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async extension done

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Joey Hess 2020-08-14 15:24:34 -04:00
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31
doc/design/external_special_remote_protocol/async_appendix.mdwn
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@ -1,5 +1,3 @@
(This is a draft and not implemented yet.)
This is an appendix to the [[external_special_remote_protocol]].
[[!toc]]
@ -10,7 +8,7 @@ Normally, an external special remote can only be used to do one thing at a
time, and when git-annex has concurrency enabled, it will start up multiple
processes for the same external special remote.
This extension lets a single external special remote process handle
The `ASYNC` extension lets a single external special remote process handle
multiple concurrent jobs, which can be useful if multiple processes
would use too many resources, or if it can be better coordinated using a
single process.
@ -28,10 +26,15 @@ that includes `ASYNC`, and the external special remote responding in kind.
EXTENSIONS INFO ASYNC
EXTENSIONS ASYNC
From this point forward, every message in the protocol is tagged with a job
number, by prefixing it with "J n".
(Older versions of git-annex will not include `ASYNC` in their extensions
list. To support them, it's a good idea for the external special remote to
fall back to using the regular protocol.)
As usual, the first message git-annex sends is generally PREPARE:
Once the extension is negotiated, messages in the protocol are
tagged with a job number, by prefixing them with "J n".
As usual, the first message git-annex sends is generally PREPARE,
which gets tagged with a job number:
J 1 PREPARE
@ -48,7 +51,7 @@ at the same time, using different job numbers:
The special remote can now perform both transfers at the same time.
If it sends PROGRESS messages for these transfers, they have to be tagged
with the job number:
with the job numbers:
J 1 PROGRESS 10
J 2 PROGRESS 500
@ -73,18 +76,11 @@ Lots of different jobs can be requested at the same time.
J 4 CHECKPRESENT Key3
J 5 CHECKPRESENT Key4
J 6 REMOVE Key3
J 6 REMOVE Key5
J 4 CHECKPRESENT-SUCCESS Key3
J 6 REMOVE-SUCCESS Key3
J 6 REMOVE-SUCCESS Key5
J 5 CHECKPRESENT-FAILURE Key4
An example of sending multiple replies to a request is `LISTCONFIGS`, eg:
J 7 LISTCONFIGS
J 7 CONFIG foo some config
J 7 CONFIG bar other config
J 7 CONFIGEND
## notes
There will be one job number for each thread that git-annex runs
@ -97,3 +93,6 @@ special remote to run that and any other jobs.
`ERROR` should not be tagged with a job number if either git-annex
or the special remote needs to send it.
`VERSION`, `EXTENSIONS` and `ERROR` are the only protocol messages
that do not get tagged with a job number.