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authorLinus Nordberg <linus@nordu.net>2015-11-10 12:44:08 +0100
committerLinus Nordberg <linus@nordu.net>2015-11-10 12:48:47 +0100
commit6e7f0485d8e42278942d64569c19f2b9f504e11a (patch)
treeb0a182d1e25426ae15c9e3c9b3f07bbc10055606 /doc/merge.txt
parent5980ad90b48623afb0c6135339fa6e5b1191d752 (diff)
Add documentation.
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+-*- markdown -*-
+
+The merge process
+=================
+
+- merge-fetch maintains a single file 'fetched' referring to a given
+ entry in 'logorder', indicating which entries are fetched and
+ sequenced so far.
+
+- merge-backup reads 'fetched' and pushes these entries to secondary
+ merge nodes, maintaining one file per secondary,
+ 'backup.<secondary>', indicating how many entries that have been
+ copied to and verified at the secondary in question.
+
+- merge-sth writes a new 'sth' file by reading the
+ 'backup.<secondary>' files into a list, picking a new tree size by
+ sorting the list (in falling order) and indexing it with the
+ 'backupquorum' config option. If the new tree size is smaller than
+ what the old 'sth' file says, no new STH is created.
+
+- merge-dist distributes 'sth' and missing entries to frontend nodes.
+
+TODO
+====
+
+- Run the three pieces in parallell.
+
+- Improve merge-fetch by parallellising it using one process per
+storage node writing to a "queue info" file (storage-node, hash) and a
+single "queue handling process" reading queue files and writing to the
+'fetched' file.