multithreading - F# MailboxProcessor questions -

i've created console program using code http://fssnip.net/3k. , found that

1. i'd add "system.console.readline() |> ignore" @ end wait finish of threads. possible tell mailboxprocessors done , program can exit itself?

2. i tried change test url "www.google.com" invalid url , got following output. possible avoid "outputting race"?

      http://www.google.co1m crawled agent 1.        agaaaent gent 3 done.        gent 2 done.        5 done.        gent 4 done.        agent usupervisor rl collector done.        done.        1 done. 

[edit]

the last output/crawling still terminated after using tomas's update http://fssnip.net/65. following output of program after changed "limit" 5 , added debugging messages. last line shows truncated url. way detect if crawlers finish execution?

[main] before crawl [crawl] before return result http://news.google.com crawled agent 1. [supervisor] reached limit http://www.gstatic.com/news/img/favicon.ico crawled agent 5. agent 2 done. [supervisor] reached limit agent 5 done. http://www.google.com/imghp?hl=en&tab=ni crawled agent 3. [supervisor] reached limit agent 3 done. http://www.google.com/webhp?hl=en&tab=nw crawled agent 4. [supervisor] reached limit agent 4 done. http://news.google.com/n 

i changed main code

printfn "[main] before crawl" crawl "http://news.google.com" 5 |> async.runsynchronously printfn "[main] after crawl" 

however, last printfn "[main] after crawl" never executed, unless add console.readline() @ end.

[edit 2]

the code runs fine under fsi. have same problem if run using fsi --use:program.fs --exec --quiet

i created snippet extends previous 1 2 features asked about: http://fssnip.net/65.

1. to solve this, added start message carries asyncreplychannel<unit>. when supervisor agent starts, waits message , saves reply channel later use. when completes, sends reply using channel.

   the function starts agent returns asynchronous workflow waits reply. can call crawl using async.runsynchronously, complete when supervisor agent completes.

2. to avoid race when printing, need synchronize prints. easiest way write new agent :-). agent receives strings , prints them output 1 one (so cannot interleaved). snippet hides standard printfn function new implementation sends strings agent.