Make config reloader file writes atomic #962
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This addresses an issue found in the Prometheus Operator, which reuses this reloader sidecar, but which then also has a second sidecar which may trigger rule-based reloads while the config sidecar is in the middle of writing out its config (in a non-atomic way): prometheus-operator/prometheus-operator#2501 I didn't add a test for this because it's hard to catch the original problem to begin with, but it has happened. Signed-off-by: Julius Volz <julius.volz@gmail.com>
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CI fails with: @juliusv I suspect you verified that the normal flow of the reloader works with this change? |
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I guess errcheck is a bit aggressive here, as the |
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Its definitely not aggressive (: it's just a matter of being explicit when you don't need error by doing: |
Signed-off-by: Julius Volz <julius.volz@gmail.com>
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I added an explicit error ignore now.
Nope :) Not beyond the existing test suite at least. |
bwplotka
approved these changes
Mar 22, 2019
pkg/reloader/reloader.go
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| @@ -199,9 +199,14 @@ func (r *Reloader) apply(ctx context.Context) error { | |||
| return errors.Wrap(err, "expand environment variables") | |||
| } | |||
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| if err := ioutil.WriteFile(r.cfgOutputFile, b, 0666); err != nil { | |||
| tmpFile := r.cfgOutputFile + ".tmp" | |||
| defer os.Remove(tmpFile) | |||
There was a problem hiding this comment.
You can satisfy errcheck by
defer func(){ _ := os.Remove(tmpFile) }()
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This addresses an issue found in the Prometheus Operator, which reuses
this reloader sidecar, but which then also has a second sidecar which
may trigger rule-based reloads while the config sidecar is in the middle
of writing out its config (in a non-atomic way):
prometheus-operator/prometheus-operator#2501
I didn't add a test for this because it's hard to catch the original
problem to begin with, but it has happened.
Signed-off-by: Julius Volz julius.volz@gmail.com