feat(logger): add logger buffer feature (#6060)

* First commit - Adding Buffer and Config classes

* First commit - Adding Buffer and Config classes

* First commit - Adding Buffer and Config classes

* First commit - Adding nox tests

* Adding new parameter to the constructor

* Starting tests

* Adding initial logic + test

* Adding initial logic + test

* Adding initial logic + test

* Unit tests for log comparasion

* Fixing logic to handle log flush

* Start flushing logs

* Adding more logic

* Adding more logic

* Adding more logic

* Refactoring buffer class

* Refactoring buffer class

* Refactoring buffer class

* More refactor

* Adding more coverage + documentation

* Adding decorator

* Refactoring variables name

* Adding more tests + propagating buffer configuration

* Adding exception fields

* Adding e2e tests

* sys.getframe is more performatic

* Chaging the max size

* Removing unecessary files

* Fix tests

* Flushing logs when log line is bigger than buffer size

* Flushing logs when log line is bigger than buffer size

* Adding documentation

* Adding documentation

* Adding documentation

* Addressing Andrea's feedback

* Addressing Andrea's feedback

* Addressing Andrea's feedback

* Refactoring parameters name + child logger + tests

* Improve documentation

* Improve docstring

Author: leandrodamascena

Diff for: aws_lambda_powertools/logging/buffer/__init__.py

@@ -0,0 +1,3 @@
+from aws_lambda_powertools.logging.buffer.config import LoggerBufferConfig
+
+__all__ = ["LoggerBufferConfig"]

Diff for: aws_lambda_powertools/logging/buffer/cache.py

@@ -0,0 +1,215 @@
+from __future__ import annotations
+
+from collections import deque
+from typing import Any
+
+
+class KeyBufferCache:
+    """
+    A cache implementation for a single key with size tracking and eviction support.
+
+    This class manages a buffer for a specific key, keeping track of the current size
+    and providing methods to add, remove, and manage cached items. It supports automatic
+    eviction tracking and size management.
+
+    Attributes
+    ----------
+    cache : deque
+        A double-ended queue storing the cached items.
+    current_size : int
+        The total size of all items currently in the cache.
+    has_evicted : bool
+        A flag indicating whether any items have been evicted from the cache.
+    """
+
+    def __init__(self):
+        """
+        Initialize a buffer cache for a specific key.
+        """
+        self.cache: deque = deque()
+        self.current_size: int = 0
+        self.has_evicted: bool = False
+
+    def add(self, item: Any) -> None:
+        """
+        Add an item to the cache.
+
+        Parameters
+        ----------
+        item : Any
+            The item to be stored in the cache.
+        """
+        item_size = len(str(item))
+        self.cache.append(item)
+        self.current_size += item_size
+
+    def remove_oldest(self) -> Any:
+        """
+        Remove and return the oldest item from the cache.
+
+        Returns
+        -------
+        Any
+            The removed item.
+        """
+        removed_item = self.cache.popleft()
+        self.current_size -= len(str(removed_item))
+        self.has_evicted = True
+        return removed_item
+
+    def get(self) -> list:
+        """
+        Retrieve items for this key.
+
+        Returns
+        -------
+        list
+            List of items in the cache.
+        """
+        return list(self.cache)
+
+    def clear(self) -> None:
+        """
+        Clear the cache for this key.
+        """
+        self.cache.clear()
+        self.current_size = 0
+        self.has_evicted = False
+
+
+class LoggerBufferCache:
+    """
+    A multi-key buffer cache with size-based eviction and management.
+
+    This class provides a flexible caching mechanism that manages multiple keys,
+    with each key having its own buffer cache. The total size of each key's cache
+    is limited, and older items are automatically evicted when the size limit is reached.
+
+    Key Features:
+    - Multiple key support
+    - Size-based eviction
+    - Tracking of evicted items
+    - Configurable maximum buffer size
+
+    Example
+    --------
+    >>> buffer_cache = LoggerBufferCache(max_size_bytes=1000)
+    >>> buffer_cache.add("logs", "First log message")
+    >>> buffer_cache.add("debug", "Debug information")
+    >>> buffer_cache.get("logs")
+    ['First log message']
+    >>> buffer_cache.get_current_size("logs")
+    16
+    """
+
+    def __init__(self, max_size_bytes: int):
+        """
+        Initialize the LoggerBufferCache.
+
+        Parameters
+        ----------
+        max_size_bytes : int
+            Maximum size of the cache in bytes for each key.
+        """
+        self.max_size_bytes: int = max_size_bytes
+        self.cache: dict[str, KeyBufferCache] = {}
+
+    def add(self, key: str, item: Any) -> None:
+        """
+        Add an item to the cache for a specific key.
+
+        Parameters
+        ----------
+        key : str
+            The key to store the item under.
+        item : Any
+            The item to be stored in the cache.
+
+        Returns
+        -------
+        bool
+            True if item was added, False otherwise.
+        """
+        # Check if item is larger than entire buffer
+        item_size = len(str(item))
+        if item_size > self.max_size_bytes:
+            raise BufferError("Cannot add item to the buffer")
+
+        # Create the key's cache if it doesn't exist
+        if key not in self.cache:
+            self.cache[key] = KeyBufferCache()
+
+        # Calculate the size after adding the new item
+        new_total_size = self.cache[key].current_size + item_size
+
+        # If adding the item would exceed max size, remove oldest items
+        while new_total_size > self.max_size_bytes and self.cache[key].cache:
+            self.cache[key].remove_oldest()
+            new_total_size = self.cache[key].current_size + item_size
+
+        self.cache[key].add(item)
+
+    def get(self, key: str) -> list:
+        """
+        Retrieve items for a specific key.
+
+        Parameters
+        ----------
+        key : str
+            The key to retrieve items for.
+
+        Returns
+        -------
+        list
+            List of items for the given key, or an empty list if the key doesn't exist.
+        """
+        return [] if key not in self.cache else self.cache[key].get()
+
+    def clear(self, key: str | None = None) -> None:
+        """
+        Clear the cache, either for a specific key or entirely.
+
+        Parameters
+        ----------
+        key : Optional[str], optional
+            The key to clear. If None, clears the entire cache.
+        """
+        if key:
+            if key in self.cache:
+                self.cache[key].clear()
+                del self.cache[key]
+        else:
+            self.cache.clear()
+
+    def has_items_evicted(self, key: str) -> bool:
+        """
+        Check if a specific key's cache has evicted items.
+
+        Parameters
+        ----------
+        key : str
+            The key to check for evicted items.
+
+        Returns
+        -------
+        bool
+            True if items have been evicted, False otherwise.
+        """
+        return False if key not in self.cache else self.cache[key].has_evicted
+
+    def get_current_size(self, key: str) -> int | None:
+        """
+        Get the current size of the buffer for a specific key.
+
+        Parameters
+        ----------
+        key : str
+            The key to get the current size for.
+
+        Returns
+        -------
+        int
+            The current size of the buffer for the key.
+            Returns 0 if the key does not exist.
+        """
+        return None if key not in self.cache else self.cache[key].current_size

Diff for: aws_lambda_powertools/logging/buffer/config.py

@@ -0,0 +1,78 @@
+from __future__ import annotations
+
+from typing import Literal
+
+
+class LoggerBufferConfig:
+    """
+    Configuration for log buffering behavior.
+    """
+
+    # Define class-level constant for valid log levels
+    VALID_LOG_LEVELS: list[str] = ["DEBUG", "INFO", "WARNING"]
+    LOG_LEVEL_BUFFER_VALUES = Literal["DEBUG", "INFO", "WARNING"]
+
+    def __init__(
+        self,
+        max_bytes: int = 20480,
+        buffer_at_verbosity: LOG_LEVEL_BUFFER_VALUES = "DEBUG",
+        flush_on_error_log: bool = True,
+    ):
+        """
+        Initialize logger buffer configuration.
+
+        Parameters
+        ----------
+        max_bytes : int, optional
+            Maximum size of the buffer in bytes
+        buffer_at_verbosity : str, optional
+            Minimum log level to buffer
+        flush_on_error_log : bool, optional
+            Whether to flush the buffer when an error occurs
+        """
+        self._validate_inputs(max_bytes, buffer_at_verbosity, flush_on_error_log)
+
+        self._max_bytes = max_bytes
+        self._buffer_at_verbosity = buffer_at_verbosity.upper()
+        self._flush_on_error_log = flush_on_error_log
+
+    def _validate_inputs(
+        self,
+        max_bytes: int,
+        buffer_at_verbosity: str,
+        flush_on_error_log: bool,
+    ) -> None:
+        """
+        Validate configuration inputs.
+
+        Parameters
+        ----------
+        Same as __init__ method parameters
+        """
+        if not isinstance(max_bytes, int) or max_bytes <= 0:
+            raise ValueError("Max size must be a positive integer")
+
+        if not isinstance(buffer_at_verbosity, str):
+            raise ValueError("Log level must be a string")
+
+        # Validate log level
+        if buffer_at_verbosity.upper() not in self.VALID_LOG_LEVELS:
+            raise ValueError(f"Invalid log level. Must be one of {self.VALID_LOG_LEVELS}")
+
+        if not isinstance(flush_on_error_log, bool):
+            raise ValueError("flush_on_error must be a boolean")
+
+    @property
+    def max_bytes(self) -> int:
+        """Maximum buffer size in bytes."""
+        return self._max_bytes
+
+    @property
+    def buffer_at_verbosity(self) -> str:
+        """Minimum log level to buffer."""
+        return self._buffer_at_verbosity
+
+    @property
+    def flush_on_error_log(self) -> bool:
+        """Flag to flush buffer on error."""
+        return self._flush_on_error_log