Amazon SQS (aws-sqs) is an easy queuing service with which you can easily send or receive 1-10 messages at a time. SQS support has been in jclouds since version 1.5.0.
You can lookup a queue by name or create one on demand. Here's a common pattern for that:
{% highlight java %} URI queue = queueApi.get(queueName); if (queue == null) { queue = queueApi.create(queueName); } {% endhighlight %}
In SQS, once you discover or create a queue, you can focus a connection to to that, by supplying the queue's url.
{% highlight java %} queueApi = context.getApi().getMessageApiForQueue(queueURI); {% endhighlight %}
Sending a message is simple, just supply the text you wish to send.
{% highlight java %} queueApi.send(“my message”); {% endhighlight %}
Receiving a message is also simple: invoke receive and if your result is not null, you have a message!
{% highlight java %} message = queueApi.receive(); {% endhighlight %}
You can check whether bulk message requests came back, by checking the status result
{% highlight java %} BatchResult acks = api.send(ImmutableMap.<String, String> builder() .put(“id1”, “test message one”) .put(“id2”, “test message two”) .put(“id3”, “test message two”) .build()); {% endhighlight %}
Note that you can receive the same message twice even in the same request!. Hence we use List, not Set.
{% highlight java %} List messages = api.receive(10); {% endhighlight %}