Managing cluster configurations

$ tt cluster COMMAND [COMMAND_OPTION ...]

tt cluster manages configurations of Tarantool applications. This command works both with local YAML files in application directories and with centralized configuration storages (etcd or Tarantool-based).

COMMAND is one of the following:

publish
show
replicaset
failover

publish

$ tt cluster publish {APPLICATION[:APP_INSTANCE] | CONFIG_URI} [FILE] [OPTION ...]

tt cluster publish publishes a cluster configuration using an arbitrary YAML file as a source.

Publishing local configurations

tt cluster publish can modify local cluster configurations stored in config.yaml files inside application directories.

To write a configuration to a local config.yaml, run tt cluster publish with two arguments:

the application name.
the path to a YAML file from which the configuration should be taken.

$ tt cluster publish myapp source.yaml

Publishing configurations in centralized storages

tt cluster publish can modify centralized cluster configurations in storages of both supported types: etcd or a Tarantool-based configuration storage.

To publish a configuration from a file to a centralized configuration storage, run tt cluster publish with a URI of this storage’s instance as the target. For example, the command below publishes a configuration from source.yaml to a local etcd instance running on the default port 2379:

$ tt cluster publish "http://localhost:2379/myapp" source.yaml

A URI must include a prefix that is unique for the application. It can also include credentials and other connection parameters. Find the detailed description of the URI format in URI format.

Publishing configurations of specific instances

In addition to whole cluster configurations, tt cluster publish can manage configurations of specific instances within applications: rewrite configurations of existing instances and add new instance configurations.

In this case, it operates with YAML fragments that describe a single instance configuration section. For example, the following YAML file can be a source when publishing an instance configuration:

# instance_source.yaml
iproto:
  listen:
  - uri: 127.0.0.1:3311

To send an instance configuration to a local config.yaml, run tt cluster publish with the application:instance pair as the target argument:

$ tt cluster publish myapp:instance-002 instance_source.yaml

To send an instance configuration to a centralized configuration storage, specify the instance name in the name argument of the storage URI:

$ tt cluster publish "http://localhost:2379/myapp?name=instance-002" instance_source.yaml

If the instance already exists, this call overwrites its configuration with the one from the file.

To add a new instance configuration from a YAML fragment, specify the name to assign to the new instance and its location in the cluster topology – replica set and group – in the --replicaset and --group options.

Note

The --group option can be omitted if the configuration contains only one group.

To add a new instance instance-003 to the replicaset-001 replica set:

tt cluster publish "http://localhost:2379/myapp?name=instance-003" instance_source.yaml --replicaset replicaset-001

Configuration validation

tt cluster publish validates configurations against the Tarantool configuration schema and aborts in case of an error. To skip the validation, add the --force option:

$ tt cluster publish myapp source.yaml --force

Publishing configurations with integrity check

Enterprise Edition

The integrity check functionality is supported by the Enterprise Edition only.

When called with the --with-integrity-check option, tt cluster publish generates a checksum of the configurations it publishes. It signs the checksum using the private key passed as the option argument, and writes it into the configuration store.

$ tt cluster publish "http://localhost:2379/myapp" source.yaml --with-integrity-check private.pem

If an application configuration is published this way, it can be checked for integrity using the --integrity-check global option.

$ tt --integrity-check public.pem cluster show myapp
$ tt --integrity-check public.pem start myapp

Learn more about integrity checks upon application startup and in runtime in the tt start reference.

To ensure the configuration integrity when updating it, call tt cluster publish with two options:

--integrity-check PUBLIC_KEY global option checks that the configuration wasn’t changed since it was published
--with-integrity-check PRIVATE_KEY generates new hash and signature for future integrity checks of the updated configuration.

$ tt --integrity-check public.pem cluster publish \
     --with-integrity-check private.pem \
     "http://localhost:2379/myapp" source.yaml

show

$ tt cluster show {APPLICATION[:APP_INSTANCE] | CONFIG_URI} [OPTION ...]

tt cluster show displays a cluster configuration.

Displaying local configurations

tt cluster show can read local cluster configurations stored in config.yaml files inside application directories.

To print a local configuration from an application’s config.yaml, specify the application name as an argument:

$ tt cluster show myapp

Displaying configurations from centralized storages

tt cluster show can display centralized cluster configurations from configuration storages of both supported types: etcd or a Tarantool-based configuration storage.

To print a cluster configuration from a centralized storage, run tt cluster show with a storage URI including the prefix identifying the application. For example, to print myapp’s configuration from a local etcd storage:

$ tt cluster show "http://localhost:2379/myapp"

Displaying configurations of specific instances

In addition to whole cluster configurations, tt cluster show can display configurations of specific instances within applications. In this case, it prints YAML fragments that describe a single instance configuration section.

To print an instance configuration from a local config.yaml, use the application:instance argument:

$ tt cluster show myapp:instance-002

To print an instance configuration from a centralized configuration storage, specify the instance name in the name argument of the URI:

$ tt cluster show "http://localhost:2379/myapp?name=instance-002"

Configuration validation

To validate configurations when printing them with tt cluster show, enable the validation by adding the --validate option:

$ tt cluster show "http://localhost:2379/myapp" --validate

replicaset

$ tt cluster replicaset SUBCOMMAND {APPLICATION[:APP_INSTANCE] | CONFIG_URI} [OPTION ...]

tt cluster replicaset manages instances in a replica set. It supports the following subcommands:

promote
demote

Important

tt cluster replicaset works only with centralized cluster configurations. To manage replica set leaders in clusters with local YAML configurations, use tt replicaset promote and tt replicaset demote.

promote

$ tt cluster replicaset promote CONFIG_URI INSTANCE_NAME [OPTION ...]

tt cluster replicaset promote promotes the specified instance, making it a leader of its replica set. This command works on Tarantool clusters with centralized configuration and with failover modes off and manual. It updates the centralized configuration according to the specified arguments and reloads it:

off failover mode: the command sets database.mode to rw on the specified instance.

Important

If failover is off, the command doesn’t consider the modes of other replica set members, so there can be any number of read-write instances in one replica set.
manual failover mode: the command updates the leader option of the replica set configuration. Other instances of this replica set become read-only.

Example:

$ tt cluster replicaset promote "http://localhost:2379/myapp" storage-001-a

demote

$ tt cluster replicaset demote CONFIG_URI INSTANCE_NAME [OPTION ...]

tt cluster replicaset demote demotes an instance in a replica set. This command works on Tarantool clusters with centralized configuration and with failover mode off.

Note

In clusters with manual failover mode, you can demote a read-write instance by promoting a read-only instance from the same replica set with tt cluster replicaset promote.

The command sets the instance’s database.mode to ro and reloads the configuration.

Important

If failover is off, the command doesn’t consider the modes of other replica set members, so there can be any number of read-write instances in one replica set.

failover

$ tt cluster failover SUBCOMMAND [OPTION ...]

tt cluster failover manages a supervised failover in Tarantool clusters.

switch
switch-status

Important

tt cluster failover works only with centralized cluster configurations stored in etcd.

switch

$ tt cluster failover switch CONFIG_URI INSTANCE_NAME [OPTION ...]

tt cluster failover switch appoints the specified instance to be a master. This command accepts the following arguments and options:

CONFIG_URI: A URI of the cluster configuration storage.
INSTANCE_NAME: An instance name.
[OPTION ...]: Options to pass to the command.

In the example below, tt cluster failover switch appoints storage-a-002 to be a master:

$ tt cluster failover switch http://localhost:2379/myapp storage-a-002
To check the switching status, run:
tt cluster failover switch-status http://localhost:2379/myapp b1e938dd-2867-46ab-acc4-3232c2ef7ffe

Note that the command output includes an identifier of the task responsible for switching a master. You can use this identifier to see the status of switching a master instance using tt cluster failover switch-status.

switch-status

$ tt cluster failover switch-status CONFIG_URI TASK_ID

tt cluster failover switch-status shows the status of switching a master instance. This command accepts the following arguments:

CONFIG_URI: A URI of the cluster configuration storage.
TASK_ID: An identifier of the task used to switch a master instance. You can find the task identifier in the tt cluster failover switch command output.

Example:

$ tt cluster failover switch-status http://localhost:2379/myapp b1e938dd-2867-46ab-acc4-3232c2ef7ffe

Implementation details

The changes that tt cluster replicaset makes to the configuration storage occur transactionally. Each call creates a new revision. In case of a revision mismatch, an error is raised.

If the cluster configuration is distributed over multiple keys in the configuration storage (for example, in two paths /myapp/config/k1 and /myapp/config/k2), the affected instance configuration can be present in more that one of them. If it is found under several different keys, the command prompts the user to choose a key for patching. You can skip the selection by adding the -f/--force option:

$ tt cluster replicaset promote "http://localhost:2379/myapp" storage-001-a --force

In this case, the command selects the key for patching automatically. A key’s priority is determined by the detail level of the instance or replica set configuration stored under this key. For example, when failover is off, a key with instance.database options takes precedence over a key with the only instance field. In case of equal priority, the first key in the lexicographical order is patched.

Authentication

There are three ways to pass the credentials for connecting to the centralized configuration storage. They all apply to both etcd and Tarantool-based storages. The following list shows these ways ordered by precedence, from highest to lowest:

Credentials specified in the storage URI: https://username:password@host:port/prefix:
```
$ tt cluster show "http://myuser:p4$$w0rD@localhost:2379/myapp"
```

tt cluster options -u/--username and -p/--password:

$ tt cluster show "http://localhost:2379/myapp" -u myuser -p p4$$w0rD

Environment variables TT_CLI_ETCD_USERNAME and TT_CLI_ETCD_PASSWORD:

$ export TT_CLI_ETCD_USERNAME=myuser
$ export TT_CLI_ETCD_PASSWORD=p4$$w0rD
$ tt cluster show "http://localhost:2379/myapp"

If connection encryption is enabled on the configuration storage, pass the required SSL parameters in the URI arguments.

URI format

A URI of the cluster configuration storage has the following format:

http(s)://[username:password@]host:port[/prefix][?arguments]

username and password define credentials for connecting to the configuration storage.
prefix is a base path identifying a specific application in the storage.
arguments defines connection parameters. The following arguments are available:
- name – a name of an instance in the cluster configuration.
- key – a target configuration key in the specified prefix.
- timeout – a request timeout in seconds. Default: 3.0.
- ssl_key_file – a path to a private SSL key file.
- ssl_cert_file – a path to an SSL certificate file.
- ssl_ca_file – a path to a trusted certificate authorities (CA) file.
- ssl_ca_path – a path to a trusted certificate authorities (CA) directory.
- ssl_ciphers – a colon-separated (:) list of SSL cipher suites the connection can use (for Tarantool-based storage only).
- verify_host – verify the certificate’s name against the host. Default true.
- verify_peer – verify the peer’s SSL certificate. Default true.

Options

-u, --username STRING¶

A username for connecting to the configuration storage.

Version:

Managing cluster configurations

publish

Publishing local configurations

Publishing configurations in centralized storages

Publishing configurations of specific instances

Configuration validation

Publishing configurations with integrity check

show

Displaying local configurations

Displaying configurations from centralized storages

Displaying configurations of specific instances

Configuration validation

replicaset

promote

demote

failover

switch

switch-status

Implementation details

Authentication

URI format

Options