Barnum

Easily manage multiple Circus instances across multiple hosts.

Configuration

Structure

Barnum currently relies on a very specific directory structure in order to discover Circus hosts:

tree /users/user1/circus
├── host1
│   ├── circus.ini
│   ├── circus.log
│   ├── watcher1.stderr.log
│   └── watcher1.stdout.log
└── init_circus -> /users/$USER/circus/init_circus

In other words, it expects that every user that is running a Circus instance will have a ~/circus directory, and that this each child directory thereof will contain a circus.ini folder. Each circus.ini file it discovered will be parsed to determine its endpoint, and the host will be derived from the name its parent. Then, ssh commands will be built from this information, and used to delegate commands across multiple users/hosts simultaneously (threaded).

Config File

You will also need a config file, so that barnum knows what to search for.

Create circus_users.yaml in the same directory as barnum.py. Its contents should look something like this:

---

- user1
- user2

Operations

barnum

Perform Circus operations across multiple hosts

System Overview

$ python barnum.py --verbose
barnum: Circus is configured on the following hosts: host1, host2
barnum: Processing host1
barnum: Processing host2
barnum: bailey cmd: ssh -q host1 bailey --verbose
barnum: bailey cmd: ssh -q host2 bailey --verbose

bailey: Derived circus user user1 from /etc/systemd/system/circus_user1_host2.service
bailey: circus cmd: circusctl --endpoint tcp://host2:8385 status
bailey: Derived circus user user2 from /etc/systemd/system/circus_user2_host1.service
bailey: circus cmd: circusctl --endpoint tcp://host1:5775 status
bailey: Derived circus user user3 from /etc/systemd/system/circus_user3_host2.service
bailey: circus cmd: circusctl --endpoint tcp://host2:5555 status
--- HOST1 ---
--------------------------------------------------------------------------------
circus_user2_host1.service  enabled active (running)
  watcher1: active
================================================================================

--- HOST2 ---
--------------------------------------------------------------------------------
circus_user1_host2.service       enabled active (running)
  watcher2: active
--------------------------------------------------------------------------------
circus_user3_host2.service     enabled active (running)
  watcher3: active
--------------------------------------------------------------------------------
circus_user4_host2.service      disabled        inactive (dead)
  No circus expected
================================================================================

What's happening here:

1. For each user in circus_users.yaml, derive the hosts it has circus instances on from the directory structure described above
2. For every host:
   1. SSH to host_n
   2. Use sysctl list-unit-files to determine all circus unit files
   3. Examine each unit file to determine the user it is for
   4. Call bailey for each user on host_n

Manage All Circus Instances on Given Host

Get status of all Circus instances run on host1:

$ python barnum.py host1 --verbose
Circus is configured on the following hosts: host1
Processing user1@host1
bailey cmd: ssh -q host1 /path/to/bailey user1 --verbose
circus cmd: circusctl --endpoint tcp://host1:5775 status
---
watcher1: active

What's happening here:

1. SSH to host1
2. Use sysctl list-unit-files to determine all circus unit files
3. Examine each unit file to determine the user it is for
4. For each user:
   1. Construct path to circus config file based on given user and host
   2. Parse config file to determine circus endpoint
   3. Call bailey for derived endpoint

Manage Specific Circus Instance on Given Host

Get status of Circus instance run by user1@host1.

$ python barnum.py user1@host1 --verbose
Circus is configured on the following hosts: host1
Processing user1@host1
bailey cmd: ssh -q host1 bailey user1 --verbose
circus cmd: circusctl --endpoint tcp://host1:5775 status
---
watcher1: active

What's happening here:

1. SSH to host1
2. Construct path to circus config file based on given user and host
3. Parse config file to determine circus endpoint
4. Call bailey for derived endpoint

Sending Commands to Bailey/Circus

There are two advanced use cases here:

1. Send commands to bailey
2. Send commands to circus
3. Send commands to both bailey and circus

It is useful to experiment with these using --dry-run, in order to prevent things from getting broken. For example,

$ python barnum.py user1@host1 --verbose --dry-run
barnum: Processing user1@host1
---
DRY RUN; would execute: ssh -q host1 bailey user1 --verbose

Send commands to bailey

This would print the help message for every bailey instance:

$ python barnum.py -- --help

To send specific circus commands to each bailey instance, you'll need to use something like the following:

$ python barnum.py user1@host1 --verbose -- -- stats

Everything following the -- will be sent directly to bailey, without any changes. bailey will then send everything after the second -- directly to circus (more on that below).

bailey

Perform Circus operations on a single hosts (but possibly multiple users)

Manage All Circus Instances on Current Host

Get status of all Circus instances run on current host (host1):

$ bailey --verbose
--- host1 ---
--------------------------------------------------------------------------------
circus_user1_host1.service      disabled        inactive (dead)
  No circus expected
--------------------------------------------------------------------------------
bailey: Derived circus user user1 from /etc/systemd/system/circus_user1_host1.service
bailey: circus cmd: circusctl --endpoint tcp://host1:5755 status
circus_user1_host1.service  enabled active (running)
  watcher1: active
================================================================================

What's happening here:

1. Use sysctl list-unit-files to determine all circus unit files
2. Examine each unit file to determine the user it is for
3. For each user:
   1. Construct path to circus config file based on given user and host
   2. Parse config file to determine circus endpoint
   3. Call bailey for derived endpoint

Manage Specific Circus Instance on Current Host

Get status of Circus instance run by user1@host1 (given user at current host).

$ bailey user1 --verbose
bailey: circus cmd: circusctl --endpoint tcp://host1:5555 status
watcher1: active

What's happening here:

1. Construct path to circus config file based on given user and host
2. Parse config file to determine circus endpoint
3. Call bailey for derived endpoint

Send commands to circus

To send specific circus commands, you'll need to use something like the following:

$ python barnum.py user1@host1 --verbose -- stats

Everything following the -- will be sent directly to circus, without any changes