624 lines
26 KiB
Python
624 lines
26 KiB
Python
import os
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import boto3
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import smtplib
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import time
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import traceback
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import json
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import random
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import signal
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from email.parser import BytesParser
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from email.policy import default
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from email.utils import getaddresses
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s3 = boto3.client('s3')
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# Environment variables (set these in the Lambda config)
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SMTP_HOST = os.environ.get('SMTP_HOST', 'mail.email-srvr.com')
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SMTP_PORT = int(os.environ.get('SMTP_PORT', '2525'))
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SMTP_USER = os.environ.get('SMTP_USER')
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SMTP_PASS = os.environ.get('SMTP_PASS')
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# Metadata key/value to mark processed objects (only set when at least one recipient delivered)
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PROCESSED_META_KEY = os.environ.get('PROCESSED_META_KEY', 'processed')
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PROCESSED_META_VALUE = os.environ.get('PROCESSED_META_VALUE', 'true')
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# Retry configuration
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MAX_RETRIES = int(os.environ.get('MAX_SMTP_RETRIES', '3'))
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BASE_RETRY_DELAY = int(os.environ.get('BASE_RETRY_DELAY', '2'))
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# Email size limit (25 MB - Lambda memory safety margin)
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MAX_EMAIL_SIZE_MB = int(os.environ.get('MAX_EMAIL_SIZE_MB', '25'))
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MAX_EMAIL_SIZE_BYTES = MAX_EMAIL_SIZE_MB * 1024 * 1024
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# ============================================================================
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# VERBESSERUNG 5: Timeout Protection
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# ============================================================================
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class TimeoutException(Exception):
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pass
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def timeout_handler(signum, frame):
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raise TimeoutException("Lambda approaching timeout")
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def domain_to_bucket(domain: str) -> str:
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return domain.replace('.', '-') + '-emails'
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def bucket_to_domain(bucket: str) -> str:
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return bucket.replace('-emails', '').replace('-', '.')
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def parse_raw_message(raw_bytes: bytes):
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try:
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# Use SMTP policy for better compatibility with various email formats
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from email.policy import SMTP
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parsed = BytesParser(policy=SMTP).parsebytes(raw_bytes)
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except Exception as e:
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print(f"Error parsing with SMTP policy: {e}, trying with default policy")
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try:
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parsed = BytesParser(policy=default).parsebytes(raw_bytes)
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except Exception as e2:
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print(f"Error parsing with default policy: {e2}")
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parsed = None
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return parsed
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def mark_object_processed(bucket: str, key: str):
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try:
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head = s3.head_object(Bucket=bucket, Key=key)
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current_metadata = head.get('Metadata', {}) or {}
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if current_metadata.get(PROCESSED_META_KEY) == PROCESSED_META_VALUE:
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print(f"Object {key} in {bucket} already marked processed.")
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return
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new_meta = current_metadata.copy()
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new_meta[PROCESSED_META_KEY] = PROCESSED_META_VALUE
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new_meta['processed_at'] = str(int(time.time()))
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# Remove processing lock
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new_meta.pop('processing_started', None)
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# Copy object onto itself replacing metadata
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s3.copy_object(
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Bucket=bucket,
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Key=key,
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CopySource={'Bucket': bucket, 'Key': key},
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Metadata=new_meta,
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MetadataDirective='REPLACE'
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)
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print(f"Marked {bucket}/{key} as processed at {new_meta['processed_at']}")
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except Exception as e:
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print("Failed to mark processed metadata:", e)
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traceback.print_exc()
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def update_retry_metadata(bucket: str, key: str, retry_count: int, last_error: str = None):
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"""Update S3 object metadata with retry information"""
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try:
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head = s3.head_object(Bucket=bucket, Key=key)
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current_metadata = head.get('Metadata', {}) or {}
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new_meta = current_metadata.copy()
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new_meta['retry_count'] = str(retry_count)
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new_meta['last_retry'] = str(int(time.time()))
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if last_error:
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# S3 metadata values must be ASCII, so we encode the error
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new_meta['last_error'] = last_error[:255].replace('\n', ' ')
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s3.copy_object(
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Bucket=bucket,
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Key=key,
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CopySource={'Bucket': bucket, 'Key': key},
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Metadata=new_meta,
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MetadataDirective='REPLACE'
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)
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print(f"Updated retry metadata for {bucket}/{key}: retry_count={retry_count}")
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except Exception as e:
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print(f"Failed to update retry metadata: {e}")
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def get_retry_count(bucket: str, key: str) -> int:
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"""Get current retry count from S3 metadata"""
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try:
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head = s3.head_object(Bucket=bucket, Key=key)
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metadata = head.get('Metadata', {}) or {}
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return int(metadata.get('retry_count', '0'))
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except Exception:
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return 0
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def is_temporary_smtp_error(error_code):
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"""Check if SMTP error code indicates a temporary failure (4xx)"""
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if isinstance(error_code, tuple) and len(error_code) >= 1:
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code = error_code[0]
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if isinstance(code, int):
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return 400 <= code < 500
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return False
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def is_spam_rejection(error_code):
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"""Check if the error is a spam rejection (should not be retried)"""
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if isinstance(error_code, tuple) and len(error_code) >= 2:
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code = error_code[0]
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message = error_code[1]
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# 554 with spam message is permanent - don't retry
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if code == 554 and b'spam' in message.lower():
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return True
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return False
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# ============================================================================
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# VERBESSERUNG 3: Exponential Backoff with Jitter
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# ============================================================================
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def send_email_with_retry(smtp_host, smtp_port, smtp_user, smtp_pass,
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frm_addr, recipients, raw_message, local_helo,
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max_retries=MAX_RETRIES):
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"""Send email with retry logic for temporary failures using exponential backoff"""
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delivered = []
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refused = {}
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last_error = None
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for attempt in range(max_retries + 1):
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if attempt > 0:
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# Exponential backoff with jitter: 2s, 4s, 8s (configurable via BASE_RETRY_DELAY)
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delay = BASE_RETRY_DELAY * (2 ** (attempt - 1))
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# Add jitter to prevent thundering herd
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jitter = random.uniform(0, delay * 0.3) # +0-30% random jitter
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total_delay = delay + jitter
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print(f"Retry attempt {attempt}/{max_retries} after {total_delay:.1f}s delay (base: {delay}s + jitter: {jitter:.1f}s)")
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time.sleep(total_delay)
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try:
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with smtplib.SMTP(smtp_host, smtp_port, timeout=30, local_hostname=local_helo) as smtp:
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smtp.ehlo()
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# Try STARTTLS
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try:
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smtp.starttls()
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smtp.ehlo()
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except Exception as e:
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print("STARTTLS not available or failed (continuing):", e)
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# Login if credentials provided
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if smtp_user and smtp_pass:
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try:
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smtp.login(smtp_user, smtp_pass)
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except Exception as e:
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print("SMTP login failed (continuing):", e)
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# Attempt to send
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try:
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send_result = smtp.sendmail(frm_addr, recipients, raw_message)
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if isinstance(send_result, dict):
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# Separate temporary and permanent failures
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temp_refused = {}
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perm_refused = {}
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for rcpt, error in send_result.items():
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if is_temporary_smtp_error(error):
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temp_refused[rcpt] = error
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else:
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perm_refused[rcpt] = error
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# If we have temporary failures and more retries, continue
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if temp_refused and attempt < max_retries:
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print(f"Temporary failures for {list(temp_refused.keys())}, will retry...")
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recipients = list(temp_refused.keys()) # Only retry temporary failures
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refused = perm_refused # Keep track of permanent failures
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last_error = str(temp_refused)
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continue
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else:
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# No temporary failures or no more retries
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refused = send_result
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delivered = [r for r in recipients if r not in refused]
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break
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else:
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# All delivered successfully
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delivered = recipients[:]
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refused = {}
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break
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except smtplib.SMTPRecipientsRefused as e:
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print(f"SMTPRecipientsRefused on attempt {attempt + 1}: {e}")
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# Check if all are temporary failures
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temp_refused = {}
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perm_refused = {}
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for rcpt, error in e.recipients.items():
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if is_temporary_smtp_error(error):
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temp_refused[rcpt] = error
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else:
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perm_refused[rcpt] = error
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if temp_refused and attempt < max_retries:
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recipients = list(temp_refused.keys())
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refused = perm_refused
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last_error = str(e)
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continue
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else:
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refused = e.recipients
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delivered = [r for r in recipients if r not in refused]
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break
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except Exception as e:
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print(f"SMTP sendmail error on attempt {attempt + 1}: {e}")
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# Check if this is a spam rejection (permanent error that shouldn't be retried)
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if hasattr(e, 'smtp_code') and hasattr(e, 'smtp_error'):
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if is_spam_rejection((e.smtp_code, e.smtp_error)):
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print(f"Email rejected as spam (permanent error), not retrying")
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refused = {r: (e.smtp_code, e.smtp_error) for r in recipients}
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delivered = []
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break
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# For other errors, check if it's worth retrying
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if attempt < max_retries:
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# Only retry if it might be temporary
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error_str = str(e)
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if '554' in error_str and 'spam' in error_str.lower():
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print(f"Email rejected as spam, not retrying")
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refused = {r: ('spam', str(e)) for r in recipients}
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delivered = []
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break
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else:
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last_error = str(e)
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continue
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else:
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traceback.print_exc()
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refused = {r: ('error', str(e)) for r in recipients}
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delivered = []
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break
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except Exception as e:
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print(f"Error connecting to SMTP host on attempt {attempt + 1}: {e}")
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if attempt < max_retries:
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last_error = str(e)
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continue
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else:
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traceback.print_exc()
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refused = {r: ('connect-error', str(e)) for r in recipients}
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delivered = []
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break
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return delivered, refused
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# ============================================================================
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# VERBESSERUNG 4: Structured Logging
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# ============================================================================
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def log_processing_result(bucket: str, key: str, delivered: list, refused: dict, retry_count: int):
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"""Log processing results to CloudWatch in structured format for easier analysis"""
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result = {
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'timestamp': int(time.time()),
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'bucket': bucket,
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'key': key,
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'delivered_count': len(delivered),
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'refused_count': len(refused),
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'retry_count': retry_count,
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'delivered_recipients': delivered,
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'refused_recipients': list(refused.keys()) if refused else [],
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'success': len(delivered) > 0
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}
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# Structured logging for CloudWatch Insights
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print(f"PROCESSING_RESULT: {json.dumps(result)}")
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return result
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# ============================================================================
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# MAIN PROCESSING FUNCTION (extracted for timeout handling)
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# ============================================================================
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def _process_email(event, context):
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"""Main email processing logic (extracted for timeout protection)"""
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print("Event:", event)
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ses = None
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try:
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rec = event['Records'][0]
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except Exception as e:
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print("No Records in event:", e)
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return {'statusCode': 400, 'body': 'No Records'}
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# Determine bucket/key and initial recipients list
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recipients = []
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bucket = None
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key = None
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is_ses_event = False
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if 'ses' in rec:
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# SES Event - vertrauenswürdig, hat die korrekten Empfänger
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is_ses_event = True
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ses = rec['ses']
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msg_id = ses['mail']['messageId']
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recipients = ses['receipt'].get('recipients', [])
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# assume first recipient domain maps to bucket
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if recipients:
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domain = recipients[0].split('@', 1)[1]
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bucket = domain_to_bucket(domain)
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prefix = f"{msg_id}"
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print(f"SES event: domain={domain}, bucket={bucket}, prefix={prefix}")
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resp_list = s3.list_objects_v2(Bucket=bucket, Prefix=prefix)
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if 'Contents' not in resp_list or not resp_list['Contents']:
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raise Exception(f"No S3 object under {prefix} in {bucket}")
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key = resp_list['Contents'][0]['Key']
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else:
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raise Exception("SES event but no recipients found")
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elif 's3' in rec:
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# S3 Event - muss Empfänger aus Headers extrahieren
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s3info = rec['s3']
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bucket = s3info['bucket']['name']
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key = s3info['object']['key']
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print(f"S3 event: bucket={bucket}, key={key}")
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# recipients will be parsed from message headers below
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else:
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raise Exception("Unknown event type")
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# ========================================================================
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# VERBESSERUNG 1: Duplicate Prevention with Processing Lock
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# ========================================================================
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try:
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head = s3.head_object(Bucket=bucket, Key=key)
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metadata = head.get('Metadata', {}) or {}
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# Check if already processed
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if metadata.get(PROCESSED_META_KEY) == PROCESSED_META_VALUE:
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processed_at = metadata.get('processed_at', 'unknown time')
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print(f"Object {key} already processed at {processed_at}")
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return {'statusCode': 200, 'body': 'already processed'}
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# Check if currently being processed (lock mechanism)
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processing_started = metadata.get('processing_started')
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if processing_started:
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processing_age = time.time() - float(processing_started)
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if processing_age < 300: # 5 minutes lock
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print(f"Object {key} is being processed by another Lambda (started {processing_age:.0f}s ago)")
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return {'statusCode': 200, 'body': 'already being processed'}
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else:
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print(f"Stale processing lock detected ({processing_age:.0f}s old), continuing")
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# Set processing lock
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new_meta = metadata.copy()
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new_meta['processing_started'] = str(int(time.time()))
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s3.copy_object(
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Bucket=bucket,
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Key=key,
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CopySource={'Bucket': bucket, 'Key': key},
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Metadata=new_meta,
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MetadataDirective='REPLACE'
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)
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print(f"Set processing lock on {key}")
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except s3.exceptions.NoSuchKey:
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print(f"Object {key} no longer exists, skipping")
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return {'statusCode': 404, 'body': 'object not found'}
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except Exception as e:
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print(f"Error checking/setting processing lock: {e}")
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# Continue anyway if lock fails (better than dropping email)
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# Check retry count - if too many retries, give up
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retry_count = get_retry_count(bucket, key)
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if retry_count >= MAX_RETRIES * 2: # Safety limit
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print(f"Object {key} has been retried {retry_count} times, giving up")
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mark_object_processed(bucket, key) # Mark as processed to prevent infinite retries
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return {'statusCode': 200, 'body': f'max retries exceeded ({retry_count})'}
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# ========================================================================
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# VERBESSERUNG 2: Memory Optimization with Size Check
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# ========================================================================
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try:
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resp = s3.get_object(Bucket=bucket, Key=key)
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content_length = int(resp.get('ContentLength', 0))
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# Safety check: Skip emails larger than MAX_EMAIL_SIZE_MB
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if content_length > MAX_EMAIL_SIZE_BYTES:
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print(f"ERROR: Email too large ({content_length/1024/1024:.1f} MB), maximum is {MAX_EMAIL_SIZE_MB} MB")
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# Mark as processed to prevent infinite retries
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mark_object_processed(bucket, key)
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return {
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'statusCode': 413, # Payload Too Large
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'body': json.dumps({
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'error': 'email_too_large',
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'size_mb': round(content_length/1024/1024, 2),
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'max_mb': MAX_EMAIL_SIZE_MB
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})
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}
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raw_bytes = resp['Body'].read()
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print(f"Loaded {len(raw_bytes)} bytes ({len(raw_bytes)/1024:.1f} KB) from s3://{bucket}/{key}")
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except Exception as e:
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print(f"ERROR reading from S3: {e}")
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traceback.print_exc()
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return {'statusCode': 500, 'body': f'S3 read error: {str(e)}'}
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parsed = parse_raw_message(raw_bytes)
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subj = parsed.get('subject', '(no subject)') if parsed else '(no subject)'
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frm_addr = None
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if parsed:
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from_addrs = getaddresses(parsed.get_all('from', []) or [])
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frm_addr = from_addrs[0][1] if from_addrs else None
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if not frm_addr:
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frm_addr = (ses['mail'].get('source') if ses else None) or ('noreply@' + (bucket_to_domain(bucket) if bucket else 'localhost'))
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print(f"From: {frm_addr}, Subject: {subj}")
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# If recipients were not provided (S3 path), extract from headers
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if not recipients and not is_ses_event:
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if parsed:
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expected_domain = bucket_to_domain(bucket).lower()
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# Debug: Print raw headers to understand what we're getting
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print(f"=== DEBUG: Header Analysis ===")
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print(f"Expected domain: {expected_domain}")
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# The email parser is case-insensitive for headers, so we only need to check once
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# Get headers using standard case (parser handles case-insensitivity)
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to_headers = parsed.get_all('to', []) or []
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cc_headers = parsed.get_all('cc', []) or []
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bcc_headers = parsed.get_all('bcc', []) or []
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if to_headers:
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print(f"Found 'To' header: {to_headers}")
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if cc_headers:
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print(f"Found 'Cc' header: {cc_headers}")
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if bcc_headers:
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print(f"Found 'Bcc' header: {bcc_headers}")
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# Parse addresses from headers
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to_addrs = [addr for _n, addr in getaddresses(to_headers) if addr]
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cc_addrs = [addr for _n, addr in getaddresses(cc_headers) if addr]
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bcc_addrs = [addr for _n, addr in getaddresses(bcc_headers) if addr]
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all_recipients = to_addrs + cc_addrs + bcc_addrs
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print(f"Parsed recipients - To: {to_addrs}, Cc: {cc_addrs}, Bcc: {bcc_addrs}")
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# Filter recipients to bucket domain with case-insensitive comparison
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# and deduplicate using a set (preserving case)
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recipients_set = set()
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recipients = []
|
|
for addr in all_recipients:
|
|
# Extract domain part (everything after @)
|
|
if '@' in addr:
|
|
addr_lower = addr.lower()
|
|
addr_domain = addr_lower.split('@')[-1]
|
|
if addr_domain == expected_domain:
|
|
# Only add if not already in set (case-insensitive deduplication)
|
|
if addr_lower not in recipients_set:
|
|
recipients_set.add(addr_lower)
|
|
recipients.append(addr) # Keep original case
|
|
print(f"Matched recipient: {addr} (domain: {addr_domain})")
|
|
else:
|
|
print(f"Skipped duplicate: {addr}")
|
|
else:
|
|
print(f"Skipped recipient: {addr} (domain: {addr_domain} != {expected_domain})")
|
|
|
|
print(f"Final recipients after domain filter and deduplication: {recipients}")
|
|
|
|
# If no recipients found, try additional headers
|
|
if not recipients:
|
|
print("WARNING: No recipients found in standard headers, checking additional headers...")
|
|
|
|
# Check for X-Original-To, Delivered-To, Envelope-To
|
|
fallback_headers = ['X-Original-To', 'Delivered-To', 'Envelope-To',
|
|
'x-original-to', 'delivered-to', 'envelope-to']
|
|
|
|
for header_name in fallback_headers:
|
|
header_val = parsed.get(header_name)
|
|
if header_val:
|
|
print(f"Found {header_name}: {header_val}")
|
|
fallback_addrs = [addr for _n, addr in getaddresses([header_val]) if addr]
|
|
for addr in fallback_addrs:
|
|
if '@' in addr and addr.split('@')[-1].lower() == expected_domain:
|
|
recipients.append(addr)
|
|
print(f"Found recipient in {header_name}: {addr}")
|
|
|
|
if not recipients:
|
|
print(f"ERROR: Could not find any recipients for domain {expected_domain}")
|
|
print(f"All addresses found: {all_recipients}")
|
|
# Print all headers for debugging
|
|
print("=== All Email Headers ===")
|
|
for key_h in parsed.keys():
|
|
print(f"{key_h}: {parsed.get(key_h)}")
|
|
print("=== End Headers ===")
|
|
else:
|
|
print("ERROR: Could not parse email headers")
|
|
recipients = []
|
|
|
|
# If after all we have no recipients, skip SMTP
|
|
delivered = []
|
|
refused = {}
|
|
if recipients:
|
|
# Use raw bytes directly (no decoding!)
|
|
raw_message = raw_bytes
|
|
|
|
# Determine HELO hostname
|
|
env_local = os.environ.get('SMTP_LOCAL_HOSTNAME')
|
|
derived_local = bucket_to_domain(bucket) if bucket else None
|
|
local_helo = env_local or derived_local or 'localhost'
|
|
|
|
print(f"Attempting SMTP send to {len(recipients)} recipients via {SMTP_HOST}:{SMTP_PORT} with local_hostname={local_helo}")
|
|
start = time.time()
|
|
|
|
# Send with retry logic
|
|
delivered, refused = send_email_with_retry(
|
|
SMTP_HOST, SMTP_PORT, SMTP_USER, SMTP_PASS,
|
|
frm_addr, recipients, raw_message, local_helo,
|
|
max_retries=MAX_RETRIES
|
|
)
|
|
|
|
print(f"SMTP completed in {time.time()-start:.2f}s delivered={delivered} refused={refused}")
|
|
|
|
# Update retry count if we had temporary failures
|
|
if refused and not delivered:
|
|
temp_failures = [r for r, e in refused.items() if is_temporary_smtp_error(e)]
|
|
if temp_failures:
|
|
update_retry_metadata(bucket, key, retry_count + 1, str(refused))
|
|
else:
|
|
print("No recipients to send to; skipping SMTP.")
|
|
|
|
# Only mark as processed if at least one recipient was delivered successfully
|
|
if delivered:
|
|
try:
|
|
mark_object_processed(bucket, key)
|
|
except Exception as e:
|
|
print("Failed to mark object processed after delivery:", e)
|
|
else:
|
|
print("No successful deliveries; NOT setting processed metadata so message can be re-evaluated later.")
|
|
|
|
# Log structured result
|
|
result = log_processing_result(bucket, key, delivered, refused, retry_count)
|
|
|
|
return {
|
|
'statusCode': 200 if delivered else 500,
|
|
'body': json.dumps(result)
|
|
}
|
|
|
|
|
|
# ============================================================================
|
|
# LAMBDA HANDLER with TIMEOUT PROTECTION
|
|
# ============================================================================
|
|
def lambda_handler(event, context):
|
|
"""
|
|
Lambda entry point with timeout protection
|
|
Recommended Lambda Configuration:
|
|
- Memory: 512 MB
|
|
- Timeout: 60 seconds
|
|
- Environment Variables:
|
|
- SMTP_HOST, SMTP_PORT, SMTP_USER, SMTP_PASS
|
|
- MAX_SMTP_RETRIES=3
|
|
- BASE_RETRY_DELAY=2
|
|
- MAX_EMAIL_SIZE_MB=25
|
|
"""
|
|
|
|
# Set up timeout protection (stop 5 seconds before Lambda timeout)
|
|
remaining_time = context.get_remaining_time_in_millis() / 1000 if context else 60
|
|
safety_margin = 5 # seconds
|
|
max_execution_time = max(10, remaining_time - safety_margin)
|
|
|
|
signal.signal(signal.SIGALRM, timeout_handler)
|
|
signal.alarm(int(max_execution_time))
|
|
|
|
try:
|
|
return _process_email(event, context)
|
|
except TimeoutException:
|
|
print(f"WARNING: Lambda approaching timeout after {max_execution_time}s, gracefully exiting")
|
|
# Don't mark as processed so it can be retried
|
|
return {
|
|
'statusCode': 408, # Request Timeout
|
|
'body': json.dumps({
|
|
'error': 'lambda_timeout',
|
|
'execution_time': max_execution_time
|
|
})
|
|
}
|
|
except Exception as e:
|
|
print(f"FATAL ERROR in lambda_handler: {e}")
|
|
traceback.print_exc()
|
|
return {
|
|
'statusCode': 500,
|
|
'body': json.dumps({
|
|
'error': 'internal_error',
|
|
'message': str(e)
|
|
})
|
|
}
|
|
finally:
|
|
signal.alarm(0) # Cancel alarm |