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You have completed Deployment with Capistrano!
You have completed Deployment with Capistrano!
Preview
Create and run a simple Capistrano task.
From your development machine's terminal:
rails new captest
In the new app's Gemfile, uncomment the capistrano-rails entry.
Change into the app's directory and run:
bundle install
bundle exec cap install
This will generate the following configuration files:
-
Capfile- Used for including required libraries
- We'll just use defaults for now
-
config/deploy.rb- Set configuration variables
set :message, "Hello, Capistrano!"
-
config/deploy/{staging,production}.rb- Defines a stage, as in
cap STAGENAME deploy - Define servers for a stage
- Define variables specific to a stage
- We'll just be defining a server here
- Defines a stage, as in
server "<YOUR HOST ADDRESS HERE>", user: "deploy", roles: ["greeter"]
-
lib/capistrano/tasks/*.rake(Note that's.rake, not.rb)- Define tasks
desc "Write a message to a file"
task :write_message do
on roles(:greeter) do
execute "echo '#{fetch :message}' >> ~/message.txt"
end
end
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I've set up a fresh Ubuntu
server with RBM, PostgreSQL and
0:00
NGINX at a hosting company.
0:04
If you need help setting these
packages up see the teacher's notes.
0:06
If you'd like to follow along using
a virtual machine instead of an actual
0:10
server you'll find info in
the teacher's notes for that too.
0:13
I have not installed Rails or Unicorn, nor
0:16
have I manually deployed my
Rails app to this server before.
0:19
This is to ensure we have a clean
environment with no hard to troubleshoot
0:23
conflicts.
0:26
We're going to let Capistrano
handle all of those details for us.
0:27
So let's exit back to our host machine.
0:31
And first we're going to create
a simple Rails app that we can
0:33
test Capistrano out with.
0:37
So I'm gonna create a new Rails app.
0:39
I'll say rails new, and we'll call
it captest, as in Capistrano test.
0:41
Okay, then I'm gonna change
into that directory.
0:50
Change directory captest.
0:53
And let's bring this up in our editor.
0:58
Okay, so first we need to
install the Capistrano Gem.
1:00
We do that by editing our Gemfile.
1:03
And there's already
an existing entry in there for
1:05
the Capistrano-Rails Gem, so
I'm just going to uncomment that.
1:10
I'll save that and go back to
the terminal and run bundle install.
1:14
That will install the Capistrano Rails Gem
which has Capistrano itself as
1:21
a dependency.
1:25
Now, we need to set this new Rails
projects up to use Capistrano.
1:26
We do that by running bundle exec cap
1:29
install, that'll run the cap executable
which is included in the Capistrano Gem.
1:35
The install sub command that we're running
here is going to create a several files
1:40
that Capistrano needs to
work with our Rails project.
1:45
Let's take a look at some of
the configuration files that Capistrano
1:48
created for us.
1:51
The first is named
Capfile with a capital C.
1:53
It'll be in the rule of our project.
1:55
It's mostly used for including y
variance that Capistrano requires.
1:58
We're just going to use the default
set of libraries for now.
2:02
So we'll leave this file alone.
2:04
Next up is a file within the config
subdirectory named deploy.rb.
2:06
It's used to set configuration variables
that'll be used to deploy your app.
2:11
For this quick test, we're not going
to need these default variables, so
2:16
let's get rid of them.
2:19
And instead,
2:20
let's create a new variable with a message
that we want to set up on our server.
2:21
So we'll set message variable up,
by calling the set method.
2:26
The first argument to set is a symbol
with the name of the variable
2:33
you want to set up.
2:36
And then we'll provide a string
with a value to set it to.
2:38
Hello, Capistrano.
2:42
Let's save that and we'll make use of this
variable later on when we set up the task.
2:47
Next step,
Capistrano created a deployed directory
2:52
which contains configuration files for
your various stages.
2:55
Here we see two stages, the production
stage and the staging stage.
2:58
The main thing you do in this file is
define servers for a stage that you'll
3:03
need to deploy to, as well as any
variables that are specific to that stage.
3:07
So here we're going to call
the server method to set up a server
3:11
that we're going to deploy to.
3:15
It's going to need an IP
address to deploy to or
3:17
we could use a host name,
if we have one configured.
3:20
So I'll paste that IP
address into a string.
3:24
That's the first argument.
3:28
Then the server method takes
a hash with various keys for
3:30
various configuration items.
3:34
The first key we're going to
wanna use is the user key which
3:36
specifies a username that we're going
to log in and deploy the app as, so
3:39
I'll use our deploy username for that.
3:43
The next key we're going to want is
an array with a list of roles that this
3:46
server plays within our app.
3:50
The usual roles Capistrano uses are app,
db, and web.
3:53
That's app as in the application server,
db as in the database server,
3:57
and web as in the web server.
4:01
A single server can fill
all three of those roles.
4:03
For this quick demo though,
we're gonna create a new role, so
4:05
I'll set up an array with
just a single item, and
4:08
the role this server is going to
play is it's going to be a greeter.
4:10
It'll store a simple greeting for us.
4:15
That's all that we need to define for
our production server, so
4:17
I'll just save this and
close out of that file.
4:20
And we won't define anything regarding
a staging environment for right now.
4:23
So we'll just leave that file alone.
4:26
The last thing that Capistrano set up for
us is a lib, capistrano, tasks directory.
4:28
Here we can create files that define tasks
that Capistrano needs to carry out when
4:37
it's deploying an app.
4:41
So let's create a new file
within this directory.
4:42
And I'm going to name
it write_message.rake.
4:46
It's important that the file extension
end in dot rake, instead of dot rb,
4:52
so that Capistrano detects it.
4:56
It uses .rake files because
Capistrano is based on another Ruby
4:58
utility called Rake which stands for
Ruby Make.
5:02
Rake is generally used to build
applications and Capistrano is just
5:06
an extension of the rake syntax that
allows for the deployment of applications.
5:10
So we've got our file created,
let's define a task now.
5:15
First you're going to need to call the
desc method to define a description for
5:18
your task.
5:23
The description method takes a string
with the description to use cell.
5:24
I'm going to say that this task
will write a message to a file.
5:28
Then we actually define the task
by calling the task method.
5:35
Task takes its symbols as its first
argument with the name of the task.
5:39
We'll call it write_message.
5:43
And then it takes block with
the actual task content.
5:48
Normally task should only run on
servers that fulfill particular roles.
5:51
We set up our production server
to fulfill the greater rule so
5:56
we're going to specify that this task
should be run on greater servers now.
5:59
We do that with the on method, then
we're going to call the roles method and
6:03
pass it to return value to the on method.
6:09
We need to pass the symbol
argument roles with
6:12
the names of the roles
that it should work on.
6:15
So we'll use a simple greeter and
6:17
the return value of roles greeter
would then get pass to the on method.
6:21
Now we need a block for the on method that
specifies what task we should carry out.
6:25
Here we're going to use
a Capistrano method called execute,
6:29
that specifies a command we should
execute on the remote server.
6:33
Execute takes a string with
the command to send and
6:37
it'll actually submit that
command to the server over SSH.
6:40
So we're going to use the echo command
on the server, to take a string and
6:44
append it to a file within our
home directory called message.txt.
6:49
As for the content of that string
we're gonna write to the file,
6:55
we'll get that from a capistrano variable.
6:58
So I'm going to interpolate the result of
the ruby statement here into the string.
7:02
And for that Ruby statement I'm going
to call the Capistrano fetch method
7:07
which will fetch the value of a variable.
7:11
We set the message variable up
in another configuration file.
7:13
So I'm going to fetch that
message variable here.
7:17
So the results of this statement is that
it will fetch the message variable and
7:22
write it out to a file within
the home directory on the server.
7:27
Let me save that, and
we'll go back to our terminal.
7:32
We can get a list of all the tasks we
have defined by running the bundle
7:36
exec cap command, and
7:41
passing it a flag of -T,
to get a list of the tasks.
7:45
There are quite a few tests that
have been predefined up here, but
7:50
down here at the bottom,
we can see our tests defined.
7:55
And as it suggests here,
we can invoke that with bundle exec
7:58
cap write_message.
8:02
Each task requires you to specify
a stage that you're going to run it on.
8:09
And I neglected to do that so,
8:12
I'm going to specify that this
should run on our production server.
8:14
So I'll run the right message task.
8:20
It alerts us to the command that
it's running on the remote server.
8:24
And then it returns us to our shell,
indicating that the deployment is done.
8:27
Let's go out to that server and
take a look at the results of our command.
8:32
So I'm gonna copy the IP address here and
I'm gonna run ssh.
8:35
I'm gonna login as the deployed
user at that IP address.
8:39
And let's take a look at the contents
of our home directory here.
8:46
We can see a new message.txt file.
8:49
And if we take a look at its contents.
8:52
There's the message that we specified
in our configuration files.
8:55
Now of course,
8:59
real deployment tasks that you set up
are going to be more complex than this.
9:00
But this is a good demonstration
of how Capistrano works.
9:03
In the next stage we're gonna
do something more useful, and
9:06
use Capistrano to deploy Rails apps.
9:09
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