From e42840a41fef273525abea06fb858eb530765b7e Mon Sep 17 00:00:00 2001
From: Yuanle Song <sylecn@gmail.com>
Date: Mon, 7 Sep 2015 20:52:08 +0800
Subject: [PATCH] support print out slow requests using -g param

---
 src/Main.hs | 49 ++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/src/Main.hs b/src/Main.hs
index 8358dd8..258a3c1 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -15,13 +15,18 @@ import qualified Options.Applicative as O
 import Data.Time.Clock (getCurrentTime, diffUTCTime)
 import Text.Printf (printf)
 
+import Data.ByteString.Char8 (pack, unpack)
+
 data AccessLog = AccessLog { clientIp :: ByteString
                            , datetime :: ByteString
                            , requestVerb :: ByteString
                            , requestPath :: ByteString
                            , statusCode :: Int
                            , browser :: ByteString
-                           , responseTime :: Int} deriving (Show)
+                           , responseTime :: Int}
+
+instance Show AccessLog where
+    show (AccessLog clientIp datetime requestVerb requestPath statusCode browser responseTime) = printf "%s [%s] \"%s %s\" %s %s %s" (unpack clientIp) (unpack datetime) (unpack requestVerb) (unpack requestPath) (show statusCode) (unpack browser) (show responseTime)
 
 ---------------
 -- log parsing
@@ -92,7 +97,8 @@ logParser = many $ parseLine <* endOfLine
 -- command line argument handling
 ----------------------------------
 
-data AppArguments = AppArguments { inputFile :: String }
+data AppArguments = AppArguments { inputFile :: String
+                                 , slowRequestDuration :: Maybe String}
 
 argumentParser :: O.Parser AppArguments
 argumentParser = AppArguments
@@ -100,7 +106,12 @@ argumentParser = AppArguments
                      (long "input"
                       <> short 'i'
                       <> metavar "ACCESS_LOG_FILE"
-                      <> help "the access filename to parse")
+                      <> help "The access log filename to parse")
+                 <*> (optional $ strOption
+                      (long "gt"
+                       <> short 'g'
+                       <> metavar "DURATION"
+                       <> help "Print requests that take longer than DURATION, duration could have a suffix of us, ms, s. Default suffix is s."))
 
 parseArguments :: IO AppArguments
 parseArguments = execParser opts
@@ -110,6 +121,29 @@ parseArguments = execParser opts
                <> progDesc "parse apache2 access log"
                <> header "a2p - parse apache2 access log")
 
+durationParser :: Parser (Int, String)
+durationParser = do
+  number <- decimal
+  suffix <- nonEmpty
+  return (number, unpack suffix)
+
+parseDuration :: ByteString -> Either String (Int, String)
+parseDuration = parseOnly durationParser
+
+-- | convert a duration string to microseconds.
+-- if there is no suffix, default is seconds.
+-- supported suffix are us (microseconds), ms (milliseconds) and s (seconds)
+toMicroseconds :: String -> Int
+toMicroseconds duration =
+    case parseDuration (pack duration) of
+      Left msg -> error ("Invalid duration: " ++ duration)
+      Right (number, unit) -> number * unitValue unit where
+                                -- convert it to microseconds
+                                unitValue "us" = 1
+                                unitValue "ms" = 1000
+                                unitValue "s" = 1000000
+                                unitValue "" = 1000000
+
 parseFile :: AppArguments -> IO ()
 parseFile args = do
   let filename = inputFile args
@@ -128,6 +162,15 @@ parseFile args = do
       else
           printf "parsed %d lines in %d seconds. (%d line/s)\n"
                  linesParsed duration (linesParsed `div` duration)
+      -- print slow requests if -g is used.
+      case slowRequestDuration args of
+        Nothing -> return ()
+        Just str -> do
+          let durationMicroseconds = toMicroseconds str
+          printf "== requests that take longer than %dus ==\n"
+                 durationMicroseconds
+          mapM_ print
+                (filter (\log -> responseTime log >= durationMicroseconds) logs)
 
 main :: IO ()
 main = parseArguments >>= parseFile
-- 
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