LabelSet = logsExternalLabels.Merge(cc.ExternalLabels.LabelSet)
 	}
 }
+
+func evaluateTemplate(config string, templateVariables map[string]any) (string, error) {
+	tpl, err := template.New("config").Parse(config)
+	if err != nil {
+		return "", err
+	}
+
+	var buf bytes.Buffer
+	err = tpl.Execute(&buf, templateVariables)
+	if err != nil {
+		return "", err
+	}
+
+	return buf.String(), nil
+}