VReplication: Support reversing read-only traffic in vtctldclient

[mattlord]

Description

This PR fixes a bug in vtctldclient, in that it did not support a needed feature that the legacy vtctlclient did (see the client transition docs). Specifically, support for using ReverseTraffic when traffic for read-only tablet types (REPLICA, RDONLY) have been switched BUT writes (PRIMARY tablet type) have not ever been before.

h/t to @rohit-nayak-ps for the additional tests that were a huge help! 🙇

Using the manual test from below, this fails with vtctldclient but works with vtctlclient:

❯ vtctldclient MoveTables --workflow commerce2customer --target-keyspace customer reversetraffic --tablet-types "rdonly,replica"
E1009 20:59:35.000461   35915 main.go:56] rpc error: code = Unknown desc = no streams found in keyspace commerce for commerce2customer_reverse

❯ vtctlclient MoveTables -- reversetraffic customer.commerce2customer --tablet_types "rdonly,replica"
W1008 19:45:47.734875   67717 log.go:39] Failed to read in config : Config File "vtconfig" Not Found in "[/Users/matt/git/vitess/examples/local]". This is optional, and can be ignored if you are not using config files. For a detailed explanation, see https://github.com/vitessio/vitess/blob/main/doc/viper/viper.md#config-files.
reversetraffic was successful for workflow customer.commerce2customer
Start State: All Reads Switched. Writes Not Switched
Current State: Reads Not Switched. Writes Not Switched

I think that it makes sense to backport this at least to v21 so that this is addressed in a minimum of 1 GA branches/releases. For those on older releases, the workaround is to use the equivalent vtctlclient command. In the end, what this really did is closer align the two implementations around how this work is done.

Manual test

alias vtctldclient='command vtctldclient --server=localhost:15999'
cd examples/local

./101_initial_cluster.sh; mysql < ../common/insert_commerce_data.sql; ./201_customer_tablets.sh; ./202_move_tables.sh; ./203_switch_reads.sh

echo -e "\nReversing traffic for reads..."
vtctldclient MoveTables --workflow commerce2customer --target-keyspace customer reversetraffic --tablet-types "rdonly,replica"
echo

With the client command output on the PR branch being:

SwitchTraffic was successful for workflow customer.commerce2customer

Start State: Reads Not Switched. Writes Not Switched
Current State: All Reads Switched. Writes Not Switched


Reversing traffic for reads...
ReverseTraffic was successful for workflow customer.commerce2customer

Start State: All Reads Switched. Writes Not Switched
Current State: Reads Not Switched. Writes Not Switched

Related Issue(s)

• Fixes: Feature Request: ReverseTraffic for only replica and rdonly tablet types #16918

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

[vitess-bot]

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[codecov]

Codecov Report

Attention: Patch coverage is 59.74026% with 31 lines in your changes missing coverage. Please review.

Project coverage is 67.15%. Comparing base (4e89152) to head (e9685d5).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/vtctl/workflow/server.go	59.25%	22 Missing ⚠️
go/vt/vtctl/workflow/traffic_switcher.go	60.86%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16920      +/-   ##
==========================================
- Coverage   69.35%   67.15%   -2.20%     
==========================================
  Files        1571     1571              
  Lines      204149   251785   +47636     
==========================================
+ Hits       141583   169087   +27504     
- Misses      62566    82698   +20132     

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[mattlord]

@rohit-nayak-ps thanks again for the help with the new tests! That was a life saver. I thought about what else to test, now that we have the new and updated e2e and unit tests and nothing obvious came to mind. If you have general suggestions please let me know and I'll work on adding/updating tests for those conditions. In the meantime I'll think about what gaps might still be left myself (haven't come up with anything yet).