cbuilder: `:set_instance_option()` may duplicate an instance

[Totktonada]

#!/usr/bin/env tarantool

local yaml = require('yaml')
local cbuilder = require('luatest.cbuilder')

local config_1 = cbuilder:new()
    :use_replicaset('r-001')
    :add_instance('i-001', {})
    :set_instance_option('i-001', 'replication.timeout', 0.1)
    :config()
print(yaml.encode(config_1))
--[[
---
groups:
  group-001:
    replicasets:
      r-001:
        instances:
          i-001:              # !! (just one)
            replication:
              timeout: 0.1
credentials:
  users:
    replicator:
      password: secret
      roles:
      - replication
    client:
      password: secret
      roles:
      - super
iproto:
  listen:
  - uri: unix/:./{{ instance_name }}.iproto
  advertise:
    peer:
      login: replicator
replication:
  timeout: 0.1
...
]]--

local config_2 = cbuilder:new(config_1)
    -- I forgot to write :use_replicaset('r-001') here
    :set_instance_option('i-001', 'replication.timeout', 1000)
    :config()
print(yaml.encode(config_2))
--[[
---
groups:
  group-001:
    replicasets:
      replicaset-001:
        instances:
          i-001:              # !! (duplicate)
            replication:
              timeout: 1000
      r-001:
        instances:
          i-001:              # !! (initial)
            replication:
              timeout: 0.1
credentials:
  users:
    replicator:
      password: secret
      roles:
      - replication
    client:
      password: secret
      roles:
      - super
iproto:
  listen:
  - uri: unix/:./{{ instance_name }}.iproto
  advertise:
    peer:
      login: replicator
replication:
  timeout: 0.1
...
]]--

So, now we have to add :use_replicaset('r-001'), when updating the configuration.

Since the instance name is unique across a cluster¹, we can find the given instance across all groups/replicasets instead of assuming default ones group-001 and replicaset-001. At least, if an explicit :use_group() and/or :use_replicaset() are not given.

If the instance is not found, raise an error instead of creating it, because there is a designated :add_instance() function.

Footnotes

1. https://github.com/tarantool/tarantool/issues/10347 ↩