How to Perform Load Testing against Nebula Graph with K6

December 1, 2021
Load Testing of K6 in Nebula Graph

Why Load Testing Matters in Nebula Graph?

The load testing for the database needs to be conducted usually so that the impact on the system can be monitored in different scenarios, such as query language rule optimization, storage engine parameter adjustment, etc.

The operating system in this article is the x86 CentOS 7.8.

The hosts where Nebula Graph is deployed are configured with 4C 16G memory, SSD disk, and 10G network.

Tools Needed for the Load Testing

  • nebula-ansible deploys Nebula Graph services.
  • nebula-importer imports data into Nebula Graph clusters.
  • k6-plugin is a K6 extension that is used to perform load testing against the Nebula Graph cluster. The extension integrates with the nebula-go client to send requests during the testing.
  • nebula-bench generates the LDBC dataset and then imports it into Nebula Graph.
  • ldbc_snb_datagen_hadoop is a LDBC data generator.

Load Testing Process Overview

The load testing conducted in this article uses the LDBC dataset generated by ldbc_snb_datagen. The testing process is as follows.

Load Testing of K6 in Nebula Graph

To deploy the topology, use one host as the load testing runner, and use three hosts to form a Nebula Graph cluster.

Load Testing of K6 in Nebula Graph

To make monitoring easier, the load testing runner also deploys:

  • Prometheus
  • Influxdb
  • Grafana
  • node-exporter

The hosts where Nebula Graph is installed also deploy:

  • node-exporter
  • process-exporter

Load Testing Steps

Use nebula-ansible to deploy Nebula Graph

  1. Set up SSH login without passwordsa. Log in,,, and respectively. Create a vesoft user and join in sudoer with NOPASSWD.b. Log in to set up SSH.
class="bash language-bash"ssh-keygen

ssh-copy-id vesoft@
ssh-copy-id vesoft@
ssh-copy-id vesoft@
  1. Download nebula-ansible, install Ansible, and modify the Ansible configuration.
class="bash language-bash"sudo yum install ansible -y
git clone
cd nebula-ansible/

The following is an example of inventory.ini.

class="yaml language-yaml"[all:vars]
# GA or nightly
install_source_type = GA
nebula_version = 2.0.1
os_version = el7
arc = x86_64
pkg = rpm

packages_dir = {{ playbook_dir }}/packages
deploy_dir = /home/vesoft/nebula
data_dir = {{ deploy_dir }}/data

# ssh user
ansible_ssh_user = vesoft

force_download = False



  1. Install and deploy Nebula Graph.
class="bash language-bash"ansible-playbook install.yml
ansible-playbook start.yml

Monitor hosts

Using docker-compose to deploy monitoring system is convenient. Docker and Docker-Compose need to be installed on the hosts first.

Log in

class="bash language-bash"git clone

cd nebula-bench
cp -r third/promethues ~/.
cp -r third/exporter ~/.

cd ~/exporter/ && docker-compose up -d

cd ~/promethues
# Modify the exporter address of monitoring nodes
# vi prometheus.yml
docker-compose up -d

# Copy exporter to,, and, and then start docker-compose

Configure the Grafana data source and dashboard. For details, see

Generate the LDBC dataset

class="bash language-bash"cd nebula-bench

sudo yum install -y git \
make \
file \
libev \
libev-devel \
gcc \
wget \
python3 \
python3-devel \
java-1.8.0-openjdk \

pip3 install --user -r requirements.txt

# Using `snb.interactive.1` parameter in ldbc_snb_datagen_hadoop. For more infor, see

python3 data

# Date generated by mv

mv target/data/test_data/ ./sf1

Import data

class="bash language-bash"cd nebula-bench
# Modify .evn
cp env .env
vi .env

The following is the example of .env

class="bash language-bash"DATA_FOLDER=sf1
class="bash language-bash"# Compile nebula-importer and K6

# Import data
python3 nebula importer

During the import process, you can focus on the following network bandwidth and disk IO writing.

Import data
Import data

Execute the load testing

class="bash language-bash"python3 stress run

According to the code source in the file scenarios, the js file will be automatically rendered and K6 will be used to test all scenarios.

After the execution is over, the js file and the result will be saved in the output folder.

Among them, latency is the latency time returned by the server, and responseTime is the time from initiating execute to response by the client. The measurement unit is μs.

class="bash language-bash"[vesoft@qa-60 nebula-bench]$ more output/result_Go1Step.json
"metrics": {
"data_sent": {
"count": 0,
"rate": 0
"checks": {
"passes": 1667632,
"fails": 0,
"value": 1
"data_received": {
"count": 0,
"rate": 0
"iteration_duration": {
"min": 0.610039,
"avg": 3.589942336582023,
"med": 2.9560145,
"max": 1004.232905,
"p(90)": 6.351617299999998,
"p(95)": 7.997563949999995,
"p(99)": 12.121579809999997
"latency": {
"min": 308,
"avg": 2266.528722763775,
"med": 1867,
"p(90)": 3980,
"p(95)": 5060,
"p(99)": 7999
"responseTime": {
"max": 94030,
"p(90)": 6177,
"p(95)": 7778,
"p(99)": 11616,
"min": 502,
"avg": 3437.376111156418,
"med": 2831
"iterations": {
"count": 1667632,
"rate": 27331.94978169588
"vus": {
"max": 100,
"value": 100,
"min": 0
class="bash language-bash"[vesoft@qa-60 nebula-bench]$ head -300 output/output_Go1Step.csv | grep -v USE
1628147822,GO 1 STEP FROM 4398046516514 OVER KNOWS,1217,1536,true,1,
1628147822,GO 1 STEP FROM 2199023262994 OVER KNOWS,1388,1829,true,94,
1628147822,GO 1 STEP FROM 1129 OVER KNOWS,1488,2875,true,14,
1628147822,GO 1 STEP FROM 6597069771578 OVER KNOWS,1139,1647,true,30,
1628147822,GO 1 STEP FROM 2199023261211 OVER KNOWS,1399,2096,true,6,
1628147822,GO 1 STEP FROM 2199023256684 OVER KNOWS,1377,2202,true,4,
1628147822,GO 1 STEP FROM 4398046515995 OVER KNOWS,1487,2017,true,39,
1628147822,GO 1 STEP FROM 10995116278700 OVER KNOWS,837,1381,true,3,
1628147822,GO 1 STEP FROM 933 OVER KNOWS,1130,3422,true,5,
1628147822,GO 1 STEP FROM 6597069771971 OVER KNOWS,1022,2292,true,60,
1628147822,GO 1 STEP FROM 10995116279952 OVER KNOWS,1221,1758,true,3,
1628147822,GO 1 STEP FROM 8796093031179 OVER KNOWS,1252,1811,true,13,
1628147822,GO 1 STEP FROM 10995116279792 OVER KNOWS,1115,1858,true,6,
1628147822,GO 1 STEP FROM 6597069777326 OVER KNOWS,1223,2016,true,4,
1628147822,GO 1 STEP FROM 8796093028089 OVER KNOWS,1361,2054,true,13,
1628147822,GO 1 STEP FROM 6597069777454 OVER KNOWS,1219,2116,true,2,
1628147822,GO 1 STEP FROM 13194139536109 OVER KNOWS,1027,1604,true,2,
1628147822,GO 1 STEP FROM 10027 OVER KNOWS,2212,3016,true,83,
1628147822,GO 1 STEP FROM 13194139544176 OVER KNOWS,855,1478,true,29,
1628147822,GO 1 STEP FROM 10995116280047 OVER KNOWS,1874,2211,true,12,
1628147822,GO 1 STEP FROM 15393162797860 OVER KNOWS,714,1684,true,5,
1628147822,GO 1 STEP FROM 6597069770517 OVER KNOWS,2295,3056,true,7,
1628147822,GO 1 STEP FROM 17592186050570 OVER KNOWS,768,1630,true,26,
1628147822,GO 1 STEP FROM 8853 OVER KNOWS,2773,3509,true,14,
1628147822,GO 1 STEP FROM 19791209307908 OVER KNOWS,1022,1556,true,6,
1628147822,GO 1 STEP FROM 13194139544258 OVER KNOWS,1542,2309,true,91,
1628147822,GO 1 STEP FROM 10995116285325 OVER KNOWS,1901,2556,true,0,
1628147822,GO 1 STEP FROM 6597069774931 OVER KNOWS,2040,3291,true,152,
1628147822,GO 1 STEP FROM 8796093025056 OVER KNOWS,2007,2728,true,29,
1628147822,GO 1 STEP FROM 21990232560726 OVER KNOWS,1639,2364,true,9,
1628147822,GO 1 STEP FROM 8796093030318 OVER KNOWS,2145,2851,true,6,
1628147822,GO 1 STEP FROM 21990232556027 OVER KNOWS,1784,2554,true,5,
1628147822,GO 1 STEP FROM 15393162796879 OVER KNOWS,2621,3184,true,71,
1628147822,GO 1 STEP FROM 17592186051113 OVER KNOWS,2052,2990,true,5,

It is also possible to execute the load testing in one scenario and continuously adjust the configuration parameters for comparison.

Concurrent reading
class="bash language-bash"# Run Go2Step with 50 virtual users and 300 seconds of duration
python3 stress run -scenario go.Go2Step -vu 50 -d 300
class="shell language-shell"INFO[0302] 2021/08/06 03:55:27 [INFO] finish init the pool

✓ IsSucceed

█ setup

█ teardown

checks...............: 100.00% ✓ 1559930 ✗ 0
data_received........: 0 B 0 B/s
data_sent............: 0 B 0 B/s
iteration_duration...: min=687.47µs avg=9.6ms med=8.04ms max=1.03s p(90)=18.41ms p(95)=22.58ms p(99)=31.87ms
iterations...........: 1559930 5181.432199/s
latency..............: min=398 avg=6847.850345 med=5736 max=222542 p(90)=13046 p(95)=16217 p(99)=23448
responseTime.........: min=603 avg=9460.857877 med=7904 max=226992 p(90)=18262 p(95)=22429 p(99)=31726.71
vus..................: 50 min=0 max=50
vus_max..............: 50 min=50 max=50

Every metric can be monitored at the same time.

Concurrent reading

checks is to verify whether the request is executed successfully. If the execution fails, the failed message will be saved in the CSV file.

class="bash language-bash"awk -F ',' '{print $NF}' output/output_Go2Step.csv|sort |uniq -c
class="bash language-bash"# Execute Go2Step with 200 virtual users and 300 seconds of duration
python3 stress run -scenario go.Go2Step -vu 200 -d 300
class="shell language-shell"INFO[0302] 2021/08/06 04:02:34 [INFO] finish init the pool

✓ IsSucceed

█ setup

█ teardown

checks...............: 100.00% ✓ 1866850 ✗ 0
data_received........: 0 B 0 B/s
data_sent............: 0 B 0 B/s
iteration_duration...: min=724.77µs avg=32.12ms med=25.56ms max=1.03s p(90)=63.07ms p(95)=84.52ms p(99)=123.92ms
iterations...........: 1866850 6200.23481/s
latency..............: min=395 avg=25280.893558 med=20411 max=312781 p(90)=48673 p(95)=64758 p(99)=97993.53
responseTime.........: min=627 avg=31970.234329 med=25400 max=340299 p(90)=62907 p(95)=84361.55 p(99)=123750
vus..................: 200 min=0 max=200
vus_max..............: 200 min=200 max=200

K6 metrics to be monitored with Grafana

The monitoring data of K6 in Grafana
Concurrent writing
class="bash language-bash"# Execute insert with 200 virtual users and 300 seconds of duration. By default, batchSize is 100.

python3 stress run -scenario go.Go2Step -vu 200 -d 300

The js file can be modified manually to adjust batchSize

class="bash language-bash"sed -i 's/batchSize = 100/batchSize = 300/g' output/InsertPersonScenario.js

# Run K6 manually

scripts/k6 run output/InsertPersonScenario.js -u 400 -d 30s --summary-trend-stats "min,avg,med,max,p(90),p(95),p(99)" --summary-export output/result_InsertPersonScenario.json --out influxdb=

If the batchSize is 300 with 400 virtual users, an error will be returned.

class="shell language-shell"INFO[0032] 2021/08/06 04:03:49 [INFO] finish init the pool

✗ IsSucceed
↳ 96% — ✓ 31257 / ✗ 1103

█ setup

█ teardown

checks...............: 96.59% ✓ 31257 ✗ 1103
data_received........: 0 B 0 B/s
data_sent............: 0 B 0 B/s
iteration_duration...: min=12.56ms avg=360.11ms med=319.12ms max=2.07s p(90)=590.31ms p(95)=696.69ms p(99)=958.32ms
iterations...........: 32360 1028.339207/s
latency..............: min=4642 avg=206931.543016 med=206162 max=915671 p(90)=320397.4 p(95)=355798.7 p(99)=459521.39
responseTime.........: min=6272 avg=250383.122188 med=239297.5 max=1497159 p(90)=384190.5 p(95)=443439.6 p(99)=631460.92
vus..................: 400 min=0 max=400
vus_max..............: 400 min=400 max=400
class="bash language-bash"awk -F ',' '{print $NF}' output/output_InsertPersonScenario.csv|sort |uniq -c
class="shell language-shell" 31660
1103 error: E_CONSENSUS_ERROR(-16)."
1 errorMsg

If E_CONSENSUS_ERROR occurs, it should be that the appendlog buffer of raft is overflown when the concurrency is large, which can be solved by adjusting relevant parameters.


  • The load testing uses the LDBC dataset standard to ensure data uniform. Even when bigger data volume, say one billion vertices, is generated, the graph schema is the same.
  • K6 is more convenient than Jmeter for the load testing. For more details, please refer
  • You can easily find the bottleneck of the system resources by simulating various scenarios or adjust parameters in Nebula Graph with the mentioned tools.

If you encounter any problems in the process of using Nebula Graph, please refer to Nebula Graph Database Manual to troubleshoot the problem. It records in detail the knowledge points and specific usage of the graph database and the graph database Nebula Graph.

Join our Slack channel if you want to discuss with the rest of the Nebula Graph community!

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