Overview of the Issue

In a VReplication workflow (e.g., MoveTables), the --workflow status and VReplicationStreamState statuses fall out of sync when resuming the workflow after an interruption:

This Copying vs Running mismatch in VReplicationStreamState when restarting a workflow can lead to faulty assumptions in monitoring and reporting (e.g., thinking copying is done when it really isn't).

Reproduction Steps

1. Spin up a new cluster, e.g.,

   ./examples/local/101_initial_cluster.sh
   

2. Insert enough data such that VReplication takes long enough to capture stats, e.g.,

   mysql < examples/common/insert_commerce_data.sql
   

   and

   mysql -e "insert into customer (email) select email from customer"
   

   ☝️ doubles the rows on every run.¹ 20,971,520 rows is enough for our purposes.

3. Spin up additional tablets in preparation for VReplication, e.g.,

   ./examples/local/201_customer_tablets.sh
   

4. Begin the VReplication, e.g.,

   vtctldclient --server localhost:15999 MoveTables --target-keyspace customer --workflow commerce2customer create --source-keyspace commerce --tables 'customer,corder'
   

5. Observe the following statuses:
   a. --workflow status

   $ vtctldclient --server localhost:15999 MoveTables --target-keyspace customer --workflow commerce2customer status --format=json
   …
    "shard_streams": {
     "customer/0": {
       "streams": [
         {
           "id": 1,
           "tablet": {
             "cell": "zone1",
             "uid": 200
           },
           "source_shard": "commerce/0",
           "position": "64425eca-d1e1-11ee-a4e7-ddc645075491:1-64",
           "status": "Copying",
           "info": "VStream Lag: 0s"
         }
   

   b. VReplicationStreamState:

   $ curl -s http://localhost:15200/debug/vars | grep "VReplicationStreamState"
   "VReplicationStreamState": {"commerce2customer.1": "Copying"},
   

   Expected: The states match (Copying and Copying).

6. Stop the workflow, e.g.,

   vtctldclient --server localhost:15999 MoveTables --target-keyspace customer --workflow commerce2customer stop --format=json
   

7. Resume the workflow, e.g.,

   vtctldclient --server localhost:15999 MoveTables --target-keyspace customer --workflow commerce2customer start --format=json
   

8. Observe the statuses again:
   a. --workflow status

   $ vtctldclient --server localhost:15999 MoveTables --target-keyspace customer --workflow commerce2customer status --format=json
   …
   "customer/0": {
   "streams": [
     {
       "id": 1,
       "tablet": {
         "cell": "zone1",
         "uid": 200
       },
       "source_shard": "commerce/0",
       "position": "64425eca-d1e1-11ee-a4e7-ddc645075491:1-65",
       "status": "Copying",
       "info": "VStream Lag: -1s; ; Tx time: Thu Feb 22 16:51:59 2024."
     }
   

   b. VReplicationStreamState

   $ curl -s http://localhost:15200/debug/vars | grep "VReplicationStreamState"
   "VReplicationStreamState": {"commerce2customer.1": "Running"},
   

   ⚠️ Unexpected: VReplicationStreamState says Running when workflow status is still Copying.

9. (Optional) Allow the copy to finish (i.e., wait a few minutes while the workflow is running). Observe both statuses are Running as expected.

Binary Version

vtgate version Version: 20.0.0-SNAPSHOT (Git revision 27be9166e1ace2708a158e9faf220cf156569e50 branch 'main') built on Thu Feb 22 17:00:55 PST 2024 by tyler@local using go1.22.0 darwin/amd64

Operating System and Environment details

- macOS 14.3.1 (23D60)
- Darwin 23.3.0
- arm64

Log Fragments

See above.