openstack/swift
Code Issues Proposed changes

Fix EC documentation of .durable quorum

Browse Source 
Update the doc to reflect the change [1] to ndata + 1
.durable files being committed before a success response
is returned for a PUT.

[1] Ifd36790faa0a5d00ec79c23d1f96a332a0ca0f0b

Change-Id: I1744d457bda8a52eb2451029c4031962e92c2bb7
This commit is contained in:
Alistair Coles 2015-10-08 18:50:20 +01:00
parent 6a9b868ae6
commit 01f9d15045
1 changed files with 5 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
doc/source/overview_erasure_code.rst
View File

@ -422,11 +422,10 @@ presence of a `ts.durable` file means, to the object server, `there is a set
of ts.data files that are durable at timestamp ts`. of ts.data files that are durable at timestamp ts`.
For the second phase of the conversation the proxy requires a quorum of For the second phase of the conversation the proxy requires a quorum of
`ec_nparity + 1` successful commits on storage nodes. This ensures that for `ec_ndata + 1` successful commits on storage nodes. This ensures that there are
as long there are sufficient (i.e. `ec_ndata`) fragment archives to reconstruct sufficient committed fragment archives for the object to be reconstructed even
the object then there will be a `.durable` file on at least one storage node. if one becomes unavailable. The reconstructor ensures that `.durable` files are
The reconstructor ensures that `.durable` files are replicated on storage nodes replicated on storage nodes where they may be missing.
where they may be missing.
Note that the completion of the commit phase of the conversation Note that the completion of the commit phase of the conversation
is also a signal for the object server to go ahead and immediately delete older is also a signal for the object server to go ahead and immediately delete older
@ -445,7 +444,7 @@ The basic flow looks like this:
* Upon receipt of commit message, object servers store a 0-byte data file as * Upon receipt of commit message, object servers store a 0-byte data file as
`<timestamp>.durable` indicating successful PUT, and send a final response to `<timestamp>.durable` indicating successful PUT, and send a final response to
the proxy server. the proxy server.
* The proxy waits for `ec_nparity + 1` object servers to respond with a * The proxy waits for `ec_ndata + 1` object servers to respond with a
success (2xx) status before responding to the client with a successful success (2xx) status before responding to the client with a successful
status. status.