Legacy Shim

To make transitioning from vtctlclient to vtctldclient easier, both binaries provide shim mechanisms to run commands with each other's CLI syntaxes (and backing RPC interfaces). Let's take each in turn.

vtctldclient LegacyVtctlCommand #

The new client provides a top-level command to run commands over the legacy vtctlclient interface. This is useful to be able to use the new client "everywhere" but still be able to use functionality from the old client that has not been migrated yet (e.g. Reshard).

For example:

$ vtctldclient --server ":15999" LegacyVtctlCommand -- Reshard show <keyspace.workflow_name>

You can also use this to transition a command in two phases, for example:

  1. Start with the existing invocation:
vtctlclient --server ":15999" -- AddCellInfo --root /mycell --server_address "${some_topo_server}:1234"
  1. Then "switch" to the new client but use the old code and syntax:
vtctldclient --server ":15999" LegacyVtctlCommand -- AddCellInfo --root /mycell --server_address "${some_topo_server}:1234"
  1. Finally, update the command to use the new code and CLI (notice the flag change from --server_address to --server-address and the removal of the --):
vtctldclient --server ":15999" AddCellInfo --root /mycell --server-address "${some_topo_server}:1234"

vtctlclient VtctldCommand #

Conversely, the old client also provides a top-level command to run commands over the new vtctldclient interface. This is useful to migrate your scripts over before necessarily deploying the new, separate binary everywhere.

Taking the same example as above, in reverse:

  1. Start with the existing invocation:
vtctlclient --server ":15999" -- AddCellInfo --root /mycell --server_address "${some_topo_server}:1234"
  1. Then switch to the new code and syntax (note the flag change from --server_address to --server-address) without switching the invoked client binary:
vtctlclient --server ":15999" -- VtctldCommand AddCellInfo --root /mycell --server-address "${some_topo_server}:1234"
  1. Finally, update the command to use the new binary, cleaning up the extra flag separators (--) as well.
vtctldclient --server ":15999" AddCellInfo --root /mycell --server-address "${some_topo_server}:1234"
Legacy Shim