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"""
This module contains operators to replicate records from
DynamoDB table to S3.
"""
from __future__ import annotations
import json
from copy import copy
from decimal import Decimal
from os.path import getsize
from tempfile import NamedTemporaryFile
from typing import IO, TYPE_CHECKING, Any, Callable, Sequence
from uuid import uuid4
from airflow.models import BaseOperator
from airflow.providers.amazon.aws.hooks.dynamodb import DynamoDBHook
from airflow.providers.amazon.aws.hooks.s3 import S3Hook
if TYPE_CHECKING:
from airflow.utils.context import Context
[docs]class JSONEncoder(json.JSONEncoder):
"""Custom json encoder implementation"""
[docs] def default(self, obj):
"""Convert decimal objects in a json serializable format."""
if isinstance(obj, Decimal):
return float(obj)
return super().default(obj)
def _convert_item_to_json_bytes(item: dict[str, Any]) -> bytes:
return (json.dumps(item, cls=JSONEncoder) + "\n").encode("utf-8")
def _upload_file_to_s3(
file_obj: IO, bucket_name: str, s3_key_prefix: str, aws_conn_id: str = "aws_default"
) -> None:
s3_client = S3Hook(aws_conn_id=aws_conn_id).get_conn()
file_obj.seek(0)
s3_client.upload_file(
Filename=file_obj.name,
Bucket=bucket_name,
Key=s3_key_prefix + str(uuid4()),
)
[docs]class DynamoDBToS3Operator(BaseOperator):
"""
Replicates records from a DynamoDB table to S3.
It scans a DynamoDB table and writes the received records to a file
on the local filesystem. It flushes the file to S3 once the file size
exceeds the file size limit specified by the user.
Users can also specify a filtering criteria using dynamodb_scan_kwargs
to only replicate records that satisfy the criteria.
.. seealso::
For more information on how to use this operator, take a look at the guide:
:ref:`howto/transfer:DynamoDBToS3Operator`
:param dynamodb_table_name: Dynamodb table to replicate data from
:param s3_bucket_name: S3 bucket to replicate data to
:param file_size: Flush file to s3 if file size >= file_size
:param dynamodb_scan_kwargs: kwargs pass to <https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/dynamodb.html#DynamoDB.Table.scan> # noqa: E501
:param s3_key_prefix: Prefix of s3 object key
:param process_func: How we transforms a dynamodb item to bytes. By default we dump the json
:param aws_conn_id: The Airflow connection used for AWS credentials.
If this is None or empty then the default boto3 behaviour is used. If
running Airflow in a distributed manner and aws_conn_id is None or
empty, then default boto3 configuration would be used (and must be
maintained on each worker node).
"""
[docs] template_fields: Sequence[str] = (
"s3_bucket_name",
"s3_key_prefix",
"dynamodb_table_name",
)
[docs] template_fields_renderers = {
"dynamodb_scan_kwargs": "json",
}
def __init__(
self,
*,
dynamodb_table_name: str,
s3_bucket_name: str,
file_size: int,
dynamodb_scan_kwargs: dict[str, Any] | None = None,
s3_key_prefix: str = "",
process_func: Callable[[dict[str, Any]], bytes] = _convert_item_to_json_bytes,
aws_conn_id: str = "aws_default",
**kwargs,
) -> None:
super().__init__(**kwargs)
self.file_size = file_size
self.process_func = process_func
self.dynamodb_table_name = dynamodb_table_name
self.dynamodb_scan_kwargs = dynamodb_scan_kwargs
self.s3_bucket_name = s3_bucket_name
self.s3_key_prefix = s3_key_prefix
self.aws_conn_id = aws_conn_id
[docs] def execute(self, context: Context) -> None:
hook = DynamoDBHook(aws_conn_id=self.aws_conn_id)
table = hook.get_conn().Table(self.dynamodb_table_name)
scan_kwargs = copy(self.dynamodb_scan_kwargs) if self.dynamodb_scan_kwargs else {}
err = None
f: IO[Any]
with NamedTemporaryFile() as f:
try:
f = self._scan_dynamodb_and_upload_to_s3(f, scan_kwargs, table)
except Exception as e:
err = e
raise e
finally:
if err is None:
_upload_file_to_s3(f, self.s3_bucket_name, self.s3_key_prefix, self.aws_conn_id)
def _scan_dynamodb_and_upload_to_s3(self, temp_file: IO, scan_kwargs: dict, table: Any) -> IO:
while True:
response = table.scan(**scan_kwargs)
items = response["Items"]
for item in items:
temp_file.write(self.process_func(item))
if "LastEvaluatedKey" not in response:
# no more items to scan
break
last_evaluated_key = response["LastEvaluatedKey"]
scan_kwargs["ExclusiveStartKey"] = last_evaluated_key
# Upload the file to S3 if reach file size limit
if getsize(temp_file.name) >= self.file_size:
_upload_file_to_s3(temp_file, self.s3_bucket_name, self.s3_key_prefix, self.aws_conn_id)
temp_file.close()
temp_file = NamedTemporaryFile()
return temp_file
