Gofer!

Gofer is a set of wrappers around the Net::SSH suite of tools to enable consistent access to remote systems.

Gofer has been written to support the needs of system automation scripts. As such, gofer will:

• automatically raise an error if a command returns a non-zero exit status
• print and capture STDOUT and STDERR automatically
• allow you to access captured STDOUT and STDERR individually or as a combined string
• override the above: return non-zero exit status instead of raising an error, suppress output
• persist the SSH connection so that multiple commands don't incur connection penalties
• allow multiple simultaneous command execution on a cluster of hosts via Gofer::Cluster

Full documentation for latest gem release is at RDoc

Examples

Instantiation

h = Gofer::Host.new('my.host.com', 'ubuntu', :keys => ['~/.ssh/id_rsa'])

Run a command

h.run "sudo stop mysqld"

Copy some files

h.upload 'file', 'remote_file'
h.download 'remote_dir', 'dir'

Interact with the filesystem

if h.exist?('remote_directory')
  h.run "rm -rf 'remote_directory'"
end

h.write("a string buffer", 'a_remote_file')
puts h.read('a_remote_file')
puts h.ls('a_remote_dir').join(", ")

Respond to command errors

h.run "false" # this will raise an error
response = h.run "false", :capture_exit_status => true # this won't ...
puts response.exit_status # and will make the exit status available

Capture output

response = h.run "echo hello; echo goodbye 1>&2\n"
puts response         # will print "hello\n"
puts response.stdout  # will also print "hello\n"
puts response.stderr  # will print "goodbye\n"
puts response.output  # will print "hello\ngoodbye\n"

Send input

response = h.run "sed 's/foo/bar/'", :stdin => "hello foo\n"
puts response.output # will print "hello bar"

Prefix output

h.output_prefix = 'apollo'        # or set :output_prefix on instantiation
h.run "echo hello; echo goodbye"  # prints apollo: hello\napollo: goodbye

Suppress output

h.run "echo noisy", :quiet => true               # don't print stdout
h.run "echo noisier 1>&2", :quiet_stderr => true # don't print stderr
h.quiet = true                                   # never print stdout

Run the same commands on multiple hosts

cluster = Gofer::Cluster.new
cluster << Gofer::Host.new('my.host.com', 'ubuntu', :keys => ['key.pem'], :output_prefix => "   my")
cluster << Gofer::Host.new('other.host.com', 'ubuntu', :keys => ['key.pem'], :output_prefix => "other")

# Run on all the hosts at once
cluster.run "hostname"

# Run on only one host at a time
cluster.max_concurrency = 1
cluster.run("sudo /etc/init.d/apache2 restart")

# Run a command on only one host
host = cluster.shuffle.first
host.run("rake migrations")

# Inspect the results from each host
results = cluster.run "echo hostname"
puts results.values.join(", ") # will print "my.host.com, other.host.com"

# Capture exceptions from each host
begin
  cluster.run "rake deploy"
rescue Gofer::ClusterError => e
  e.errors.each do |host, exception|
    $stderr.puts "Failed on #{host} with #{exception}, rolling back ..."
    host.run "rake rollback"
  end
  raise e
end

Testing

• Ensure that your user can ssh as itself to localhost using the key in ~/.ssh/id_rsa.
• Run rspec spec or bundle install && rake spec
• rbenv users can run test.sh and ensure their code works on Ruby versions we support

Contributing

Contributions should be via pull request. Please add tests and a note in the README.md for new functionality. Please use 1.8.7-compatible syntax.

TODO

• ls, exists?, directory? should use sftp if available rather than shell commands
• Deal with timeouts/disconnects on persistent connections
• Release 1.0 & use Semver
• Add unit tests, bring in Travis.ci
• Local system usage (eg Gofer::Localhost.new.run "hostname")

License

(The MIT License)

Copyright (c) 2011-13 Michael Pearson

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.