albatross/app/vmmd_log.ml

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(* (c) 2017 Hannes Mehnert, all rights reserved *)
(* the process responsible for event log *)
(* communication channel is a single unix domain socket shared between vmmd and
vmm_log. There are two commands from vmmd to vmm_log, history and data. *)
(* internally, a ring buffer for the last N events is preserved in memory
each new event is directly written to disk! *)
open Lwt.Infix
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let my_version = `AV2
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let broadcast prefix wire t =
Lwt_list.fold_left_s (fun t (id, s) ->
Vmm_lwt.write_wire s wire >|= function
| Ok () -> t
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| Error `Exception -> Vmm_trie.remove id t)
t (Vmm_trie.collect prefix t)
let write_complete s cs =
let l = Cstruct.len cs in
let b = Cstruct.to_bytes cs in
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let rec w off =
let len = l - off in
Lwt_unix.write s b off len >>= fun n ->
if n = len then Lwt.return_unit else w (off + n)
in
w 0
let read_from_file file =
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Vmm_lwt.read_from_file file >|= fun data ->
let logs = Vmm_asn.logs_of_disk my_version data in
List.rev logs
let write_to_file file =
let mvar = Lwt_mvar.create_empty () in
let rec write_loop ?(retry = true) ?log_entry ?fd () =
match fd with
| None when retry ->
Lwt_unix.openfile file Lwt_unix.[O_APPEND;O_CREAT;O_WRONLY] 0o600 >>= fun fd ->
write_loop ~retry:false ?log_entry ~fd ()
| None ->
Logs.err (fun m -> m "retry is false, exiting") ;
Lwt.return_unit
| Some fd ->
(match log_entry with
| None -> Lwt_mvar.take mvar
| Some l -> Lwt.return l) >>= fun log_entry ->
let data = Vmm_asn.log_to_disk my_version log_entry in
Lwt.catch
(fun () -> write_complete fd data >|= fun () -> (true, None, Some fd))
(fun e ->
Logs.err (fun m -> m "exception %s while writing" (Printexc.to_string e)) ;
Vmm_lwt.safe_close fd >|= fun () ->
(retry, Some log_entry, None)) >>= fun (retry, log_entry, fd) ->
write_loop ~retry ?log_entry ?fd ()
in
mvar, write_loop
let send_history s ring id ts =
let elements =
match ts with
| None -> Vmm_ring.read ring
| Some since -> Vmm_ring.read_history ring since
in
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let res =
List.fold_left (fun acc (ts, event) ->
let sub = Vmm_core.Log.name event in
if Vmm_core.Name.is_sub ~super:id ~sub
then (ts, event) :: acc
else acc)
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[] elements
in
(* just need a wrapper in tag = Log.Data, id = reqid *)
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Lwt_list.fold_left_s (fun r (ts, event) ->
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match r with
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| Ok () ->
let header = Vmm_commands.{ version = my_version ; sequence = 0L ; name = id } in
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Vmm_lwt.write_wire s (header, `Data (`Log_data (ts, event)))
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| Error e -> Lwt.return (Error e))
(Ok ()) (List.rev res)
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let tree = ref Vmm_trie.empty
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let handle_data s mvar ring hdr entry =
if not (Vmm_commands.version_eq hdr.Vmm_commands.version my_version) then begin
Logs.warn (fun m -> m "unsupported version") ;
Lwt.return_unit
end else begin
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Vmm_lwt.write_wire s (hdr, `Success `Empty) >>= fun _ ->
Vmm_ring.write ring entry ;
Lwt_mvar.put mvar entry >>= fun () ->
let data' = (hdr, `Data (`Log_data entry)) in
broadcast hdr.Vmm_commands.name data' !tree >|= fun tree' ->
tree := tree'
end
let read_data mvar ring s =
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let rec loop () =
Vmm_lwt.read_wire s >>= function
| Error _ ->
Logs.err (fun m -> m "error while reading") ;
Lwt.return_unit
| Ok (hdr, `Data (`Log_data entry)) ->
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handle_data s mvar ring hdr entry >>= fun () ->
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loop ()
| Ok wire ->
Logs.warn (fun m -> m "unexpected wire %a" Vmm_commands.pp_wire wire) ;
Lwt.return_unit
in
loop ()
let handle mvar ring s addr () =
Logs.info (fun m -> m "handling connection from %a" Vmm_lwt.pp_sockaddr addr) ;
Vmm_lwt.read_wire s >>= begin function
| Error _ ->
Logs.err (fun m -> m "error while reading") ;
Lwt.return_unit
| Ok (hdr, `Data (`Log_data entry)) ->
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handle_data s mvar ring hdr entry >>= fun () ->
read_data mvar ring s
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| Ok (hdr, `Command (`Log_cmd lc)) ->
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if not (Vmm_commands.version_eq hdr.Vmm_commands.version my_version) then begin
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Logs.warn (fun m -> m "unsupported version") ;
Lwt.return_unit
end else begin
match lc with
| `Log_subscribe ts ->
let tree', ret = Vmm_trie.insert hdr.Vmm_commands.name s !tree in
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tree := tree' ;
(match ret with
| None -> Lwt.return_unit
| Some s' -> Vmm_lwt.safe_close s') >>= fun () ->
let out = `Success `Empty in
Vmm_lwt.write_wire s (hdr, out) >>= function
| Error _ -> Logs.err (fun m -> m "error while sending reply for subscribe") ;
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Lwt.return_unit
| Ok () ->
send_history s ring hdr.Vmm_commands.name ts >>= function
| Error _ -> Logs.err (fun m -> m "error while sending history") ; Lwt.return_unit
| Ok () ->
(* command processing is finished, but we leave the socket open
until read returns (either with a message we ignore or a failure from the closed connection) *)
Vmm_lwt.read_wire s >|= fun _ -> ()
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end
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| Ok wire ->
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Logs.warn (fun m -> m "ignoring %a" Vmm_commands.pp_wire wire) ;
Lwt.return_unit
end >>= fun () ->
Vmm_lwt.safe_close s
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let jump _ file sock =
Sys.(set_signal sigpipe Signal_ignore) ;
Lwt_main.run
((Lwt_unix.file_exists sock >>= function
| true -> Lwt_unix.unlink sock
| false -> Lwt.return_unit) >>= fun () ->
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let s = Lwt_unix.(socket PF_UNIX SOCK_STREAM 0) in
Lwt_unix.(bind s (ADDR_UNIX sock)) >>= fun () ->
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Lwt_unix.listen s 1 ;
let ring = Vmm_ring.create `Startup () in
read_from_file file >>= fun entries ->
List.iter (Vmm_ring.write ring) entries ;
let mvar, writer = write_to_file file in
let start = Ptime_clock.now (), `Startup in
Lwt_mvar.put mvar start >>= fun () ->
Vmm_ring.write ring start ;
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let rec loop () =
Lwt_unix.accept s >>= fun (cs, addr) ->
Lwt.async (handle mvar ring cs addr) ;
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loop ()
in
Lwt.pick [ loop () ; writer () ]) ;
`Ok ()
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open Cmdliner
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open Vmm_cli
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let socket =
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let doc = "socket to use" in
Arg.(value & opt string (Vmm_core.socket_path `Log) & info [ "socket" ] ~doc)
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let file =
let doc = "File to write the log to" in
Arg.(value & opt string "/var/log/albatross" & info [ "logfile" ] ~doc)
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let cmd =
Term.(ret (const jump $ setup_log $ file $ socket)),
Term.info "vmm_log" ~version:"%%VERSION_NUM%%"
let () = match Term.eval cmd with `Ok () -> exit 0 | _ -> exit 1