Merge pull request Cloud-Foundations#168 from rgooch/master

filegen-server: add LookupGeneratorVariable and Contains template functions.

Author: rgooch

cmd/filegen-server/README.md

@@ -77,12 +77,13 @@ The configuration file contains zero or more lines of the form:
 use to generate data for the specified *pathname*. The following generator types
 are supported:
 
-- **DynamicTemplateFile** pathname *filename*: the contents of *filename* are
-  used as a template to generate the file data. If the file contains sections of
-  the form `{{.MyVar}}` then the value of the `MyVar` variable from the MDB for
-  the host are used to replace the section. If *filename* changes (replaced with
-  a different inode), then the data are regenerated and distributed to all
-  machines
+- **DynamicTemplateFile** pathname *filename* [*variablesFile*]: the contents of
+  *filename* are used as a template to generate the file data. If the file
+  contains sections of the form `{{.MyVar}}` then the value of the `MyVar`
+  variable from the MDB for the host are used to replace the section. If
+  *filename* changes (replaced with a different inode), then the data are
+  regenerated and distributed to all machines. If specified, optional key:value
+  pairs are loaded from the *variablesFile* in JSON format
 
 - **File** pathname *filename*: the contents of *filename* are used to provide
   the file data. If *filename* changes (replaced with a different inode), then
@@ -108,10 +109,12 @@ are supported:
   be written to the standard output in JSON format, stored in the `Data` and
   `SecondsValid` fields.
 
-- **StaticTemplateFile** pathname *filename*: the contents of *filename* are
-  used as a template to generate the file data. If the file contains sections of
-  the form `{{.MyVar}}` then the value of the `MyVar` variable from the MDB for
-  the host are used to replace the section
+- **StaticTemplateFile** pathname *filename* [*variablesFile*]: the contents of
+  *filename* are used as a template to generate the file data. If the file
+  contains sections of the form `{{.MyVar}}` then the value of the `MyVar`
+  variable from the MDB for the host are used to replace the section. If
+  specified, optional key:value pairs are loaded from the *variablesFile* in
+  JSON format
 
 - **URL** pathname *url*: a HTTP POST request will be sent to the URL specified
   by *url* containing JSON-encoded MDB data in the request body. The *pathname*
@@ -222,8 +225,10 @@ These template files use the go [text/template](https://pkg.go.dev/text/template
 standard package. Template functions can be defined and added to the funcMap to process
 MDB fields in the template. The following template functions are available:
 
+* `Contains`: returns `true` if the second string is contained in the first
 * `GetSplitPart`: splits a string based on the given separator, then returns a
-                substring given the index of the split array
+                  substring given the index of the split array
+* `LookupGeneratorVariable`: lookup value in the generator variables map
 * `ToLower`: returns the lowercase version of a string
 * `ToUpper`: returns the uppercase version of a string
 

lib/filegen/api.go

@@ -128,8 +128,21 @@ func (m *Manager) RegisterProgrammeForPath(pathname, programmePath string) {
 // The template file syntax is defined by the text/template standard package.
 func (m *Manager) RegisterTemplateFileForPath(pathname string,
 	templateFile string, watchForUpdates bool) error {
-	return m.registerTemplateFileForPath(pathname, templateFile,
-		watchForUpdates)
+	return m.registerTemplateFileForPath(pathname, TemplateFileConfig{
+		TemplateFile:    templateFile,
+		WatchForUpdates: watchForUpdates,
+	})
+}
+
+// RegisterTemplateFileForPathWithConfig registers a template file for a
+// specific pathname.
+// The template file is used to generate the data, modified by the machine data.
+// If the template file changes and WatchForUpdates is true, the template file
+// is re-read and the data are regenerated.
+// The template file syntax is defined by the text/template standard package.
+func (m *Manager) RegisterTemplateFileForPathWithConfig(pathname string,
+	config TemplateFileConfig) error {
+	return m.registerTemplateFileForPath(pathname, config)
 }
 
 // RegisterUrlForPath registers a URL where a HTTP POST request may be sent to
@@ -149,3 +162,9 @@ func (m *Manager) RegisterUrlForPath(pathname, URL string) {
 func (m *Manager) WriteHtml(writer io.Writer) {
 	m.writeHtml(writer)
 }
+
+type TemplateFileConfig struct {
+	TemplateFile    string
+	VariablesFile   string
+	WatchForUpdates bool
+}

lib/filegen/template.go

@@ -12,35 +12,47 @@ import (
 
 	"github.com/Cloud-Foundations/Dominator/lib/fsutil"
 	"github.com/Cloud-Foundations/Dominator/lib/hash"
+	"github.com/Cloud-Foundations/Dominator/lib/json"
 	"github.com/Cloud-Foundations/Dominator/lib/log"
 	"github.com/Cloud-Foundations/Dominator/lib/mdb"
 	"github.com/Cloud-Foundations/Dominator/lib/objectserver/memory"
 )
 
 var funcMap = template.FuncMap{
+	"Contains":     strings.Contains,
 	"GetSplitPart": getSplitPart,
-	"ToLower": strings.ToLower,
-	"ToUpper": strings.ToUpper,
+	"ToLower":      strings.ToLower,
+	"ToUpper":      strings.ToUpper,
 }
 
 type templateGenerator struct {
 	objectServer    *memory.ObjectServer
 	logger          log.Logger
 	template        *template.Template
+	variables       map[string]string
 	notifierChannel chan<- string
 }
 
 func (m *Manager) registerTemplateFileForPath(pathname string,
-	templateFile string, watchForUpdates bool) error {
+	config TemplateFileConfig) error {
 	tgen := &templateGenerator{
 		objectServer: m.objectServer,
 		logger:       m.logger}
 	tgen.notifierChannel = m.registerHashGeneratorForPath(pathname, tgen)
-	if watchForUpdates {
-		readCloserChannel := fsutil.WatchFile(templateFile, m.logger)
+	if config.VariablesFile != "" {
+		// TODO(rgooch): consider making this watch for updates.
+		variables := make(map[string]string)
+		err := json.ReadFromFile(config.VariablesFile, &variables)
+		if err != nil {
+			return err
+		}
+		tgen.variables = variables
+	}
+	if config.WatchForUpdates {
+		readCloserChannel := fsutil.WatchFile(config.TemplateFile, m.logger)
 		go tgen.handleReadClosers(readCloserChannel)
 	} else {
-		file, err := os.Open(templateFile)
+		file, err := os.Open(config.TemplateFile)
 		if err != nil {
 			return err
 		}
@@ -90,11 +102,19 @@ func (tgen *templateGenerator) handleReadCloser(
 	if err != nil {
 		return err
 	}
-	tmpl, err := template.New("generatorTemplate").Funcs(funcMap).Parse(string(data))
+	tmpl := template.New("generatorTemplate").Funcs(funcMap)
+	if tgen.variables != nil {
+		tmpl.Funcs(template.FuncMap{"LookupGeneratorVariable": tgen.lookup})
+	}
+	tmpl, err = tmpl.Parse(string(data))
 	if err != nil {
 		return err
 	}
 	tgen.template = tmpl
 	tgen.notifierChannel <- ""
 	return nil
 }
+
+func (tgen *templateGenerator) lookup(s string) string {
+	return tgen.variables[s]
+}

lib/filegen/util/load.go

@@ -18,12 +18,12 @@ type configType struct {
 }
 
 var configs = map[string]configType{
-	"DynamicTemplateFile": {1, 1, dynamicTemplateFileGenerator},
+	"DynamicTemplateFile": {1, 2, dynamicTemplateFileGenerator},
 	"File":                {1, 1, fileGenerator},
 	"MdbFieldDirectory":   {2, 3, mdbFieldDirectoryGenerator},
 	"MDB":                 {0, 0, mdbGenerator},
 	"Programme":           {1, 1, programmeGenerator},
-	"StaticTemplateFile":  {1, 1, staticTemplateFileGenerator},
+	"StaticTemplateFile":  {1, 2, staticTemplateFileGenerator},
 	"URL":                 {1, 1, urlGenerator},
 }
 
@@ -58,7 +58,14 @@ func loadConfiguration(manager *filegen.Manager, filename string) error {
 
 func dynamicTemplateFileGenerator(manager *filegen.Manager, pathname string,
 	params []string) error {
-	return manager.RegisterTemplateFileForPath(pathname, params[0], true)
+	config := filegen.TemplateFileConfig{
+		TemplateFile:    params[0],
+		WatchForUpdates: true,
+	}
+	if len(params) > 1 {
+		config.VariablesFile = params[1]
+	}
+	return manager.RegisterTemplateFileForPathWithConfig(pathname, config)
 }
 
 func fileGenerator(manager *filegen.Manager, pathname string,
@@ -98,7 +105,13 @@ func programmeGenerator(manager *filegen.Manager, pathname string,
 
 func staticTemplateFileGenerator(manager *filegen.Manager, pathname string,
 	params []string) error {
-	return manager.RegisterTemplateFileForPath(pathname, params[0], false)
+	config := filegen.TemplateFileConfig{
+		TemplateFile: params[0],
+	}
+	if len(params) > 1 {
+		config.VariablesFile = params[1]
+	}
+	return manager.RegisterTemplateFileForPathWithConfig(pathname, config)
 }
 
 func urlGenerator(manager *filegen.Manager, pathname string,