Fix indefinitely stuck FPM status processes

After switching to dedicated status port provided by php-fpm, the fpm exporter seems to be stuck on connecting to the fcgi. Only way to fix it is connect another procces to the same fpm port. This suggest some issues in the php (8.0) itself, but to overcome that let's allow next request to acctually try connect and unlock all stuck processes

Author: t-tomalak

phpfpm/phpfpm.go

@@ -15,9 +15,11 @@
 package phpfpm
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
+	"net/http"
 	"net/url"
 	"regexp"
 	"strconv"
@@ -163,36 +165,63 @@ func (p *Pool) Update() (err error) {
 
 	defer fcgi.Close()
 
-	env := map[string]string{
-		"SCRIPT_FILENAME": path,
-		"SCRIPT_NAME":     path,
-		"SERVER_SOFTWARE": "go / php-fpm_exporter",
-		"REMOTE_ADDR":     "127.0.0.1",
-		"QUERY_STRING":    "json&full",
-	}
+	// Process might hang on execution indefinitely there, and block other requests.
+	// This still allows for goroutine to live forever, if either of the requests will not finish.
+	done := make(chan *http.Response, 1)
+	errCh := make(chan error, 1)
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+	defer cancel()
+
+	go func(ctx context.Context, ch chan *http.Response, errCh chan error) {
+		env := map[string]string{
+			"SCRIPT_FILENAME": path,
+			"SCRIPT_NAME":     path,
+			"SERVER_SOFTWARE": "go / php-fpm_exporter",
+			"REMOTE_ADDR":     "127.0.0.1",
+			"QUERY_STRING":    "json&full",
+		}
 
-	resp, err := fcgi.Get(env)
-	if err != nil {
-		return p.error(err)
-	}
+		res, err := fcgi.Get(env)
+		if err != nil {
+			errCh <- p.error(err)
+			return
+		}
 
-	defer resp.Body.Close()
+		select {
+		case <-ctx.Done():
+			// request is already done, let's just release response resources
+			res.Body.Close()
+		default:
+			//
+			ch <- res
+		}
 
-	content, err := ioutil.ReadAll(resp.Body)
-	if err != nil {
-		return p.error(err)
-	}
+	}(ctx, done, errCh)
 
-	content = JSONResponseFixer(content)
+	select {
+	case err = <-errCh:
+		return err
+	case <-ctx.Done():
+		return ctx.Err()
+	case resp := <-done:
+		defer resp.Body.Close()
+
+		content, err := io.ReadAll(resp.Body)
+		if err != nil {
+			return p.error(err)
+		}
 
-	log.Debugf("Pool[%v]: %v", p.Address, string(content))
+		content = JSONResponseFixer(content)
 
-	if err = json.Unmarshal(content, &p); err != nil {
-		log.Errorf("Pool[%v]: %v", p.Address, string(content))
-		return p.error(err)
-	}
+		log.Debugf("Pool[%v]: %v", p.Address, string(content))
 
-	return nil
+		if err = json.Unmarshal(content, &p); err != nil {
+			log.Errorf("Pool[%v]: %v", p.Address, string(content))
+			return p.error(err)
+		}
+
+		return nil
+	}
 }
 
 func (p *Pool) error(err error) error {