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Add configurable timezone support with environment variables

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serversdwn
2026-01-12 16:31:33 +00:00
parent 6b363b0788
commit 2cb96a7a1c
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.env.example Normal file
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# SLMM Configuration
# Copy this file to .env and customize as needed
# Timezone Configuration
# Set the timezone offset from UTC (in hours)
# Examples:
# -5 = EST (Eastern Standard Time)
# -4 = EDT (Eastern Daylight Time)
# 0 = UTC
# +1 = CET (Central European Time)
# -8 = PST (Pacific Standard Time)
TIMEZONE_OFFSET=-5
# Optional: Timezone name for logging (cosmetic only)
TIMEZONE_NAME=EST
# CORS Configuration (comma-separated list of allowed origins)
CORS_ORIGINS=*

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TIMEZONE_CONFIGURATION.md Normal file
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# Timezone Configuration for SLMM
## Overview
The SLMM system now supports configurable timezone settings. All timestamps are stored internally in UTC for consistency, but the system can interpret FTP timestamps and display times in your local timezone.
## Configuration
### Environment Variables
Set the following environment variables to configure your timezone:
#### `TIMEZONE_OFFSET` (required)
The number of hours offset from UTC. Use negative numbers for zones west of UTC, positive for east.
**Examples:**
- `-5` = EST (Eastern Standard Time, UTC-5)
- `-4` = EDT (Eastern Daylight Time, UTC-4)
- `0` = UTC (Coordinated Universal Time)
- `+1` = CET (Central European Time, UTC+1)
- `-8` = PST (Pacific Standard Time, UTC-8)
**Default:** `-5` (EST)
#### `TIMEZONE_NAME` (optional)
A friendly name for your timezone, used in log messages.
**Examples:**
- `EST`
- `EDT`
- `UTC`
- `PST`
**Default:** Auto-generated from offset (e.g., "UTC-5")
### Setup Instructions
#### Option 1: Using .env file (Recommended)
1. Copy the example file:
```bash
cd /home/serversdown/slmm
cp .env.example .env
```
2. Edit `.env` and set your timezone:
```bash
TIMEZONE_OFFSET=-5
TIMEZONE_NAME=EST
```
3. Make sure your application loads the .env file (you may need to install `python-dotenv`):
```bash
pip install python-dotenv
```
4. Update `app/main.py` to load the .env file (add at the top):
```python
from dotenv import load_dotenv
load_dotenv()
```
#### Option 2: System Environment Variables
Set the environment variables in your shell or service configuration:
```bash
export TIMEZONE_OFFSET=-5
export TIMEZONE_NAME=EST
```
Or add to your systemd service file if running as a service.
#### Option 3: Docker/Docker Compose
If using Docker, add to your `docker-compose.yml`:
```yaml
services:
slmm:
environment:
- TIMEZONE_OFFSET=-5
- TIMEZONE_NAME=EST
```
Or pass via command line:
```bash
docker run -e TIMEZONE_OFFSET=-5 -e TIMEZONE_NAME=EST ...
```
## How It Works
### Data Flow
1. **FTP Timestamps**: When the system reads file timestamps via FTP from the NL43 device, they are assumed to be in your configured timezone
2. **Conversion**: Timestamps are immediately converted to UTC for internal storage
3. **Database**: All timestamps in the database are stored in UTC
4. **API Responses**: Timestamps are sent to the frontend as UTC ISO strings
5. **Frontend Display**: The browser automatically converts UTC timestamps to the user's local timezone for display
### Example
If you're in EST (UTC-5) and the FTP shows a file timestamp of "Jan 11 21:57":
1. System interprets: `Jan 11 21:57 EST`
2. Converts to UTC: `Jan 12 02:57 UTC` (adds 5 hours)
3. Stores in database: `2026-01-12T02:57:00`
4. Sends to frontend: `2026-01-12T02:57:00` (with 'Z' added = UTC)
5. Browser displays: `Jan 11, 9:57 PM EST` (converts back to user's local time)
### Timer Calculation
The measurement timer calculates elapsed time correctly because:
- `measurement_start_time` is stored in UTC
- FTP folder timestamps are converted to UTC
- Frontend calculates `Date.now() - startTime` using UTC milliseconds
- All timezone offsets cancel out, giving accurate elapsed time
## Troubleshooting
### Timer shows wrong elapsed time
1. **Check your timezone setting**: Make sure `TIMEZONE_OFFSET` matches your actual timezone
```bash
# Check current setting in logs when SLMM starts:
grep "Using timezone" data/slmm.log
```
2. **Verify FTP timestamps**: FTP timestamps from the device should be in your local timezone
- If the device is configured for a different timezone, adjust `TIMEZONE_OFFSET` accordingly
3. **Restart the service**: Changes to environment variables require restarting the SLMM service
### Logs show unexpected timezone
Check the startup logs:
```bash
tail -f data/slmm.log | grep timezone
```
You should see:
```
Using timezone: EST (UTC-5)
```
If not, the environment variable may not be loaded correctly.
## Daylight Saving Time (DST)
**Important:** This configuration uses a fixed offset. If you need to account for Daylight Saving Time:
- **During DST (summer)**: Set `TIMEZONE_OFFSET=-4` (EDT)
- **During standard time (winter)**: Set `TIMEZONE_OFFSET=-5` (EST)
- You'll need to manually update the setting when DST changes (typically March and November)
**Future Enhancement:** Automatic DST handling could be implemented using Python's `zoneinfo` module with named timezones (e.g., "America/New_York").
## Default Behavior
If no environment variables are set:
- **TIMEZONE_OFFSET**: Defaults to `-5` (EST)
- **TIMEZONE_NAME**: Defaults to `UTC-5`
This means the system will work correctly for EST deployments out of the box.

30
app/services.py
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@@ -9,8 +9,9 @@ import asyncio
import contextlib
import logging
import time
import os
from dataclasses import dataclass
from datetime import datetime
from datetime import datetime, timezone, timedelta
from typing import Optional, List
from sqlalchemy.orm import Session
from ftplib import FTP
@@ -20,6 +21,16 @@ from app.models import NL43Status
logger = logging.getLogger(__name__)
# Configurable timezone offset
# Set via environment variable TIMEZONE_OFFSET (hours from UTC)
# Default: -5 (EST - Eastern Standard Time, UTC-5)
# Examples: -5 for EST, -4 for EDT, 0 for UTC, +1 for CET
TIMEZONE_OFFSET_HOURS = float(os.getenv("TIMEZONE_OFFSET", "-5"))
TIMEZONE_OFFSET = timedelta(hours=TIMEZONE_OFFSET_HOURS)
TIMEZONE_NAME = os.getenv("TIMEZONE_NAME", f"UTC{TIMEZONE_OFFSET_HOURS:+.0f}")
logger.info(f"Using timezone: {TIMEZONE_NAME} (UTC{TIMEZONE_OFFSET_HOURS:+.0f})")
@dataclass
class NL43Snapshot:
@@ -744,21 +755,30 @@ class NL43Client:
modified_timestamp = None
try:
from datetime import datetime
# Get current time in configured timezone for year comparison
now_local = datetime.utcnow() + TIMEZONE_OFFSET
# Try parsing with time (recent files: "Jan 07 14:23")
try:
dt = datetime.strptime(modified_str, "%b %d %H:%M")
# Add current year since it's not in the format
dt = dt.replace(year=datetime.now().year)
# Assume FTP timestamp is in the configured timezone
dt = dt.replace(year=now_local.year)
# If the resulting date is in the future, it's actually from last year
if dt > datetime.now():
if dt > now_local:
dt = dt.replace(year=dt.year - 1)
modified_timestamp = dt.isoformat()
# Convert local timezone to UTC
dt_utc = dt - TIMEZONE_OFFSET
modified_timestamp = dt_utc.isoformat()
except ValueError:
# Try parsing with year (older files: "Dec 25 2025")
dt = datetime.strptime(modified_str, "%b %d %Y")
modified_timestamp = dt.isoformat()
# Convert local timezone to UTC
dt_utc = dt - TIMEZONE_OFFSET
modified_timestamp = dt_utc.isoformat()
except Exception as e:
logger.warning(f"Failed to parse timestamp '{modified_str}': {e}")