Can I use spring-retry on no response?

Question

Reading the docs I didn't see any mention of retrying if a call is taking too long. Does the RetryPolicy allow you to cancel a call before any response is received and initiate a retry?

Answer 1

A crucial part of the retry pattern is an exception, otherwise it cannot be called "retry" if no exception.

Your "too long request" easily fits into a request timeout concept which is usual fail in client with a RequestTimeoutException. So, your retry advice for the service call with a timeout should be configured to catch such an exception and retry on it.

This is really not a retry pattern responsibility to cancel request since there are just might not be such a hook or the cancelation can be too involved.

See for example, RestTemplate and its SimpleClientHttpRequestFactory:

/**
 * Set the underlying URLConnection's read timeout (in milliseconds).
 * A timeout value of 0 specifies an infinite timeout.
 * <p>Default is the system's default timeout.
 * @see URLConnection#setReadTimeout(int)
 */
public void setReadTimeout(int readTimeout) {

And its delegate:

/**
 * Sets the read timeout to a specified timeout, in
 * milliseconds. A non-zero value specifies the timeout when
 * reading from Input stream when a connection is established to a
 * resource. If the timeout expires before there is data available
 * for read, a java.net.SocketTimeoutException is raised. A
 * timeout of zero is interpreted as an infinite timeout.
 *
 * <p> Some non-standard implementation of this method ignores the
 * specified timeout. To see the read timeout set, please call
 * getReadTimeout().
 *
 * @param timeout an {@code int} that specifies the timeout
 * value to be used in milliseconds
 * @throws IllegalArgumentException if the timeout parameter is negative
 *
 * @see #getReadTimeout()
 * @see InputStream#read()
 * @since 1.5
 */
public void setReadTimeout(int timeout) {

The RestTemplate will wrap that SocketTimeoutException into a ResourceAccessException: Using sping's restTemplate with a timeout, how do I detect a timeout?