VReplication: Optimize replication on target tablets

[mattlord]

Description

This PR makes two performance optimizations affecting execution time and resource usage:

1. For the copy phase: optimize the generation of row values that are used to build bulk INSERT statements
2. For the running/replicating phase: enable the VPlayerBatching feature by default. This was added in v18 in VReplication VPlayer: support statement and transaction batching #14502. It has been enabled in a number of relevant endtoend tests ever since and it has been used in PlanetScale for a number of important workflows. Enabling it early in the v22 lifecycle also gives us a good 3-6 months for it to bake further on main.

Summary:

• Copy phase
  • The time it took to finish the copy phase went from 548 seconds to 489: approximately an 11% improvement
  • The tablet memory usage/allocations went from 19,842.93MiB to 2,667.88MiB: approximately a 7.43x improvement
• Running phase
  • The time it took to catch up when subsequently inserting another 10,000,000 rows after the copy phase ended went from 270 seconds to 40 seconds: approximately a 6.75x improvement

The detailed results of the testing can be seen here: https://gist.github.com/mattlord/d6161a1c27f203a497b7bd6a69e7c467

The test setup was created this way:

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

# Enable the pprof endpoints
diff --git a/examples/common/scripts/vttablet-up.sh b/examples/common/scripts/vttablet-up.sh
index daa40aee89..282cd0553e 100755
--- a/examples/common/scripts/vttablet-up.sh
+++ b/examples/common/scripts/vttablet-up.sh
@@ -54,6 +54,7 @@ vttablet \
  --service_map 'grpc-queryservice,grpc-tabletmanager,grpc-updatestream' \
  --pid_file $VTDATAROOT/$tablet_dir/vttablet.pid \
  --heartbeat_on_demand_duration=5s \
+ --pprof-http \
  > $VTDATAROOT/$tablet_dir/vttablet.out 2>&1 &



# Setup function to time the copy phase completion
function wait_for_workflow_running() {
    local keyspace=customer
    local workflow=commerce2customer
    local wait_secs=900
    local result=""

    echo "Waiting for the ${workflow} workflow in the ${keyspace} keyspace to finish the copy phase..."

    for _ in $(seq 1 ${wait_secs}); do
        result=$(vtctldclient Workflow --keyspace="${keyspace}" show --workflow="${workflow}" 2>/dev/null | grep "Copy phase completed")
        if [[ ${result} != "" ]]; then
            break
        fi
        sleep 1
    done;

    if [[ ${result} == "" ]]; then
        echo "Timed out after ${wait_secs} seconds waiting for the ${workflow} workflow in the ${keyspace} keyspace to reach the running state"
    else
        echo "The ${workflow} workflow in the ${keyspace} keyspace is now running. $(sed -rn 's/.*"(Copy phase.*)".*/\1/p' <<< "${result}")."
    fi
}


# Setup the commerce keyspace
./101_initial_cluster.sh


# Load data in the customer table
table_file="${VTDATAROOT}/vt_0000000100/data/vt_commerce/customer.ibd"
commerce_primary_uid=$(vtctldclient GetTablets --keyspace commerce --tablet-type primary --shard "0" | awk '{print $1}' | cut -d- -f2 | bc)

# Generate 5MiB of initial data
size=$((5*1024*1024))
while [[ $(stat -f "%z" "${table_file}") -lt ${size} ]]; do
    command mysql -u root --socket "${VTDATAROOT}/vt_0000000${commerce_primary_uid}/mysql.sock" vt_commerce -e "insert into customer (customer_id, email) values (${RANDOM}*${RANDOM}, '${RANDOM}_person@planetscale.com')" 2> /dev/null
done

say "Initial data load completed"

# Grow that to at least 10GiB
size=$((10*1024*1024*1024))
i=1
while [[ $(stat -f "%z" "${table_file}") -lt ${size} ]]; do
    command mysql -u root --socket "${VTDATAROOT}/vt_0000000${commerce_primary_uid}/mysql.sock" vt_commerce -e "insert into customer (email) select concat(${i}, email) from customer limit 5000000"
    let i=i+1
done

say "Full data load completed"


# Setup the customer keyspace
./201_customer_tablets.sh


# Move the customer table from the commerce keyspace to the customer keyspace
customer_primary_uid=$(vtctldclient GetTablets --keyspace customer --tablet-type primary --shard "0" | awk '{print $1}' | cut -d- -f2 | bc)

# Profile target primary in a different shell
go tool pprof -seconds 130 "http://localhost:15${customer_primary_uid}/debug/pprof/profile"
(pprof) top 20 -ignore_regex runtime -cum

# Immediately start the workflow
vtctldclient MoveTables --workflow commerce2customer --target-keyspace customer create --source-keyspace commerce --tablet-types primary --tables "customer"
date
wait_for_workflow_running
date

say "Workflow is running"

go tool pprof "http://localhost:15${customer_primary_uid}/debug/pprof/allocs"
(pprof) top 30


# Now see how long it takes to replicate 10,000,000 new rows
command mysql -u root --socket "${VTDATAROOT}/vt_0000000${commerce_primary_uid}/mysql.sock" vt_commerce -e "insert into customer (email) select concat(${i}, email) from customer limit 10000000"
sleep 1
date
while [[ $(vtctldclient Workflow --keyspace="customer" show --workflow="commerce2customer" 2>/dev/null | jq -r '.[] | .[0].max_v_replication_transaction_lag') -gt 1 ]]; do
    sleep 1
done
date


# Cancel the workflow
vtctldclient MoveTables --workflow commerce2customer --target-keyspace customer cancel

Related Issue(s)

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: Document VReplicationExperimentalFlagVPlayerBatching enabled by default website#1888

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[codecov]

Codecov Report

Attention: Patch coverage is 96.55172% with 1 line in your changes missing coverage. Please review.

Project coverage is 67.41%. Comparing base (4980d6f) to head (5f15e3f).

Files with missing lines	Patch %	Lines
...blet/tabletmanager/vreplication/replicator_plan.go	96.42%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17166      +/-   ##
==========================================
+ Coverage   67.39%   67.41%   +0.02%     
==========================================
  Files        1570     1570              
  Lines      252892   252887       -5     
==========================================
+ Hits       170437   170486      +49     
+ Misses      82455    82401      -54     

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[mattlord]

This change will be reverted before merging.

[mattlord]

After thinking about it more, I'd like to keep this enabled for the examples. Seems like a good case for it. I can remove/revert the change though if others disagree. If we do keep it here, I could also add it for vtgate and vtctld.

[mattlord]

This is unrelated, but I noticed that it was not correct as I was doing testing.

[mattlord]

I'll open a separate PR for this since it's worth a quick backport to v19 to prevent a panic if the error we got back from the query was NOT an SQL error.

[mattlord]

The comments in this file are unrelated to this PR but I wanted to get them into main after the field number gap came up in a discussion.

[mattlord]

Putting back in Draft to investigate test failures that seemingly came out of nowhere....

[mattlord]

Putting back in Draft to investigate test failures that seemingly came out of nowhere....

Addressed via f0f61db and 21564fd

[mattlord]

You can see the reason for the vdiff test changes in the commit message: f0f61db