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Bound buffer for reading stats #14523

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merged 1 commit into from
Oct 16, 2023
Merged

Bound buffer for reading stats #14523

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4 changes: 3 additions & 1 deletion pkg/autoscaler/metrics/http_scrape_client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,9 @@ func statFromProto(body io.Reader) (Stat, error) {
b := pool.Get().(*bytes.Buffer)
b.Reset()
defer pool.Put(b)
_, err := b.ReadFrom(body)
// 6 8-byte fields (+2 bytes marshalling), one hostname, 20 bytes extra space
r := io.LimitedReader{R: body, N: 6*10 + 256 + 20}
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@skonto skonto Oct 19, 2023 •
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nit: Should not this be 255 for the max hostname? 🤔

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Extra-nit: you might need two bytes for the tag + length if the string is actually 256 bytes long, plus another possible tag + length for the entire message.

Proto doesn't have a way to express / enforce that a string is less than a certain size. The goal here is simply to avoid accidentally reading e.g. 5MB or more into an in-memory buffer when we know the actual report should be less than 1KB.

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@skonto skonto Oct 20, 2023 •
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Out of curiosity (haven't checked), what about using grpc instead?

_, err := b.ReadFrom(&r)
if err != nil {
return emptyStat, fmt.Errorf("reading body failed: %w", err)
}
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15 changes: 15 additions & 0 deletions pkg/autoscaler/metrics/http_scrape_client_test.go
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Expand Up @@ -95,6 +95,21 @@ func TestHTTPScrapeClientScrapeProtoErrorCases(t *testing.T) {
responseCode: http.StatusOK,
responseType: "text/html",
expectedErr: errUnsupportedMetricType.Error(),
}, {
name: "LongStat",
responseCode: http.StatusOK,
responseType: "application/protobuf",
stat: Stat{
// We don't expect PodName to be 600 characters long
PodName: strings.Repeat("a123456789", 60),
AverageConcurrentRequests: 1.1,
AverageProxiedConcurrentRequests: 1.1,
RequestCount: 33.2,
ProxiedRequestCount: 33.2,
ProcessUptime: 12345.678,
Timestamp: 1697431278,
},
expectedErr: "unmarshalling failed: unexpected EOF",
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nit: any way to distinguish we hit the limit vs EOF on the wire?

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Not easily. Technically, we could also end up skipping a bunch of extra garbage after a valid proto, but since the proto contains a length at the start, we can tell whether we read the whole proto or not just by reading the beginning. (In fact, it would be nice if the generated proto code had a method that read from an io.Reader, but it doesn't seem to.)

}}

for _, test := range testCases {
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