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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>		6 months ago
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backoff	control/controlclient: remove unused reference to mapCtx (#17614)	6 months ago
checkchange	net/dns, ipn/ipnlocal: fix regressions from change moving away from deephash	7 months ago
cibuild	all: update copyright and license headers	3 years ago
clientmetric	util/clientmetric: fix regression causing Metric.v to be uninitialised	6 months ago
cloudenv	feature/featuretags, all: add build features, use existing ones in more places	7 months ago
cmpver	util/cmpver: add Less/LessEq helper funcs	2 years ago
codegen	cmd/viewer, types/views: implement support for json/v2 (#16852)	9 months ago
cstruct	…
ctxkey	…
deephash	wgengine/wgcfg: remove two unused Config fields	6 months ago
dirwalk	all: use tstest.Replace more	3 years ago
dnsname	util/dnsname: fix test error message	6 months ago
eventbus	util/eventbus: use unbounded event queues for DeliveredEvents in subscribers	6 months ago
execqueue	syncs: add Mutex/RWMutex alias/wrappers for future mutex debugging	6 months ago
expvarx	syncs: add Mutex/RWMutex alias/wrappers for future mutex debugging	6 months ago
goroutines	syncs: add Mutex/RWMutex alias/wrappers for future mutex debugging	6 months ago
groupmember	…
hashx	…
httphdr	util/httphdr: add new package for parsing HTTP headers (#9797)	3 years ago
httpm	…
limiter	all: rename variables with lowercase-l/uppercase-I	6 months ago
lineiter	…
lineread	…
linuxfw	all: rename variables with lowercase-l/uppercase-I	6 months ago
lru	all: rename variables with lowercase-l/uppercase-I	6 months ago
mak	…
multierr	…
must	…
nocasemaps	…
osdiag	go.mod: bump golang.org/x/crypto (#17907)	6 months ago
osshare	clientupdate, util/osshare, util/winutil, version: improve Windows GUI filename resolution and WinUI build awareness	7 months ago
osuser	ssh/tailssh: add Plan 9 support for Tailscale SSH	1 year ago
pidowner	…
pool	util/pool: add package for storing and using a pool of items	2 years ago
precompress	…
progresstracking	…
prompt	util/prompt: add a default and take default in non-interactive cases	7 months ago
quarantine	…
race	…
racebuild	…
rands	…
reload	…
ringlog	syncs: add Mutex/RWMutex alias/wrappers for future mutex debugging	6 months ago
safediff	cmd/jsonimports: add static analyzer for consistent "json" imports (#17669)	6 months ago
set	control/controlclient: restore aggressive Direct.Close teardown	7 months ago
singleflight	util/singleflight: add DoChanContext	2 years ago
slicesx	util/slicesx: add AppendNonzero	1 year ago
stringsx	…
syspolicy	all: rename variables with lowercase-l/uppercase-I	6 months 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	1 year ago
topk	…
truncate	…
usermetric	feature/featuretags: make usermetrics modular	7 months ago
vizerror	…
winutil	all: rename variables with lowercase-l/uppercase-I	6 months ago
zstdframe	all: use Go 1.22 range-over-int	2 years ago