tm-outage-sim-server

A simple Tendermint outage simulator server to allow one to easily start or stop Tendermint nodes for experimentation and QA purposes.

Overview

tm-outage-sim-server runs a simple HTTP server alongside a Tendermint node. It allows one to send an up or down command via an HTTP POST request to bring the Tendermint service up or down, respectively.

Security

Do not run this service continuously alongside a production Tendermint instance. Despite the fact that the current version of tm-outage-sim-server includes a basic HTTP authentication requirement, this might still allow an attacker to stop your Tendermint node should they discover your password.

This application requires the relevant system privileges to be able to interact with the Tendermint service. For example, if a user outage-sim were responsible for running this server, one could put the following configuration in /etc/sudo.d/outage-sim:

outage-sim ALL=(ALL) NOPASSWD: /bin/systemctl start tendermint, /bin/systemctl stop tendermint, /sbin/pidof tendermint

This is because tm-outage-sim-server calls all of the above commands to interact with the Tendermint service via sudo calls.

See this discussion for more details.

Requirements

The following are minimum requirements for running this application:

• A UNIX variant that uses systemd
• Correctly configured sudo privileges for the user that will be running the tm-outage-sim-server service.
• Tendermint v0.29.1+

To build tm-outage-sim-server, you will need:

• Golang v1.12+

Running

To run the application alongside Tendermint as a systemd service, use the following systemd configuration file (/etc/systemd/system/tm-outage-sim-server.service):

[Unit]
Description=Tendermint Outage Simulator
Requires=network-online.target
After=network-online.target

[Service]
Restart=on-failure
User=outage-sim
Group=outage-sim
PermissionsStartOnly=true
ExecStart=/usr/bin/tm-outage-sim-server -addr 0.0.0.0:26680 -u loadtest -p "#2a#12#ac6f8zq9vvugNb3QXeOV9.RGFHeu8a7qhf9WIRAfH69a0k2j7J7wy"
StandardOutput=syslog
StandardError=syslog
SyslogIdentifier=outage-sim

[Install]
WantedBy=multi-user.target

Note how the bcrypt hash above has its $ symbols replaced with #. One could simply escape the $ symbols too, however, but tm-outage-sim-server supports bcrypt hashes specified in this alternative format to make such files marginally more readable.

Then:

# Make sure systemd finds the new service
systemctl daemon-reload

# Start the outage simulator
service tm-outage-sim-server start

By default, the server binds to 0.0.0.0:26680.

Usage

To bring the Tendermint service up or down, simply do an HTTP POST to the server:

# Bring Tendermint up
curl -s -X POST -d "up" http://tm-load-test:[email protected]:26680

# Bring Tendermint down
curl -s -X POST -d "down" http://tm-load-test:[email protected]:26680