client/setec: single-flight dynamic lookups #98
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danderson
approved these changes
Feb 16, 2024
For callers like scertec, it is very likely that a dynamic lookup may have a large number of goroutines that all want the same secrets near a (re)start. Single-flight the lookup so they don't all pound the secrets service and then race on poking the value into the store.
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bradfitz
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bradfitz
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client/setec/store.go
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| } else if !errors.Is(err, context.DeadlineExceeded) && !errors.Is(err, context.Canceled) { | ||
| return nil, err | ||
| } | ||
| // Cancelled or deadline exceeed. If it was us, we'll fall off the loop. | ||
| } | ||
| s.logf("[store] added new undeclared secret %q", name) | ||
| return s.secretLocked(name), nil | ||
| return nil, ctx.Err() |
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You don't return the best error here in the case of the non-coalesced caller hitting its timeout: rather than seeing a net/http Client Do timeout with a certain URL wrapping a timeout error, you'll instead just get a timeout.
On line 384 maybe add an || ctx.Err() != nil around the whole thing? Or look at the Result.Shared value?
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That makes sense to me. I found the formulation a little tricky with the negations as they were, so I reworked it a bit, see what you think.
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From a discussion with @bradfitz. We already have single-flighting in the
store for polls anyway, so this is a straightforward extension.
For callers like scertec, it is very likely that a dynamic lookup may have a
large number of goroutines that all want the same secrets near a (re)start.
Single-flight the lookup so they don't all pound the secrets service and then
race on poking the value into the store.