Deadlock scenario:
1. Due to scheduling, the state runner sends one snapshot into
snapCh and then attempts to send a second. The first send succeeds
because the channel is buffered, but the second blocks.
2. Separately, Manager.Watch is called by the xDS server after
getting a discovery request from Envoy. This function acquires the
manager lock and then blocks on receiving the CurrentSnapshot from
the state runner.
3. Separately, there is a Manager goroutine that reads the snapshots
from the channel in step 1. These reads are done to notify proxy
watchers, but they require holding the manager lock. This goroutine
goes to acquire that lock, but can't because it is held by step 2.
Now, the goroutine from step 3 is waiting on the one from step 2 to
release the lock. The goroutine from step 2 won't release the lock until
the goroutine in step 1 advances. But the goroutine in step 1 is waiting
for the one in step 3. Deadlock.
By making this send non-blocking step 1 above can proceed. The coalesce
timer will be reset and a new valid snapshot will be delivered after it
elapses or when one is requested by xDS.
This allows setting ForceWithoutCrossSigning when reconfiguring the CA
for any provider, in order to forcibly move to a new root in cases where
the old provider isn't reachable or able to cross-sign for whatever
reason.
This commit makes a number of changes that should make
TestLoad_FullConfig easier to work with, and make the test more like
real world scenarios.
* use separate files in testdata/ dir to store the config source.
Separate files are much easier to edit because editors can syntax
highlight json/hcl, and it makes strings easier to find. Previously
trying to find strings would match strings used in other tests.
* use the exported config.Load interface instead of internal NewBuilder
and BuildAndValidate.
* remove the tail config overrides, which are only necessary with
nonZero works.
This commit reduces the interface to Load() a bit, in preparation for
unexporting NewBuilder and having everything call Load.
The three arguments are reduced to a single argument by moving the other
two into the options struct.
The three return values are reduced to two by moving the RuntimeConfig
and Warnings into a LoadResult struct.
Previously the ServiceManager had to run a separate goroutine so that it could block on a channel
send/receive instead of a lock. Using this mutex with TryLock allows us to cancel the lock when
the serviceConfigWatch is stopped.
Without this change removing the ServiceManager.Start goroutine would not be possible because
when AddService is called it acquires the stateLock. While that lock is held, if there are
existing watches for the service, the old watch will be stopped, and the goroutine holding the
lock will attempt to wait for that watcher goroutine to exit.
If the goroutine is handling an update (serviceConfigWatch.handleUpdate) then it can block on
acquiring the stateLock and deadlock the agent. With this change the context is cancelled as
and the goroutine will exit instead of waiting on the stateLock.
The ServiceManager.Start goroutine was used to serialize calls to
agent.addServiceInternal.
All the goroutines which sent events to the channel would block waiting
for a response from that same goroutine, which is effectively the same
as a synchronous call without any channels.
This commit removes the goroutine and channels, and instead calls
addServiceInternal directly. Since all of these goroutines will need to
take the agent.stateLock, the mutex handles the serializing of calls.
Move the field into the struct for addServiceLocked. Also don't require
setting a default value, so that the callers can leave it as nil if they
don't already have a snapshot.
Replace with the existing AddServiceRequest struct. These structs are
almost identical. Additionally, the only reason the serviceRegistration
struct existed was to recreate an AddServiceRequest.
By storing and re-using the AddServiceRequest we remove the need to
translate into one type and back to the original type.
We also remove the extra parameters to a function, because those values
are already available from the AddServiceRequest field.
Also a minor optimization to only call tokens.AgentToken() when
necessary. Previous it was being called every time, but the value was
being ignored if the AddServiceRequest had a token.
Handle the decision to use ServiceManager in a single place. Instead of
calling ServiceManager.AddService, then calling back into
addServiceInternal, only call ServiceManager.AddService if we are going
to use it.
This change removes some small duplication and removes a branch from the
AddService flow.
The temprorary variables make it much harder to trace where and how struct
fields are used. If a field is only used a small number of times than
refer to the field directly.
The method is only used in tests, and only exists for legacy calls.
There was one other package which used this method in tests. Export
the AddServiceRequest and a couple of its fields so the new function can
be used in those tests.
This way we only have to wait for the serf barrier to pass once before
we can make use of federation state APIs Without this patch every
restart needs to re-compute the change.
