[elastic] Cache the results of 'invokeGo()' call (#76)

'invokeGo' is used to get the import outline of the specified folder(package),
so there are duplications that will slow down the go langserver.

Since go langserver serves several repos at the same time, use LRU cache
in case of blow up the memory. 'determineRootDirsCached' serves single view,
i.e. single workspace folder, 'golistDriverLRUCached' serves single
subfolder, i.e. package. Given that we will skip 'vendor' folder, for now,
the number of the repos are simultaneously indexing is very low, that's
why set the 'determineRootDirsCached' entry number to 16.

Future plan:

skip the 'vendor' file
download the deps during the initialize request
eliminate the 'invokeGo' call
find a better approach to handle the 'vendor' folder

Author: Henry Wong

.ci/Dockerfile

@@ -7,7 +7,8 @@ ENV GO111MODULE=off
 RUN apk add --no-cache --quiet make curl git jq unzip tree && \
      apk add bash && \
      go get golang.org/x/sync/errgroup && \
-     go get golang.org/x/xerrors
+     go get golang.org/x/xerrors && \
+     go get github.com/hashicorp/golang-lru
 
 VOLUME /go/src/golang.org/x/tools
 WORKDIR /go/src/golang.org/x/tools

.travis.yml

@@ -24,6 +24,7 @@ env:
 before_install:
   - go get golang.org/x/sync/errgroup
   - go get golang.org/x/xerrors
+  - go get github.com/hashicorp/golang-lru
 
 matrix:
   fast_finish: true

appveyor.yml

@@ -26,6 +26,7 @@ environment:
 build_script:
   - go get golang.org/x/sync/errgroup
   - go get golang.org/x/xerrors
+  - go get github.com/hashicorp/golang-lru
   # TODO(henrywong) For now, there are problems about the windows test.
   # - go test ./internal/lsp -v
   - mkdir go-langserver-windows

go.mod

@@ -3,6 +3,7 @@ module golang.org/x/tools
 go 1.11
 
 require (
+	github.com/hashicorp/golang-lru v0.5.3
 	golang.org/x/net v0.0.0-20190620200207-3b0461eec859
 	golang.org/x/sync v0.0.0-20190423024810-112230192c58
 	golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7

go.sum

@@ -1,3 +1,5 @@
+github.com/hashicorp/golang-lru v0.5.3 h1:YPkqC67at8FYaadspW/6uE0COsBxS2656RLEr8Bppgk=
+github.com/hashicorp/golang-lru v0.5.3/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859 h1:R/3boaszxrf1GEUWTVDzSKVwLmSJpwZ1yqXm8j0v2QI=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=

go/packages/golist.go

@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"go/types"
+	"hash/fnv"
 	"io/ioutil"
 	"log"
 	"os"
@@ -22,6 +23,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/hashicorp/golang-lru"
 	"golang.org/x/tools/go/internal/packagesdriver"
 	"golang.org/x/tools/internal/gopathwalk"
 	"golang.org/x/tools/internal/semver"
@@ -91,7 +93,7 @@ func goListDriver(cfg *Config, patterns ...string) (*driverResponse, error) {
 	var rootDirs map[string]string
 	var rootDirsReady = make(chan struct{})
 	go func() {
-		rootDirs = determineRootDirs(cfg)
+		rootDirs = determineRootDirsLRUCached(cfg)
 		close(rootDirsReady)
 	}()
 	getRootDirs := func() map[string]string {
@@ -101,7 +103,7 @@ func goListDriver(cfg *Config, patterns ...string) (*driverResponse, error) {
 
 	// always pass getRootDirs to golistDriver
 	golistDriver := func(cfg *Config, patterns ...string) (*driverResponse, error) {
-		return golistDriver(cfg, getRootDirs, patterns...)
+		return golistDriverLRUCached(cfg, getRootDirs, patterns...)
 	}
 
 	// Determine files requested in contains patterns
@@ -597,6 +599,36 @@ func otherFiles(p *jsonPackage) [][]string {
 	return [][]string{p.CFiles, p.CXXFiles, p.MFiles, p.HFiles, p.FFiles, p.SFiles, p.SwigFiles, p.SwigCXXFiles, p.SysoFiles}
 }
 
+type goListResult struct {
+	response *driverResponse
+	err      error
+}
+
+var (
+	goListLRUCache       *lru.Cache
+	createGoListLRUCache sync.Once
+	goListLRUEntries     = 16 * 32
+)
+
+func golistDriverLRUCached(cfg *Config, rootsDirs func() map[string]string, words ...string) (*driverResponse, error) {
+	createGoListLRUCache.Do(func() {
+		goListLRUCache, _ = lru.New(goListLRUEntries)
+	})
+
+	h := fnv.New32a()
+	h.Write([]byte(cfg.Dir))
+	h.Write([]byte(words[len(words)-1]))
+	hashKey := h.Sum32()
+	if val, ok := goListLRUCache.Get(hashKey); ok {
+		res := val.(goListResult)
+		return res.response, res.err
+	} else {
+		res, err := golistDriver(cfg, rootsDirs, words...)
+		goListLRUCache.Add(hashKey, goListResult{res, err})
+		return res, err
+	}
+}
+
 // golistDriver uses the "go list" command to expand the pattern
 // words and return metadata for the specified packages. dir may be
 // "" and env may be nil, as per os/exec.Command.

go/packages/golist_overlay.go

@@ -10,6 +10,9 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"sync"
+
+	"github.com/hashicorp/golang-lru"
 )
 
 // processGolistOverlay provides rudimentary support for adding
@@ -194,6 +197,30 @@ func hasTestFiles(p *Package) bool {
 	return false
 }
 
+type determineRootDirsResult struct {
+	roots map[string]string
+}
+
+var (
+	determineRootDirsLRUCache *lru.Cache
+	createRootLRUCache        sync.Once
+	rootLRUEntries            = 16
+)
+
+func determineRootDirsLRUCached(cfg *Config) map[string]string {
+	createRootLRUCache.Do(func() {
+		determineRootDirsLRUCache, _ = lru.New(rootLRUEntries)
+	})
+	if val, ok := determineRootDirsLRUCache.Get(cfg.Dir); ok {
+		res := val.(determineRootDirsResult)
+		return res.roots
+	} else {
+		roots := determineRootDirs(cfg)
+		determineRootDirsLRUCache.Add(cfg.Dir, determineRootDirsResult{roots})
+		return roots
+	}
+}
+
 // determineRootDirs returns a mapping from directories code can be contained in to the
 // corresponding import path prefixes of those directories.
 // Its result is used to try to determine the import path for a package containing