Please check usage of ResourceAccessException vs. RestClientException wrapping IOException in DefaultRestClient

[helmut-hackl-dynatrace]

Affects: spring web 6.1.11

it's not really clear when a ResourceAccessException (wrapping an IOException) or its base class RestClientException (which can also wrap an IOException) is thrown in org.springframework.web.client.DefaultRestClient.

eg.
when calling responseWrapper.hasEmptyMessageBody() in readWithMessageConverters and the getBody() call to an underlying ReactorNettyClientResponse does timeout (wrapped into an IOException) - i would expect a ResourceAccessException.

 /**
 * Exception thrown when an I/O error occurs.
 *
 * @author Arjen Poutsma
 * @since 3.0
 */
public class ResourceAccessException extends RestClientException {

from stacktrace:

2024-09-02 03:46:34.003 UTC WARN [svm25641,dynatrace.launcher] [qtp242113956-122375] ClusterAppManifestsFetcherImpl: Cannot fetch app icon from cluster endpoint https://svm25641.apps.internal.dynatrace.com/platform-internal/cluster-internal/manifest/dynatrace.classic.databases/icon
org.springframework.web.client.RestClientException: Error while extracting response for type [org.springframework.core.io.Resource] and content type [image/png]
	at org.springframework.web.client.DefaultRestClient.readWithMessageConverters(DefaultRestClient.java:240)
	at org.springframework.web.client.DefaultRestClient$DefaultResponseSpec.readBody(DefaultRestClient.java:685)
	at org.springframework.web.client.DefaultRestClient$DefaultResponseSpec.toEntityInternal(DefaultRestClient.java:655)
	at org.springframework.web.client.DefaultRestClient$DefaultResponseSpec.toEntity(DefaultRestClient.java:644)

Caused by: java.io.IOException: null
	at org.springframework.http.client.ReactorNettyClientRequest.convertException(ReactorNettyClientRequest.java:143)
	at org.springframework.http.client.ReactorNettyClientResponse.getBody(ReactorNettyClientResponse.java:87)
	at org.springframework.web.client.DefaultRestClient$DefaultConvertibleClientHttpResponse.getBody(DefaultRestClient.java:748)
	at org.springframework.web.client.IntrospectingClientHttpResponse.hasEmptyMessageBody(IntrospectingClientHttpResponse.java:83)
	at org.springframework.web.client.DefaultRestClient.readWithMessageConverters(DefaultRestClient.java:203)
	... 176 common frames omitted
Caused by: io.netty.handler.timeout.ReadTimeoutException: null

[rstoyanchev]

I think ResourceAccessException is about early I/O issues that result from request execution, and that does not include I/O errors from handling the response.