terraform/internal/providercache/dir.go

275 lines
11 KiB
Go

package providercache
import (
"io/ioutil"
"log"
"path/filepath"
"sort"
"strings"
"github.com/hashicorp/terraform/addrs"
"github.com/hashicorp/terraform/internal/getproviders"
)
// Dir represents a single local filesystem directory containing cached
// provider plugin packages that can be both read from (to find providers to
// use for operations) and written to (during provider installation).
//
// The contents of a cache directory follow the same naming conventions as a
// getproviders.FilesystemMirrorSource, except that the packages are always
// kept in the "unpacked" form (a directory containing the contents of the
// original distribution archive) so that they are ready for direct execution.
//
// A Dir also pays attention only to packages for the current host platform,
// silently ignoring any cached packages for other platforms.
//
// Various Dir methods return values that are technically mutable due to the
// restrictions of the Go typesystem, but callers are not permitted to mutate
// any part of the returned data structures.
type Dir struct {
baseDir string
targetPlatform getproviders.Platform
// metaCache is a cache of the metadata of relevant packages available in
// the cache directory last time we scanned it. This can be nil to indicate
// that the cache is cold. The cache will be invalidated (set back to nil)
// by any operation that modifies the contents of the cache directory.
//
// We intentionally don't make effort to detect modifications to the
// directory made by other codepaths because the contract for NewDir
// explicitly defines using the same directory for multiple purposes
// as undefined behavior.
metaCache map[addrs.Provider][]CachedProvider
}
// NewDir creates and returns a new Dir object that will read and write
// provider plugins in the given filesystem directory.
//
// If two instances of Dir are concurrently operating on a particular base
// directory, or if a Dir base directory is also used as a filesystem mirror
// source directory, the behavior is undefined.
func NewDir(baseDir string) *Dir {
return &Dir{
baseDir: baseDir,
targetPlatform: getproviders.CurrentPlatform,
}
}
// NewDirWithPlatform is a variant of NewDir that allows selecting a specific
// target platform, rather than taking the current one where this code is
// running.
//
// This is primarily intended for portable unit testing and not particularly
// useful in "real" callers, with the exception of terraform-bundle.
func NewDirWithPlatform(baseDir string, platform getproviders.Platform) *Dir {
return &Dir{
baseDir: baseDir,
targetPlatform: platform,
}
}
// AllAvailablePackages returns a description of all of the packages already
// present in the directory. The cache entries are grouped by the provider
// they relate to and then sorted by version precedence, with highest
// precedence first.
//
// This function will return an empty result both when the directory is empty
// and when scanning the directory produces an error.
//
// The caller is forbidden from modifying the returned data structure in any
// way, even though the Go type system permits it.
func (d *Dir) AllAvailablePackages() map[addrs.Provider][]CachedProvider {
if err := d.fillMetaCache(); err != nil {
log.Printf("[WARN] Failed to scan provider cache directory %s: %s", d.baseDir, err)
return nil
}
return d.metaCache
}
// ProviderVersion returns the cache entry for the requested provider version,
// or nil if the requested provider version isn't present in the cache.
func (d *Dir) ProviderVersion(provider addrs.Provider, version getproviders.Version) *CachedProvider {
if err := d.fillMetaCache(); err != nil {
return nil
}
for _, entry := range d.metaCache[provider] {
// We're intentionally comparing exact version here, so if either
// version number contains build metadata and they don't match then
// this will not return true. The rule of ignoring build metadata
// applies only for handling version _constraints_ and for deciding
// version precedence.
if entry.Version == version {
return &entry
}
}
return nil
}
// ProviderLatestVersion returns the cache entry for the latest
// version of the requested provider already available in the cache, or nil if
// there are no versions of that provider available.
func (d *Dir) ProviderLatestVersion(provider addrs.Provider) *CachedProvider {
if err := d.fillMetaCache(); err != nil {
return nil
}
entries := d.metaCache[provider]
if len(entries) == 0 {
return nil
}
return &entries[0]
}
func (d *Dir) fillMetaCache() error {
// For d.metaCache we consider nil to be different than a non-nil empty
// map, so we can distinguish between having scanned and got an empty
// result vs. not having scanned successfully at all yet.
if d.metaCache != nil {
log.Printf("[TRACE] providercache.fillMetaCache: using cached result from previous scan of %s", d.baseDir)
return nil
}
log.Printf("[TRACE] providercache.fillMetaCache: scanning directory %s", d.baseDir)
allData, err := getproviders.SearchLocalDirectory(d.baseDir)
if err != nil {
log.Printf("[TRACE] providercache.fillMetaCache: error while scanning directory %s: %s", d.baseDir, err)
return err
}
// The getproviders package just returns everything it found, but we're
// interested only in a subset of the results:
// - those that are for the current platform
// - those that are in the "unpacked" form, ready to execute
// ...so we'll filter in these ways while we're constructing our final
// map to save as the cache.
//
// We intentionally always make a non-nil map, even if it might ultimately
// be empty, because we use that to recognize that the cache is populated.
data := make(map[addrs.Provider][]CachedProvider)
for providerAddr, metas := range allData {
for _, meta := range metas {
if meta.TargetPlatform != d.targetPlatform {
log.Printf("[TRACE] providercache.fillMetaCache: ignoring %s because it is for %s, not %s", meta.Location, meta.TargetPlatform, d.targetPlatform)
continue
}
if _, ok := meta.Location.(getproviders.PackageLocalDir); !ok {
// PackageLocalDir indicates an unpacked provider package ready
// to execute.
log.Printf("[TRACE] providercache.fillMetaCache: ignoring %s because it is not an unpacked directory", meta.Location)
continue
}
packageDir := filepath.Clean(string(meta.Location.(getproviders.PackageLocalDir)))
execFile := findProviderExecutableInLocalPackage(meta)
if execFile == "" {
// If the package doesn't contain a suitable executable then
// it isn't considered to be part of our cache.
log.Printf("[TRACE] providercache.fillMetaCache: ignoring %s because it is does not seem to contain a suitable plugin executable", meta.Location)
continue
}
log.Printf("[TRACE] providercache.fillMetaCache: including %s as a candidate package for %s %s", meta.Location, providerAddr, meta.Version)
data[providerAddr] = append(data[providerAddr], CachedProvider{
Provider: providerAddr,
Version: meta.Version,
PackageDir: filepath.ToSlash(packageDir),
ExecutableFile: filepath.ToSlash(execFile),
})
}
}
// After we've built our lists per provider, we'll also sort them by
// version precedence so that the newest available version is always at
// index zero. If there are two versions that differ only in build metadata
// then it's undefined but deterministic which one we will select here,
// because we're preserving the order returned by SearchLocalDirectory
// in that case..
for _, entries := range data {
sort.SliceStable(entries, func(i, j int) bool {
// We're using GreaterThan rather than LessThan here because we
// want these in _decreasing_ order of precedence.
return entries[i].Version.GreaterThan(entries[j].Version)
})
}
d.metaCache = data
return nil
}
// This is a helper function to peep into the unpacked directory associated
// with the given package meta and find something that looks like it's intended
// to be the executable file for the plugin.
//
// This is a bit messy and heuristic-y because historically Terraform used the
// filename itself for local filesystem discovery, allowing some variance in
// the filenames to capture extra metadata, whereas now we're using the
// directory structure leading to the executable instead but need to remain
// compatible with the executable names bundled into existing provider packages.
//
// It will return a zero-length string if it can't find a file following
// the expected convention in the given directory.
func findProviderExecutableInLocalPackage(meta getproviders.PackageMeta) string {
packageDir, ok := meta.Location.(getproviders.PackageLocalDir)
if !ok {
// This should never happen because the providercache package only
// uses the local unpacked directory layout. If anything else ends
// up in here then we'll indicate that no executable is available,
// because all other locations require a fetch/unpack step first.
return ""
}
infos, err := ioutil.ReadDir(string(packageDir))
if err != nil {
// If the directory itself doesn't exist or isn't readable then we
// can't access an executable in it.
return ""
}
// For a provider named e.g. tf.example.com/awesomecorp/happycloud, we
// expect an executable file whose name starts with
// "terraform-provider-happycloud", followed by zero or more additional
// characters. If there _are_ additional characters then the first one
// must be an underscore or a period, like in thse examples:
// - terraform-provider-happycloud_v1.0.0
// - terraform-provider-happycloud.exe
//
// We don't require the version in the filename to match because the
// executable's name is no longer authoritative, but packages of "official"
// providers may continue to use versioned executable names for backward
// compatibility with Terraform 0.12.
//
// We also presume that providers packaged for Windows will include the
// necessary .exe extension on their filenames but do not explicitly check
// for that. If there's a provider package for Windows that has a file
// without that suffix then it will be detected as an executable but then
// we'll presumably fail later trying to run it.
wantPrefix := "terraform-provider-" + meta.Provider.Type
// We'll visit all of the directory entries and take the first (in
// name-lexical order) that looks like a plausible provider executable
// name. A package with multiple files meeting these criteria is degenerate
// but we will tolerate it by ignoring the subsequent entries.
for _, info := range infos {
if info.IsDir() {
continue // A directory can never be an executable
}
name := info.Name()
if !strings.HasPrefix(name, wantPrefix) {
continue
}
remainder := name[len(wantPrefix):]
if len(remainder) > 0 && (remainder[0] != '_' && remainder[0] != '.') {
continue // subsequent characters must be delimited by _
}
return filepath.Join(string(packageDir), name)
}
// If we fall out here then nothing has matched.
return ""
}