X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FMain.hs;h=1b7458fe880c83463038abbc2de73be16f3d09ff;hb=a2c2a1a6865be7b4cd17fb72de635bb9385728b9;hp=829440ec35fa1a364d11a6b9605edf866df0bd94;hpb=d4d924b26e451aec9ad84b6d9d376ba2aeab3422;p=dead%2Fhtsn.git diff --git a/src/Main.hs b/src/Main.hs index 829440e..1b7458f 100644 --- a/src/Main.hs +++ b/src/Main.hs @@ -5,9 +5,8 @@ module Main where import Control.Concurrent (threadDelay) -import Control.DeepSeq (deepseq) import Control.Exception.Base (bracket) -import Control.Monad (forever, when) +import Control.Monad (when) import Data.List (isPrefixOf) import Data.Maybe (isNothing) import Data.Monoid ((<>)) @@ -29,6 +28,7 @@ import System.IO ( stderr, stdout ) import System.IO.Error (catchIOError) +import System.Timeout (timeout) import CommandLine (get_args) import Configuration (Configuration(..), merge_optional) @@ -36,18 +36,17 @@ import ExitCodes ( exit_no_feed_hosts, exit_no_password, exit_no_username ) -import FeedHosts (FeedHosts(..)) import qualified OptionalConfiguration as OC ( OptionalConfiguration(..), from_rc ) -import Terminal (hPutRedLn, putGreenLn) +import Terminal (putGreenLn, report_error) +import TSN.FeedHosts (FeedHosts(..)) import TSN.Xml (parse_xmlfid, xml_prologue) -report_error :: String -> IO () -report_error = hPutRedLn stderr - - +-- | Receive a single line of text from a Handle, echoing it to stdout +-- in the process. +-- recv_line :: Handle -> IO String recv_line h = do line <- hGetLine h @@ -55,8 +54,15 @@ recv_line h = do return line +-- | Takes a Configuration, and an XML document (as a String). The XML +-- document is written to the output directory, as specified by the +-- Configuration. +-- +-- This can fail, but we don't purposefully throw any exceptions. If +-- something goes wrong, we would rather log it and keep going. +-- save_document :: Configuration -> String -> IO () -save_document cfg doc = do +save_document cfg doc = case maybe_path of Nothing -> report_error "ERROR: document missing XML_File_ID element." @@ -71,8 +77,11 @@ save_document cfg doc = do filename = fmap (++ ".xml") xmlfid maybe_path = fmap ((output_directory cfg) ) filename + -- | Loop forever, writing the buffer to file whenever a new XML --- prologue is seen. +-- prologue is seen. This is the low-level "loop forever" function +-- that we stay in as long as we are connected to one feed. +-- loop :: Configuration -> Handle -> [String] -> IO () loop !cfg !h !buffer = do line <- recv_line h @@ -87,7 +96,8 @@ loop !cfg !h !buffer = do save_document cfg document loop cfg h [line] -- empty the buffer before looping again else - loop cfg h (line : buffer) -- append line to the head of the buffer and loop + -- append line to the head of the buffer and loop + loop cfg h (line : buffer) log_in :: Configuration -> Handle -> IO () @@ -104,8 +114,8 @@ log_in cfg h = do report_error "ERROR: didn't receive password prompt." else do send_line h (password cfg) - banner <- recv_line h -- "The Sports Network" - banner `deepseq` return () + _ <- recv_line h -- "The Sports Network" + return () where username_prompt = "Username: " password_prompt = "Password: " @@ -124,29 +134,46 @@ log_in cfg h = do recv_prompt :: Handle -> IO String recv_prompt = recv_chars 10 -connect_and_loop :: Configuration -> IO () -connect_and_loop cfg = +connect_and_loop :: Configuration -> String -> IO () +connect_and_loop cfg host = do + putStrLn $ "Connecting to " ++ host ++ "..." bracket acquire_handle release_handle action + return () where - --acquire_handle = connectTo "feed1.sportsnetwork.com" (PortNumber 4500) - acquire_handle = connectTo "feed2.sportsnetwork.com" (PortNumber 4500) - --acquire_handle = connectTo "127.0.0.1" (PortNumber 13337) + five_seconds :: Int + five_seconds = 5000000 + + acquire_handle = connectTo host (PortNumber 4500) release_handle = hClose action h = do -- No buffering anywhere. hSetBuffering h NoBuffering - log_in cfg h - loop cfg h [] + + -- The feed is often unresponsive after we send out username. It + -- happens in a telnet session, too (albeit less frequently?), + -- so there might be a bug on their end. + -- + -- If we dump the packets with tcpdump, it looks like their + -- software is getting confused: they send us some XML in + -- the middle of the log-in procedure. In any case, the easiest + -- fix is to disconnect and try again. + -- + login_worked <- timeout five_seconds $ log_in cfg h + case login_worked of + Nothing -> putStrLn "Login timed out (5s)." + Just _ -> loop cfg h [] -- | A wrapper around threadDelay which takes seconds instead of -- microseconds as its argument. +-- thread_sleep :: Int -> IO () thread_sleep seconds = do let microseconds = seconds * (10 ^ (6 :: Int)) threadDelay microseconds +-- | The entry point of the program. main :: IO () main = do rc_cfg <- OC.from_rc @@ -156,6 +183,10 @@ main = do -- prefering the command-line ones. let opt_config = rc_cfg <> cmd_cfg + -- This is necessary because if the user specifies an empty list of + -- hostnames in e.g. the config file, we want to bail rather than + -- fall back on the default list (which gets merged from a + -- Configuration below). when (null $ get_feed_hosts (OC.feed_hosts opt_config)) $ do report_error "ERROR: no feed hosts supplied." exitWith (ExitFailure exit_no_feed_hosts) @@ -172,9 +203,25 @@ main = do -- set in either the config file or on the command-line. let cfg = (def :: Configuration) `merge_optional` opt_config + -- This may be superstition (and I believe stderr is unbuffered), + -- but it can't hurt. hSetBuffering stderr NoBuffering hSetBuffering stdout NoBuffering - forever $ do - catchIOError (connect_and_loop cfg) (report_error . show) - thread_sleep 10 -- Wait 10s before attempting to reconnect. + -- Begin connecting to our feed hosts, starting with the first one. + round_robin cfg 0 + + where + -- | This is the top-level "loop forever" function. If an + -- exception is thrown, it will propagate up to this point, where + -- it will be logged and ignored in style. + -- + -- Afterwards, we recurse (call ourself) again to loop more forevers. + -- + round_robin :: Configuration -> Int -> IO () + round_robin cfg feed_host_idx = do + let hosts = get_feed_hosts $ feed_hosts cfg + let host = hosts !! feed_host_idx + catchIOError (connect_and_loop cfg host) (report_error . show) + thread_sleep 10 -- Wait 10s before attempting to reconnect. + round_robin cfg $ (feed_host_idx + 1) `mod` (length hosts)