As Dave says, you can do this using line-seq, but you'll have to
accumulate some state as you read the lines so you can return all the
lines for a given thread's ReqStart to ReqEnd. Once you've returned
that block, you can delete the state for that thread-id, so your
accumulated state will only contain the 'active' requests. If you're
processing a very large file, you're best returning a lazy sequence of
the data.
Something like this should get you started:
(require [clojure.java.io :as io])
(defn parse-line
[s]
(let [[_ thread_id tag value] (re-find #"^(\d+)\s+(\S+)\s+(.+)$" s)]
[thread_id tag value]))
(defn parse-lines
([lines]
(parse-lines lines {}))
([lines state]
(lazy-seq
(when (seq lines)
(let [[thread-id tag value] (parse-line (first lines))
state (assoc-in state [thread-id tag]
(conj (get-in state [thread-id tag] []) value))]
(if (= tag "ReqEnd")
(cons (get state thread-id) (parse-lines (rest lines)
(dissoc state thread-id)))
(parse-lines (rest lines) state)))))))
(defn parse-log-file
[file]
(with-open [logfile (io/reader file)]
(doall
(filter #(and (get % "ReqStart") (get % "ReqEnd"))
(parse-lines (line-seq logfile))))))
On 21 October 2012 02:54, Dave <d...@sevenventures.net> wrote:
> Clojurists - I'm fairly new to Clojure and didn't realize how broken I've
> become using imperative languages all my life. I'm stumped as to how to
> parse a Varnish (www.varnish-cache.org) log file using Clojure. The main
> problem is that for a single request a varnish log file generates multiple
> log lines and each line is interspersed with lines from other threads.
> These log files can be several gigabytes in size (so using a stable sort of
> the entire log by thread id is out of the question).
>
> Below I've included a small example log file and an example output Clojure
> data structure. Let me thank everyone in advance for any hints / help they
> can provide on this seemingly simple problem.
>
> Rules of the Varnish Log File
>
> The first number on each line is the thread id (not unique and gets reused
> frequently)
> Each ReqStart marks the start of a request and the last number on the line
> is the unique transaction id (e.g. 118591777)
> ReqEnd denote the end of the processing of the request by the thread
> Each line is atomically written, however many threads generate log lines
> that are interspersed with other requests (threads)
> These log files can be VERY large (10+ Gigabytes in the case of my
> application) so using a stable sort by thread id or anything that loads the
> entire file into memory is out of the question.
>
>
> Example Varnish Log file
> 40 ReqEnd c 118591771 1350759605.775758028 1350759611.249602079
> 5.866879225 5.473801851 0.000042200
> 15 ReqStart c 10.102.41.121 4187 118591777
> 15 RxRequest c GET
> 15 RxURL c /json/engagement
> 15 RxHeader c host: www.example.com
> 30 ReqStart c 10.102.41.121 3906 118591802
> 15 RxHeader c Accept: application/json
> 30 RxRequest c GET
> 30 RxURL c /ws/boxtops/user/
> 30 RxHeader c host: www.example.com
> 15 ReqEnd c 118591777 1350759605.775758028 1350759611.249602079
> 5.866879225 5.473801851 0.000042200
> 30 RxHeader c Accept: application/xml
> 30 ReqEnd c 118591802 1350759611.326084614 1350759611.329720259
> 0.005002737 0.003598213 0.000037432
> 15 ReqStart c 10.102.41.121 4187 118591808
> 15 RxRequest c GET
> 15 RxURL c /ws/boxtops/user/
> 30 ReqStart c 10.102.41.121 3906 118591810
> 15 RxHeader c host: www.example.com
> 15 RxHeader c Accept: application/xml
> 30 RxRequest c GET
> 30 RxURL c /registration/success
> 30 RxHeader c host: www.example.com
> 46 TxRequest - GET
> 30 RxHeader c Accept: text/html
> 46 TxURL - /registration/success
> 15 ReqEnd c 118591808 1350759611.442447424 1350759611.444925785
> 0.016906023 0.002441406 0.000036955
> 30 ReqEnd c 118591810 1350759611.521781683 1350759611.525400877
> 0.098322868 0.003532171 0.000087023
>
> Desired Output
> {
> 118591802
> { :ReqStart ["10.102.41.121 3906 118591802"]
> :RxRequest ["GET"]
> :RxURL ["/ws/boxtops/user/"]
> :RxHeader ["host: www.example.com" "Accept: application/xml"]
> or better yet
> :RxHeader {:host "www.example.com" :Accept "application/xml"}
> :ReqEnd ["118591802 1350759611.326084614 1350759611.329720259
> 0.005002737 0.003598213 0.000037432"] }
> 118591777
> { :ReqStart ["10.102.41.121 4187 118591777"]
> :RxRequest ["GET"]
> :RxURL ["/json/engagement"]
> :RxHeader ["host: www.example.com" "Accept: application/json"]
> :ReqEnd ["118591777 1350759605.775758028 1350759611.249602079
> 5.866879225 5.473801851 0.000042200" ]}
> 118591808
> { :ReqStart [10.102.41.121 4187 118591808]
> :RxRequest ["GET"]
> :RxURL ["/ws/boxtops/user/"]
> :RxHeader ["host: www.example.com" "Accept: application/xml"]
> :ReqEnd ["118591808 1350759611.442447424 1350759611.444925785
> 0.016906023 0.002441406 0.000036955"] }
> 118591810
> { :ReqStart ["10.102.41.121 3906 118591810"]
> :RxRequest ["GET"]
> :RxURL ["/registration/success"]
> :RxHeader ["host: www.example.com" "Accept: text/html]
> :ReqEnd ["118591810 1350759611.521781683 1350759611.525400877
> 0.098322868 0.003532171 0.000087023"] }
> }
>
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