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Extending tstat_send with additional transports

This document is primarily meant for people in ESnet/LBL that might that might be extending the code base, but it might be useful for external users as well.

Initially, tstat_send only supported sending the tstat JSON objects to a RabbitMQ server for archiving. Adding additional transports (for example: to send the JSON objects to a REST endpoint) is not too difficult.

The first thing to do is to pick a single word name for your new transport type - e.g.: rest, redis, etc. This will be used as a term of art at various points in these instructions.

Config file

Add a new stanza to the config file (documented in README.md) using the name of your new transport type (example: [rest]). This is where you will put any configuration directives specific to your new transport.

Both host and port values are required in your new stanza. Define username and password here as well and enable them in your new class (see below).

New transport class

A new transport class should start by sub-classing tstat_transport.transport.BaseTransport. There are a couple of methods to override in this subclass:

_init_

Call the superclass constructor first to let it pull in and validate the required "global" configuration values from the config file. The optional boolean kwarg init_user_pass=True can be passed to the superclass constructor to pull in the username and password values from the config file if you need them.

Then parse/validate any transport specific configuration variables (see transport.BaseTransport._safe_cfg_val()), and set up any persistent connections. An HTTP based transport that can just use the default configuration variables and doesn't have a persistent connection might not need any of this.

send()

Fairly self explanatory. A void method. The inherited class member self._payload will have the string version of the list of JSON objects ready to go. Fill in the code to send the payload string to the remote server. Like a POST using one of the python http libraries.

(optional) set_payload()

Does not need to be overridden by default. But if you really need to massage or modify the JSON lists passed in by the parser, do something like this:

def set_payload(self, p_load):
    new_json_list = self._reformat_json(p_load)
    self._payload = new_json_list

Transport map

The dict transport.TRANSPORT_MAP contains the mappings between the "transport type name" and the class that will be used to process that type. Add a new key using the new transport name (the same one used in the config file stanza), and point it at the new transport class.

TRANSPORT_MAP = dict(
    rabbit=RabbitMQTransport,
    rest=MyNewRestTransport,
)

Now use the --transport argument to tell the tool do use the new transport type instead of the default one:

tstat_send --directory ./tstat --transport rest