Sigenergy DC Charger Switch Bug Causes Connection Storm

The Problem: A TypeError in the DC Charger Switch

Have you encountered a mysterious connection storm or found your Sigenergy inverter sensors suddenly unavailable? If you're using the Sigenergy integration with Home Assistant, especially version 1.1.9, you might be hitting a nasty bug. This bug stems from a TypeError within the DC charger switch entity (switch.sigen_inverter_dc_charger_dc_charging). It occurs when the system tries to check the is_on state, specifically in the switch.py file at line 116. The core of the issue is that the dc_charger_output_power is returning None instead of a numerical value, leading to an attempt to compare NoneType with an int. This seemingly small comparison error triggers a domino effect that can bring your entire Sigenergy monitoring system to a halt.

When this TypeError strikes, it's not just a minor glitch. The integration, trying desperately to recover, starts an endless loop of reconnection attempts. This aggressive retrying floods your network with Modbus TCP connection requests. We're talking about connections accumulating in a SYN_SENT state, with reports of over 54 stuck connections observed. Imagine your Sigenergy inverter as a busy server; this constant barrage of connection requests effectively overwhelms it. The inverter then stops responding, leading to a critical situation where all Sigenergy sensors become unavailable. To get things back to normal, you'll likely find yourself needing to restart your entire Home Assistant system, which is a far from ideal solution for such a critical piece of hardware.

Understanding the Root Cause: NoneType vs. int Comparison

Let's dive a little deeper into why this TypeError is so disruptive. In programming, data types are crucial. When the Sigenergy integration checks if the DC charger is active, it looks at a value called dc_charger_output_power. Ideally, this value should always be a number – zero if the charger isn't outputting power, or a positive number if it is. However, under certain circumstances, this value isn't a number at all; it's None. The None value signifies the absence of data. The code, however, is written with the expectation that it will always receive a number. It tries to perform a comparison, like checking if dc_charger_output_power > 0. When it attempts this comparison with None (i.e., None > 0), Python throws a TypeError because you can't directly compare None with an integer using the greater-than operator. It's like trying to ask if 'nothing' is greater than zero – it doesn't make logical sense in the context of numerical comparison.

This type of error is often indicative of a communication issue or a temporary data retrieval failure from the Sigenergy inverter. Perhaps the inverter temporarily lost power, or there was a brief network interruption when the integration tried to fetch this specific piece of data. Instead of gracefully handling this missing data point by, for example, assuming the charger is off or logging a more specific warning, the integration encounters a hard error. This hard error halts the normal operation of the switch entity and, as we've seen, triggers a cascade of unfortunate events. The integration's recovery mechanism, which is designed to be helpful, ends up causing more harm by aggressively retrying and overwhelming the system. It’s a classic case of an error-handling strategy backfiring due to unexpected data.

The Cascade of Failure: From TypeError to System Overload

When the TypeError occurs, it’s not an isolated incident. Instead, it acts as a trigger for a series of escalating problems. The immediate consequence, as highlighted in the logs, is the TypeError: '>' not supported between instances of 'NoneType' and 'int' originating from the is_on method of the DC charger switch. This error happens because the integration is trying to determine if the DC charger is active by checking if its output power is greater than zero. When dc_charger_output_power returns None, this comparison fails catastrophically.

This failure puts the integration into a frantic recovery mode. It starts attempting to re-establish its connection and refresh its data, but because the underlying issue (the None value) persists or the system is already destabilized, these attempts are unsuccessful and repetitive. This constant, failed reconnection cycle is what leads to the 'connection storm'. Each failed attempt consumes resources and ties up network ports. The logs show WARNING messages indicating Connection error: Modbus Error: [Connection] Not connected and ConnectionException/Timeout during read. These warnings appear repeatedly for various Modbus addresses, confirming that the system is struggling to maintain a stable Modbus TCP connection with the inverter.

As more and more Modbus TCP connections get stuck in the SYN_SENT state – a state where a connection has been initiated but not yet acknowledged – the inverter's network stack becomes saturated. It's like having too many people trying to enter a building through a single door at the same time; eventually, the door gets jammed, and no one can get in or out. The Sigenergy inverter, faced with this overwhelming number of half-open and failed connection attempts, eventually stops responding altogether. This unresponsive state is critical because the inverter is the source of all the sensor data. When the inverter goes offline from the perspective of Home Assistant, all the associated sensors naturally become unavailable. You’ll see their states change to unavailable, leaving you blind to your energy production and consumption. The only way to break this cycle and restore communication is often a full restart of the Home Assistant system, which clears the stuck network connections and allows a fresh start with the inverter.

Impact on Modbus and Network Stability

The Modbus protocol is the backbone of communication between Home Assistant and your Sigenergy inverter. It's a robust protocol, but like any system, it has its limits. When the DC charger switch encounters a TypeError and the integration enters its aggressive reconnection loop, the Modbus TCP client within the integration begins to hammer the inverter with connection requests. Each request attempts to establish a TCP connection on port 502, the standard port for Modbus TCP. If the inverter is busy or the connection fails due to other network issues, the connection might not be properly closed. Instead, it lingers in a state like SYN_SENT.

Imagine each connection as a phone call. Normally, you make a call, have your conversation, and hang up. But in this bug scenario, the integration is repeatedly trying to call the inverter, the call often fails or gets dropped, but the line remains busy. If this happens dozens of times, your phone line (the inverter's network interface) gets clogged with these phantom calls. The inverter’s operating system, trying to manage all these half-established calls, gets bogged down. This leads to timeouts and further connection errors, as seen in the logs: Modbus Error: [Connection] Not connected. The repeated ConnectionException/Timeout messages are direct evidence of the inverter becoming unreachable via Modbus due to this network saturation. This instability doesn't just affect the DC charger entity; it renders the entire Modbus communication unreliable, leading to the unavailability of all sensors that rely on Modbus data. The system becomes fragile, and any further network hiccups can exacerbate the problem.

Why a Restart is Necessary (and a Sign of a Deeper Issue)

Restarting Home Assistant is often the only immediate fix because it effectively tears down all active network connections managed by Home Assistant, including the stuck Modbus TCP sessions. When Home Assistant restarts, it closes all its open sockets and frees up resources. This allows for a clean slate when the Sigenergy integration attempts to reconnect to the inverter. The inverter, no longer bombarded with stale connection requests, can then establish new, healthy connections. However, the necessity of a full system restart is a strong indicator that the bug is not being handled gracefully by the integration. A well-designed integration should be able to recover from transient communication errors without causing system-wide instability. It should implement proper error handling, perhaps by backing off reconnection attempts, logging the error more clearly, or defaulting to a safe state for the affected entity. Relying on a full system restart to clear the issue points to a deficiency in the integration's error management and resilience.

Reproduction Steps and Diagnostic Insights

Reproducing this bug requires having the Sigenergy integration set up in Home Assistant, specifically version 1.1.9, and likely involves a scenario where the dc_charger_output_power value from the Sigenergy inverter is temporarily unavailable or None. While the exact trigger conditions might vary, it's often related to the inverter's state or transient network communication issues. The core of the bug lies in the switch.py file, line 116, within the is_on function of the DC charger switch. Here, a lambda function attempts to check if data.get("dc_chargers", {}).get(identifier, {}).get("dc_charger_output_power", 0) > 0. The issue arises when dc_charger_output_power returns None, and the comparison None > 0 is executed, leading to the TypeError.

Once this TypeError occurs, the sequence of events described earlier unfolds: the integration enters a recovery loop, connection errors mount, the inverter becomes unresponsive, and all sensors go offline. The provided logs clearly illustrate this progression, starting with the TypeError stack trace and followed by numerous WARNING messages about Modbus connection failures. These connection errors are not the primary cause but a direct consequence of the integration's frantic, failed recovery attempts after the initial TypeError.

Leveraging the Diagnostics File

The diagnostics file, such as the config_entry-sigen-01K9ZZHPHWAQ0XF4PVJWC6AGRE.json provided, is an invaluable tool for debugging such issues. This file contains a snapshot of the integration's configuration and state at the time the diagnostics were generated. It can offer insights into the data the integration was receiving, the configuration parameters, and potentially reveal patterns that precede the TypeError. While it might not contain the exact None value that triggered the error (as it's a snapshot), it helps developers understand the context. For instance, it can show the structure of the data object that the is_on_fn lambda function receives, helping to pinpoint why dc_charger_output_power might be missing or None in certain situations. It can also provide information about network settings and device details, which could be relevant if network instability is a contributing factor.

Checklist for Reporting

When reporting bugs like this, following a structured approach is crucial for developers to quickly understand and address the problem. The provided checklist is excellent: "I searched existing issues and discussions," "I attached logs and/or diagnostics," and "This is not a support request; it describes a reproducible bug." Adhering to these points ensures that the development team has all the necessary information to investigate effectively. By providing a clear description of the bug, including the specific error message, the affected component, the integration version, and the observed consequences (like connection storms and sensor unavailability), users significantly speed up the debugging process. The diagnostic file and logs act as direct evidence, allowing developers to examine the exact conditions and data involved, moving from guesswork to a concrete analysis of the problem. This collaborative approach, supported by detailed reporting, is key to maintaining a stable and reliable smart home environment.

The Fix: Graceful Error Handling for DC Charger State

Addressing the TypeError in the Sigenergy DC charger switch requires implementing more robust error handling within the integration. The fundamental fix involves ensuring that the is_on_fn lambda function, or the underlying code it calls, correctly handles cases where dc_charger_output_power might be None. Instead of directly comparing None with 0, the code should explicitly check if the value is None before attempting any numerical comparison. If the value is None, it should be treated as if the charger is off, or at least not actively outputting power, and return False for the is_on state. This prevents the TypeError from occurring in the first place.

A more defensive approach would be to modify the lambda function to something like this:

is_on_fn=lambda data, identifier: (power := data.get("dc_chargers", {}).get(identifier, {}).get("dc_charger_output_power")) is not None and power > 0

This revised lambda first retrieves the dc_charger_output_power. It then checks if power is not None. Only if power is a valid value (not None) does it proceed to check if power > 0. If power is None, the entire expression evaluates to False, correctly indicating that the charger is not considered 'on' without raising an error. This simple modification ensures that the integration doesn't crash when faced with missing data for the output power.

Preventing Connection Storms and Sensor Downtime

By fixing the TypeError, the primary trigger for the cascade of problems is removed. When the is_on state is determined without error, the integration will no longer enter the aggressive, repetitive reconnection loop. This directly prevents the accumulation of stuck Modbus TCP connections in the SYN_SENT state. Consequently, the Sigenergy inverter will not be overwhelmed by a flood of connection requests, reducing the likelihood of it becoming unresponsive. If the inverter remains responsive, it can continue to serve data to Home Assistant, ensuring that all Sigenergy sensors remain available and functional. The need for a full Home Assistant restart to clear network states would also be eliminated, leading to a much more stable and reliable experience.

Long-Term Stability and Future Considerations

This bug highlights the importance of thorough testing and defensive programming in integrations that interact with hardware. Future versions of the Sigenergy integration should prioritize robust error handling for all data points retrieved from the inverter. This includes not only checking for None values but also ensuring that received data conforms to expected types and ranges. Implementing timeouts and retry mechanisms with exponential backoff, rather than immediate retries, can also prevent overwhelming the connected device during transient network issues. Additionally, clearer logging of recoverable errors would aid users and developers in diagnosing problems without requiring extensive troubleshooting. For users, keeping the integration updated to the latest stable version is crucial, as fixes like this are often backported or addressed in subsequent releases. Regularly checking the integration's GitHub repository or Home Assistant community forums for known issues and updates is a good practice for maintaining a smooth smart home experience.

For more information on Modbus communication and Home Assistant integrations, you can refer to the Modbus Documentation on Home Assistant and the Sigenergy Integration GitHub Repository.