Application log is the traditional way to monitor an application/service. On *nix-based system, Syslog is a common but powerful tool for centrally monitoring applications logs. The primary use of syslog is for system management as capturing log data is critical for sysadmin, devOp team, or system analysts, etc. This log data is helpful in case of investigating/troubleshooting problems and maintaining healthy functioning of systems.
Syslog offers a standard log format and a standard alert system with different severity levels to applications in form of a log API. Log daemons such as rsyslog are versatile and flexible with various configuration options that enable different way to interact with the logs: log to file, log to a remote server via network (TCP, UDP sockets), log to local Unix domain socket. Log clients or log analytic applications can collect log data from the log daemon via these interfaces.
Although it is feasible to directly read log messages from the regular syslog output files, it is more preferable to collect log data from the daemon using the socket interface since socket is more suitable for data streaming. TCP/UDP sockets can be used to access log data from the network (TCP/IP). But if the application runs locally on the same machine as the log daemon, Unix domain socket (UDS) may be the best option.
Unix Domain Socket is an inter-process communication mechanism that allows bidirectional data exchange between processes running on the same machine. Thus, UDSs can avoid some checks and operations (like routing); which makes them faster and lighter than IP sockets.
In this post, we will learn how to collect log data from syslog via UDS in C. We will use rsyslog as log daemon in this post.
A use case will be presented at the end of the post.
Working on my DIY robot software (Jarvis) in headless mode, i came across a situation where i needed to monitor the system resource such as CPU, battery, memory, network and temperature to measure the "greedy" of my robotic application. Furthermore, as the robot was battery powered, battery safety was a real concern, so i needed something to monitor the battery and shutdown the system when the battery was low to protect it from falling bellow the usable voltage range.
So i've searched for an application/service that allows me to:
None of existing applications/services satisfy all of these requirements, especially, the battery monitoring feature. So i've decided to write a small service that i called sysmond
.
sysmond
is a simple service that monitors and collects system information such as battery, temperature, memory, CPU, and network usage. The service can be used as backend for applications that need to consult system status. Although it is a part of Jarvis ecosystem, sysmond
is a generic service and can be easily adapted to other use cases.
Example of AntOS web application that fetches data from sysmond
and visualize it as real-time graphs on my Jarvis robot system. Detail on the use case can be found here
Sysmond
monitors resource available on the system via the user space sysfs interface provided by the linux kernel.
Update: The image is now available on Docker Hub at: https://hub.docker.com/r/xsangle/antosaio (image:
xsangle/antosaio:latest
). This post has been updated with the latest instructions on how to host a local instance of AntOS VDE using Docker.
Building and setting up AntOS from scratch can be complex, as it requires configuring and connecting many backend and front-end components. To simplify the use of AntOS as a self-hosted environment, I have created a Docker image layer for an all-in-one AntOS system that contains everything needed to host AntOS on your server. This layer allows you to build a minimal Docker image with a working AntOS system out-of-the-box:
The Docker images are available at: https://hub.docker.com/r/xsangle/antosaio/
Follow the steps below to create an AntOS instance. First, create the working directory (e.g., /tmp/antos
). All user data will be stored in this location. In this example, we use /tmp/antos
, but in a real scenario, you should use a permanent storage location.
# modify with your own working directory
mkdir -p /tmp/antos
Run a container with docker
docker run \
-p 8080:80 \
--rm \
-v /tmp/antos:/app \
-e ANTOS_USER=demo \
-e ANTOS_PASSWORD=demo \
-it xsangle/antosaio:latest
Or with docker compose: docker-compose.yml
version: '3.7'
services:
antos:
image: xsangle/antosaio:latest
privileged: true
restart: always
ports:
- 8080:80
container_name: antos_demo
deploy:
resources:
limits:
memory: 200m
cpus: '0.5'
hostname: demo
environment:
- ANTOS_USER=demo
- ANTOS_PASSWORD=demo
volumes:
- /tmp/antos/:/app
Run:
docker compose up
AntOS is now accessible via http://localhost:8080/os/
or using IP address http://YOUR_MACHINE_IP:8080/os/
The docker image provides user with a ready to go (out-of-the-box) AntOS VDE system. This is useful in many user-cases: