Use read replicas

[nikhilo]

I've implemented support for routing read operations to read replicas. Here's what the changes do:

1. Added new types and definitions:

• Added role field to the node record to track master/replica status
• Added redis_command_type() type for read/write/admin operations
• Added READ_COMMANDS macro with a comprehensive list of read-only Redis commands

2. Added replica node tracking:

• Added get_replicas_for_slot/2 to find replica nodes for a given slot
• Added parse_node_role/1 to identify node roles from cluster output
• Added update_node_role/2 to update node roles in the slots map

3. Modified command routing:

• Added is_read_command/1 to identify read operations
• Added get_pool_for_command/3 to route commands based on operation type
• Modified split_by_pools/5 to use the new routing logic

4. Updated cluster node parsing:

• Modified parse_cluster_nodes/2 to properly set node roles when parsing cluster output

The new behavior works as follows:

1. For read operations (commands in READ_COMMANDS):

• First tries to find a replica node for the slot
• If replicas are available, routes the command to a replica
• If no replicas are available, falls back to the master node

2. For write operations (all other commands):

• Always routes to the master node for that slot

This implementation:

• Automatically identifies read operations
• Load balances read operations across available replicas
• Maintains write operations on master nodes
• Gracefully falls back to master nodes when replicas are unavailable
• Preserves all existing functionality for write operations
• The changes are backward compatible and should work seamlessly with existing Redis cluster configurations.

This code was generated using Cursor