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Logger Worker

The LoggerWorker manages the persistence of historical data (tags, alarms, events) into the database. It handles batch writing, database maintenance (backups/vacuum), and reconnection logic.

class automation.workers.logger.LoggerWorker(manager, period=10.0)

A background worker thread that handles database operations.

It performs the following tasks: 1. Periodically writes buffered tag data to the database. 2. Manages SQLite database backups and maintenance (vacuuming). 3. Handles database reconnection logic. 4. Checks and maintains OPC UA client connections.

check_opcua_connection(self)

Checks the status of OPC UA clients and attempts reconnection if necessary.

daemon

A boolean value indicating whether this thread is a daemon thread.

This must be set before start() is called, otherwise RuntimeError is raised. Its initial value is inherited from the creating thread; the main thread is not a daemon thread and therefore all threads created in the main thread default to daemon = False.

The entire Python program exits when only daemon threads are left.

getName(self)

Return a string used for identification purposes only.

This method is deprecated, use the name attribute instead.

get_stop_event(self)

Returns the stop event object.

Returns:

  • threading.Event: The event used to signal the thread to stop.
get_tags_from_queue(self, _queue)

Retrieves tag data from the queue and filters it based on configuration.

Parameters:

  • _queue (Queue): The queue containing tag updates.

Returns:

  • list: A list of tag data dictionaries ready for insertion.
ident

Thread identifier of this thread or None if it has not been started.

This is a nonzero integer. See the get_ident() function. Thread identifiers may be recycled when a thread exits and another thread is created. The identifier is available even after the thread has exited.

isDaemon(self)

Return whether this thread is a daemon.

This method is deprecated, use the daemon attribute instead.

is_alive(self)

Return whether the thread is alive.

This method returns True just before the run() method starts until just after the run() method terminates. See also the module function enumerate().

join(self, timeout=None)

Wait until the thread terminates.

This blocks the calling thread until the thread whose join() method is called terminates -- either normally or through an unhandled exception or until the optional timeout occurs.

When the timeout argument is present and not None, it should be a floating point number specifying a timeout for the operation in seconds (or fractions thereof). As join() always returns None, you must call is_alive() after join() to decide whether a timeout happened -- if the thread is still alive, the join() call timed out.

When the timeout argument is not present or None, the operation will block until the thread terminates.

A thread can be join()ed many times.

join() raises a RuntimeError if an attempt is made to join the current thread as that would cause a deadlock. It is also an error to join() a thread before it has been started and attempts to do so raises the same exception.

name

A string used for identification purposes only.

It has no semantics. Multiple threads may be given the same name. The initial name is set by the constructor.

native_id

Native integral thread ID of this thread, or None if it has not been started.

This is a non-negative integer. See the get_native_id() function. This represents the Thread ID as reported by the kernel.

reconnect_to_db(self)

Attempts to reconnect to the database if the connection is lost.

run(self)

Main worker loop.

Continuously: 1. Checks database connectivity. 2. Backs up SQLite DB if needed. 3. Writes queued tags to the database. 4. Reconnects to DB if connection lost. 5. Checks OPC UA connections. 6. Sleeps for the configured period.

setDaemon(self, daemonic)

Set whether this thread is a daemon.

This method is deprecated, use the .daemon property instead.

setName(self, name)

Set the name string for this thread.

This method is deprecated, use the name attribute instead.

sqlite_db_backup(self)

Performs a backup of the SQLite database if it exceeds 1GB.

It copies the database file to the db/backups directory, clears the historical tables (TagValue, AlarmSummary, Events, Logs), and performs a VACUUM command to reclaim disk space.

start(self)

Start the thread's activity.

It must be called at most once per thread object. It arranges for the object's run() method to be invoked in a separate thread of control.

This method will raise a RuntimeError if called more than once on the same thread object.

stop(self)

Signals the worker thread to stop execution.