Add basic k6 load test for PA/50 district project

I manually filled out a 50 district PA project and exported it as a HAR
file. From there, I used har-to-k6 converter to produce a k6 load test.
Lastly, I created a few parameters to make the test more reusable:

- JWT_AUTH_TOKEN: A DistrictBuilder JWT authentication token
- DB_PROJECT_ID: A DistrictBuilder project UUID (PA; 50 districts)
- DB_DOMAIN: The DistrictBuilder instance domain where the project above
  resides

Author: hectcastro

CHANGELOG.md

@@ -10,7 +10,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Project page sharing & read-only mode [#449](https://github.com/PublicMapping/districtbuilder/pull/449)
-- Set keep-alive timeout higher than ALB idle timeout[#448](https://github.com/PublicMapping/districtbuilder/pull/448)
+- Set keep-alive timeout higher than ALB idle timeout [#448](https://github.com/PublicMapping/districtbuilder/pull/448)
+- Add basic k6 load test for PA/50 district project [#448](https://github.com/PublicMapping/districtbuilder/pull/448)
 
 ### Changed
 

load-tests/README.md

@@ -0,0 +1,58 @@
+# Load Testing
+
+This [k6](https://k6.io/) based load testing project is focused on automating
+user requests that are known to stress parts of the application. All of the
+components necessary to execute a load test are encapsulated in this directory.
+
+## Variables
+
+- `JWT_AUTH_TOKEN`: A DistrictBuilder JWT authentication token
+- `DB_PROJECT_ID`: A DistrictBuilder project UUID (PA; 50 districts)
+- `DB_DOMAIN`: The DistrictBuilder instance domain where the project above resides
+
+## Running
+
+Below is an example of how to invoke an instance of the load test with Docker
+Compose:
+
+```console
+$ export DB_JWT_AUTH_TOKEN="..."
+$ export DB_PROJECT_ID="f1824edc-588c-43d9-a094-1b914470910d"
+$ export DB_DOMAIN="app.staging.districtbuilder.org"
+$ docker-compose run --rm k6
+
+          /\      |‾‾| /‾‾/   /‾‾/
+     /\  /  \     |  |/  /   /  /
+    /  \/    \    |     (   /   ‾‾\
+   /          \   |  |\  \ |  (‾)  |
+  / __________ \  |__| \__\ \_____/ .io
+
+  execution: local
+     script: /scripts/pa-50-districts.js
+     output: -
+
+  scenarios: (100.00%) 1 scenario, 20 max VUs, 3m30s max duration (incl. graceful stop):
+           * default: 20 looping VUs for 3m0s (gracefulStop: 30s)
+
+
+running (3m26.9s), 00/20 VUs, 60 complete and 0 interrupted iterations
+default ✓ [======================================] 20 VUs  3m0s
+
+    █ Picking PA districts
+
+    data_received..............: 386 MB 1.9 MB/s
+    data_sent..................: 1.9 MB 9.3 kB/s
+    group_duration.............: avg=1m5s     min=57.16s  med=1m4s     max=1m15s   p(90)=1m14s    p(95)=1m14s
+    http_req_blocked...........: avg=1.38ms   min=100ns   med=200ns    max=92.56ms p(90)=500ns    p(95)=600ns
+    http_req_connecting........: avg=211.51µs min=0s      med=0s       max=16ms    p(90)=0s       p(95)=0s
+    http_req_duration..........: avg=2.98s    min=32.23ms med=2.34s    max=15.69s  p(90)=5.78s    p(95)=8.22s
+    http_req_receiving.........: avg=519.78ms min=14.3µs  med=268.25µs max=10.05s  p(90)=1.69s    p(95)=2.42s
+    http_req_sending...........: avg=83.68µs  min=21.9µs  med=72.95µs  max=985.8µs p(90)=130.32µs p(95)=142.11µs
+    http_req_tls_handshaking...: avg=871.29µs min=0s      med=0s       max=60.4ms  p(90)=0s       p(95)=0s
+    http_req_waiting...........: avg=2.46s    min=31.95ms med=1.61s    max=15.69s  p(90)=5.26s    p(95)=7.2s
+    http_reqs..................: 1320   6.379084/s
+    iteration_duration.........: avg=1m6s     min=58.16s  med=1m5s     max=1m16s   p(90)=1m15s    p(95)=1m15s
+    iterations.................: 60     0.289958/s
+    vus........................: 4      min=4  max=20
+    vus_max....................: 20     min=20 max=20
+```

load-tests/docker-compose.yml

@@ -0,0 +1,11 @@
+version: "3"
+services:
+  k6:
+    image: loadimpact/k6
+    environment:
+      - DB_JWT_AUTH_TOKEN
+      - DB_PROJECT_ID
+      - DB_DOMAIN=${DB_DOMAIN:-app.staging.districtbuilder.org}
+    volumes:
+      - ./:/scripts/
+    command: run /scripts/pa-50-districts.js