Fix connection pool leak when response is not modified - #4260
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When checkNotModified short-circuits writeTo for GET/HEAD, writeToInternal never runs, so RestClientProxyExchange does not close the upstream ClientHttpResponse and Apache HttpClient connections stay leased. Close the ClientHttpResponse stored in CLIENT_RESPONSE_ATTR on the not-modified path so the connection returns to the pool. Fixes spring-cloudgh-4259 Signed-off-by: arimu1 <19286898+arimu1@users.noreply.github.com>
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Fixes #4259
Description
When a proxied GET/HEAD response is short-circuited as HTTP 304 Not Modified in
AbstractGatewayServerResponse#writeTo,writeToInternalis never invoked. That path is whereRestClientProxyExchange/ClientHttpRequestFactoryProxyExchangeclose the upstreamClientHttpResponseand return the connection to the pool.As a result, with Apache HttpComponents Client 5, leased connections are not released after conditional requests that evaluate to not modified.
Change
On the not-modified short-circuit, close the
ClientHttpResponsestored inMvcUtils.CLIENT_RESPONSE_ATTR(same attribute the reporter’s workaround interceptor closed), then clear the attribute.No change to the 304 short-circuit behavior itself—only resource cleanup when the body write is skipped.
Tests
RestClientProxyExchangeTests#exchangeWhenNotModifiedThenClosesClientResponse(If-None-Match + matching ETag → 304 andClientHttpResponse.close())./mvnw -pl spring-cloud-gateway-server-webmvc -am test -Dtest=RestClientProxyExchangeTests(Temurin 21): 2/2Notes