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Azure Web App Log Streaming Utility

A robust command-line utility for streaming logs from Azure Web Apps with support for deployment slots, local file logging, and automatic reconnection.

Features

• Stream logs from any Azure Web App
• Support for deployment slots
• Optional local log file with automatic size management
• Automatic reconnection if the Azure CLI stream disconnects
• Clean exit handling with CTRL+C

Installation

# Clone or download this GIST
curl -o az-webapp-log-stream.sh https://gist.githubusercontent.com/IAmStoxe/[gist-id]/raw/az-webapp-log-stream.sh
chmod +x az-webapp-log-stream.sh

Prerequisites

• Azure CLI installed and logged in (az login)
• Appropriate permissions to access the target web app's logs

Usage

./az-webapp-log-stream.sh <app_name> <resource_group> [slot] [--logfile path/to/logfile]

Arguments

Argument	Required	Description
app_name	Yes	Name of the Azure Web App
resource_group	Yes	Azure Resource Group containing the app
slot	No	Deployment slot name (omit for production slot)
--logfile	No	Path to save logs locally

Examples

Stream logs from production slot:

./az-webapp-log-stream.sh myapp myresourcegroup

Stream logs from a specific deployment slot:

./az-webapp-log-stream.sh myapp myresourcegroup staging

Stream logs and save to a local file:

./az-webapp-log-stream.sh myapp myresourcegroup --logfile ./app_logs.txt

Stream logs from a slot and save to a local file:

./az-webapp-log-stream.sh myapp myresourcegroup staging --logfile ./staging_logs.txt

Behavior Notes

• Log files are automatically truncated when they exceed 5MB to prevent disk space issues
• The script automatically attempts to reconnect if the Azure log stream disconnects
• Press CTRL+C to cleanly exit the script

Author

Created by IAmStoxe

License

MIT

tail_appservice.sh

#!/bin/bash
#------------------------------------------------------------------------------
# Azure Web App Log Streaming Utility
#
# PURPOSE: Stream logs from an Azure Web App, with optional logging to file
# and automatic reconnection if the stream disconnects.
#
# USAGE: ./script.sh <app_name> <resource_group> [slot] [--logfile path/to/logfile]
#------------------------------------------------------------------------------

# ===== Command-line argument handling =====
# First positional arguments are critical for Azure resource identification
APP_NAME="$1"
RESOURCE_GROUP="$2"
SLOT="$3"  # Optional deployment slot (defaults to production if not specified)
LOGFILE=""  # Will be set if --logfile flag is provided
MAX_SIZE=$((5 * 1024 * 1024))  # 5MB maximum log file size

# Parse optional flags that can appear anywhere in the argument list
# How: Loop through all arguments searching for the --logfile flag
# Why: Allows for more flexible command-line syntax
while [[ $# -gt 0 ]]; do
    case $1 in
    --logfile)
        LOGFILE="$2"  # Capture the logfile path provided after the --logfile flag
        shift 2  # Skip past both the flag and its value
        ;;
    *)
        shift  # Skip any non-recognized arguments
        ;;
    esac
done

# ===== Input validation =====
# What: Ensure required parameters are provided
# Why: Fail fast with helpful usage message if mandatory fields are missing
if [ -z "$APP_NAME" ] || [ -z "$RESOURCE_GROUP" ]; then
    echo "Usage: $0 <app_name> <resource_group> [slot] [--logfile path/to/logfile]"
    exit 1
fi

# ===== Signal handling =====
# What: Set up clean exit on Ctrl+C
# Why: Provide user feedback and graceful termination
trap "echo -e '\n[+] Stopping log tail...'; exit 0" SIGINT

# ===== Initial status output =====
echo "[+] Starting log tail for app: $APP_NAME (slot: ${SLOT:-production})"
# Only show logfile info if a logfile was specified
[ -n "$LOGFILE" ] && echo "[+] Logging to: $LOGFILE (max: $((MAX_SIZE / 1024 / 1024))MB)"

# ===== Log processing function =====
# What: Process each line of the log stream
# How: Read from stdin, display to console, and optionally write to logfile
# Why: Encapsulates log processing logic for reuse in the main loop
log_and_check_size() {
    while read -r line; do
        # Always display the log line to stdout
        echo "$line"
        
        # If a logfile was specified, write to it and manage its size
        if [ -n "$LOGFILE" ]; then
            echo "$line" >>"$LOGFILE"
            
            # Check file size to prevent unbounded growth
            # Why: Prevent filling disk space with too many logs
            size=$(stat -c %s "$LOGFILE")
            if ((size > MAX_SIZE)); then
                echo "[!] Logfile exceeded $((MAX_SIZE / 1024 / 1024))MB, truncating..."
                : >"$LOGFILE"  # Truncate file by writing empty string to it
            fi
        fi
        
        # Detect disconnection in Azure CLI log stream
        # Why: Azure CLI sometimes disconnects with an "aborted" message
        if echo "$line" | grep -q "^aborted$"; then
            echo "[!] Aborted detected in log stream. Reconnecting in 3s..."
            break  # Exit the loop to trigger reconnection
        fi
    done
}

# ===== Main log streaming loop =====
# What: Continuously connect to Azure log stream, handling disconnections
# How: Loop forever, executing the Azure CLI command and piping to our processor
# Why: Maintain persistent connection to logs despite intermittent failures
while true; do
    echo "[*] Connecting to Azure log stream..."
    
    # Connect to the appropriate log stream based on whether a slot was specified
    if [ -n "$SLOT" ]; then
        # Stream logs for the specified deployment slot
        az webapp log tail --name "$APP_NAME" --resource-group "$RESOURCE_GROUP" --slot "$SLOT" 2>&1 | log_and_check_size
    else
        # Stream logs for the production slot
        az webapp log tail --name "$APP_NAME" --resource-group "$RESOURCE_GROUP" 2>&1 | log_and_check_size
    fi
    
    # Brief pause before reconnecting
    # Why: Prevent rapid connection attempts if there's a persistent issue
    sleep 3
done