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Posted to reviews@spark.apache.org by "vinodkc (via GitHub)" <gi...@apache.org> on 2026/07/17 00:12:13 UTC
[PR] [SPARK-58162][Connect] Bound the unbounded RetryException retry loop in reattach path [spark]
vinodkc opened a new pull request, #57320:
URL: https://github.com/apache/spark/pull/57320
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### What changes were proposed in this pull request?
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When a Spark Connect client runs a query, it stays connected to the server through a "reattach" mechanism that can reconnect if the stream drops. If certain errors happen during that reconnect, the client throws an internal RetryException and tries again.
The problem: this particular retry has no limit — no max attempts, no waiting between tries, no time cap. If the error keeps happening, the client retries forever and the query just hangs.
This can happen in two situations:
1. The server says it can't find the operation or session (for example, a load balancer sent the request to the wrong server that never got it).
2. The reconnect keeps timing out (the connection is dead but nobody noticed).
This PR puts a time limit on that retry loop:
- It adds a setting, `maxRetryExceptionElapsedTime`, that defaults to 1 hour. The client keeps retrying as before, but once it has spent a total of 1 hour retrying this specific error, it gives up.
- When it gives up, it reports the real underlying error (like a timeout) instead of a confusing internal marker, so the user knows what actually went wrong.
- The same fix is applied to both the Scala client and the Python (PySpark) client so they behave identically.
- The 1-hour limit can be changed by advanced users through the client builder (Scala) or a constructor argument (Python). There's no new config file setting or command-line flag.
- The 1-hour limit only counts time spent stuck in the RetryException retry loop — not the total runtime of your query.
- The clock starts on the first RetryException and only accumulates while the client is repeatedly failing to reattach (connection dead, operation not found, reconnect timing out).
- As long as the server is making progress and sending results back, no RetryException is being thrown, so the clock never starts. A query can run for 6 hours, 12 hours, or longer with zero impact.
### Why are the changes needed?
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Today, the only reason this loop ever stops is that a separate feature — gRPC keepalive, which detects dead connections — happens to be on and working. That is not something the retry logic should depend on:
- The "operation/session not found" case doesn't benefit from keepalive at all; it can spin forever regardless.
- If keepalive is turned off or misconfigured on the client, the loop can hang even against a perfectly healthy server.
Under the default setup the hang is usually avoided, so this is best seen as closing a hidden gap and hardening the client — the retry loop now stops on its own instead of depending on another feature being configured correctly everywhere.
### Does this PR introduce _any_ user-facing change?
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Yes. Behavior is unchanged until the 1-hour default limit is reached — at which point a previously infinite hang now surfaces the real underlying error instead. Advanced users can adjust the limit via the new Builder method / constructor argument.
Scope of the limit: the timer is measured within a single next()/hasNext() call and only advances on consecutive DEADLINE_EXCEEDED-driven reattaches with no successful response in between — it is not a cumulative counter across a job's lifetime. Idle streams are unaffected: the server completes an idle reattach stream cleanly every senderMaxStreamDuration (default 2 min, well under the client's ~10-min reattach deadline), which the client handles as a graceful reattach that does not touch the timer. The limit therefore only trips when a single call fails continuously for the full hour, i.e. a genuinely dead connection.
### How was this patch tested?
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Added tests in `SparkConnectClientRetriesSuite`, `test_client_retries.py` covering: the limit is enforced, below-limit retries still work (non-regression), the fallback when no underlying cause is attached, the timer starting only at the first `RetryException`, and the default value.
One `SparkConnectClientSuite` test exercises the whole path end-to-end against a test server that never responds.
Each test was checked to hang without the fix reproducing the original bug and confirming they are real regression guards.
### Was this patch authored or co-authored using generative AI tooling?
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Yes, Generated-by: Claude Code (sonnet-5)
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Re: [PR] [SPARK-58162][Connect] Bound the unbounded RetryException retry loop in reattach path [spark]
Posted by "cloud-fan (via GitHub)" <gi...@apache.org>.
cloud-fan commented on PR #57320:
URL: https://github.com/apache/spark/pull/57320#issuecomment-5023469851
**Merge Summary:**
- merged into master https://github.com/apache/spark/commit/b9a3de5bc23190d21517e7111a7bfaa7e09d7bdd
- merged into branch-4.x https://github.com/apache/spark/commit/19002876b470e051e274c62171d2e0769d75d4dd
*Posted by `merge_spark_pr.py`*
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Re: [PR] [SPARK-58162][Connect] Bound the unbounded RetryException retry loop in reattach path [spark]
Posted by "cloud-fan (via GitHub)" <gi...@apache.org>.
cloud-fan commented on code in PR #57320:
URL: https://github.com/apache/spark/pull/57320#discussion_r3604453015
##########
python/pyspark/sql/tests/connect/client/test_client_retries.py:
##########
@@ -256,6 +270,104 @@ def test_deadline_exceeded_not_retried_by_retry_handler(self):
self.assertEqual(tries, 1)
self.assertEqual(len(sleep_tracker.times), 0)
+ def test_retry_exception_bounded_by_elapsed_time(self):
+ # Each attempt simulates a full 10-min reattach deadline elapsing before RetryException
+ # is raised. The elapsed clock starts on the first RetryException, after that attempt
+ # already advanced the clock, so with a 1-hour bound and a 10-min-per-attempt advance the
+ # loop gives up after bound // increment + 1 = 7 attempts: attempts 1-6 leave elapsed
+ # < 1h, and attempt 7 leaves elapsed = 6 * 10min = 1h >= bound, tripping the throw.
+ client = SparkConnectClient("sc://foo/;token=bar")
+ clock = FakeClock()
+ cause = TestException("deadline exceeded", code=grpc.StatusCode.DEADLINE_EXCEEDED)
+ tries = 0
+ with self.assertRaises(TestException) as cm:
+ for attempt in Retrying(
+ client._retry_policies,
+ sleep=lambda t: None,
+ now=clock.now,
+ max_retry_exception_elapsed_time=DEFAULT_MAX_RETRY_EXCEPTION_ELAPSED_TIME,
+ ):
+ with attempt:
+ tries += 1
+ clock.advance(10 * 60)
+ raise RetryException() from cause
+ self.assertIs(cm.exception, cause)
+ self.assertEqual(tries, 7)
+
+ def test_retry_exception_below_bound_keeps_retrying(self):
+ # Non-regression: well under the elapsed-time budget, RetryException retries should
+ # keep behaving as before (immediate retry, no policy consulted) until success.
+ client = SparkConnectClient("sc://foo/;token=bar")
+ clock = FakeClock()
+ tries = 0
+ for attempt in Retrying(
+ client._retry_policies,
+ sleep=lambda t: None,
+ now=clock.now,
+ max_retry_exception_elapsed_time=DEFAULT_MAX_RETRY_EXCEPTION_ELAPSED_TIME,
+ ):
+ with attempt:
+ tries += 1
+ if tries <= 3:
+ clock.advance(10)
+ raise RetryException()
+ self.assertEqual(tries, 4)
+
+ def test_retry_exception_bare_no_cause_raises_self_when_bound_exceeded(self):
+ # If a RetryException has no attached cause (e.g. the OPERATION_NOT_FOUND/
+ # SESSION_NOT_FOUND path, which today raises a bare RetryException), falling back to
+ # raising the bare RetryException itself once the bound is exceeded.
Review Comment:
This conditional is a sentence fragment.
```suggestion
# If a RetryException has no attached cause (e.g. the OPERATION_NOT_FOUND/
# SESSION_NOT_FOUND path, which today raises a bare RetryException), fall back to
# raising the bare RetryException itself once the bound is exceeded.
```
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Re: [PR] [SPARK-58162][Connect] Bound the unbounded RetryException retry loop in reattach path [spark]
Posted by "vinodkc (via GitHub)" <gi...@apache.org>.
vinodkc commented on code in PR #57320:
URL: https://github.com/apache/spark/pull/57320#discussion_r3605553877
##########
python/pyspark/sql/tests/connect/client/test_client_retries.py:
##########
@@ -256,6 +270,104 @@ def test_deadline_exceeded_not_retried_by_retry_handler(self):
self.assertEqual(tries, 1)
self.assertEqual(len(sleep_tracker.times), 0)
+ def test_retry_exception_bounded_by_elapsed_time(self):
+ # Each attempt simulates a full 10-min reattach deadline elapsing before RetryException
+ # is raised. The elapsed clock starts on the first RetryException, after that attempt
+ # already advanced the clock, so with a 1-hour bound and a 10-min-per-attempt advance the
+ # loop gives up after bound // increment + 1 = 7 attempts: attempts 1-6 leave elapsed
+ # < 1h, and attempt 7 leaves elapsed = 6 * 10min = 1h >= bound, tripping the throw.
+ client = SparkConnectClient("sc://foo/;token=bar")
+ clock = FakeClock()
+ cause = TestException("deadline exceeded", code=grpc.StatusCode.DEADLINE_EXCEEDED)
+ tries = 0
+ with self.assertRaises(TestException) as cm:
+ for attempt in Retrying(
+ client._retry_policies,
+ sleep=lambda t: None,
+ now=clock.now,
+ max_retry_exception_elapsed_time=DEFAULT_MAX_RETRY_EXCEPTION_ELAPSED_TIME,
+ ):
+ with attempt:
+ tries += 1
+ clock.advance(10 * 60)
+ raise RetryException() from cause
+ self.assertIs(cm.exception, cause)
+ self.assertEqual(tries, 7)
+
+ def test_retry_exception_below_bound_keeps_retrying(self):
+ # Non-regression: well under the elapsed-time budget, RetryException retries should
+ # keep behaving as before (immediate retry, no policy consulted) until success.
+ client = SparkConnectClient("sc://foo/;token=bar")
+ clock = FakeClock()
+ tries = 0
+ for attempt in Retrying(
+ client._retry_policies,
+ sleep=lambda t: None,
+ now=clock.now,
+ max_retry_exception_elapsed_time=DEFAULT_MAX_RETRY_EXCEPTION_ELAPSED_TIME,
+ ):
+ with attempt:
+ tries += 1
+ if tries <= 3:
+ clock.advance(10)
+ raise RetryException()
+ self.assertEqual(tries, 4)
+
+ def test_retry_exception_bare_no_cause_raises_self_when_bound_exceeded(self):
+ # If a RetryException has no attached cause (e.g. the OPERATION_NOT_FOUND/
+ # SESSION_NOT_FOUND path, which today raises a bare RetryException), falling back to
+ # raising the bare RetryException itself once the bound is exceeded.
Review Comment:
Fixed.
Thanks
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Re: [PR] [SPARK-58162][Connect] Bound the unbounded RetryException retry loop in reattach path [spark]
Posted by "cloud-fan (via GitHub)" <gi...@apache.org>.
cloud-fan closed pull request #57320: [SPARK-58162][Connect] Bound the unbounded RetryException retry loop in reattach path
URL: https://github.com/apache/spark/pull/57320
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