Read Strategy

By default, Valkey GLIDE directs read commands to the primary node that owns a specific slot. For applications that prioritize read throughput and can tolerate possibly stale data, Valkey GLIDE provides the flexibility to route reads to replica nodes.

Valkey GLIDE provides support for next read strategies, allowing you to choose the one that best fits your specific use case.

Strategy	Description
PRIMARY	Always read from primary, in order to get the freshest data
PREFER_REPLICA	Spread requests between all replicas in a round robin manner. If no replica is available, route the requests to the primary
AZ_AFFINITY	Spread the read requests between replicas in the same client’s availability zone in a round robin manner, falling back to other replicas or the primary if needed.
AZ_AFFINITY_REPLICAS_AND_PRIMARY	Spread the read requests among nodes within the client’s availability zone in a round robin manner, prioritizing local replicas, then the local primary, and falling back to other replicas or the primary if needed.

Example: Use PREFER_REPLICA Read Strategy

from glide import (
    GlideClusterClient,
    GlideClusterClientConfiguration,
    NodeAddress,
    ReadFrom
)

addresses = [NodeAddress(host="address.example.com", port=6379)]
client_config = GlideClusterClientConfiguration(addresses, read_from=ReadFrom.PREFER_REPLICA)

client = await GlideClusterClient.create(client_config)
await client.set("key1", "val1")
# get will read from one of the replicas
await client.get("key1")

Example: Use AZ_AFFINITY Read Strategy

If ReadFrom strategy is AZ_AFFINITY, ‘client_az’ setting is required to ensures that readonly commands are directed to replicas within the specified AZ if exits.

from glide import (
    GlideClusterClient,
    GlideClusterClientConfiguration,
    NodeAddress,
    ReadFrom
)

addresses = [NodeAddress(host="address.example.com", port=6379)]
client_config = GlideClusterClientConfiguration(addresses, read_from=ReadFrom.AZ_AFFINITY, client_az="us-east-1a")

client = await GlideClusterClient.create(client_config)
await client.set("key1", "val1")
# get will read from one of the replicas in the same client's availability zone if exits.
await client.get("key1")

Example: Use AZ_AFFINITY_REPLICAS_AND_PRIMARY Read Strategy

If ReadFrom strategy is AZ_AFFINITY_REPLICAS_AND_PRIMARY, ‘client_az’ setting is required to ensures that readonly commands are directed to replicas or primary within the specified AZ if exits.

from glide import (
    GlideClusterClient,
    GlideClusterClientConfiguration,
    NodeAddress,
    ReadFrom
)

addresses = [NodeAddress(host="address.example.com", port=6379)]
client_config = GlideClusterClientConfiguration(addresses, read_from=ReadFrom.AZ_AFFINITY_REPLICAS_AND_PRIMARY, client_az="us-east-1a")

client = await GlideClusterClient.create(client_config)
await client.set("key1", "val1")
# get will read from one of the replicas or the primary in the same client's availability zone if exits.
await client.get("key1")