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Nick Khyl 1ccece0f78 util/eventbus: use unbounded event queues for DeliveredEvents in subscribers ... Bounded DeliveredEvent queues reduce memory usage, but they can deadlock under load. Two common scenarios trigger deadlocks when the number of events published in a short period exceeds twice the queue capacity (there's a PublishedEvent queue of the same size): - a subscriber tries to acquire the same mutex as held by a publisher, or - a subscriber for A events publishes B events Avoiding these scenarios is not practical and would limit eventbus usefulness and reduce its adoption, pushing us back to callbacks and other legacy mechanisms. These deadlocks already occurred in customer devices, dev machines, and tests. They also make it harder to identify and fix slow subscribers and similar issues we have been seeing recently. Choosing an arbitrary large fixed queue capacity would only mask the problem. A client running on a sufficiently large and complex customer environment can exceed any meaningful constant limit, since event volume depends on the number of peers and other factors. Behavior also changes based on scheduling of publishers and subscribers by the Go runtime, OS, and hardware, as the issue is essentially a race between publishers and subscribers. Additionally, on lower-end devices, an unreasonably high constant capacity is practically the same as using unbounded queues. Therefore, this PR changes the event queue implementation to be unbounded by default. The PublishedEvent queue keeps its existing capacity of 16 items, while subscribers' DeliveredEvent queues become unbounded. This change fixes known deadlocks and makes the system stable under load, at the cost of higher potential memory usage, including cases where a queue grows during an event burst and does not shrink when load decreases. Further improvements can be implemented in the future as needed. Fixes #17973 Fixes #18012 Signed-off-by: Nick Khyl <nickk@tailscale.com>		2 weeks ago
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backoff	control/controlclient: remove unused reference to mapCtx (#17614)	1 month ago
checkchange	net/dns, ipn/ipnlocal: fix regressions from change moving away from deephash	2 months ago
cibuild	all: update copyright and license headers	3 years ago
clientmetric	util/clientmetric: fix regression causing Metric.v to be uninitialised	3 weeks ago
cloudenv	feature/featuretags, all: add build features, use existing ones in more places	2 months ago
cmpver	util/cmpver: add Less/LessEq helper funcs	2 years ago
codegen	cmd/viewer, types/views: implement support for json/v2 (#16852)	4 months ago
cstruct	all: use Go 1.21's binary.NativeEndian	11 months ago
ctxkey	all: use reflect.TypeFor now available in Go 1.22 (#11078)	2 years ago
deephash	wgengine/wgcfg: remove two unused Config fields	3 weeks ago
dirwalk	all: use tstest.Replace more	3 years ago
dnsname	util/dnsname: fix test error message	3 weeks ago
eventbus	util/eventbus: use unbounded event queues for DeliveredEvents in subscribers	2 weeks ago
execqueue	syncs: add Mutex/RWMutex alias/wrappers for future mutex debugging	2 weeks ago
expvarx	syncs: add Mutex/RWMutex alias/wrappers for future mutex debugging	2 weeks ago
goroutines	syncs: add Mutex/RWMutex alias/wrappers for future mutex debugging	2 weeks ago
groupmember	util/groupmember: fail earlier if group doesn't exist, use slices.Contains	2 years ago
hashx	all: use Go 1.22 range-over-int	2 years ago
httphdr	util/httphdr: add new package for parsing HTTP headers (#9797)	2 years ago
httpm	util/httpm: don't run test if .git doesn't exist	2 years ago
limiter	all: rename variables with lowercase-l/uppercase-I	2 weeks ago
lineiter	types/result, util/lineiter: add package for a result type, use it	1 year ago
lineread	all: update copyright and license headers	3 years ago
linuxfw	all: rename variables with lowercase-l/uppercase-I	2 weeks ago
lru	all: rename variables with lowercase-l/uppercase-I	2 weeks ago
mak	util/mak: delete long-deprecated, unused, pre-generics NonNil func	7 months ago
multierr	all: use Go 1.22 range-over-int	2 years ago
must	util/must: add Get2 for functions that return two values	6 months ago
nocasemaps	all: use Go 1.22 range-over-int	2 years ago
osdiag	go.mod: bump golang.org/x/crypto (#17907)	2 weeks ago
osshare	clientupdate, util/osshare, util/winutil, version: improve Windows GUI filename resolution and WinUI build awareness	2 months ago
osuser	ssh/tailssh: add Plan 9 support for Tailscale SSH	8 months ago
pidowner	types/result, util/lineiter: add package for a result type, use it	1 year ago
pool	util/pool: add package for storing and using a pool of items	2 years ago
precompress	all: update copyright and license headers	3 years ago
progresstracking	ipn/localapi: add support for multipart POST to file-put	2 years ago
prompt	util/prompt: add a default and take default in non-interactive cases	2 months ago
quarantine	all: update copyright and license headers	3 years ago
race	all: use Go 1.22 range-over-int	2 years ago
racebuild	all: update copyright and license headers	3 years ago
rands	wgengine/magicsock: use math/rands/v2	2 years ago
reload	all: use math/rand/v2 more	2 years ago
ringlog	syncs: add Mutex/RWMutex alias/wrappers for future mutex debugging	2 weeks ago
safediff	cmd/jsonimports: add static analyzer for consistent "json" imports (#17669)	1 month ago
set	control/controlclient: restore aggressive Direct.Close teardown	2 months ago
singleflight	util/singleflight: add DoChanContext	2 years ago
slicesx	util/slicesx: add AppendNonzero	10 months ago
stringsx	util/stringsx: add package for extra string functions, like CompareFold	12 months ago
syspolicy	all: rename variables with lowercase-l/uppercase-I	2 weeks ago
sysresources	util/sysresources, magicsock: scale DERP buffer based on system memory	3 years ago
testenv	nettest, *: add option to run HTTP tests with in-memory network	8 months ago
topk	all: use Go 1.22 range-over-int	2 years ago
truncate	util/truncate: support []byte as well (#11614)	2 years ago
usermetric	feature/featuretags: make usermetrics modular	2 months ago
vizerror	util/vizerror: add WrapWithMessage	1 year ago
winutil	all: rename variables with lowercase-l/uppercase-I	2 weeks ago
zstdframe	all: use Go 1.22 range-over-int	2 years ago