* Fix bug in cache where TTLs are effectively ignored
This mostly affects streaming since streaming will immediately return from Fetch calls when the state is Closed on eviction which causes the race condition every time.
However this also affects all other cache types if the fetch call happens to return between the eviction and then next time around the Get loop by any client.
There is a separate bug that allows cache items to be evicted even when there are active clients which is the trigger here.
* Add changelog entry
* Update .changelog/9978.txt
Prepopulate was setting entry.Expiry.HeapIndex to 0. Previously this would result in a call to heap.Fix(0)
which wasn't correct, but was also not really a problem because at worse it would re-notify.
With the recent change to extract cachettl it was changed to call Update(idx), which would have updated
the wrong entry.
A previous commit removed the setting of entry.Expiry so that the HeapIndex would be reported
as -1, and this commit adds a test and handles the -1 heap index.
And remove duplicate notifications.
Instead of performing the check in the heap implementation, check the
index in the higher level interface (Add,Remove,Update) and notify if one
of the relevant indexes is 0.
This will apply cache throttling parameters are properly applied:
* cache.EntryFetchMaxBurst
* cache.EntryFetchRate
When values are updated, a log is displayed in info.
This implements a solution for #7863
It does:
Add a new config cache.entry_fetch_rate to limit the number of calls/s for a given cache entry, default value = rate.Inf
Add cache.entry_fetch_max_burst size of rate limit (default value = 2)
The new configuration now supports the following syntax for instance to allow 1 query every 3s:
command line HCL: -hcl 'cache = { entry_fetch_rate = 0.333}'
in JSON
{
"cache": {
"entry_fetch_rate": 0.333
}
}
The rationale behind removing them is that all of our own code (xDS, builtin connect proxy) use the cache notification mechanism. This ensures that the blocking fetch behind the scenes is always executing. Therefore the only way you might go to get a certificate and have to wait is when 1) the request has never been made for that cert before or 2) you are using the v1/agent/connect/ca/leaf API for retrieving the cert yourself.
In the first case, the refresh change doesn’t alter the behavior. In the second case, it can be mitigated by using blocking queries with that API which just like normal cache notification mechanism will cause the blocking fetch to be initiated and to get leaf certs as soon as needed.
If you are not using blocking queries, or Envoy/xDS, or the builtin connect proxy but are retrieving the certs yourself then the HTTP endpoint might take a little longer to respond.
This also renames the RefreshTimeout field on the register options to QueryTimeout to more accurately reflect that it is used for any type that supports blocking queries.
Blocking queries issues will still be uncancellable (that cannot be helped until we get rid of net/rpc). However this makes it so that if calling getWithIndex (like during a cache Notify go routine) we can cancell the outer routine. Previously it would keep issuing more blocking queries until the result state actually changed.
A few of the unexported functions in agent/cache took a large number of
arguments. These arguments were effectively overrides for values that
were provided in RequestInfo.
By using a struct we can not only reduce the number of arguments, but
also simplify the logic by removing the need for overrides.
Previously the SupportsBlocking option was specified by a method on the
type, and all the other options were specified from RegisterOptions.
This change moves RegisterOptions to a method on the type, and moves
SupportsBlocking into the options struct.
Currently there are only 2 cache-types. So all cache-types can implement
this method by embedding a struct with those predefined values. In the
future if a cache type needs to be registered more than once with different
options it can remove the embedded type and implement the method in a way
that allows for paramaterization.
This should very slightly reduce the amount of memory required to store each item in
the cache.
It will also enable setting different TTLs based on the type of result. For example
we may want to use a shorter TTL when the result indicates the resource does not exist,
as storing these types of records could easily lead to a DOS caused by
OOM.
These two notify functions are very similar. There appear to be just
enough differences that trying to parameterize the differences may not
improve things.
For now, reduce some of the cosmetic differences so that the material
differences are more obvious.
Use named returned so that the caller has a better idea of what these
bools mean.
Return early to reduce the scope, and make it more obvious what values
are returned in which cases. Also reduces the number of conditional
expressions in each case.
This change moves all the typeEntry lookups to the first step in the exported methods,
and makes unexporter internals accept the typeEntry struct.
This change is primarily intended to make it easier to extract the container of caches
from the Cache type.
It may incidentally reduce locking in fetch, but that was not a goal.
Fixes#6521
Ensure that initial failures to fetch an agent cache entry using the
notify API where the underlying RPC returns a synthetic index of 1
correctly recovers when those RPCs resume working.
The bug in the Cache.notifyBlockingQuery used to incorrectly "fix" the
index for the next query from 0 to 1 for all queries, when it should
have not done so for queries that errored.
Also fixed some things that made debugging difficult:
- config entry read/list endpoints send back QueryMeta headers
- xds event loops don't swallow the cache notification errors
All these changes should have no side-effects or change behavior:
- Use bytes.Buffer's String() instead of a conversion
- Use time.Since and time.Until where fitting
- Drop unnecessary returns and assignment
* Fix race condition during a cache get
Check the entry we pulled out of the cache while holding the lock had Fetching set.
If it did then we should use the existing Waiter instead of calling fetch. The reason
this is better than just calling fetch is that fetch re-gets the entry out of the
entries map and the previous fetch may have finished. Therefore this prevents
erroneously starting a new fetch because we just missed the last update.
* Fix race condition fully
The first commit still allowed for the following scenario:
• No entry existing when checked in getWithIndex while holding the read lock
• Then by time we had reached fetch it had been created and finished.
* always use ok when returning
* comment mentioning the reading from entries.
* use cacheHit consistently
