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layer.go
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layer.go
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/*
* Copyright 2018-2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package libpak
import (
"fmt"
"os"
"path/filepath"
"reflect"
"github.com/heroku/color"
"github.com/pelletier/go-toml"
"github.com/buildpacks/libcnb"
"github.com/paketo-buildpacks/libpak/sherpa"
"github.com/paketo-buildpacks/libpak/bard"
)
// LayerContributor is a helper for implementing a libcnb.LayerContributor in order to get consistent logging and
// avoidance.
type LayerContributor struct {
// ExpectedMetadata is the metadata to compare against any existing layer metadata.
ExpectedMetadata interface{}
// Logger is the logger to use.
Logger bard.Logger
// Name is the user readable name of the contribution.
Name string
// ExpectedTypes indicates the types that should be set on the layer.
ExpectedTypes libcnb.LayerTypes
}
// NewLayerContributor creates a new instance.
func NewLayerContributor(name string, expectedMetadata interface{}, expectedTypes libcnb.LayerTypes) LayerContributor {
return LayerContributor{
ExpectedMetadata: expectedMetadata,
Name: name,
ExpectedTypes: expectedTypes,
}
}
// LayerFunc is a callback function that is invoked when a layer needs to be contributed.
type LayerFunc func() (libcnb.Layer, error)
// Contribute is the function to call when implementing your libcnb.LayerContributor.
func (l *LayerContributor) Contribute(layer libcnb.Layer, f LayerFunc) (libcnb.Layer, error) {
raw, err := toml.Marshal(l.ExpectedMetadata)
if err != nil {
return libcnb.Layer{}, fmt.Errorf("unable to encode metadata\n%w", err)
}
expected := map[string]interface{}{}
if err := toml.Unmarshal(raw, &expected); err != nil {
return libcnb.Layer{}, fmt.Errorf("unable to decode metadata\n%w", err)
}
l.Logger.Debugf("Expected metadata: %+v", expected)
l.Logger.Debugf("Actual metadata: %+v", layer.Metadata)
// TODO: compare entire layer not just metadata (in case build, launch, or cache have changed)
if reflect.DeepEqual(expected, layer.Metadata) {
l.Logger.Headerf("%s: %s cached layer", color.BlueString(l.Name), color.GreenString("Reusing"))
layer.LayerTypes = l.ExpectedTypes
return layer, nil
}
l.Logger.Headerf("%s: %s to layer", color.BlueString(l.Name), color.YellowString("Contributing"))
if err := os.RemoveAll(layer.Path); err != nil {
return libcnb.Layer{}, fmt.Errorf("unable to remove existing layer directory %s\n%w", layer.Path, err)
}
if err := os.MkdirAll(layer.Path, 0755); err != nil {
return libcnb.Layer{}, fmt.Errorf("unable to create layer directory %s\n%w", layer.Path, err)
}
layer, err = f()
if err != nil {
return libcnb.Layer{}, err
}
layer.LayerTypes = l.ExpectedTypes
layer.Metadata = expected
return layer, nil
}
// DependencyLayerContributor is a helper for implementing a libcnb.LayerContributor for a BuildpackDependency in order
// to get consistent logging and avoidance.
type DependencyLayerContributor struct {
// Dependency is the dependency being contributed.
Dependency BuildpackDependency
// DependencyCache is the cache to use to get the dependency.
DependencyCache DependencyCache
// ExpectedTypes indicates the types that should be set on the layer.
ExpectedTypes libcnb.LayerTypes
// ExpectedMetadata contains metadata describing the expected layer
ExpectedMetadata interface{}
// Logger is the logger to use.
Logger bard.Logger
// RequestModifierFuncs is an optional Request Modifier to use when downloading the dependency.
RequestModifierFuncs []RequestModifierFunc
}
// NewDependencyLayer returns a new DependencyLayerContributor for the given BuildpackDependency and a BOMEntry describing the layer contents.
//
// Deprecated: this method uses `libcnb.BOMEntry` which has been deprecated upstream, a future version will drop
// support for `libcnb.BOMEntry` which will change this method signature
func NewDependencyLayer(dependency BuildpackDependency, cache DependencyCache, types libcnb.LayerTypes) (DependencyLayerContributor, libcnb.BOMEntry) {
c := DependencyLayerContributor{
Dependency: dependency,
ExpectedMetadata: dependency,
DependencyCache: cache,
ExpectedTypes: types,
}
entry := dependency.AsBOMEntry()
entry.Metadata["layer"] = c.LayerName()
if types.Launch {
entry.Launch = true
}
if !(types.Launch && !types.Cache && !types.Build) {
// launch-only layers are the only layers NOT guaranteed to be present in the build environment
entry.Build = true
}
return c, entry
}
// DependencyLayerFunc is a callback function that is invoked when a dependency needs to be contributed.
type DependencyLayerFunc func(artifact *os.File) (libcnb.Layer, error)
// Contribute is the function to call whe implementing your libcnb.LayerContributor.
func (d *DependencyLayerContributor) Contribute(layer libcnb.Layer, f DependencyLayerFunc) (libcnb.Layer, error) {
lc := NewLayerContributor(d.Name(), d.ExpectedMetadata, d.ExpectedTypes)
lc.Logger = d.Logger
return lc.Contribute(layer, func() (libcnb.Layer, error) {
artifact, err := d.DependencyCache.Artifact(d.Dependency, d.RequestModifierFuncs...)
if err != nil {
return libcnb.Layer{}, fmt.Errorf("unable to get dependency %s\n%w", d.Dependency.ID, err)
}
defer artifact.Close()
return f(artifact)
})
}
// LayerName returns the conventional name of the layer for this contributor
func (d *DependencyLayerContributor) LayerName() string {
return d.Dependency.ID
}
// Name returns the human readable name of the layer
func (d *DependencyLayerContributor) Name() string {
return fmt.Sprintf("%s %s", d.Dependency.Name, d.Dependency.Version)
}
// HelperLayerContributor is a helper for implementing a libcnb.LayerContributor for a buildpack helper application in
// order to get consistent logging and avoidance.
type HelperLayerContributor struct {
// Path is the path to the helper application.
Path string
// BuildpackInfo describes the buildpack that provides the helper
BuildpackInfo libcnb.BuildpackInfo
// Logger is the logger to use.
Logger bard.Logger
// Names are the names of the helpers to create
Names []string
}
// NewHelperLayer returns a new HelperLayerContributor and a BOMEntry describing the layer contents.
//
// Deprecated: this method uses `libcnb.BOMEntry` which has been deprecated upstream, a future version will drop
// support for `libcnb.BOMEntry` which will change this method signature
func NewHelperLayer(buildpack libcnb.Buildpack, names ...string) (HelperLayerContributor, libcnb.BOMEntry) {
c := HelperLayerContributor{
Path: filepath.Join(buildpack.Path, "bin", "helper"),
Names: names,
BuildpackInfo: buildpack.Info,
}
entry := libcnb.BOMEntry{
Name: "helper",
Metadata: map[string]interface{}{
"layer": c.Name(),
"names": names,
"version": buildpack.Info.Version,
},
Launch: true,
}
return c, entry
}
// Name returns the conventional name of the layer for this contributor
func (h HelperLayerContributor) Name() string {
return filepath.Base(h.Path)
}
// Contribute is the function to call whe implementing your libcnb.LayerContributor.
func (h HelperLayerContributor) Contribute(layer libcnb.Layer) (libcnb.Layer, error) {
lc := NewLayerContributor("Launch Helper", h.BuildpackInfo, libcnb.LayerTypes{
Launch: true,
})
lc.Logger = h.Logger
return lc.Contribute(layer, func() (libcnb.Layer, error) {
in, err := os.Open(h.Path)
if err != nil {
return libcnb.Layer{}, fmt.Errorf("unable to open %s\n%w", h.Path, err)
}
defer in.Close()
out := filepath.Join(layer.Path, "helper")
if err := sherpa.CopyFile(in, out); err != nil {
return libcnb.Layer{}, fmt.Errorf("unable to copy %s to %s", h.Path, out)
}
for _, n := range h.Names {
link := layer.Exec.FilePath(n)
h.Logger.Bodyf("Creating %s", link)
f := filepath.Dir(link)
if err := os.MkdirAll(f, 0755); err != nil {
return libcnb.Layer{}, fmt.Errorf("unable to create %s\n%w", f, err)
}
if err := os.Symlink(out, link); err != nil {
return libcnb.Layer{}, fmt.Errorf("unable to link %s to %s\n%w", out, link, err)
}
}
return layer, nil
})
}