A pika-based python RabbitMQ client for use in the CLIMB-tree project
Project description
Varys - A python RabbitMQ client for CLIMB-TRE
TODO:
- Test SSL support with CA-signed certificates
Installation
Conda installation will be simplest for most users, and can be achieved with the following command:
conda install -c conda-forge varys
Alternatively, varys can be installed directly from this repository by doing the following:
git clone https://github.com/CLIMB-TRE/varys.git
cd varys
pip install .
Configuration
Varys uses a JSON format configuration file to provide credentials to connect to RabbitMQ, the path to this configuration file should either be provided with the VARYS_CFG
environmental variable or using config_path
argument when instantiating varys, this will override an environmental variable.
An example of the configuration file format is available here.
Basic Usage
First the varys object must be instantiated, like so:
import varys
varys_client = varys(profile="test_user",
logfile="/var/log/varys_test.log",
log_level="DEBUG"
)
Profile will control which set of credentials the client will read from the config file.
Once the base object has been instantiated you are ready to send or receive messages from the RabbitMQ server:
The queue_suffix
argument must be provided the first time a message is sent or receeived to/from a queue after varys is instantiated so that the varys may create or bind the queue (exchange + . + queue_suffix
) if it already exists.
Sending
message = {"foo": "bar"}
varys_client.send(message=message,
exchange="test_exchange",
queue_suffix="test_suffix"
)
Messages must be a python object that can be serialised into JSON format using json.dumps() which includes the following types: dict, list, tuple, str, int, float, True, False, None.
Receiving one message at a time
import json
message = varys_client.receive(exchange="test_exchange",
queue_suffix="test_suffix",
block=True
)
deserialised_message = json.loads(message.body)
print(deserialised_message)
This will block execution until a message is received unless the block
argument is set to False
, in this case if there are no messages to be received the return value will be None
object.
If a message is received it will be a varys_message
object which has the following attributes:
basic_deliver -> A pika.spec.Basic.Deliver Should be irrelevant for normal usage but documentation available at this link.
properties -> A pika.BasicProperties
object, containing header information about the message if provided when sending. Should be irrelevant for normal usage.
body -> The message body in serialised JSON format, generally a user will wish to convert this to a python object equivalent for ease of use with json.loads()
Receiving multiple messages at a time
import json
messages = varys_client.receive_batch(exchange="test_exchange",
queue_suffix="test_suffix",
)
for message in messages:
deserialised_message = json.loads(message.body)
print(deserialised_message)
This will never block execution and will always return a python list object containing all available messages as varys_message
objects which should then be iterated through and treated as above. In the case of there being no messages available, this list will be empty and will evaluate to False
.
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