### Display Help for Retainless Daily Churn Command

Source: https://github.com/retainless/retainless-collector/blob/main/README.md

Get detailed information about the `daily-churn` command, including its purpose, how survival rate is measured, and an example of its output format. The output is always a CSV file.

```bash
$ retainless daily-churn --help
Usage: retainless daily-churn [options]

Survival rate (or fall-off rate) is the number of users who still find your site
useful after a specified number of days, as measured by the duration between
their first visit and their last visit.

Example output:

CohortDay,DayOffset,UsersSurviving,PoolSize,CohortSize
2025-10-08,0,100,100,100
2025-10-08,1,25,100,100
2025-10-08,2,22,25,100
2025-10-08,3,20,22,100
2025-10-08,4,18,20,100
2025-10-09,0,100,100,100
2025-10-09,1,25,100,100
2025-10-09,2,20,25,100
2025-10-09,3,16,20,100

Options:
  -h, --help  display help for command
```

--------------------------------

### Configure NPM for GitHub Registry and Install Retainless CLI

Source: https://github.com/retainless/retainless-collector/blob/main/README.md

Configure your NPM client to use the GitHub Package Registry and install the Retainless CLI globally. This requires a GitHub Personal Access Token. Remember to replace GITHUB_TOKEN with your actual token.

```bash
echo '//npm.pkg.github.com/:_authToken=GITHUB_TOKEN' >> ~/.npmrc
echo '@retainless:registry=https://npm.pkg.github.com' >> ~/.npmrc
npm install -g @retainless/cli
```

```bash
# to upgrade the CLI:
npm install -g @retainless/cli@latest
```

--------------------------------

### Analyze Daily Churn and Pipe Output to File

Source: https://github.com/retainless/retainless-collector/blob/main/README.md

Execute the `daily-churn` command with specified start and end dates and redirect the CSV output to a file. Status messages are printed to STDERR.

```bash
$ retainless --start 2025-10-01 --end 2025-10-31 daily-churn > ~/Documents/DailyChurn.csv
Loading periods..............................++++++++++
```

--------------------------------

### Display Help for Retainless CLI

Source: https://github.com/retainless/retainless-collector/blob/main/README.md

View the available options and commands for the Retainless CLI. Use the --help flag for general usage or for specific commands.

```bash
$ retainless --help
Usage: retainless [options] [command]

Options:
  -s --start <string>  Earliest period (default: "2025-10-01")
  -e --end <string>    Latest period (default: "2025-10-31")
  -h, --help           display help for command

Commands:
  daily-churn          survival rate of users based on their first visit
  daily-retention      daily retention rate of users
  weekly-retention     weekly retention rate of users
  help [command]       display help for command
```

--------------------------------

### Retainless Architecture: Log Processor Diagram

Source: https://github.com/retainless/retainless-collector/blob/main/README.md

This PlantUML diagram illustrates the data flow and processing steps within the Retainless Log Processor. It covers reading user data, generating new period ranges, hashing access logs, calculating session lengths, and storing new period and user data.

```plantuml
@startuml
title Retainless Architecture: Log Processor

boundary Lambda
database DynamoDB
database CloudWatch

[-> Lambda: EventBridge Scheduler\nDaily, early morning ~2AM local
Lambda -> DynamoDB: Read all `Period` rows\n& their salts
Lambda -> Lambda: Generate new `Period` range\n from last `Period` end to midnight
Lambda -> DynamoDB: Read `Users` in any known `Period`\n(aka hashable users)
Lambda -> CloudWatch: Query access logs for `Period` range
group
  Lambda -> Lambda: Group access logs by UserId (today's\nfingerprint): `hash(ip + ua + salt + secret)`
end
group
  Lambda -> Lambda: Calculate `sessionLength` and\n`requestCount`
  Lambda -> Lambda: Hash `ip + ua` with `salt + secret`\nof all prior `Period` rows
  alt If any match
    Lambda -> Lambda: Link & copy to `priorVisits` array
    note right Lambda: When we lose the prior `Period` salt\nwe will also lose the ability to discover &\nlink Users of that Period. By copying, we\nhave "renewed" this user for a fresh\nretention period under a new UserId.\n\nThis has impacts on statistic calculation!
  end
end
Lambda -> DynamoDB: Write new `Period` with 30-day expiry
Lambda -> DynamoDB: Write new `User` rows for new `Period`

== Later ==

CloudWatch -> CloudWatch: Retention period\nexpiration
DynamoDB -> DynamoDB: TTL expiration of\nold `Period` rows 
@enduml
```

--------------------------------

### Deploy Retainless Collector with Terraform on AWS

Source: https://github.com/retainless/retainless-collector/blob/main/README.md

Use this Terraform module to deploy the retainless-collector to AWS. Ensure your CloudWatch Logs group ARN and log stream name are correctly specified. Check for the latest versions at the provided GitHub releases URL.

```terraform
module "retainless" {
  # note: check for new versions at https://github.com/retainless/retainless-collector/releases
  source = "git::https://github.com/retainless/retainless-collector.git//aws/terraform?ref=v0.1.1"

  log_group_arn   = "arn:aws:logs:us-east-1:123456789876:log-group:/aws/cloudfront/cdn-prod-access-logs:*"
  log_stream_name = "CloudFront_EA123456789EEAA"
}
```

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