roachprod: fix VM creation and disk type detection in grow command

[shailendra-patel]

This commit fixes two bugs in the roachprod grow command:

1. Fixed VM creation failure due to hostname collisions. Previously, we were using the same VM name multiple times across different zones, causing "RESOURCE_ALREADY_EXISTS" errors. The fix extracts the hostname allocation logic into a new helper function (computeHostNamesPerZone) that properly distributes unique hostnames across zones.

2. Fixed incorrect disk type detection in instance group templates. We were checking d.InitializeParams.DiskType for "SCRATCH" instead of d.Type, which prevented proper identification of local SSD volumes.

The bug is likely to be introduced in #137956

Epic: none

Release note: None

[cockroach-teamcity]

This change is 

[github-actions]

🟢 Sysbench [SQL, 3node, oltp_read_write]

Metric	Old Commit	New Commit	Delta	Note	Threshold
⚪ sec/op	9.683m ±3%	9.653m ±3%	~	p=0.912 n=10	3.0%
⚪ errs/op	0.000 ±0%	0.000 ±0%	~	p=1.000 n=10	0.0%
🟢 allocs/op	10.16k ±0%	10.15k ±0%	-0.13%	p=0.005 n=10	2.0%
🟢 B/op	2.183Mi ±0%	2.179Mi ±0%	-0.20%	p=0.023 n=10	2.0%

Reproduce

benchdiff binaries:

mkdir -p benchdiff/3393c69/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/3393c699d77ba04fa4eef871fea0a5b6179d0c2d/bin/pkg_sql_tests benchdiff/3393c69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/3393c69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
mkdir -p benchdiff/b0b0e69/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/b0b0e695f4623659574ebf45a5a140bb58673082/bin/pkg_sql_tests benchdiff/b0b0e69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/b0b0e69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests

benchdiff command:

benchdiff --run=^BenchmarkSysbench/SQL/3node/oltp_read_write$ --old=b0b0e69 --new=3393c69 ./pkg/sql/tests

⚪ Sysbench [KV, 1node, local, oltp_read_only]

Metric	Old Commit	New Commit	Delta	Note	Threshold
⚪ sec/op	687.7µ ±1%	690.8µ ±1%	~	p=0.075 n=10	2.0%
⚪ errs/op	0.000 ±0%	0.000 ±0%	~	p=1.000 n=10	0.0%
⚪ allocs/op	439.0 ±0%	439.0 ±0%	~	p=1.000 n=10	1.5%
⚪ B/op	254.2Ki ±0%	254.2Ki ±0%	~	p=0.631 n=10	1.5%

Reproduce

benchdiff binaries:

mkdir -p benchdiff/3393c69/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/3393c699d77ba04fa4eef871fea0a5b6179d0c2d/bin/pkg_sql_tests benchdiff/3393c69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/3393c69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
mkdir -p benchdiff/b0b0e69/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/b0b0e695f4623659574ebf45a5a140bb58673082/bin/pkg_sql_tests benchdiff/b0b0e69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/b0b0e69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests

benchdiff command:

benchdiff --run=^BenchmarkSysbench/KV/1node_local/oltp_read_only$ --old=b0b0e69 --new=3393c69 ./pkg/sql/tests

🟢 Sysbench [KV, 1node, local, oltp_write_only]

Metric	Old Commit	New Commit	Delta	Note	Threshold
⚪ sec/op	1.374m ±1%	1.376m ±1%	~	p=0.971 n=10	2.5%
⚪ errs/op	0.000 ±0%	0.000 ±0%	~	p=1.000 n=10	0.0%
⚪ allocs/op	1.397k ±0%	1.397k ±0%	~	p=0.745 n=10	1.8%
🟢 B/op	290.5Ki ±0%	289.8Ki ±0%	-0.23%	p=0.003 n=10	1.8%

Reproduce

benchdiff binaries:

mkdir -p benchdiff/3393c69/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/3393c699d77ba04fa4eef871fea0a5b6179d0c2d/bin/pkg_sql_tests benchdiff/3393c69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/3393c69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
mkdir -p benchdiff/b0b0e69/bin/1058449141
gcloud storage cp gs://cockroach-microbench-ci/builds/b0b0e695f4623659574ebf45a5a140bb58673082/bin/pkg_sql_tests benchdiff/b0b0e69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests
chmod +x benchdiff/b0b0e69/bin/1058449141/cockroachdb_cockroach_pkg_sql_tests

benchdiff command:

benchdiff --run=^BenchmarkSysbench/KV/1node_local/oltp_write_only$ --old=b0b0e69 --new=3393c69 ./pkg/sql/tests

Artifacts

download:

mkdir -p new
gcloud storage cp gs://cockroach-microbench-ci/artifacts/3393c699d77ba04fa4eef871fea0a5b6179d0c2d/13460265651-1/\* new/
mkdir -p old
gcloud storage cp gs://cockroach-microbench-ci/artifacts/b0b0e695f4623659574ebf45a5a140bb58673082/13460265651-1/\* old/

Legend

• ⚪ Neutral: No significant performance change.
• 🟡 Warning: Slight degradation, likely due to variance, but still within thresholds.
• 🔴 Regression: Likely performance regression, requiring investigation.
• 🟢 Improvement: Possible performance gain.

No regressions detected!

built with commit: 3393c699d77ba04fa4eef871fea0a5b6179d0c2d

[BabuSrithar]

Please explore adding test cases.

[nameisbhaskar]

LGTM!