package prepared_query import ( "fmt" "reflect" "regexp" "strings" "github.com/hashicorp/consul/agent/structs" "github.com/hashicorp/hil" "github.com/hashicorp/hil/ast" "github.com/mitchellh/copystructure" ) // IsTemplate returns true if the given query is a template. func IsTemplate(query *structs.PreparedQuery) bool { return query.Template.Type != "" } // CompiledTemplate is an opaque object that can be used later to render a // prepared query template. type CompiledTemplate struct { // query keeps a copy of the original query for rendering. query *structs.PreparedQuery // trees contains a map with paths to string fields in a structure to // parsed syntax trees, suitable for later evaluation. trees map[string]ast.Node // re is the compiled regexp, if they supplied one (this can be nil). re *regexp.Regexp // removeEmptyTags will cause the service tags to be stripped of any // empty strings after interpolation. removeEmptyTags bool } // Compile validates a prepared query template and returns an opaque compiled // object that can be used later to render the template. func Compile(query *structs.PreparedQuery) (*CompiledTemplate, error) { // Make sure it's a type we understand. if query.Template.Type != structs.QueryTemplateTypeNamePrefixMatch { return nil, fmt.Errorf("Bad Template.Type '%s'", query.Template.Type) } // Start compile. ct := &CompiledTemplate{ trees: make(map[string]ast.Node), removeEmptyTags: query.Template.RemoveEmptyTags, } // Make a copy of the query to use as the basis for rendering later. dup, err := copystructure.Copy(query) if err != nil { return nil, err } var ok bool ct.query, ok = dup.(*structs.PreparedQuery) if !ok { return nil, fmt.Errorf("Failed to copy query") } // Walk over all the string fields in the Service sub-structure and // parse them as HIL. parse := func(path string, v reflect.Value) error { tree, err := hil.Parse(v.String()) if err != nil { return fmt.Errorf("Bad format '%s' in Service%s: %s", v.String(), path, err) } ct.trees[path] = tree return nil } if err := walk(&ct.query.Service, parse); err != nil { return nil, err } // If they supplied a regexp then compile it. if ct.query.Template.Regexp != "" { var err error ct.re, err = regexp.Compile(ct.query.Template.Regexp) if err != nil { return nil, fmt.Errorf("Bad Regexp: %s", err) } } // Finally do a test render with the supplied name prefix. This will // help catch errors before run time, and this is the most minimal // prefix it will be expected to run with. The results might not make // sense and create a valid service to lookup, but it should render // without any errors. if _, err = ct.Render(ct.query.Name, structs.QuerySource{}); err != nil { return nil, err } return ct, nil } // Render takes a compiled template and renders it for the given name. For // example, if the user looks up foobar.query.consul via DNS then we will call // this function with "foobar" on the compiled template. func (ct *CompiledTemplate) Render(name string, source structs.QuerySource) (*structs.PreparedQuery, error) { // Make it "safe" to render a default structure. if ct == nil { return nil, fmt.Errorf("Cannot render an uncompiled template") } // Start with a fresh, detached copy of the original so we don't disturb // the prototype. dup, err := copystructure.Copy(ct.query) if err != nil { return nil, err } query, ok := dup.(*structs.PreparedQuery) if !ok { return nil, fmt.Errorf("Failed to copy query") } var matches []string if ct.re != nil { matches = ct.re.FindStringSubmatch(name) } // Create a safe match function that can't fail at run time. It will // return an empty string for any invalid input. match := ast.Function{ ArgTypes: []ast.Type{ast.TypeInt}, ReturnType: ast.TypeString, Variadic: false, Callback: func(inputs []interface{}) (interface{}, error) { i, ok := inputs[0].(int) if ok && i >= 0 && i < len(matches) { return matches[i], nil } return "", nil }, } // Build up the HIL evaluation context. config := &hil.EvalConfig{ GlobalScope: &ast.BasicScope{ VarMap: map[string]ast.Variable{ "name.full": ast.Variable{ Type: ast.TypeString, Value: name, }, "name.prefix": ast.Variable{ Type: ast.TypeString, Value: query.Name, }, "name.suffix": ast.Variable{ Type: ast.TypeString, Value: strings.TrimPrefix(name, query.Name), }, "agent.segment": ast.Variable{ Type: ast.TypeString, Value: source.Segment, }, }, FuncMap: map[string]ast.Function{ "match": match, }, }, } // Run through the Service sub-structure and evaluate all the strings // as HIL. eval := func(path string, v reflect.Value) error { tree, ok := ct.trees[path] if !ok { return nil } res, err := hil.Eval(tree, config) if err != nil { return fmt.Errorf("Bad evaluation for '%s' in Service%s: %s", v.String(), path, err) } if res.Type != hil.TypeString { return fmt.Errorf("Expected Service%s field to be a string, got %s", path, res.Type) } v.SetString(res.Value.(string)) return nil } if err := walk(&query.Service, eval); err != nil { return nil, err } if ct.removeEmptyTags { tags := make([]string, 0, len(query.Service.Tags)) for _, tag := range query.Service.Tags { if tag != "" { tags = append(tags, tag) } } query.Service.Tags = tags } return query, nil }