davisp commented on a change in pull request #1370: [5/5] Clustered Purge
Implementation
URL: https://github.com/apache/couchdb/pull/1370#discussion_r197284544
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File path: src/fabric/src/fabric_rpc.erl
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@@ -298,6 +314,104 @@ with_db(DbName, Options, {M,F,A}) ->
rexi:reply(Error)
end.
+
+read_repair_filter(DbName, Docs, NodeRevs, Options) ->
+ set_io_priority(DbName, Options),
+ case get_or_create_db(DbName, Options) of
+ {ok, Db} ->
+ try
+ read_repair_filter(Db, Docs, NodeRevs)
+ after
+ couch_db:close(Db)
+ end;
+ Error ->
+ rexi:reply(Error)
+ end.
+
+
+% A read repair operation may have been triggered by a node
+% that was out of sync with the local node. Thus, any time
+% we receive a read repair request we need to check if we
+% may have recently purged any of the given revisions and
+% ignore them if so.
+%
+% This is accomplished by looking at the purge infos that we
+% have locally that have not been replicated to the remote
+% node. The logic here is that we may have received the purge
+% request before the remote shard copy. So to check that we
+% need to look at the purge infos that we have locally but
+% have not yet sent to the remote copy.
+%
+% NodeRevs is a list of the {node(), [rev()]} tuples passed
+% as the read_repair option to update_docs.
+read_repair_filter(Db, Docs, NodeRevs) ->
+ [#doc{id = DocId} | _] = Docs,
+ Nodes = lists:usort([Node || {Node, _} <- NodeRevs, Node /= node()]),
+ NodeSeqs = get_node_seqs(Db, Nodes),
Review comment:
Also, the reason for that is that this is a read repair is only ever called
from fabric_doc_open and fabric_doc_open_revs and we're just sending the
revisions that we get from each node in the response. And worst case would be
every node in the cluster if we ever improved that algorithm to do parallel
opens.
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