From ed4bdee6fa544a2c45a557726723b2a7d7e1958b Mon Sep 17 00:00:00 2001
From: Fae Charlton <fae.charlton@elastic.co>
Date: Fri, 22 Nov 2019 10:58:11 -0500
Subject: [PATCH] Workaround for missing offsets in Azure's OffsetFetchResponse

---
 broker.go | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/broker.go b/broker.go
index 81467498c..6a7dbeee1 100644
--- a/broker.go
+++ b/broker.go
@@ -387,6 +387,23 @@ func (b *Broker) FetchOffset(request *OffsetFetchRequest) (*OffsetFetchResponse,
 		return nil, err
 	}
 
+	// In new consumer group / partition pairs, Microsoft's Azure Event Hubs
+	// communicates the "no error / new offset" state by omitting the requested
+	// entries from the OffsetFetchResponse (in contrast to other implementations
+	// which indicate this by returning an explicit offset of -1). To handle this
+	// case, we check all entries in the request and add an offset to the response
+	// table for any that are missing.
+	for topic, partitions := range request.partitions {
+		if response.Blocks[topic] == nil {
+			response.Blocks[topic] = make(map[int32]*OffsetFetchResponseBlock)
+		}
+		for _, p := range partitions {
+			if response.Blocks[topic][p] == nil {
+				response.Blocks[topic][p] = &OffsetFetchResponseBlock{Offset: -1}
+			}
+		}
+	}
+
 	return response, nil
 }