Merge branch 'feature/fault_tolerance' into develop

.gitignore

 pymongodump
+recovery
 tests.py
 .mypy_cache
+.recovery*

lib/utils.py

@@ -3,6 +3,7 @@ import pymongo
 import json
 import re
 import time
+import datetime
 import multiprocessing as mp
 from math import ceil
 from typing import List
@@ -15,7 +16,16 @@ import logging
 logger = logging.getLogger(__name__)
 
 
-def filesystem_writer(queue: mp.Queue, header: str) -> None:
+def filesystem_writer(
+        queue: mp.Queue,
+        header: str,
+        host: str,
+        port: int,
+        database: str,
+        pagesize: int,
+        output_dir: str,
+        recovery_file: str)\
+        -> None:
     """
     Reads the CSV pages from the queue and writes them to filesystem
 
@@ -31,13 +41,27 @@ def filesystem_writer(queue: mp.Queue, header: str) -> None:
     logger.debug(
         "Worker {} launched: filesystem_writer executing"
         .format(os.getpid()))
+    if recovery_file:
+        recovery_file_path = recovery_file
+    else:
+        recovery_file_path = build_recovery_filepath(database)
+        create_recovery_file(
+            recovery_file_path, host, port, database, pagesize)
 
     while True:
-        csv_page = queue.get()
+        page_number, csv_page = queue.get()
+
         if csv_page == "END":
             logger.info("Writing loop finished")
+            os.remove(recovery_file_path)
+            break
+        elif csv_page == "ERROR":
+            logger.error("Dumping recovery file and exiting")
+            if recovery_file_path >= 0:
+                dump_error_recovery_file(recovery_file_path, page_number)
             break
-        if globals.timing and csv_page is not None:
+        elif csv_page is not None:
+            if globals.timing:
                 time0 = time.time()
             for output_path in csv_page.keys():
                 logger.debug("Dumping tweets for " + output_path)
@@ -50,11 +74,14 @@ def filesystem_writer(queue: mp.Queue, header: str) -> None:
                     generate_path(output_path, header)
                     with open(output_path, "a") as writer:
                         writer.write(csv_page[output_path])
-        if globals.timing and csv_page is not None:
-            time1 = time.time()
+            if page_number >= 0:
+                update_recovery_file(recovery_file_path, page_number)
+            if globals.timing:
                 logger.critical(
                     "Time spent writing tweet page to FS: {}s"
-                .format(time1 - time0))
+                    .format(time.time() - time0))
+            else:
+                continue
 
 
 def process_page(
@@ -80,6 +107,7 @@ def process_page(
     :param queue: queue were processed data await to be written to FS
     """
 
+    try:
         logger.debug(
             "Worker {} launched: process_page executing".format(os.getpid()))
         if globals.timing:
@@ -93,15 +121,20 @@ def process_page(
         for tweet in tweets_page:
             csv_tweet_output_path =\
                 get_tweet_output_path(tweet, output_dir)
+            try:
                 csv_tweet_contents =\
                     "\n" + str(convert_tweet_to_csv(header, tweet))
-
+            except TweetConversionException as exc:
+                logger.error(exc.message)
+                logger.error("Origin tweet:\n" + str(exc.tweet))
+                logger.error("Discarding tweet and proceeding...")
+                continue
             if csv_tweet_output_path not in buffer_tweets.keys():
                 buffer_tweets[csv_tweet_output_path] = ""
             buffer_tweets[csv_tweet_output_path] += csv_tweet_contents
         client.close()
 
-    queue.put(buffer_tweets)
+        queue.put((page_number, buffer_tweets))
 
         logger.debug("Page {} enqueued".format(page_number))
         if globals.timing:
@@ -110,6 +143,10 @@ def process_page(
                 "Time processing & buffering tweet page: {}s"
                 .format(time1 - time0))
 
+    except Exception:
+        raise ExceptionAtPage(
+            "Something failed while processing page", page_number)
+
 
 def get_tweet_output_path(tweet: dict, output_dir: str) -> str:
     """
@@ -206,13 +243,109 @@ def convert_tweet_to_csv(header: str, tweet: dict) -> str:
               fields in CSV form
     """
 
+    try:
         flat_tweet = json2csv.flatten_dictionary(tweet)
+    except Exception:
+        raise TweetConversionException(
+            "Error when flattening tweet", tweet)
+    try:
         csv_tweet = json2csv.json2csv(flat_tweet, True, 5, False)
-    csv_appendable_tweet = format_csv.get_csv_line(header, csv_tweet)
-
+    except Exception:
+        raise TweetConversionException(
+            "Error when trying to convert tweet to CSV", flat_tweet)
+    try:
+        csv_appendable_tweet = format_csv.get_csv_line(
+            header, csv_tweet)
+    except Exception:
+        raise TweetConversionException(
+            "Error when formatting CSV tweet", csv_tweet)
     return csv_appendable_tweet
 
 
+def build_recovery_filepath(dbname: str) -> str:
+    """
+    Build the path of a recovery file
+
+    :param dbname: name of the database being queried
+    :returns: the path of the recovery file generated in this execution
+    """
+    recovery_dir = "./recovery"
+    if not os.path.isdir(recovery_dir):
+        os.mkdir(recovery_dir)
+    now = datetime.datetime.now()
+    datetime_str = "%04d%02d%02d-%02d%02d%02d" %\
+        (now.year, now.month, now.day, now.hour, now.minute, now.second)
+    recovery_file_path = os.path.join(
+        recovery_dir,
+        "recovery_" + dbname + "_" + datetime_str + ".json")
+
+    return recovery_file_path
+
+
+def create_recovery_file(
+        file_path: str,
+        host: str,
+        port: int,
+        database: str,
+        page_size: int)\
+        -> None:
+    """
+    In case of error, dump information to file to allow recovery
+
+    :param host: address of the host to which the script connected
+    :param port: port of the Mongo database
+    :param database: name of the database being queried
+    :param page_size: size of the page that was being used
+    """
+
+    recovery_file_contents = {}
+    recovery_file_contents["host"] = host
+    recovery_file_contents["port"] = port
+    recovery_file_contents["database"] = database
+    recovery_file_contents["pagesize"] = page_size
+    recovery_file_contents["dumped_pages"] = []
+
+    with open(file_path, "w") as f:
+        json.dump(recovery_file_contents, f)
+
+    logger.error("Generated recovery file at {}".format(file_path))
+
+
+def update_recovery_file(
+        file_path: str,
+        page_number: int)\
+        -> None:
+    """
+    Add a new page to the list of already dumped pages in the recovery
+    file
+    :param file_path: path to the recovery file
+    :param page_number: number of the page that was safely written
+    """
+
+    with open(file_path, "r") as f:
+        recovery_file_contents = json.load(f)
+    recovery_file_contents["dumped_pages"].append(page_number)
+    with open(file_path, "w") as f:
+        json.dump(recovery_file_contents, f)
+
+
+def dump_error_recovery_file(
+        file_path: str,
+        page_number: int)\
+        -> None:
+    """
+    Add information pointing to the page where error was detected
+    :param file_path: path to the recovery file
+    :param page_number: number of the page that crashed
+    """
+
+    with open(file_path, "r") as f:
+        recovery_file_contents = json.load(f)
+    recovery_file_contents["error_page"] = page_number
+    with open(file_path, "w") as f:
+        json.dump(recovery_file_contents, f)
+
+
 #########################
 #  TWEET DB PAGINATION  #
 #########################
@@ -292,3 +425,38 @@ def file_length(file_path: str) -> int:
         for i, l in enumerate(f):
             pass
         return i
+
+
+#######################
+#  CUSTOM EXCEPTIONS  #
+#######################
+class ExceptionAtPage(Exception):
+    """
+    Exception designed to be raised when the conversion of a page of
+    tweets taken from Mongo fails
+    """
+
+    def __init__(self, message: str, error_page: int):
+        """
+        :param message: str descriptive of the error
+        :param error_page: int indicating the number of page that failed
+        """
+
+        self.message = message
+        self.error_page = error_page
+
+
+class TweetConversionException(Exception):
+    """
+    Should be raised when a tweet raises an exception in the process of
+    being converted
+    """
+
+    def __init__(self, message: str, tweet: str):
+        """
+        :param message: str descriptive of the error
+        :param tweet: str with the contents of the tweet that caused the
+        failure
+        """
+        self.message = message
+        self.tweet = tweet

pymongoexport_csv.py

@@ -2,9 +2,11 @@
 
 import pymongo
 import os
+import sys
 import argparse
 import logging
 import time
+import json
 import multiprocessing as mp
 from config import globals
 from lib import utils
@@ -17,6 +19,7 @@ parser.add_argument("-p", "--port", type=int, default=27017)
 parser.add_argument("-s", "--pagesize", type=int, default=1000)
 parser.add_argument("-v", "--verbose", action="store_true")
 parser.add_argument("-t", "--timing", action="store_true")
+parser.add_argument("-r", "--recovery", type=str)
 parser.add_argument("database", type=str)
 args = parser.parse_args()
 
@@ -44,11 +47,30 @@ if args.timing:
     time0 = time.time()
 
 # MongoDB connection to get page index
-client = pymongo.MongoClient(args.host, args.port)
-database_tweets = client[args.database]["tweets"]
-page_index = utils.get_page_index(database_tweets, args.pagesize)
-client.close()
-logger.debug(
+if args.recovery:
+    with open(args.recovery) as f:
+        recovery_data = json.load(f)
+    client = pymongo.MongoClient(
+        recovery_data["host"], recovery_data["port"])
+    database_tweets = client[recovery_data["database"]]["tweets"]
+    full_page_index = utils.get_page_index(
+        database_tweets, recovery_data["pagesize"])
+    client.close()
+    page_index = [page for page in full_page_index
+                  if page not in recovery_data["dumped_pages"]]
+    if "error_page" in recovery_data:
+        logger.debug("Discarding corrupted page")
+        page_index.remove(recovery_data.pop("error_page"))
+    logger.debug(
+        "Resuming collection conversion. {} of {} pages left."
+        .format(len(page_index), len(full_page_index)))
+
+else:
+    client = pymongo.MongoClient(args.host, args.port)
+    database_tweets = client[args.database]["tweets"]
+    page_index = utils.get_page_index(database_tweets, args.pagesize)
+    client.close()
+    logger.debug(
         "Database {} partitioned in {} pages of {} tweets (maximum)"
         .format(args.database, len(page_index), args.pagesize))
 
@@ -65,17 +87,31 @@ def process_data_page(
 
 # Launch single process to write to the filesystem
 writer_worker = mp.Process(
-    target=utils.filesystem_writer, args=(task_queue, header, ))
+    target=utils.filesystem_writer,
+    args=(task_queue, header, args.host, args.port,
+          args.database, args.pagesize, output_dir, args.recovery))
 writer_worker.start()
 
 # Launch pool of workers to perform the format conversion
-with mp.Pool() as pool:
+try:
+    with mp.Pool() as pool:
         pool.map(process_data_page, page_index)
-task_queue.put("END")
+except utils.ExceptionAtPage as exc:
+    logger.error("Error detected at page {}".format(exc.error_page))
+    task_queue.put((exc.error_page, "ERROR"))
+    sys.exit(1)
+except (Exception, KeyboardInterrupt):
+    logger.error("Error detected")
+    task_queue.put((-2, "ERROR"))
+    sys.exit(1)
+
+task_queue.put((-1, "END"))
+
 
 if globals.timing:
     time1 = time.time()
 utils.generate_metadata_file(output_dir)
+logger.info("Metadata file created")
 if globals.timing:
     logger.critical(
         "Time spent generating metadata file: {}s"
@@ -83,3 +119,5 @@ if globals.timing:
     logger.critical(
         "Total execution time: {}s"
         .format(time.time() - time0))
+
+logger.info("Conversion completed successfully!!")