Document cost impacts (#29)

* replace on push with workflow_dispatch to reduce costs

* document about costs

* bump version

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## v0.2.4
+
+- Document a projected cost analysis in the README
+
 ## v0.2.3
 
 - Add test coverage in CI

README.md

@@ -164,9 +164,7 @@ look like for keeping flag definitions updated in KV
 name: Update Flag Definitions in KV
 
 on:
-  push:
-    branches:
-      - main
+  workflow_dispatch:
 
 jobs:
   update:
@@ -189,4 +187,33 @@ jobs:
 
 All that's needed is to set `URL_TO_KV` and `DENO_KV_ACCESS_TOKEN` (see above
 for their definitions) as environment secrets in the `flagDefinitions`
-environment (which can be created in Github at Settings > Environments).
+environment (which can be created in Github at Settings > Environments). Then
+manually running the workflow will update the flag definitions in KV.
+
+## Cost Analysis
+
+A flag definitions file will be on the order of 1-10 kb in size. Let's take 10
+kb as the worse scenario. This is small compared to the
+[Deno Deploy free tier limit](https://deno.com/deploy/pricing) of 1 GB for KV
+storage.
+
+Imagine a scenario where a project autoscales from 0 isolates at night to a
+steady 10 isolates during the day, and a feature flag update is made once per
+day.
+
+This will result in 30 writes to KV per month, for a total of 300 kb. 1 KV write
+unit is 1 kb, so this would total 300 write units per month. This is small
+compared to the Deno Deploy free tier limit of 300,000 KV write units per month.
+
+Every isolate spin up will read the 10kb flag definitions from KV, and then a
+feature flag update will cause another read from the KV watcher, for a total of
+20 kb per isolate per day, and so 6,000 kb per month. The feature flag update
+also reads the 10 kb flag definitions from KV, adding 300 kb per month for a
+total of 6,300 kb per month. 1 KV read unit is 4 kb, so this would total 1,575
+read units per month. This is small compared to the Deno Deploy free tier limit
+of 450,000 KV read units per month.
+
+If instead 100 isolates are spun up per day (e.g. from autoscaling back down,
+then up, then down, etc...), the read units used should still be small compared
+to the free tier limits. If instead 1,000 isolates or more are spun up per day,
+the read units used will become a significant fraction of the free tier limits.

deno.json

@@ -1,6 +1,6 @@
 {
   "name": "@grunet/openfeature-for-denodeploy",
-  "version": "0.2.3",
+  "version": "0.2.4",
   "exports": "./src/index.ts",
   "tasks": {
     "format": "deno fmt",

examples/attribute-targeting/updateFlagDefinitionsInKv.yaml

@@ -3,15 +3,13 @@
 # 1. Copy it to .github/workflows
 # 2. Add a working-directory of examples/attribute-targeting to the Update FLag Definitions step
 # 3. Add URL_TO_KV and DENO_KV_ACCESS_TOKEN as environment secrets
-# 4. Remove the main branch restriction of on:push:
+# 4. Replace the workflow_dispatch: with on:push:
 # Then test by pushing changes to a test branch
 
 name: Update Flag Definitions in KV
 
 on:
-  push:
-    branches:
-      - main
+  workflow_dispatch:
 
 jobs:
   update: