Troubleshooting

Problems with replica

Examples:

• Missing .xlog file between LSN 5137088 {1: 240379, 2: 4750534, 5: 146175} and 5137379 {1: 240379, 2: 4750825, 5: 146175} which means that master lost one or more of their xlog files, please check it
• Duplicate key exists in unique index "primary" in space "T1" with old tuple

Solution:

If you have some replication conflicts and issues that you don’t know how to deal with, try to rebootstrap the replica.

(!) Make sure that you have your data safe on the master before rebootstrap.

1. Stop the instance
2. Delete snapshots and xlogs
3. Preserve cluster-wide config (config dir)
4. Restart the instance

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.

   tt connect /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})" | tt connect \
  /var/run/tarantool/<app-name>.<instance-name>.control -f -
  

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 replicaset leader or change instance advertise URI.

Broken failover promote in Cartridge 2.7.7/2.7.8

When updating on Cartridge 2.7.7/2.7.8 while trying to promote a replica you can see an error like this: Cannot appoint non-electable instance.

This is a known bug in Cartridge 2.7.7/2.7.8, which is fixed in Cartridge 2.7.9.

To fix this issue, you need to update Cartridge to version 2.7.9 or higher.

Or you can use the following workaround:

require('cartridge.lua-api.topology').set_electable_servers({uuid1, uuid2, ... uuidN}) -- list all of your uuids here

A ‘Connection refused’ error in unconfigured instance since 2.7.4

Before v2.7.4, an unconfigured instance was bound to the 0.0.0.0 interface. Given that 0.0.0.0 accepts connections on any IP address assigned to the machine, this might impose additional security risks.

With v2.7.4 version, an unconfigured instance resolves the advertise_uri host and binds to it. You can check that the instance’s advertise_uri is resolved to a network interface (not loopback) as follows:

dig +short place_advertise_uri_here

‘Address already in use’ errors

There are the following known ‘Address already in use’ errors:

• CartridgeCfgError: Socket bind error (<port>/udp): Address already in use
• HttpInitError: <…> Can’t create tcp_server: Address already in use
• RemoteControlError: Can’t start server on <host>:<port>: Address already in use

You can see these errors in Tarantool logs only. The reason causing these errors is that Tarantool cannot use the binary (for example, 3301) or HTTP (for example, 8081) port. As a result, the instance cannot be configured and fails with an error.

To fix an error, follow the steps below:

1. Determine which port is busy.

2. Use the lsof command to determine the application that uses this port:

   sudo lsof -i :<port>
   

   Note that without sudo you can see only the current user’s processes.

3. Determine the connection type, for example:

   # An outgoing connection on the 50858 port
   TCP 192.168.100.17:50858->google.com:https (ESTABLISHED)
   
   # Waiting for incoming requests on the 3301 port.
   TCP localhost:3301 (LISTEN)
   

4. For an outgoing connection, you need to adjust the port range used to choose the local port, for example:

   echo "32768 61000" > /proc/sys/net/ipv4/ip_local_port_range
   /etc/rc.d/init.d/network restart
   

5. For an incoming connection, do one of the following:

   • For Google Chrome, etcd, nginx, or other application, you need to adjust settings to release a busy port.
   • For Tarantool, you might have an incorrect cluster topology or there might be several clusters running simultaneously. In this case, please contact Tarantool support.