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Summit2Day3.md

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+# [2nd Summit](Summit) Day 3
+
+10-Nov-2011, Mozilla SF.
+
+No video due to technical problems.
+
+## Attendees
+* Zooko
+* David-Sarah
+* Zancas
+* Brian
+* Bill Frantz
+* Sam Stoller
+
+## Goals
+
+* David-Sarah to present LAE's s3-backend branch
+* figure out merge plan for s3-backend and accounting
+* figure out leasedb crawler: detailed case analysis
+
+## Topics
+
+* (one-person) Tahoe InstallFest!
+ * successfully got Tahoe installed on Bill Frantz's laptop. Excitement
+   ensued from its lack of XCode and gcc. Eggs were built and
+   installation proceeded smoothly.
+* (one-person) LAE Customer Setup!
+ * successfully (eventually) got Brian signed up as an LAE customer.
+   Kinda neat to include a PGP fingerprint on a signup form. Succeeded
+   in uploading a (small) test file.
+* quick review of LAE's s3-backend branch (davidsarah)
+ * brian hesitant about apparent complexity, but mitigated by the
+   pre-existing messy complexity of the non-pluggable-backend code.
+ * all parties looking forward to ripping out lease code and replacing
+   with whatever comes out of brian's Accounting project
+ * s3 backend currently has memory-footprint problems with large shares
+ * branch also includes extra cleanups:
+   `twisted.python.filepath`-ification, whitespace cleanups,
+   `Interface`-de-parameterization, client-side comment fixes.
+   Hopefully these will turn into separate patches which can be landed
+   separately.
+* discussion of mutable-file CAP stuff
+ * proposal to use two-phase commit and locking to improve mutable-file
+   data preservation
+ * general idea would be that servers allow one client to lock the next
+   version of a share (for some limited time), then clients obtain lock
+   on all shares before committing to a change. If clients observe
+   contention (i.e. they are refused a lock because some second client
+   already grabbed it), abandon all locks and back off.
+ * additional idea: servers retain previous version of share until a
+   third phase lets them delete it. Clients obtain lock, upload+commit
+   to v2, when all servers report success, clients delete v1. Some
+   failure cases result in mix of (v1-only) and (v1+v2) servers. Repair
+   would need to spot these and be able to roll back to v1. Servers
+   would need to report all versions that had been committed. Readers
+   could see v1 and v2 and deliver v1 if v2 is not recoverable.