Two settings that decide whether a deployment survives load, neither of which
appeared in any template.
The connection pool. Left unset, Go's defaults apply, and MaxIdleConns is 2:
under load almost every request opens a TCP connection and closes it again,
local ports run out, and the process answers "can't assign requested address"
to everything. Not slower - unavailable. A sweep against MySQL collapsed to
zero successful responses at 64 concurrent requests without these, and served
13,846 req/s with no errors once they were set.
The queue buffer. poolSize is the point at which messages start being dropped,
not a tuning knob: a full queue discards the message and returns an error
rather than blocking, and each stream has one consumer goroutine writing to the
database. At the previous default of 100 a load test lost over 60% of them; at
1000, none. Login and operation logs travel this queue, so what gets lost is
audit data - though only when logger.enableddb is on.
Both carry the reasoning in the file, because the failure mode of each is
invisible until it happens in production.
A rejected request answered 200 with the failure only in the body, so every
layer that reads the status line counted it as served: load balancers, metrics,
client-side retry. A load test against this reported the limiter's own
rejections as successful traffic and overstated throughput more than tenfold.
The threshold was a constant in the middleware, which made 200 QPS the ceiling
of every deployment with nothing in the configuration to reveal it. It now
reads extend.rateLimit.inboundQPS; an absent value keeps 200, so an upgrade
changes nothing, and zero disables the limiter for a deployment behind its own
gateway.
Also drops Strategy: system.BBR. Reading sentinel's source, the adaptive
strategy is consulted only for Load and CpuUsage - for InboundQPS the trigger
count is compared directly - so it read as if the limit adapted to the machine
when it never did.
The sample had producer/consumer nested keys (streamMaxLength,
approximateMaxLength, visibilityTimeout, bufferSize, concurrency,
blockingTimeout, reclaimInterval) that don't exist on config.RedisQueue —
checked against sdk/config/queue.go, which only reads addr, password, and the
embedded RedisOptions fields, plus group, key_prefix and max_attempts. Filling
in the old sample as written would compile and start fine, since it's YAML
under a key the struct doesn't declare, and every one of those settings would
be silently ignored.
Replaced with the fields the struct actually has. Still commented out —
redis stays opt-in, this only fixes what filling it in would produce.
zhangwenjian