Added rate limiting functionality. Not tested as things ran just fine for the 1700 trials I downloaded.

history_downloader/downloader.py

@@ -3,8 +3,9 @@ import requests
 import psycopg2 as psyco
 from datetime import datetime
 from bs4 import BeautifulSoup
-
-from multiprocessing import Pool
+from multiprocessing import Pool, Value
+import math
+import time
 
 
 def get_highest_version_number(response):
@@ -25,7 +26,6 @@ def get_highest_version_number(response):
     for row in reversed(table_rows):
         # if it is <td headers="VersionNumber">xx</td> then it contains what we need.
         for td in row.findChildren("td"):
-            print("\n", td)
             if ("headers" in td.attrs) and (td.attrs["headers"][0]=="VersionNumber"):
                 #Note the use of [0] above. attribute elements are lists.
                 version_number = int(td.text)
@@ -69,26 +69,52 @@ def upload_response(db_cursor, nct_id, version_a, version_b, response):
         )
     ) 
 
-def download_and_handle_errors(cursor, nct_id, version_a, version_b):
+def download_and_handle_errors(cursor, nct_id, version_a, version_b, delay_time, reset_time):
     """
     Request a page, checking for http error codes, and handle the errors as requested.
     """
+    #sleep log10(counts of delays)
+    time.sleep(math.log10(delay_time.value))
+
     #request page
     r = make_request(nct_id, version_a, version_b)
     #check for 
     if r.status_code == 200:
         upload_response(cursor,nct_id,version_a, version_b, r)
+    elif r.status_code == 503:
+        # write http code to http.responses
+        upload_response(cursor, nct_id, version_a, version_b, r)
+        # write incomplete to http.download_status
+        write_incomplete(cursor,nct_id)
+        # tell all other processes to slow down the request speed
+        delay_time.value += 1
+        # Delay
+        print("Recieved 503 on {}, increasing delay count to {}".format(nct_id, delay_tiome))
+        time.sleep(reset_time)
     else:
         #TODO: this should handle errors by
-        #  - [ ] write http code to http.responses
-        #  - [ ] write incomplete to http.download_status
-        #  - [ ] tell all other processes to slow down the request speed
-        #  - [x] raise exception
-        raise Exception("Download of {} (versions {},{}) returned http code != 200".format(nct_id,version_a,version_b))
+        # write http code to http.responses
+        upload_response(cursor, nct_id, version_a, version_b, r)
+        # write incomplete to http.download_status
+        write_incomplete(cursor,nct_id)
+        # raise exception
+        #raise Exception("Download of {} (versions {},{}) returned http code {}".format(nct_id,version_a,version_b, r.status_code))
     
+        # Delay
+        time.sleep(reset_time)
     return r
 
-def download_trial_records(nct_id, db_connection_specs):
+def write_incomplete(cursor, nct_id):
+    """
+    Flags a trial as not having been fully downloaded.
+    """
+    query = """
+    INSERT INTO HTTP.DOWNLOAD_STATUS (NCT_ID,STATUS)
+        %s, 'Incomplete'::HTTP.HISTORY_DOWNLOAD_STATUS
+    """
+    cursor.execute(query, [nct_id] )
+
+def download_trial_records(nct_id, db_connection_specs, delay_time, reset_time):
     """
     Manage the download of all records associated with a given trial.
     It uses a single connection and cursor for downloading the entire trial.
@@ -108,7 +134,7 @@ def download_trial_records(nct_id, db_connection_specs):
         with db_conn.cursor() as cursor:
 
             #upload the first two versions
-            r = download_and_handle_errors(cursor, nct_id, 1, 2)
+            r = download_and_handle_errors(cursor, nct_id, 1, 2, delay_time, reset_time)
             #extract last version
             v = get_highest_version_number(r)
 
@@ -119,13 +145,13 @@ def download_trial_records(nct_id, db_connection_specs):
             elif v % 2 == 0:
                 for version_a, version_b in step_generator(v):
                     #download the history, handling any errors as they come up, and submitting it to the database.
-                    download_and_handle_errors(cursor, nct_id, version_a, version_b)
+                    download_and_handle_errors(cursor, nct_id, version_a, version_b, delay_time, reset_time)
             elif v % 2 == 1:
                 #if there are an odd number of submissions treat at as even
                 for version_a, version_b in step_generator(v):
-                    download_and_handle_errors(cursor, nct_id, version_a, version_b)
+                    download_and_handle_errors(cursor, nct_id, version_a, version_b, delay_time, reset_time)
                 #now handle an odd number of versions by downloading the 1 vs (end) comparison.
-                download_and_handle_errors(cursor, nct_id, 1, v)
+                download_and_handle_errors(cursor, nct_id, 1, v, delay_time, reset_time)
 
             #now mark the trial as having been downloaded
             cursor.execute(
@@ -229,26 +255,27 @@ if __name__ == "__main__":
     dbc = DBConnectionCreator(
             dbname="aact_db"
             ,user="python_downloader"
-            ,host="localhost"
+            ,host="will-office"
             ,port=5432
             ,password="download")
     
-    #lambda that parameterizes the downloader, allowing it to be passed to the pool.
-    def downloader(nct):
-        download_trial_records(nct, dbc)
 
     #db connection
     with dbc.new() as con:
-        #select lists to download
-        #flag_trials_of_interest(con) #SHould only be run once
-
 
         #get list of nct_ids
-        nctids = reserve_trials(con, 10)
+        nctids = reserve_trials(con, 1500)
         print(nctids)
 
+    
+    reset_time = 10
+    delay_time = Value("I",1)
+    #lambda that parameterizes the downloader, allowing it to be passed to the pool.
+    def downloader(nct):
+        download_trial_records(nct, dbc, delay_time, reset_time)
+
         #start analyzing them
-    with Pool(processes=4) as process_pool:
+    with Pool(processes=12) as process_pool:
         process_pool.map(downloader, nctids)