[tahoe-lafs-trac-stream] [Tahoe-LAFS] #3773: Merge adding lease with renewing lease (for immutables)

[Tahoe-LAFS]

#3773: Merge adding lease with renewing lease (for immutables)
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 Reporter:  itamarst  |          Owner:  itamarst
     Type:  task      |         Status:  new
 Priority:  normal    |      Milestone:  HTTP Storage Protocol
Component:  unknown   |        Version:  n/a
 Keywords:            |  Launchpad Bug:
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 1. From a client perspective, the goal is just to have a lease, whether
 it's a new lease or renewing a lease is irrelevant; renewing is
 essentially an optimization detail on server side.
 2. Cancelling leases is not actually supported.
 3. The way lease renewal secrets are generated is likely to change in the
 switchover from foolscap to HTTP.
 4. Internally, the server _already_ treats renewing a lease as potentially
 adding a new one if renewal fails.

 As such, the distinction between adding a lease and renewing a lease is
 unnecessary (presuming item 4 is actually correct!).

 Therefore, we should merge the two into a single operation:

 1. Validate item 4 above, since it's critical requirement for the rest of
 this.
 2. In Foolscap client, switch to only using renewal code path.
 3. Make sure server creating new lease when renewal fails is well tested,
 so users don't lose data.
 4. On server-side, leave new lease Foolscap endpoint in place for
 backwards compat.
 5. In new GBS HTTP protocol spec, switch to a single end point for lease
 creation/renewal, and remove all references to lease cancellation secret.

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Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/3773>
Tahoe-LAFS <https://Tahoe-LAFS.org>
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