Alerts & Webhooks

New in v10

Dozzle v10 introduces a powerful alerting system that lets you monitor container logs, resource metrics, and lifecycle events, and receive notifications when specific conditions are met. Alerts use customizable expressions to filter containers and trigger conditions, and can send notifications to webhooks, Slack, Discord, ntfy, or Dozzle Cloud.

Alert Types

Dozzle supports three kinds of alerts, all configured the same way from the Notifications page:

Type	Triggers on	Example use case
Log	A log message matching a pattern	5xx errors, stack traces
Metric	CPU / memory crossing a threshold	Container exceeding 90% CPU
Event	Container lifecycle events from Docker	OOM kills, unhealthy containers

Each alert pairs a container expression (which containers to watch) with a trigger expression (the condition to fire on).

IMPORTANT

Alert and destination configurations are stored in the /data directory. You must mount this directory as a volume to persist your notification settings across container restarts.

sh

docker run -v /var/run/docker.sock:/var/run/docker.sock -v /path/to/data:/data -p 8080:8080 amir20/dozzle:latest

docker-compose.yml

services:
  dozzle:
    image: amir20/dozzle:latest
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - /path/to/data:/data
    ports:
      - 8080:8080

Setting Up a Destination

Before creating alerts, you need to configure at least one notification destination. Navigate to the Notifications page in Dozzle and click Add Destination.

Webhook

Webhooks send an HTTP POST request to a URL of your choice. Dozzle includes built-in payload templates for popular services:

• Slack — formatted with blocks and markdown
• Discord — formatted for Discord webhook API
• ntfy — formatted for ntfy.sh push notifications
• Custom — generic JSON payload you can customize

You can also write your own payload template using Go's text/template syntax. The following variables are available:

Variable	Description
{{.Detail}}	Summary (log message or metric values)
{{.Container.Name}}	Container name
{{.Container.Image}}	Container image
{{.Container.HostName}}	Docker host name
{{.Container.State}}	Container state
{{.Log.Message}}	Log message content
{{.Log.Level}}	Log level
{{.Log.Timestamp}}	Log timestamp
{{.Log.Stream}}	Stream type (stdout/stderr)
{{.Stat.CPUPercent}}	CPU usage percentage
{{.Stat.MemoryPercent}}	Memory usage percentage
{{.Stat.MemoryUsage}}	Memory usage in bytes
{{.Subscription.Name}}	Alert rule name

TIP

Use the Test button to verify your webhook is working before saving.

Dozzle Cloud

You can also send alerts to Dozzle Cloud for centralized monitoring across multiple Dozzle instances. See the Dozzle Cloud guide for more details.

Creating an Alert

Navigate to the Notifications page and click Add Alert. Every alert has a container expression plus one of a log, metric, or event trigger expression.

Container Expression

The container expression selects which containers to monitor. Available properties:

Property	Type	Example
name	string	name contains "api"
image	string	image == "nginx:latest"
state	string	state == "running"
health	string	health == "unhealthy"
hostName	string	hostName == "prod-host"
labels	map	labels["env"] == "production"

You can combine conditions with && (AND), || (OR), and ! (NOT):

name contains "api" && labels["env"] == "production"

Log Alerts

Log Expression

The log expression filters which log messages trigger the alert. Available properties:

Property	Type	Example
message	string/map	message contains "error"
level	string	level == "error"
stream	string	stream == "stderr"
type	string	type == "complex"

For JSON logs, you can access nested fields using dot notation:

message.status >= 500 && message.path contains "/api"

Supported string operators include contains, startsWith, endsWith, and matches (regex).

Log Examples

Alert on all errors from production containers:

Container: labels["env"] == "production"
Log:       level == "error"

Alert on HTTP 5xx errors from API containers:

Container: name contains "api"
Log:       message.status >= 500

Alert on any stderr output from a specific image:

Container: image startsWith "myapp/"
Log:       stream == "stderr"

Alert on slow API responses from production:

Container: name contains "api" && labels["env"] == "production"
Log:       message.duration > 5000 && message.path contains "/api"

Alert on authentication failures using regex:

Container: name contains "auth" || name contains "gateway"
Log:       message matches "(?i)(unauthorized|forbidden|invalid token)"

NOTE

The alert editor includes autocomplete and real-time validation. You can preview matched containers and logs before saving.

Metric Alerts

Metric alerts fire when a container's CPU or memory usage crosses a threshold. The trigger expression is evaluated against a smoothed average of stats sampled over a rolling window, which avoids false alarms from short spikes.

Metric Expression

Available properties:

Property	Type	Description
cpu	number	CPU usage percentage (0–100, per core-adjusted)
memory	number	Memory usage percentage (0–100)
memoryUsage	number	Memory usage in bytes

Cooldown & Sample Window

• Sample window — how many seconds of stats are averaged before the expression is evaluated. Longer windows smooth out spikes; shorter windows react faster.
• Cooldown — minimum seconds between consecutive triggers for the same container. Prevents alert floods when a container stays above threshold.

Metric Examples

High CPU on production containers:

Container: labels["env"] == "production"
Metric:    cpu > 90

Memory pressure on a specific service:

Container: name contains "api"
Metric:    memory > 85

Absolute memory usage (1 GiB):

Container: name == "postgres"
Metric:    memoryUsage > 1073741824

Event Alerts

Event alerts fire on Docker container lifecycle events — useful for catching crashes, OOM kills, and health status changes without parsing logs.

Event Expression

Available properties:

Property	Type	Description
name	string	Event name (see below)
actorId	string	Docker actor ID (usually the container ID)
attributes	map	Event attributes from Docker (varies by event type)
timestamp	time	When the event occurred

Common Docker event names include start, stop, die, kill, oom, restart, destroy, and health_status.

Event Examples

Alert when any production container dies:

Container: labels["env"] == "production"
Event:     name == "die"

Alert on OOM kills:

Container: true
Event:     name == "oom"

Alert when a container becomes unhealthy:

Container: true
Event:     name == "health_status" && attributes["health_status"] == "unhealthy"

Alert on unexpected exits (non-zero exit code):

Container: name contains "worker"
Event:     name == "die" && attributes["exitCode"] != "0"

Managing Alerts

From the Notifications page, you can:

• Enable/disable alerts without deleting them
• Edit alert expressions and destinations
• View statistics including trigger count, matched containers, and last triggered time
• Delete alerts that are no longer needed