chore(client/retry): include error info in logs when retry occurs (#487)

On a request retry, it logs an info message stating that an error was encountered and information about the retry process but it hasn't included any details about the error that is causing the retry. This PR updates the logging to include the status if it is a server error and the http error kind if a transport error occurred. While the last error when retries are exhausted is returned up the call stack, the intermediate errors need not be exactly the same. It is helpful to include some minimum information about what error triggered a retry each time it happens.

Author: philjb

src/client/retry.rs

@@ -421,7 +421,8 @@ impl RetryableRequest {
 
  let sleep = ctx.backoff();
  info!(
- "Encountered server error, backing off for {} seconds, retry {} of {}",
+ "Encountered server error with status {}, backing off for {} seconds, retry {} of {}",
+ status,
  sleep.as_secs_f32(),
  ctx.retries,
  ctx.max_retries,
@@ -445,7 +446,8 @@ impl RetryableRequest {
  }
  let sleep = ctx.backoff();
  info!(
- "Encountered transport error backing off for {} seconds, retry {} of {}: {}",
+ "Encountered transport error of kind {:?}, backing off for {} seconds, retry {} of {}: {}",
+ e.kind(),
  sleep.as_secs_f32(),
  ctx.retries,
  ctx.max_retries,