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<main>
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<article id="content">
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<header>
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<h1 class="title">Module <code>usb_detector.api_client</code></h1>
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</header>
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<section id="section-intro">
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<details class="source">
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<summary>
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<span>Expand source code</span>
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</summary>
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<pre><code class="python">import json
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import requests
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import logging
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from time import sleep
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from diskcache import Deque
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from requests import HTTPError, ConnectionError
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from requests.exceptions import InvalidSchema
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_uri = None # server uri (url, port, and endpoint)
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_cache = None # cache (failed payloads)
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_config = None # instance of Config
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def api_client_set_config(config):
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"""Initializes the client API module.
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This function is meant to be called prior to calling any other function
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of the API module. It stores the instance of Config (config manager)
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into a private variable. It also initializes the cache for unsuccessful
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payloads and constructs a URI (endpoint on the server side).
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:param config: instance of Config which holds all values defined
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in the configuration file.
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"""
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# Store the variables globally within the module (file).
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global _config, _cache, _uri
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# Store the instance of Config and initialize the cache.
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_config = config
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_cache = _init_cache()
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# Creates the URI which is made of the server url, port, and path (endpoint).
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_uri = config.server_url + ":" + config.server_port + config.server_endpoint
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def _init_cache():
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""" Initializes and returns a disk-based cache.
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The cache holds payloads that the application failed
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to send to the server. It periodically attempts to resend
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them to the server. All parameters can be seen in the
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configuration file.
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:return: instance of a new cache (Deque - FIFO)
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"""
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return Deque(directory=_config.cache_dir)
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def send_data(payload: dict):
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"""Sends a payload off to the server.
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This function is called whenever a USB is connected
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or disconnected. If there is no internet connection or the
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server is not up and running, the payload will be stored
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into the disk cache.
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:param payload: payload to be sent to the server
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"""
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# Make sure that the URI has been constructed properly.
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# It is supposed to be done by calling the api_client_set_config function
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# with appropriate parameters.
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if _uri is None:
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logging.warning(f"sending payload = {payload} failed because uri is set to None")
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_cache_failed_payload(payload)
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return
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try:
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logging.info(f"sending payload = {payload} to {_uri}")
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response = requests.post(url=_uri, data=json.dumps(payload))
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logging.info(f"response text: {response.text}")
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except (ConnectionError, InvalidSchema):
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logging.warning(f"sending payload = {payload} to {_uri} failed")
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_cache_failed_payload(payload)
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except HTTPError as error:
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logging.error(f"HTTP Error ({_uri}) payload = {payload}, {error}")
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_cache_failed_payload(payload)
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def _cache_failed_payload(payload: dict):
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""" Caches a payload.
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This function is called when the application fails to send a payload
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to the server. The payload gets stored into a file-based cache from which
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it will be periodically retrieved as the client will attempt to send
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it to the server again. All parameters regarding the cache can be found
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in the configuration file.
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:param payload: payload to be cached
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"""
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# If the cache is "full", discard the oldest record.
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if len(_cache) >= _config.cache_max_entries:
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oldest_payload = _cache.pop()
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logging.warning(f"cache is full - discarding payload = {oldest_payload}")
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# Store the payload into the cache.
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logging.info(f"adding payload = {payload} into cache")
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_cache.append(payload)
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def _resend_cached_payloads():
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"""Reattempts to send cached payloads to the server (API).
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In the configuration file, there is a predefined number of
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payloads that can be sent to the server with each call of this function.
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This function is called periodically from api_client_run in order
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to resend failed payloads to the server.
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"""
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# Calculate how many payload will be sent to the server
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retries = min(_config.cache_max_retries, len(_cache))
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logging.info(f"emptying the cache ({retries} records)")
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# Send the payloads to the server one by one.
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for _ in range(0, retries):
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payload = _cache.pop()
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send_data(payload)
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def api_client_run():
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""" Keeps resending failed payloads to the server.
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This function is instantiated as a thread that periodically
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calls the _resend_cached_payloads function in order to empty
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the cache (failed payloads). The period can be set in the
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configuration file.
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"""
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while True:
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# Resend a predefined amount of failed payloads to the server.
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_resend_cached_payloads()
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# Sleep for a predefined amount of seconds.
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sleep(_config.cache_retry_period_seconds)</code></pre>
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</details>
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</section>
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<section>
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</section>
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<section>
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</section>
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<section>
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<h2 class="section-title" id="header-functions">Functions</h2>
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<dl>
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<dt id="usb_detector.api_client.api_client_run"><code class="name flex">
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<span>def <span class="ident">api_client_run</span></span>(<span>)</span>
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</code></dt>
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<dd>
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<div class="desc"><p>Keeps resending failed payloads to the server.</p>
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<p>This function is instantiated as a thread that periodically
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calls the _resend_cached_payloads function in order to empty
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the cache (failed payloads). The period can be set in the
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configuration file.</p></div>
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<details class="source">
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<summary>
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<span>Expand source code</span>
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</summary>
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<pre><code class="python">def api_client_run():
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""" Keeps resending failed payloads to the server.
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This function is instantiated as a thread that periodically
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calls the _resend_cached_payloads function in order to empty
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the cache (failed payloads). The period can be set in the
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configuration file.
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"""
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while True:
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# Resend a predefined amount of failed payloads to the server.
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_resend_cached_payloads()
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# Sleep for a predefined amount of seconds.
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sleep(_config.cache_retry_period_seconds)</code></pre>
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</details>
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</dd>
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<dt id="usb_detector.api_client.api_client_set_config"><code class="name flex">
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<span>def <span class="ident">api_client_set_config</span></span>(<span>config)</span>
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</code></dt>
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<dd>
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<div class="desc"><p>Initializes the client API module.</p>
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<p>This function is meant to be called prior to calling any other function
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of the API module. It stores the instance of Config (config manager)
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into a private variable. It also initializes the cache for unsuccessful
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payloads and constructs a URI (endpoint on the server side).</p>
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<p>:param config: instance of Config which holds all values defined
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in the configuration file.</p></div>
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<details class="source">
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<summary>
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<span>Expand source code</span>
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</summary>
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<pre><code class="python">def api_client_set_config(config):
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"""Initializes the client API module.
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This function is meant to be called prior to calling any other function
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of the API module. It stores the instance of Config (config manager)
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into a private variable. It also initializes the cache for unsuccessful
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payloads and constructs a URI (endpoint on the server side).
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:param config: instance of Config which holds all values defined
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in the configuration file.
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"""
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# Store the variables globally within the module (file).
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global _config, _cache, _uri
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# Store the instance of Config and initialize the cache.
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_config = config
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_cache = _init_cache()
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# Creates the URI which is made of the server url, port, and path (endpoint).
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_uri = config.server_url + ":" + config.server_port + config.server_endpoint</code></pre>
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</details>
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</dd>
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<dt id="usb_detector.api_client.send_data"><code class="name flex">
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<span>def <span class="ident">send_data</span></span>(<span>payload: dict)</span>
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</code></dt>
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<dd>
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<div class="desc"><p>Sends a payload off to the server.</p>
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<p>This function is called whenever a USB is connected
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or disconnected. If there is no internet connection or the
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server is not up and running, the payload will be stored
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into the disk cache.</p>
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<p>:param payload: payload to be sent to the server</p></div>
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<details class="source">
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<summary>
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<span>Expand source code</span>
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</summary>
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<pre><code class="python">def send_data(payload: dict):
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"""Sends a payload off to the server.
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This function is called whenever a USB is connected
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or disconnected. If there is no internet connection or the
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server is not up and running, the payload will be stored
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into the disk cache.
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:param payload: payload to be sent to the server
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"""
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# Make sure that the URI has been constructed properly.
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# It is supposed to be done by calling the api_client_set_config function
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# with appropriate parameters.
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if _uri is None:
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logging.warning(f"sending payload = {payload} failed because uri is set to None")
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_cache_failed_payload(payload)
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return
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try:
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logging.info(f"sending payload = {payload} to {_uri}")
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response = requests.post(url=_uri, data=json.dumps(payload))
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logging.info(f"response text: {response.text}")
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except (ConnectionError, InvalidSchema):
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logging.warning(f"sending payload = {payload} to {_uri} failed")
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_cache_failed_payload(payload)
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except HTTPError as error:
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logging.error(f"HTTP Error ({_uri}) payload = {payload}, {error}")
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_cache_failed_payload(payload)</code></pre>
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</details>
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</dd>
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</dl>
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<h1>Index</h1>
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<li><h3>Super-module</h3>
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<li><code><a title="usb_detector" href="index.html">usb_detector</a></code></li>
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<li><h3><a href="#header-functions">Functions</a></h3>
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<li><code><a title="usb_detector.api_client.api_client_run" href="#usb_detector.api_client.api_client_run">api_client_run</a></code></li>
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<li><code><a title="usb_detector.api_client.api_client_set_config" href="#usb_detector.api_client.api_client_set_config">api_client_set_config</a></code></li>
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<li><code><a title="usb_detector.api_client.send_data" href="#usb_detector.api_client.send_data">send_data</a></code></li>
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<p>Generated by <a href="https://pdoc3.github.io/pdoc" title="pdoc: Python API documentation generator"><cite>pdoc</cite> 0.10.0</a>.</p>
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