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fix: Make HttpLoadQueuePeon degrade gracefully instead of throwing on fetch failure #20128

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fix: Make HttpLoadQueuePeon degrade gracefully instead of throwing on fetch failure #20128

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12 changes: 10 additions & 2 deletions server/src/main/java/org/apache/druid/server/coordinator/loading/HttpLoadQueuePeon.java
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Original file line number Diff line number Diff line change
Expand Up @@ -178,7 +178,13 @@ private SegmentLoadingCapabilities fetchSegmentLoadingCapabilities()
return defaultCapabilities;
} else if (HttpServletResponse.SC_OK != responseHandler.getStatus()) {
log.makeAlert("Received status[%s] when fetching loading capabilities from server[%s]", responseHandler.getStatus(), serverId);
throw new RE("Received status[%s] when fetching loading capabilities from server[%s]", responseHandler.getStatus(), serverId);
int batchSize = config.getBatchSize() == null ? 1 : config.getBatchSize();
SegmentLoadingCapabilities defaultCapabilities = new SegmentLoadingCapabilities(batchSize, batchSize);
log.warn(
"Failed to fetch loading capabilities from server[%s]. Received status[%s]. Using default capabilities[%s].",
serverId, responseHandler.getStatus(), defaultCapabilities
);
return defaultCapabilities;
}

return jsonMapper.readValue(
Expand All @@ -187,7 +193,9 @@ private SegmentLoadingCapabilities fetchSegmentLoadingCapabilities()
);
}
catch (Throwable th) {
throw new RE(th, "Received error while fetching historical capabilities from Server[%s].", serverId);
log.warn(th, "Failed to fetch loading capabilities from server[%s]. Using default capabilities.", serverId);

@FrankChen021 FrankChen021 Aug 25, 2026

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[P2] Fallback swallows fatal and interruption signals

The Throwable catch now converts fatal Errors and InterruptedException into a normal peon. This can mask JVM-level failures and clear interruption without restoring the thread flag. Catch only expected request/parsing exceptions, while rethrowing fatal errors and preserving interruption.

int batchSize = config.getBatchSize() == null ? 1 : config.getBatchSize();
return new SegmentLoadingCapabilities(batchSize, batchSize);

@FrankChen021 FrankChen021 Aug 25, 2026

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[P2] Transient failures permanently throttle the peon

serverCapabilities is initialized once and cached for the peon's lifetime. After a temporary timeout, 5xx, or malformed response, the stored fallback remains active indefinitely; with no configured batchSize this reduces normal and turbo loading to one segment per batch. Retry capability discovery or refresh the fallback.

}
}

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