better defaults for flush queue parallelism (#5091)

* better defaults for flush queue length

* changelog

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## Main
 
+* [5091](https://github.com/grafana/loki/pull/5091) **owen-d**: Changes `ingester.concurrent-flushes` default to 32
 * [4879](https://github.com/grafana/loki/pull/4879) **cyriltovena**: LogQL: add __line__ function to | line_format template.
 * [5081](https://github.com/grafana/loki/pull/5081) **SasSwart**: Add the option to configure memory ballast for Loki
 * [5085](https://github.com/grafana/loki/pull/5085) **aknuds1**: Upgrade Cortex to [e0807c4eb487](https://github.com/cortexproject/cortex/compare/4e9fc3a2b5ab..e0807c4eb487) and Prometheus to [692a54649ed7](https://github.com/prometheus/prometheus/compare/2a3d62ac8456..692a54649ed7)

docs/sources/configuration/_index.md

@@ -1071,7 +1071,7 @@ lifecycler:
 
 # How many flushes can happen concurrently from each stream.
 # CLI flag: -ingester.concurrent-flushes
-[concurrent_flushes: <int> | default = 16]
+[concurrent_flushes: <int> | default = 32]
 
 # How often should the ingester see if there are any blocks to flush
 # CLI flag: -ingester.flush-check-period

pkg/ingester/ingester.go

@@ -100,7 +100,7 @@ func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
 	cfg.WAL.RegisterFlags(f)
 
 	f.IntVar(&cfg.MaxTransferRetries, "ingester.max-transfer-retries", 0, "Number of times to try and transfer chunks before falling back to flushing. If set to 0 or negative value, transfers are disabled.")
-	f.IntVar(&cfg.ConcurrentFlushes, "ingester.concurrent-flushes", 16, "")
+	f.IntVar(&cfg.ConcurrentFlushes, "ingester.concurrent-flushes", 32, "")
 	f.DurationVar(&cfg.FlushCheckPeriod, "ingester.flush-check-period", 30*time.Second, "")
 	f.DurationVar(&cfg.FlushOpTimeout, "ingester.flush-op-timeout", 10*time.Second, "")
 	f.DurationVar(&cfg.RetainPeriod, "ingester.chunks-retain-period", 0, "")