// Copyright (C) 2016-2019 Vincent Ambo <mail@tazj.in>
//
// This file is part of Kontemplate.
//
// Kontemplate is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
package context
import (
"fmt"
"path"
"strings"
"github.com/tazjin/kontemplate/util"
)
type ResourceSet struct {
// Name of the resource set. This can be used in include/exclude statements during kontemplate runs.
Name string `json:"name"`
// Path to the folder containing the files for this resource set. This defaults to the value of the 'name' field
// if unset.
Path string `json:"path"`
// Values to include when interpolating resources from this resource set.
Values map[string]interface{} `json:"values"`
// Args to pass on to kubectl for this resource set.
Args []string `json:"args"`
// Nested resource sets to include
Include []ResourceSet `json:"include"`
// Parent resource set for flattened resource sets. Should not be manually specified.
Parent string
}
type Context struct {
// The name of the kubectl context
Name string `json:"context"`
// Global variables that should be accessible by all resource sets
Global map[string]interface{} `json:"global"`
// File names of YAML or JSON files including extra variables that should be globally accessible
VariableImportFiles []string `json:"import"`
// The resource sets to include in this context
ResourceSets []ResourceSet `json:"include"`
// Variables imported from additional files
ImportedVars map[string]interface{}
// Explicitly set variables (via `--var`) that should override all others
ExplicitVars map[string]interface{}
// This field represents the absolute path to the context base directory and should not be manually specified.
BaseDir string
}
func contextLoadingError(filename string, cause error) error {
return fmt.Errorf("Context loading failed on file %s due to: \n%v", filename, cause)
}
// Attempt to load and deserialise a Context from the specified file.
func LoadContext(filename string, explicitVars *[]string) (*Context, error) {
var ctx Context
err := util.LoadData(filename, &ctx)
if err != nil {
return nil, contextLoadingError(filename, err)
}
ctx.BaseDir = path.Dir(filename)
// Prepare the resource sets by resolving parents etc.
ctx.ResourceSets = flattenPrepareResourceSetPaths(&ctx.BaseDir, &ctx.ResourceSets)
// Add variables explicitly specified on the command line
ctx.ExplicitVars, err = loadExplicitVars(explicitVars)
if err != nil {
return nil, fmt.Errorf("Error setting explicit variables: %v\n", err)
}
// Add variables loaded from import files
ctx.ImportedVars, err = ctx.loadImportedVariables()
if err != nil {
return nil, contextLoadingError(filename, err)
}
// Merge variables defined at different levels. The
// `mergeContextValues` function is documented with the merge
// hierarchy.
ctx.ResourceSets = ctx.mergeContextValues()
if err != nil {
return nil, contextLoadingError(filename, err)
}
return &ctx, nil
}
// Kontemplate supports specifying additional variable files with the
// `import` keyword. This function loads those variable files and
// merges them together with the context's other global variables.
func (ctx *Context) loadImportedVariables() (map[string]interface{}, error) {
allImportedVars := make(map[string]interface{})
for _, file := range ctx.VariableImportFiles {
// Ensure that the filename is not merged with the baseDir if
// it is set to an absolute path.
var filePath string
if path.IsAbs(file) {
filePath = file
} else {
filePath = path.Join(ctx.BaseDir, file)
}
var importedVars map[string]interface{}
err := util.LoadData(filePath, &importedVars)
if err != nil {
return nil, err
}
allImportedVars = *util.Merge(&allImportedVars, &importedVars)
}
return allImportedVars, nil
}
// Correctly prepares the file paths for resource sets by inferring implicit paths and flattening resource set
// collections, i.e. resource sets that themselves have an additional 'include' field set.
// Those will be regarded as a short-hand for including multiple resource sets from a subfolder.
// See https://github.com/tazjin/kontemplate/issues/9 for more information.
func flattenPrepareResourceSetPaths(baseDir *string, rs *[]ResourceSet) []ResourceSet {
flattened := make([]ResourceSet, 0)
for _, r := range *rs {
// If a path is not explicitly specified it should default to the resource set name.
// This is also the classic behaviour prior to kontemplate 1.2
if r.Path == "" {
r.Path = r.Name
}
// Paths are made absolute by resolving them relative to the context base,
// unless absolute paths were specified.
if !path.IsAbs(r.Path) {
r.Path = path.Join(*baseDir, r.Path)
}
if len(r.Include) == 0 {
flattened = append(flattened, r)
} else {
for _, subResourceSet := range r.Include {
if subResourceSet.Path == "" {
subResourceSet.Path = subResourceSet.Name
}
subResourceSet.Parent = r.Name
subResourceSet.Name = path.Join(r.Name, subResourceSet.Name)
subResourceSet.Path = path.Join(r.Path, subResourceSet.Path)
subResourceSet.Values = *util.Merge(&r.Values, &subResourceSet.Values)
flattened = append(flattened, subResourceSet)
}
}
}
return flattened
}
// Merges the context and resource set variables according in the
// desired precedence order.
//
// For now the reasoning behind the merge order is from least specific
// in relation to the cluster configuration, which means that the
// precedence is (in ascending order):
//
// 1. Default values in resource sets.
// 2. Values imported from files (via `import:`)
// 3. Global values in a cluster configuration
// 4. Values set in a resource set's `include`-section
// 5. Explicit values set on the CLI (`--var`)
//
// For a discussion on the reasoning behind this order, please consult
// https://github.com/tazjin/kontemplate/issues/142
func (ctx *Context) mergeContextValues() []ResourceSet {
updated := make([]ResourceSet, len(ctx.ResourceSets))
// Merging has to happen separately for every individual
// resource set to make use of the default values:
for i, rs := range ctx.ResourceSets {
// Begin by loading default values from the resource
// sets configuration.
//
// Resource sets are used across different cluster
// contexts and the default values in them have the
// lowest precedence.
defaultValues := loadDefaultValues(&rs, ctx)
// Continue by merging default values with values
// imported from external files. Those values are also
// used across cluster contexts, but have higher
// precedence than defaults.
merged := util.Merge(defaultValues, &ctx.ImportedVars)
// Merge global values defined in the cluster context:
merged = util.Merge(merged, &ctx.Global)
// Merge values configured in the resource set's
// `include` section:
merged = util.Merge(merged, &rs.Values)
// Merge values defined explicitly on the CLI:
merged = util.Merge(merged, &ctx.ExplicitVars)
// Continue with the newly merged resource set:
rs.Values = *merged
updated[i] = rs
}
return updated
}
// Loads default values for a resource set collection from
// path/to/set/default.{json|yaml}.
func loadDefaultValues(rs *ResourceSet, c *Context) *map[string]interface{} {
var defaultVars map[string]interface{}
for _, filename := range util.DefaultFilenames {
err := util.LoadData(path.Join(rs.Path, filename), &defaultVars)
if err == nil {
return &defaultVars
}
}
// The actual error is not inspected here. The reasoning for
// this is that in case of serious problems (e.g. permission
// issues with the folder / folder not existing) failure will
// occur a bit later anyways.
//
// Otherwise we'd have to differentiate between
// file-not-found-errors (no default values specified) and
// other errors here.
return &rs.Values
}
// Prepares the variables specified explicitly via `--var` when
// executing kontemplate for adding to the context.
func loadExplicitVars(vars *[]string) (map[string]interface{}, error) {
explicitVars := make(map[string]interface{}, len(*vars))
for _, v := range *vars {
varParts := strings.SplitN(v, "=", 2)
if len(varParts) != 2 {
return nil, fmt.Errorf(`invalid explicit variable provided (%s), name and value should be separated with "="`, v)
}
explicitVars[varParts[0]] = varParts[1]
}
return explicitVars, nil
}
