Nano Dev Console Service

The Nano Dev Console is a lightweight, drop-in module for any Nano-based application that gives you runtime visibility into events, logs, and system metrics. It exposes a small HTTP UI + JSON endpoints and requires no code changes in your app beyond adding the dependency.

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Features

• Live event stream with pause & export (excludes Dev Console’s own HTTP requests)
• Live logs with pause & export
• System snapshot (PID, heap usage, CPU %, thread counts, service list)
• Change runtime configurations via Config panel
• Zero app wiring — subscribes to all event channels automatically

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Compatibility

• Nano: Tested with 2025.1.4
• Java: Recommended LTS 21 (no issues detected with JDK 25 until now)
• Packaging: JAR

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Installation

1. Build and install this project locally:

mvn clean install

2. Add the dependency to your Nano app:

<!-- Dev Console -->
<dependency>
  <groupId>org.nanonative</groupId>
  <artifactId>devconsole</artifactId>
  <version>1.0.0</version>
</dependency>

<!-- Your app must already depend on Nano -->
<dependency>
  <groupId>org.nanonative</groupId>
  <artifactId>nano</artifactId>
  <version>${nano.version}</version>
</dependency>

Once on the classpath, the service starts with your app and exposes the UI.

        Nano nano = new Nano(Map.of(
            CONFIG_SERVICE_HTTP_PORT, "8080"
        ), new DevConsoleService(), new HttpServer(), new MyAppService(), new OtherAppService());

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Configuration

Config keys are registered via Nano’s config system. You can set them via your usual mechanism (e.g., env, file, system props). Defaults shown below.

Key	Type	Default	Description
dev_console_max_events	int	1000	Max events retained in memory
dev_console_max_logs	int	1000	Max logs retained in memory
dev_console_url	string	/ui	UI path under /dev-console (e.g., /alex → UI at /dev-console/alex)

Examples

# HTTP UI (local)
http://localhost:8080/dev-console/ui

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Metrics shown in the UI

• Memory Usage (MB): Process memory reported by Nano.

• Heap Usage (%): % of current heap used; relative to your -Xmx setting.

• CPU Usage (%): Process CPU load

  • Interpreted as share of total machine CPU (0–100 per JVM, not per core)

• Thread Count: Application thread counts and other JVM threads.

• Total Events: Cumulative events seen by the application.

You can pause charts to inspect, and export events/logs as text.

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How it works (under the hood)

• Subscribes to all event channels, handles Dev Console HTTP events internally, and records everything else in memory concurrent deques.
• Uses (ConcurrentLinkedDeque) and weakly consistent iteration for low overhead and high concurrency;
• Filters out its own HTTP requests so UI traffic doesn’t pollute the event stream.

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Security & Ops

• Intended for development/test by default. For production, do not include DevConsoleService().
• Memory footprint scales with maxEvents. 1 GB heap comfortably holds ~1.5K events. add ~800 events per extra GB of -Xmx.
• The Dev console stores state in memory only; restart clears histories.
• If needed to run this project (Main) as a standalone:

• Add plugin to the pom of this project:

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>exec-maven-plugin</artifactId>
  <version>3.2.0</version>
  <configuration>
    <mainClass>org.nanonative.devconsole.Main</mainClass>
  </configuration>
</plugin>

• Remove the provided scope of Nano artifact in the pom

Recommendations for users

Pick a budget, then size maxEvents: For your current event payloads, a conservative rule of thumb from these runs is: 1 GB heap comfortably holds ~1.5k events, Logs are lightweight String objects and 10K logs are estimated to take around ~2 MB (0.02 GB) add ~900 events per extra GB of -Xmx (ConcurrentLinkedDeque accounts a tiny memory for linkage) For long-running, high-throughput workloads, the table below guides memory sizing. The Retained events mark the point at which Nano terminated with EVENT_APP_OOM (OutOfMemory Error)

GC	-Xmx	MaxDirectMemorySize	Retained events
G1	1 g	64 m	1836
G1	1 g	128 m	1943
G1	1 g	256 m	2100
ZGC	1 g	256 m	1580
G1	2 g	256 m	2633
G1	2 g	512 m	2399
G1	3 g	256 m	3584
G1	3 g	512 m	2102

Note: These tests were performed by keeping the -Xms and -Xmx values same.

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URLs & Endpoints

The Dev Console is mounted under BASE_URL = /dev-console.

Method	Path	Description
GET	/dev-console/system-info	JSON snapshot of system & JVM info
GET	/dev-console/events	JSON list of recent events
GET	/dev-console/logs	JSON list of recent logs
PATCH	/dev-console/config	Update runtime config (see below)
GET	/dev-console/<uiPath> (default /ui)	Dev Console UI (HTML)
GET	/dev-console/{fileName}	Static UI assets

Note: Dev Console HTTP requests are not recorded as events.