Unix System Monitoring Over SSH

SshSysMon is a system/server monitoring tool that executes all of its operations over SSH without the need for installing agents across machines.

Its goal is to provide simple self-hosted monitoring and alerting for small numbers of lightweight servers without the traditional overhead of a monitoring system.

It monitors things in /proc and with simple command executions to monitor system vitals such as: memory, cpu load, drive space, swap, etc.

Setup

Installation

Via PyPi

pip install sshsysmon

Manually (No Install)

# Requires python 2.x and pip:
sudo apt-get install -y python python-pip python-dev

# Download the latest SshSysMon:
wget -O - https://github.com/zix99/sshsysmon/archive/master.tar.gz | tar xzv

# Make sure the dependencies are installed:
cd sshsysmon-master/
sudo pip install -r requirements.txt

# Test it out!
./sshmon summary examples/starter.yml

Setting up a ssh key pair

You only need to do this if you are monitoring a remote server.

The best way to connect to remote servers is with private key created and added to the authorized_hosts file on all systems you are interested in monitoring. While password authentication is supported, this is the easiest way to guarantee continued authentication to other hosts.

On debian-based linux systems, setting up a key-pair to use with SSH is easy. I would recommend you make a new linux user to only do monitoring on each machine, but it isn't required.

# 1. Create a new SSH key if you don't already have one. Follow the prompts, but leave the password blank
ssh-keygen

# 2. Install it on a user on another machine that you want to monitor
ssh-copy-id username@remotehost

Running

The service has two commands, summary and check.

Summary

summary will print out a human-readable summary of all servers specified in the config. It is a great way to validate your config.

It can be executed with:

./sshmon.py summary examples/starter.yml

It also can be told to use various templates. See templating section below. Eg, to use the html template:

./sshmon.py -f html summary examples/starter.yml

Check

check is meant to be executed as part of a scheduled job, and will notify all channels in the config if a condition is unmet.

It can be excuted with:

./sshmon.py check <myconfig.yml>

Running Scheduled Job

The best way to run the service automatically is with a cron job.

Edit your cron jobs with

crontab -e

Add an entry that runs the script every few hours: (or minutes, whatever you like)

0 */4 * * * /path/to/sshmon.py check /path/to/config.yml

Configuration

Configuration is written in yaml and is a set of servers, with a list of monitors with alarms, notification channels and connection details.

See the Examples folder for more sample configs.

An example simple configuration might look something like this:

meta: #Meta section (Optional). Used by summary templates
  title: "My Cluster Summary"
  author: "Me"

servers:
  "Name of server":
    driver: ssh
    config:
      host: myhostname.com
      username: myuser
    channels: # Notification targets
      - type: email
        config:
          toAddr: myemail@gmail.com
          subject: "Something went wrong on {server}"
    monitors: # All alerts and inspectors
      - type: memory
        alarms:
          "Low Swap": "swap_free.mb < 50"
          "Low Memory": "mem_free.mb < 5"
      - type: disk
        alarms:
          "Low Disk Space": "disk_free.gb < 5"
        summarize: false # Optional, use if you don't want a monitor to show up in the summary

You can often use YAML's inheritance to simplify your config for more than 1 server. Each config section also has a corresponding + version to add more in addition to something merged in. eg. monitors+.

All servers are iterated through, and queried for given inspector types. The resulting metrics are compared to the alarms, and if any of them are unmet, a notification it sent to all configured channels.

Data Format

All sizes (that is, number of bytes), is enapsulated by the ByteSize class, which has helper methods for both friendly output, and size casting in the form of b, kb, mb, etc. eg, you can write mem_free.mb > 50.

All timedelta's are encapsulated by the TimeSpan class, which has properties that expose reduced forms. They are seconds, minutes, hours, and days.

Percentages will always be presented in their 0-100 form.

---

Application

Components

The applications is built on three components: Drivers, Inspectors, and Channels.

Each has its corresponding folder with abstract implementation. They are loaded dynamically with their name or path provided in the configuration.

Drivers

Drivers are classes that define how to read information from a server. By default, there are two drivers:

Local

The local driver is only for your local machine. There is no config for this driver.

SSH

The SSH driver is for reaching out to remote machines. There are several config paramters for this driver:

• host - The hostname of the machine (IP or Domain)
• username - The username to connect with
• password - (Not recommended, use key instead) The ssh user's password
• key - The path to the private key to use to connect (Default: ~/.ssh/id_rsa)
• port - The port to connect to the machine on (Default: 22)
• path - The path which proc is located (Default: /proc)

--

Channels

Channels define what can happen if an alert fires. There a few built-in.

There are a few variables passed in that can be used to format part of the commands:

• server - The server that the alert triggered on
• alert - The alert that triggered (the name)
• inspector - The inspector that triggered the alert
• statement - The statement of the inspector that fired the alert

stdout

Writes tab-separated data to stdout. Can be appended to file with bash >> operator.

Arguments:

• timeFormat - Either ctime or epoch, the format which time is output. Default: ctime
• format - The format string used to write output. Default: {time}\t{server}\t{inspector}\t{alert}

command

Executes a shell command on the machine in which the script is running.

Arguments:

• command - The shell command to execute

email

Sends an email via a SMTP server.

By default, it assumes a local SMTP server is setup. For more complex configs, such as how to use gmail, see the examples.

Arguments:

• toAddr - The address to send the email to
• fromAddr - The address the email should come from (default: username@hostname)
• host - The SMTP host (default: localhost)
• port - The SMTP port (default: 25)
• subject - Subject line of email (has reasonable default)
• username - Username to authenticate with smtp server (default: none)
• password - Password to authenticate with smtp server (default: none)
• tls - Should use tls (default: false)
• ssl - Should use ssl (default: false)

webhook

Calls an http/https endpoint and passes it the JSON model.

Arguments:

• url - The URL to call
• method - The method to use in the http request (default: POST)
• headers - A dict of any additional headers to add to the request
• verifySSL - Whether or not to verify SSL cert (default: True)

--

Inspectors (Alert Types)

Inspects are parsers that know how to read data from a driver and make sense of it.

Memory (memory)

The memory driver returns metrics about the systems memory:

Metrics: mem_total, mem_free, cached, swap_total, swap_free

Disk Space (disk)

The Disk driver returns status of the disk space (in GB)

Config:

• device - The name of the device (Optional, eg /dev/sda)
• mount - The mount point of the device (default: /)

Metrics: size, used, available, percent_full

Load Average (loadavg)

The load average inspector returns the system's current 1/5/15 minute load average.

Metrics: load_1m, load_5m, load_15m

Process Monitor (process)

This inspector will allow you monitor a process on the given machine.

It takes in one required config name. This will use wildcard matching with * and ?.

Metrics: user, pid, cpu, mem, tty

TCP (tcp)

The TCP inspector will try to establish a connection on a given port with the same remote as the driver. It's important to note that this does not go over SSH, and will not verify anything more than that the port is willing to establish a connection.

Config:

• ports: A list, single port, or CSV of ports to check

Metrics:

• A dictionary of the requested ports, prefixed with port_, and true if they are open, otherwise false (eg port_22)
• A special all metric which will be true if all ports are open

HTTP (http)

The Http connector will attempt to do a GET request on a http/https endpoint, and return the data if able.

Config:

• path: The path to request on (default '/')
• port: The port to request at (default 80 for http, 443 for https)
• https: True/false if https (default: http)
• json: true/false if it should attempt to parse the response as json (Default: false)
• match: A regex to match against (default: None)

Metrics:

• success: A true/false whether the request returns a 2xx, and all requirements were met (matches, or parses)
• match: Whether or not the regex matched. None if no match requested
• json: The parsed json, if requested
• url: The requested url

Custom Command (exec)

exec runs a custom command and returns stdout, stderr, and status (returncode).

Config:

• command: The shell command to execute
• environment: Optional object of environment variables (Default: {})
• json: Try to parse the command's output as json (Default: false)
• extract: Dict of name:path pairs to extract as metrics, eg a.[1].c (Default: None) See: Extracting Typed Json below; json must be true

Properties extracted as metrics can be used in alarms

Metrics:

If json, those will be the output metrics instead

• stdout: The out string of the command
• stderr: The err string of the command
• status: The returncode of the command (0 means normal)

File/Path Metadata (FileMeta)

filemeta gathers all the metadata of all files in a path

Config:

• path: Path to gather the file data
• match: Matcher to select files within path
• maxDepth: The max depth it searches for files
• minDepth: The min depth it searches for files

Metrics:

• count: Number of files that match
• oldest: The TimeSpan object of the oldest file
• newest: The TimeSpan object of the newest file
• largest: ByteSize of the largest file
• smallest: ByteSize of smallest file
• files: Array of files
  • path: Path to the file
  • size: ByteSize of the file
  • last_access: access date
  • last_modified: last modified time
  • age: TimeSpan since last modified

Networking Metrics (network)

network gathers information about the network usage of system interfaces.

Config:

• match: Wildcard match to interface name (Default: None)
• hideEmpty: Hide interfaces that are empty (no traffic) (Default: False)

Metrics:

• totals
  • received
  • tranmitted
• interfaces

Core System Metrics (system)

Metrics:

• uptime: TimeSpan of the time up
• idle: CPU time that is idle

Data

Extracting Typed Objects

In cases where SshSysMon can parse and explore json applications, you might want to interpret data in a certain way. For example, it may be useful to grab a nested property and compute the TimeSpan from now.

Object path selections are separated by ., and the optional type follows a :

For example, if you have this object:

{
  "a" : {
    "b" : [
      "2018-12-15T15:57:17.619242731+01:00"
    ]
  }
}

And you wanted to extract the number of time that has passed between that date and now, your selector would be a.b.[0]:TimeSpanFromNow

The following types are supported:

• str: Convert object to string
• int: Convert object to int
• TimeSpan: Assume object is int number-of-seconds, and make TimeSpan
• TimeSpanFromNow: Assume object is parseable datetime, and compute TimeSpan between then and now
• DateTime: Parse string as datetime

Templating

SshSysMon uses handlebars to template its summary output. See the templating for more information.

Writing Your Own Component

To learn how to write a specific type of component, visit its readme in the appropriate subfolder.

All components must define def create(args): as a well-known method to instantiate the class. args will be the configuration dict given in the configuration.