Fix lease expiration check #19092
Fix lease expiration check #19092
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The new test checks if `leasingKV.Get()` correctly checks for lease expiration by checking if it (incorrectly) returns stale values when network partitioned from the rest of the system. Signed-off-by: Upamanyu Sharma <[email protected]>
This helps fix the failing test TestLeasingGetChecksForExpiration. Previously, the `leasing` library relied on *not* receiving something over the `session.Done()` channel in `readySession()`. Failing to immediately receive over the channel does not guarantee that the lease is actually still valid. Signed-off-by: Upamanyu Sharma <[email protected]>
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client/v3/lease.go
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| @@ -136,6 +136,10 @@ type Lease interface { | |||
| // (see https://github.com/etcd-io/etcd/pull/7866) | |||
| KeepAlive(ctx context.Context, id LeaseID) (<-chan *LeaseKeepAliveResponse, error) | |||
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| // Unexpired returns true iff the lease is unexpired (more precisely: iff the | |||
| // lease was unexpired during the execution of the Unexpired() call). | |||
| Unexpired(id LeaseID) bool | |||
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Let's avoid negative logic in the interface. !Expired(id) should be simpler.
Signed-off-by: Upamanyu Sharma <[email protected]>
Fixes #19091.
This PR adds and uses a client-side
Unexpired()method that determines if a lease is valid by checking if its expiration time is after the current time. This helps fix a bug in the clientleasinglibrary, and provides a general API to check if a lease is valid, which was not previously exposed to users.This adds a new test for
leasingwhich does a few Puts and Gets with delays and with a client that gets network partitioned. The test fails often on the oldleasingimplementation. The bug withinleasingwas here:etcd/client/v3/leasing/kv.go
Lines 469 to 473 in 9fa35e5
This code tries to determine if a session is "ready" by checking if an non-blocking receive on
lkv.session.Done()fails. However, failing to immediately receive on achandoes not guarantee anything: the other side's send orclosemay just have been delayed by a bit.Fortunately for reproducing the problem, there's a delay already present in the code: the
Done()channel is closed by a background loop that sleeps and periodically checks whether the lease is expired. If the lease expires while this loop is sleeping, there is a delay between the true expiration time and when theDone()channel is closed, which seems to make the test fail relatively reliably (it still sometimes takes a few tries to get a failure).Using
Unexpired(), the test always appears to pass.I couldn't find other places using etcd leases with the problematic pattern from the
leasinglibrary, but I'm admittedly not sure how theLeaselibrary is used by others.