There is a bug during upgrade from 6.6.x to 7.x when transactional ATR/client record documents are present.
1. There was an optimization done in 7.0(
MB-43704) to skip ATR/client records in projector and generate UpdateSeqno message in such a case.
2. In a mixed mode cluster, projector on 7.0.4 will skip any document with prefix "_txn:"(i.e. ATR/client records or any user created document with prefix "_txn:")
3. The problem is that a 6.6.5 indexer node cannot understand and process an UpdateSeqno message. So these UpdateSeqno messages will get skipped on the indexer node. If these UpdateSeqno messages correspond to SnapEnd of a DCP snapshot marker, indexer will keep waiting indefinitely and lead to index build hang.
|For Gerrit Dashboard: MB-54681|
|183453,4||MB-54681 Fix transaction record skipping at projector||unstable||indexing||Status: MERGED||+2||+1|
|183474,2||MB-54688 Fix transaction record skipping at projector||cheshire-cat||indexing||Status: ABANDONED||0||0|
|183476,2||MB-54688 Fix transaction record skipping at projector||cheshire-cat||indexing||Status: MERGED||+2||+1|
|185973,1||MB-54689 [BP 7.1.4] Fix transaction record skipping at projector||7.1.4||indexing||Status: MERGED||+2||+1|
|186518,1||MB-55216 [BP 7.2.0] Fix transaction record skipping at projector||neo||indexing||Status: MERGED||+2||+1|