Command #

VDiff takes different sub-commands or actions similar to how the MoveTables/Reshard commands work. The first argument is the <keyspace.workflow> followed by an <action>. The following actions are supported:

Start a New VDiff #

These take the same parameters as VDiff1 and schedule VDiff to run on the primary tablet of each target shard to verify the subset of data that will live on the given shard. Please note that if you do not specify a sub-command or action then create is assumed (this eases the transition from VDiff1 to VDiff2). If you do not pass a specific UUID then one will be generated.

VDiff -- [--source_cell=<cell>] [--target_cell=<cell>] [--tablet_types=in_order:RDONLY,REPLICA,PRIMARY]
       [--limit=<max rows to diff>] [--tables=<table list>] [--format=json] [--auto-retry] [--verbose] [--max_extra_rows_to_compare=1000]
       [--update-table-stats] [--filtered_replication_wait_time=30s] [--debug_query] [--only_pks] [--wait] [--wait-update-interval=1m]
       <keyspace.workflow> create [<UUID>]

Each scheduled VDiff has an associated UUID which is returned by the create action. You can use it to monitor progress. Example:

$ vtctlclient --server=localhost:15999 VDiff -- customer.commerce2customer
VDiff bf9dfc5f-e5e6-11ec-823d-0aa62e50dd24 scheduled on target shards, use show to view progress

Resume a Previous VDiff #

The resume action allows you to resume a previously completed VDiff, picking up where it left off and comparing the records where the Primary Key column(s) are greater than the last record processed — with the progress and other status information saved when the run ends. This allows you to do approximate rolling or differential VDiffs (e.g. done after MoveTables finishes the initial copy phase and then again just before SwitchTraffic).

VDiff -- [--source_cell=<cell>] [--target_cell=<cell>] [--tablet_types=in_order:RDONLY,REPLICA,PRIMARY]
       [--limit=<max rows to diff>] [--tables=<table list>] [--format=json] [--auto-retry] [--verbose] [--max_extra_rows_to_compare=1000]
       [--update-table-stats] [--filtered_replication_wait_time=30s] [--debug_query] [--only_pks] [--wait] [--wait-update-interval=1m]
       <keyspace.workflow> resume <UUID>

Example:

$ vtctlclient --server=localhost:15999 VDiff -- customer.commerce2customer resume 4c664dc2-eba9-11ec-9ef7-920702940ee0
VDiff 4c664dc2-eba9-11ec-9ef7-920702940ee0 resumed on target shards, use show to view progress

Show Progress/Status of a VDiff #

VDiff -- <keyspace.workflow> show {<UUID> | last | all}

You can either show a specific UUID or use the last convenience shorthand to look at the most recently created VDiff. Example:

$ vtctlclient --server=localhost:15999 VDiff -- customer.commerce2customer show last

VDiff Summary for customer.commerce2customer (4c664dc2-eba9-11ec-9ef7-920702940ee0)
State:        completed
RowsCompared: 196
HasMismatch:  false
StartedAt:    2022-06-26 22:44:29
CompletedAt:  2022-06-26 22:44:31

Use "--format=json" for more detailed output.

$ vtctlclient --server=localhost:15999 VDiff -- --format=json customer.commerce2customer show last
{
	"Workflow": "commerce2customer",
	"Keyspace": "customer",
	"State": "completed",
	"UUID": "4c664dc2-eba9-11ec-9ef7-920702940ee0",
	"RowsCompared": 196,
	"HasMismatch": false,
	"Shards": "0",
	"StartedAt": "2022-06-26 22:44:29",
	"CompletedAt": "2022-06-26 22:44:31"
}

$ vtctlclient --server=localhost:15999 VDiff -- --format=json customer.p1c2 show daf1f03a-03ed-11ed-9ab8-920702940ee0
{
	"Workflow": "p1c2",
	"Keyspace": "customer",
	"State": "started",
	"UUID": "daf1f03a-03ed-11ed-9ab8-920702940ee0",
	"RowsCompared": 51,
	"HasMismatch": false,
	"Shards": "-80,80-",
	"StartedAt": "2022-07-15 03:26:03",
	"Progress": {
		"Percentage": 48.57,
		"ETA": "2022-07-15 03:26:10"
	}
}

show all lists all VDiffs created for the specified keyspace and workflow.

Stopping a VDiff #

VDiff -- <keyspace.workflow> stop <UUID>

The stop action allows you to stop a running VDiff for any reason — for example, the load on the system(s) may be too high at the moment and you want to postpone the work until off hours. You can then later use the resume action to start the VDiff again from where it left off. Example:

$ vtctlclient --server=localhost:15999 VDiff -- --format=json customer.commerce2customer stop ad9bd40e-0c92-11ed-b568-920702940ee0
{
	"UUID": "ad9bd40e-0c92-11ed-b568-920702940ee0",
	"Action": "stop",
	"Status": "completed"
}

Delete VDiff Results #

VDiff -- <keyspace.workflow> delete {<UUID> | all}

You can either delete a specific UUID or use the all shorthand to delete all VDiffs created for the specified keyspace and workflow. Example:

$ vtctlclient --server=localhost:15999 VDiff -- customer.commerce2customer delete all
VDiff delete status is completed on target shards

$ vtctlclient --server=localhost:15999 VDiff -- --format=json customer.commerce2customer delete all
{
	"Action": "delete",
	"Status": "completed"
}

Description #

VDiff does a row by row comparison of all tables associated with the workflow, diffing the source keyspace and the target keyspace and reporting counts of missing/extra/unmatched rows.

It is highly recommended that you do this before you finalize a workflow with SwitchTraffic.

Parameters #

--source_cell #

optional
default all

--target_cell #

optional
default all

--tablet_types #

optional
default in_order:RDONLY,REPLICA,PRIMARY

--filtered_replication_wait_time #

optional
default 30s

--limit #

optional
default 9223372036854775807

--tables #

optional
default all tables in the workflow

--format #

optional
default text (unstructured text output)

--auto-retry #

optional
default true

--verbose #

optional

--wait #

optional

--wait-update-interval #

optional
default 1m (1 minute)

--max_extra_rows_to_compare #

optional
default 1000

--debug_query #

optional

--only_pks #

optional

--update-table-stats #

optional

keyspace.workflow #

mandatory