Readonly replica selection

[adam-fowler]

• Add readOnlyReplicaSelection selection to ValkeyClientConfiguration
• Add new parameter nodeSelection to ValkeyClusterClient.nodeClient(for:). Before calling this work out if commands you want to run are readOnly and then combined with ValkeyClientConfiguration. readOnlyReplicaSelection work out the nodeSelection parameter.

[github-actions]

✅ Pull request no significant performance differences ✅

Summary

New baseline 'pull_request' is WITHIN the 'main' baseline thresholds.

Full Benchmark Comparison

Comparing results between 'main' and 'pull_request'

Host '83df2ba50b57' with 4 'x86_64' processors with 15 GB memory, running:
#18~24.04.1-Ubuntu SMP Sat Jun 28 04:46:03 UTC 2025

ValkeyBenchmarks

Client: GET benchmark metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	75	77	77	81	82	82	82	6
pull_request	74	76	76	79	80	80	80	6
Δ	-1	-1	-1	-2	-2	-2	-2	0
Improvement %	1	1	1	2	2	2	2	0

Client: GET benchmark | parallel 20 | 20 concurrent connections metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	73	76	79	82	85	87	87	28
pull_request	73	76	79	84	87	95	95	28
Δ	0	0	0	2	2	8	8	0
Improvement %	0	0	0	-2	-2	-9	-9	0

Connection: GET benchmark metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	4	4	4	4	4	4	4	8
pull_request	4	4	4	4	4	4	4	8
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

Connection: GET benchmark – NoOpTracer metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	7	8	8	10	11	11	11	8
pull_request	7	8	8	10	11	11	11	8
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

Connection: Pipeline array benchmark metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	33	33	33	34	34	34	34	6
pull_request	33	33	34	34	34	34	34	6
Δ	0	0	1	0	0	0	0	0
Improvement %	0	0	-3	0	0	0	0	0

Connection: Pipeline benchmark metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	33	33	33	34	34	34	34	6
pull_request	33	33	33	34	34	34	34	6
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

HashSlot – {user}.whatever metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	0	0	0	0	0	0	0	18
pull_request	0	0	0	0	0	0	0	18
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

ValkeyCommandEncoder – Command with 7 words metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	0	0	0	0	0	0	0	754
pull_request	0	0	0	0	0	0	0	755
Δ	0	0	0	0	0	0	0	1
Improvement %	0	0	0	0	0	0	0	1

ValkeyCommandEncoder – Simple GET metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	0	0	0	0	0	0	0	1908
pull_request	0	0	0	0	0	0	0	1911
Δ	0	0	0	0	0	0	0	3
Improvement %	0	0	0	0	0	0	0	3

ValkeyCommandEncoder – Simple MGET 15 keys metrics

Malloc (total): results within specified thresholds, fold down for details.

Malloc (total) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	0	0	0	0	0	0	0	343
pull_request	0	0	0	0	0	0	0	360
Δ	0	0	0	0	0	0	0	17
Improvement %	0	0	0	0	0	0	0	17

[nilanshu-sharma]

Mostly looks good. Added some comments around support for reads from all nodes.

[nilanshu-sharma]

Since this is for replica selection, can we just call it ValkeyClientConfiguration.ReplicaSelection ?

[nilanshu-sharma]

In future we would also want to add support for other flavors of valkey such as non-cluster mode clusters such as pure client side shared clusters with 1 leader and n replicas. For such configurations the replicas take read by default. So having a generic name like ValkeyClientConfiguration.ReplicaSelection will also make sense for that flavor of Valkey.

[adam-fowler]

I included ReadOnly in the name because it is for readonly commands. To make it clearer I could call it ReadOnlyCommandReplicaSelection.

[adam-fowler]

I actually renamed it to ReadOnlyCommandNodeSelection as it can return the primary node as well

[nilanshu-sharma]

LGTM, thanks!
It's failing some documentation related checks but looks good overall.