From a4ac720ebaed13776346f8d91d79d4762d7af321 Mon Sep 17 00:00:00 2001
From: "polylane[bot]" <277585245+polylane[bot]@users.noreply.github.com>
Date: Tue, 15 Sep 2026 15:29:05 +0200
Subject: [PATCH] fix(checker): raise probe response body cap to 10 MiB (#2727)

* fix(checker): cap probe response body read to prevent OOM-kill waves

Co-authored-by: polylane[bot] <277585245+polylane[bot]@users.noreply.github.com>

* fix(checker): raise probe response body cap to 10 MiB

Co-authored-by: polylane[bot] <277585245+polylane[bot]@users.noreply.github.com>

Co-authored-by: polylane[bot] <277585245+polylane[bot]@users.noreply.github.com>

---------

Co-authored-by: Maximilian Kaske <56969857+mxkaske@users.noreply.github.com>
Co-authored-by: polylane[bot] <277585245+polylane[bot]@users.noreply.github.com>
---
 apps/checker/checker/http.go      |  8 +++++++-
 apps/checker/checker/http_test.go | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/apps/checker/checker/http.go b/apps/checker/checker/http.go
index f85f0a0f..aef56126 100644
--- a/apps/checker/checker/http.go
+++ b/apps/checker/checker/http.go
@@ -43,6 +43,10 @@ type Response struct {
 	Timing    Timing            `json:"timing"`
 }
 
+// maxResponseBodyBytes caps the read of a probed response body so a large body
+// cannot OOM the 512 MB checker machines (exit 137 waves).
+const maxResponseBodyBytes = 10 << 20 // 10 MiB
+
 // decodeBase64Body decodes a data URL base64 body if needed
 func decodeBase64Body(body string) ([]byte, error) {
 	data := strings.Split(body, ",")
@@ -145,7 +149,9 @@ func Http(ctx context.Context, client *http.Client, inputData request.HttpChecke
 
 	defer response.Body.Close()
 
-	body, err := io.ReadAll(response.Body)
+	// Cap the response body: an endpoint returning a large body would
+	// otherwise OOM these 512 MB machines (fleet-wide exit 137 waves).
+	body, err := io.ReadAll(io.LimitReader(response.Body, maxResponseBodyBytes))
 
 	timing.TransferDone = time.Now().UTC().UnixMilli()
 
diff --git a/apps/checker/checker/http_test.go b/apps/checker/checker/http_test.go
index 070717a9..b09c89fc 100644
--- a/apps/checker/checker/http_test.go
+++ b/apps/checker/checker/http_test.go
@@ -28,6 +28,24 @@ func NewTestClient(fn RoundTripFunc) *http.Client {
 	}
 }
 
+func Test_HttpCapsResponseBody(t *testing.T) {
+	client := NewTestClient(func(req *http.Request) *http.Response {
+		return &http.Response{
+			StatusCode: http.StatusOK,
+			Body:       io.NopCloser(bytes.NewReader(bytes.Repeat([]byte("b"), 20<<20))),
+			Header:     make(http.Header),
+		}
+	})
+
+	got, err := checker.Http(context.Background(), client, request.HttpCheckerRequest{URL: "https://openstat.us", CronTimestamp: 1})
+	if err != nil {
+		t.Fatalf("Http() error = %v", err)
+	}
+	if got.Body != string(bytes.Repeat([]byte("b"), 10<<20)) {
+		t.Errorf("Http() body length = %d, want %d (capped by maxResponseBodyBytes)", len(got.Body), 10<<20)
+	}
+}
+
 func Test_ping(t *testing.T) {
 
 	type args struct {
-- 
2.51.2