watch: support multiple containers for tar implementation #10860
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milas
requested review from
nicksieger,
ndeloof,
StefanScherer,
ulyssessouza,
glours and
laurazard
and removed request for
a team
Support services with scale > 1 for the tar watch sync. Add a "lossy" multi-writer specific to pipes that writes the tar data to each `io.PipeWriter`, which is connected to `stdin` for the `tar` process being exec'd in the container. The data is written serially to each writer. This could be adjusted to do concurrent writes but that will rapidly increase the I/O load, so is not done here - in general, 99% of the time you'll be developing (and thus using watch/sync) with a single replica of a service. If a write fails, the corresponding `io.PipeWriter` is removed from the active set and closed with an error. This means that a single container copy failing won't stop writes to the others that are succeeding. Of course, they will be in an inconsistent state afterwards still, but that's a different problem. Signed-off-by: Milas Bowman <milas.bowman@docker.com>
glours
approved these changes
Aug 2, 2023
Codecov ReportPatch coverage:
Additional details and impacted files@@ Coverage Diff @@
## v2 #10860 +/- ##
==========================================
- Coverage 59.88% 58.29% -1.60%
==========================================
Files 118 120 +2
Lines 10064 10377 +313
==========================================
+ Hits 6027 6049 +22
- Misses 3440 3728 +288
- Partials 597 600 +3
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What I did
Support services with scale > 1 for the tar watch sync.
Add a "lossy" multi-writer specific to pipes that writes the tar data to each
io.PipeWriter, which is connected tostdinfor thetarprocess being exec'd in the container.The data is written serially to each writer. This could be adjusted to do concurrent writes but that will rapidly increase the I/O load, so is not done here - in general, 99% of the time you'll be developing (and thus using watch/sync) with a single replica of a service.
If a write fails, the corresponding
io.PipeWriteris removed from the active set and closed with an error.This means that a single container copy failing won't stop writes to the others that are succeeding. Of course, they will be in an inconsistent state afterwards still, but that's a different problem.
(not mandatory) A picture of a cute animal, if possible in relation to what you did
