support semaphore limiting + context-cancellation of Gitea API requests

api.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
@@ -45,8 +46,16 @@ type MarkdownRequest struct {
 }
 
 // repos gets a list of Git repositories in this organisation.
-func (this *Application) repos() ([]Repo, error) {
+func (this *Application) repos(ctx context.Context) ([]Repo, error) {
-	resp, err := http.Get(this.cfg.Gitea.URL + `api/v1/orgs/` + url.PathEscape(this.cfg.Gitea.Org) + `/repos`)
+	this.apiSem.Acquire(ctx, 1)
+	defer this.apiSem.Release(1)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, this.cfg.Gitea.URL+`api/v1/orgs/`+url.PathEscape(this.cfg.Gitea.Org)+`/repos`, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return nil, err
 	}
@@ -67,8 +76,16 @@ func (this *Application) repos() ([]Repo, error) {
 
 // repoFile gets a single file from the default branch of the git repository
 // Usually the default branch is `master`.
-func (this *Application) repoFile(repo, filename string) ([]byte, error) {
+func (this *Application) repoFile(ctx context.Context, repo, filename string) ([]byte, error) {
-	resp, err := http.Get(this.cfg.Gitea.URL + `api/v1/repos/` + url.PathEscape(this.cfg.Gitea.Org) + `/` + url.PathEscape(repo) + `/contents/` + url.PathEscape(filename))
+	this.apiSem.Acquire(ctx, 1)
+	defer this.apiSem.Release(1)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, this.cfg.Gitea.URL+`api/v1/repos/`+url.PathEscape(this.cfg.Gitea.Org)+`/`+url.PathEscape(repo)+`/contents/`+url.PathEscape(filename), nil)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return nil, err
 	}
@@ -87,8 +104,16 @@ func (this *Application) repoFile(repo, filename string) ([]byte, error) {
 	return cr.Content, nil
 }
 
-func (this *Application) filesInDirectory(repo, dir string) ([]ReaddirEntry, error) {
+func (this *Application) filesInDirectory(ctx context.Context, repo, dir string) ([]ReaddirEntry, error) {
-	resp, err := http.Get(this.cfg.Gitea.URL + `api/v1/repos/` + url.PathEscape(this.cfg.Gitea.Org) + `/` + url.PathEscape(repo) + `/contents/` + dir) // n.b. $dir param not escaped
+	this.apiSem.Acquire(ctx, 1)
+	defer this.apiSem.Release(1)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, this.cfg.Gitea.URL+`api/v1/repos/`+url.PathEscape(this.cfg.Gitea.Org)+`/`+url.PathEscape(repo)+`/contents/`+dir, nil) // n.b. $dir param not escaped
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return nil, err
 	}
@@ -121,13 +146,13 @@ func (this *Application) filesInDirectory(repo, dir string) ([]ReaddirEntry, err
 
 // imageFilesForRepo finds documentation images for the repository.
 // It searches the dist/ and doc/ subdirectories.
-func (this *Application) imageFilesForRepo(repo string) ([]ReaddirEntry, error) {
+func (this *Application) imageFilesForRepo(ctx context.Context, repo string) ([]ReaddirEntry, error) {
 
 	ret := []ReaddirEntry{}
 
 	for _, dirName := range []string{`dist`, `doc`} {
 
-		files, err := this.filesInDirectory(repo, dirName)
+		files, err := this.filesInDirectory(ctx, repo, dirName)
 		if err != nil {
 			return nil, fmt.Errorf("readdir(%s): %w", dirName, err)
 		}
@@ -142,8 +167,16 @@ func (this *Application) imageFilesForRepo(repo string) ([]ReaddirEntry, error)
 	return ret, nil
 }
 
-func (this *Application) topicsForRepo(repo string) ([]string, error) {
+func (this *Application) topicsForRepo(ctx context.Context, repo string) ([]string, error) {
-	resp, err := http.Get(this.cfg.Gitea.URL + `api/v1/repos/` + url.PathEscape(this.cfg.Gitea.Org) + `/` + url.PathEscape(repo) + `/topics`)
+	this.apiSem.Acquire(ctx, 1)
+	defer this.apiSem.Release(1)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, this.cfg.Gitea.URL+`api/v1/repos/`+url.PathEscape(this.cfg.Gitea.Org)+`/`+url.PathEscape(repo)+`/topics`, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return nil, err
 	}
@@ -163,19 +196,27 @@ func (this *Application) topicsForRepo(repo string) ([]string, error) {
 }
 
 // renderMarkdown calls the remote Gitea server's own markdown renderer.
-func (this *Application) renderMarkdown(repoName string, body string) ([]byte, error) {
+func (this *Application) renderMarkdown(ctx context.Context, repoName string, body string) ([]byte, error) {
-	req := MarkdownRequest{
+	this.apiSem.Acquire(ctx, 1)
+	defer this.apiSem.Release(1)
+
+	jb, err := json.Marshal(MarkdownRequest{
 		Context: this.cfg.Gitea.URL + url.PathEscape(this.cfg.Gitea.Org) + `/` + url.PathEscape(repoName) + `/src/branch/master`,
 		Mode:    "gfm", // magic constant - Github Flavoured Markdown
 		Text:    body,
-	}
+	})
-
-	jb, err := json.Marshal(req)
 	if err != nil {
 		return nil, err
 	}
 
-	resp, err := http.Post(this.cfg.Gitea.URL+`api/v1/markdown/`, `application/json`, bytes.NewReader(jb))
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, this.cfg.Gitea.URL+`api/v1/markdown/`, bytes.NewReader(jb))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set(`Content-Type`, `application/json`)
+	req.Header.Set(`Content-Length`, fmt.Sprintf("%d", len(jb)))
+
+	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return nil, err
 	}
@@ -189,8 +230,18 @@ func (this *Application) renderMarkdown(repoName string, body string) ([]byte, e
 }
 
 // renderMarkdownRaw calls the remote Gitea server's own markdown renderer.
-func (this *Application) renderMarkdownRaw(body []byte) ([]byte, error) {
+func (this *Application) renderMarkdownRaw(ctx context.Context, body []byte) ([]byte, error) {
-	resp, err := http.Post(this.cfg.Gitea.URL+`api/v1/markdown/raw`, `text/plain`, bytes.NewReader(body))
+	this.apiSem.Acquire(ctx, 1)
+	defer this.apiSem.Release(1)
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, this.cfg.Gitea.URL+`api/v1/markdown/raw`, bytes.NewReader(body))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set(`Content-Type`, `text/plain`)
+	req.Header.Set(`Content-Length`, fmt.Sprintf("%d", len(body)))
+
+	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return nil, err
 	}

config.toml.sample

@@ -5,6 +5,7 @@ BindTo="0.0.0.0:5656"
 [Gitea]
 URL="https://gitea.com/"
 Org="gitea"
+MaxConnections=2 # Use zero for unlimited
 
 [Redirect]
 "old-project-name" = "new-project-name"

go.mod

@@ -2,4 +2,7 @@ module teafolio
 
 go 1.13
 
-require github.com/BurntSushi/toml v0.3.1
+require (
+	github.com/BurntSushi/toml v0.3.1
+	golang.org/x/sync v0.0.0-20200317015054-43a5402ce75a
+)

go.sum

@@ -1,2 +1,4 @@
 github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+golang.org/x/sync v0.0.0-20200317015054-43a5402ce75a h1:WXEvlFVvvGxCJLG6REjsT03iWnKLEWinaScsxF2Vm2o=
+golang.org/x/sync v0.0.0-20200317015054-43a5402ce75a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

main.go

@@ -14,12 +14,14 @@ import (
 	"strings"
 
 	"github.com/BurntSushi/toml"
+	"golang.org/x/sync/semaphore"
 )
 
 type Config struct {
 	BindTo string
 	Gitea  struct {
 		URL, Org       string
+		MaxConnections int64
 	}
 	Redirect map[string]string
 	Template struct {
@@ -33,6 +35,7 @@ type Application struct {
 	cfg Config
 
 	rxRepoPage, rxRepoImage *regexp.Regexp
+	apiSem                  *semaphore.Weighted
 }
 
 func (this *Application) Templatepage(w http.ResponseWriter, r *http.Request, pageDesc, extraHead string, cb func()) {
@@ -77,7 +80,9 @@ func (this *Application) internalError(w http.ResponseWriter, r *http.Request, e
 }
 
 func (this *Application) Homepage(w http.ResponseWriter, r *http.Request) {
-	repos, err := this.repos()
+	ctx := r.Context()
+
+	repos, err := this.repos(ctx)
 	if err != nil {
 		this.internalError(w, r, fmt.Errorf("listing repos: %w", err))
 		return
@@ -85,7 +90,7 @@ func (this *Application) Homepage(w http.ResponseWriter, r *http.Request) {
 
 	topics := make(map[string][]string)
 	for _, repo := range repos {
-		if t, err := this.topicsForRepo(repo.Name); err == nil {
+		if t, err := this.topicsForRepo(ctx, repo.Name); err == nil {
 			topics[repo.Name] = t
 		}
 	}
@@ -175,8 +180,9 @@ func (this *Application) Homepage(w http.ResponseWriter, r *http.Request) {
 }
 
 func (this *Application) Bannerpage(w http.ResponseWriter, r *http.Request, repoName string) {
+	ctx := r.Context()
 
-	images, err := this.imageFilesForRepo(repoName)
+	images, err := this.imageFilesForRepo(ctx, repoName)
 	if err != nil {
 		this.internalError(w, r, fmt.Errorf("listing images: %w", err))
 		return
@@ -193,11 +199,11 @@ func (this *Application) Bannerpage(w http.ResponseWriter, r *http.Request, repo
 }
 
 func (this *Application) Repopage(w http.ResponseWriter, r *http.Request, repoName string) {
-
+	ctx := r.Context()
 	repoURL := this.cfg.Gitea.URL + url.PathEscape(this.cfg.Gitea.Org) + `/` + url.PathEscape(repoName)
 	extraHead := ""
 
-	readme, err := this.repoFile(repoName, `README.md`)
+	readme, err := this.repoFile(ctx, repoName, `README.md`)
 	if err != nil {
 		this.internalError(w, r, fmt.Errorf("loading README.md: %w", err))
 		return
@@ -217,20 +223,20 @@ func (this *Application) Repopage(w http.ResponseWriter, r *http.Request, repoNa
 		lines = append([]string{lines[0], lines[1], extraBadgesMd, ""}, lines[2:]...)
 	}
 
-	readmeHtml, err := this.renderMarkdown(repoName, strings.Join(lines, "\n"))
+	readmeHtml, err := this.renderMarkdown(ctx, repoName, strings.Join(lines, "\n"))
 	if err != nil {
 		this.internalError(w, r, fmt.Errorf("rendering markdown: %w", err))
 		return
 	}
 
-	images, err := this.imageFilesForRepo(repoName)
+	images, err := this.imageFilesForRepo(ctx, repoName)
 	if err != nil {
 		this.internalError(w, r, fmt.Errorf("listing images: %w", err))
 		return
 	}
 
 	// If the Git repository contains a top-level go.mod file, allow vanity imports
-	if goMod, err := this.repoFile(repoName, `go.mod`); err == nil {
+	if goMod, err := this.repoFile(ctx, repoName, `go.mod`); err == nil {
 
 		// Check the first line should be `module MODULENAME\n`
 		firstLine := bytes.SplitN(goMod, []byte("\n"), 2)[0]
@@ -384,5 +390,12 @@ func main() {
 		app.cfg.Gitea.URL += `/`
 	}
 
+	// Create semaphore
+	if app.cfg.Gitea.MaxConnections == 0 { // unlimited
+		app.apiSem = semaphore.NewWeighted(99999)
+	} else {
+		app.apiSem = semaphore.NewWeighted(app.cfg.Gitea.MaxConnections)
+	}
+
 	log.Fatal(http.ListenAndServe(app.cfg.BindTo, &app))
 }