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Python/1 tutorial tweaks.

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This commit is contained in:
Marek Majkowski 2010-10-05 16:31:10 +01:00
parent c68ccb2f9d
commit 277ef2af18
2 changed files with 56 additions and 11 deletions
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31
python/tutorial-one.md
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@ -73,7 +73,14 @@ RabbitMQ uses a weird jargon, but it's simple once you'll get it. For example:
</div></center>
* _A queue_ is the name for a mailbox. It lives inside RabbitMQ.
* _A queue_ is the name for a mailbox. It lives inside
RabbitMQ. Although messages flow through RabbitMQ and your
applications, they can be stored only inside a _queue_. A _queue_
is not bound by any limits, it can store how many messages you
like - it's essentially an infinite buffer. Many _producers_ can send
messages that go to the one queue, many _consumers_ can try to
receive data from one _queue_.
<center><div class="dot_bitmap">
<img src="http://github.com/rabbitmq/rabbitmq-tutorials/raw/master/_img/9bdb70c65ab8b2aa1f6b0b85c2931a54.png" alt="Dot graph" width="76" height="29" />
@ -170,8 +177,17 @@ _test_:
</td></tr></table>
At that point we're ready to send a message. Our first message will contain
a string _Hello World!_. We are going to send it to our _test_ queue:
At that point we're ready to send a message. Our first message will
contain a string _Hello World!_ and we want to send it to our _test_
queue.
In RabbitMQ a message never goes directly to the queue, it always
needs to go through an _exchange_. But let's not get dragged by the
details - you can read more about _exchanges_ in third part of this
tutorial. All we need to know now is how to use a default exchange
identified by an empty string. That exchange is a special one that
allows us to specify exactly to which queue the message should go.
The queue name is specified by the `routing_key` variable:
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><code class="python"> 9
10
@ -212,6 +228,12 @@ run the command as many times you like, and only one queue will be created.
</pre></div>
</td></tr></table>
You may ask why to declare queue again - we have already declared it
in our previous code. We could have avoided that if we always run the
`send.py` program before this one. But we're not sure yet which
program to run as first. In such case it's a good practice to repeat
declaring the queue in both programs.
Receiving messages from the queue is a bit more complex. Whenever we receive
a message, a `callback` function is called. In our case
@ -235,6 +257,9 @@ interested in messages from our _test_ queue:
</pre></div>
</td></tr></table>
For that command to succeed we must be sure that a queue which we want
to subscribe to exists. Fortunately we're confident about that - we've
created a queue above - using `queue_declare`.
And finally, we enter a never-ending loop that waits for data and runs callbacks
whenever necessary.

36
python/tutorial-one.mdx
View File

@ -76,7 +76,14 @@ RabbitMQ uses a weird jargon, but it's simple once you'll get it. For example:
}
{% enddot %}
* _A queue_ is the name for a mailbox. It lives inside RabbitMQ.
* _A queue_ is the name for a mailbox. It lives inside
RabbitMQ. Although messages flow through RabbitMQ and your
applications, they can be stored only inside a _queue_. A _queue_
is not bound by any limits, it can store how many messages you
like - it's essentially an infinite buffer. Many _producers_ can send
messages that go to the one queue, many _consumers_ can try to
receive data from one _queue_.
{% dot -Gsize="10,0.3" -Grankdir=LR%}
digraph G {
@ -183,18 +190,25 @@ _test_:
{% highlight python linenos=true linenostart=8 %}
channel.queue_declare(queue='test')
{% endhighlight %}
At that point we're ready to send a message. Our first message will contain
a string _Hello World!_. We are going to send it to our _test_ queue:
At that point we're ready to send a message. Our first message will
contain a string _Hello World!_ and we want to send it to our _test_
queue.
In RabbitMQ a message never goes directly to the queue, it always
needs to go through an _exchange_. But let's not get dragged by the
details - you can read more about _exchanges_ in third part of this
tutorial. All we need to know now is how to use a default exchange
identified by an empty string. That exchange is a special one that
allows us to specify exactly to which queue the message should go.
The queue name is specified by the `routing_key` variable:
{% highlight python linenos=true linenostart=9 %}
channel.basic_publish(exchange='',
routing_key='test',
body='Hello World!')
@ -238,11 +252,16 @@ run the command as many times you like, and only one queue will be created.
{% highlight python linenos=true linenostart=8 %}
channel.queue_declare(queue='test')
{% endhighlight %}
You may ask why to declare queue again - we have already declared it
in our previous code. We could have avoided that if we always run the
`send.py` program before this one. But we're not sure yet which
program to run as first. In such case it's a good practice to repeat
declaring the queue in both programs.
Receiving messages from the queue is a bit more complex. Whenever we receive
a message, a `callback` function is called. In our case
@ -250,7 +269,6 @@ this function will print on the screen the contents of the message.
{% highlight python linenos=true linenostart=9 %}
def callback(ch, method, header, body):
print " [x] Received %.20r" % (body,)
@ -262,13 +280,15 @@ interested in messages from our _test_ queue:
{% highlight python linenos=true linenostart=11 %}
channel.basic_consume(callback,
queue='test',
no_ack=True)
{% endhighlight %}
For that command to succeed we must be sure that a queue which we want
to subscribe to exists. Fortunately we're confident about that - we've
created a queue above - using `queue_declare`.
And finally, we enter a never-ending loop that waits for data and runs callbacks
whenever necessary.