Troubleshooting

Editing clusterwide configuration in WebUI returns an error

Examples:

• NetboxConnectError: "localhost:3302": Connection refused;
• Prepare2pcError: Instance state is OperationError, can't apply config in this state.

The root problem: all cluster instances are equal, and all of them store a copy of clusterwide configuration, which must be the same. If an instance degrades (can’t accept new configuration) – the quorum is lost. This prevents further configuration modifications to avoid inconsistency.

But sometimes inconsistency is needed to repair the system, at least partially and temporarily. It can be achieved by disabling degraded instances.

Solution:

1. Connect to the console of the alive instance.

   tarantoolctl connect unix/:/var/run/tarantool/<app-name>.<instance-name>.control
   

2. Inspect what’s going on.

   cartridge = require('cartridge')
   report = {}
   for _, srv in pairs(cartridge.admin_get_servers()) do
       report[srv.uuid] = {uri = srv.uri, status = srv.status, message = srv.message}
   end
   return report
   

3. If you’re ready to proceed, run the following snippet. It’ll disable all instances which are not healthy. After that, you can use the WebUI as usual.

   disable_list = {}
   for uuid, srv in pairs(report) do
       if srv.status ~= 'healthy' then
          table.insert(disable_list, uuid)
       end
   end
   return cartridge.admin_disable_servers(disable_list)
   

4. When it’s necessary to bring disabled instances back, re-enable them in a similar manner:

   cartridge = require('cartridge')
   enable_list = {}
   for _, srv in pairs(cartridge.admin_get_servers()) do
       if srv.disabled then
          table.insert(enable_list, srv.uuid)
       end
   end
   return cartridge.admin_enable_servers(enable_list)
   

An instance is stuck in the ConnectingFullmesh state upon restart

Example:

The root problem: after restart, the instance tries to connect to all its replicas and remains in the ConnectingFullmesh state until it succeeds. If it can’t (due to replica URI unavailability or for any other reason) – it’s stuck forever.

Solution:

Set the replication_connect_quorum option to zero. It may be accomplished in two ways:

• By restarting it with the corresponding option set (in environment variables or in the instance configuration file);

• Or without restart – by running the following one-liner:

  echo "box.cfg({replication_connect_quorum = 0})" | tarantoolctl connect \
  unix/:/var/run/tarantool/<app-name>.<instance-name>.control
  

I want to run an instance with a new advertise_uri

The root problem: advertise_uri parameter is persisted in the clusterwide configuration. Even if it changes upon restart, the rest of the cluster keeps using the old one, and the cluster may behave in an odd way.

Solution:

The clusterwide configuration should be updated.

1. Make sure all instances are running and not stuck in the ConnectingFullmesh state (see above).

2. Make sure all instances have discovered each other (i.e. they look healthy in the WebUI).

3. Run the following snippet in the Tarantool console. It’ll prepare a patch for the clusterwide configuration.

   cartridge = require('cartridge')
   members = require('membership').members()
   
   edit_list = {}
   changelog = {}
   for _, srv in pairs(cartridge.admin_get_servers()) do
       for _, m in pairs(members) do
           if m.status == 'alive'
           and m.payload.uuid == srv.uuid
           and m.uri ~= srv.uri
           then
               table.insert(edit_list, {uuid = srv.uuid, uri = m.uri})
               table.insert(changelog, string.format('%s -> %s (%s)', srv.uri, m.uri, m.payload.alias))
               break
           end
       end
   end
   return changelog
   

   As a result you’ll see a brief summary like the following one:

   localhost:3301> return changelog
   ---
   - - localhost:13301 -> localhost:3301 (srv-1)
     - localhost:13302 -> localhost:3302 (srv-2)
     - localhost:13303 -> localhost:3303 (srv-3)
     - localhost:13304 -> localhost:3304 (srv-4)
     - localhost:13305 -> localhost:3305 (srv-5)
   ...
   

4. Finally, apply the patch:

   cartridge.admin_edit_topology({servers = edit_list})
   

The cluster is doomed, I’ve edited the config manually. How do I reload it?

But if you’re still determined to reload the configuration manually, you can do (in the Tarantool console):

function reload_clusterwide_config()
    local changelog = {}

    local ClusterwideConfig = require('cartridge.clusterwide-config')
    local confapplier = require('cartridge.confapplier')

    -- load config from filesystem
    table.insert(changelog, 'Loading new config...')

    local cfg, err = ClusterwideConfig.load('./config')
    if err ~= nil then
        return changelog, string.format('Failed to load new config: %s', err)
    end

    -- check instance state
    table.insert(changelog, 'Checking instance config state...')

    local roles_configured_state = 'RolesConfigured'
    local connecting_fullmesh_state = 'ConnectingFullmesh'

    local state = confapplier.wish_state(roles_configured_state, 10)

    if state == connecting_fullmesh_state then
        return changelog, string.format(
            'Failed to reach %s config state. Stuck in %s. ' ..
                'Call "box.cfg({replication_connect_quorum = 0})" in instance console and try again',
            roles_configured_state, state
        )
    end

    if state ~= roles_configured_state then
        return changelog, string.format(
            'Failed to reach %s config state. Stuck in %s',
            roles_configured_state, state
        )
    end

    -- apply config changes
    table.insert(changelog, 'Applying config changes...')

    cfg:lock()
    local ok, err = confapplier.apply_config(cfg)
    if err ~= nil then
        return changelog, string.format('Failed to apply new config: %s', err)
    end

    table.insert(changelog, 'Cluster-wide configuration was successfully updated')

    return changelog
end

reload_clusterwide_config()

This snippet reloads the configuration on a single instance. All other instances continue operating as before.

Repairing cluster using Cartridge CLI repair

command

Cartridge CLI has repair command since version 2.3.0.

It can be used to get current topology, remove instance from cluster, change repicaset leader or change instance advertise URI.