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Merge pull request xapi-project#2264 from jonludlam/CP-12513-for-trunk2
CP-12513: Give xapi the ability to manage xenvm daemons
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| Original file line number | Diff line number | Diff line change |
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| (* | ||
| * Copyright (C) 2015 Citrix Systems Inc. | ||
| * | ||
| * This program is free software; you can redistribute it and/or modify | ||
| * it under the terms of the GNU Lesser General Public License as published | ||
| * by the Free Software Foundation; version 2.1 only. with the special | ||
| * exception on linking described in file LICENSE. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU Lesser General Public License for more details. | ||
| *) | ||
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| (* | ||
| * Code to manage xenvmd | ||
| * | ||
| * This is a little bit of a layering violation. | ||
| * | ||
| *) | ||
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| module D=Debug.Make(struct let name="xapi_xenvmd" end) | ||
| open D | ||
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| (* Thrown if we'd like to start a xenvmd process but there's no config file for it *) | ||
| exception NoConfigFile | ||
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| (* This exception should be internal to this file *) | ||
| exception NoLockFile | ||
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| (* This is a bad exception. We never expect this to happen. *) | ||
| exception XenvmdFailed of string * string | ||
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| (* The storage backends know about these paths *) | ||
| let lockfile_path sr = Printf.sprintf "/var/lib/xenvmd/%s.lock" sr | ||
| let configfile_path sr = Printf.sprintf "/etc/xenvm.d/VG_XenStorage-%s.xenvmd.config" sr | ||
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||
| (* We need to be able to talk SMAPIv2 in order to find out which SRs | ||
| are currently attached to this host. For that, we need an RPC | ||
| function, a URL to talk to and the client module itself. *) | ||
|
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||
| let rpc x = | ||
| if !Xcp_client.use_switch | ||
| then Xcp_client.json_switch_rpc !(Storage_interface.queue_name) x | ||
| else Xcp_client.http_rpc Xmlrpc.string_of_call Xmlrpc.response_of_string ~srcstr:"xapi" ~dststr:"smapiv2" Storage_interface.uri x | ||
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| let local_url () = Http.Url.(Http { host="127.0.0.1"; auth=None; port=None; ssl=false }, { uri = "/services/SM"; query_params=["pool_secret",!Xapi_globs.pool_secret] } ) | ||
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| module SM = Storage_interface.Client(struct let rpc = rpc end) | ||
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| (******************************************************************************************) | ||
| (***** Helper functions *****) | ||
|
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| (* [assert_file_present file exn] will raise [exn] if [file] does not | ||
| exist *) | ||
| let assert_file_present file exn = | ||
| try | ||
| ignore(Unix.stat file) | ||
| with | ||
| | Unix.Unix_error (Unix.ENOENT, _, _) -> raise exn | ||
| | e -> raise e | ||
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| (* [get_cmdname pid] returns a string option of the name of the | ||
| executable corresponding to a running process *) | ||
| let get_cmdname pid = | ||
| try | ||
| Some (Unix.readlink (Printf.sprintf "/proc/%d/exe" pid) |> Filename.basename) | ||
| with e -> | ||
| info "Unable to read the /proc tree for pid (%d) - has the process already died?" pid; | ||
| None | ||
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| (* [check_is name x] is an internal function to test whether a value | ||
| [x] is equal to [name]. If so, returns 'Some x'. This is helpful | ||
| for using options in a monadic fashion. *) | ||
| let check_is name x = | ||
| if x=name | ||
| then Some x | ||
| else begin | ||
| info "check_is: expecting %s, got %s" name x; | ||
| None | ||
| end | ||
|
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| (****************************************************************************************) | ||
|
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| (* It is the responsibility of the SR backends to write the config | ||
| file for xenvmd. Only they know which devices xenvmd should be | ||
| talking to *) | ||
| let assert_config_present sr = assert_file_present (configfile_path sr) NoConfigFile | ||
|
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| (* [is_running sr] checks to see whether xenvmd is running for a | ||
| particular SR. It does this by attempting to lock the | ||
| pidfile. Xenvmd will itself lock the pidfile while it is up, so | ||
| xapi's attempt will fail if the process still exists. *) | ||
| let is_running sr = | ||
| debug "Checking for xenvmd running for sr: %s" sr; | ||
| try | ||
| let l = lockfile_path sr in | ||
| assert_file_present l NoLockFile; | ||
| let fd = Unix.openfile l [ Unix.O_WRONLY; Unix.O_CREAT ] 0o0644 in | ||
| Pervasiveext.finally | ||
| (fun () -> Unix.lockf fd Unix.F_TEST 1) | ||
| (fun () -> Unix.close fd); | ||
| debug "Locked successfully: xenvmd not running"; | ||
| false | ||
| with | ||
| | NoLockFile -> debug "Caught NoLockFile (xenvmd not running)"; false (* Lockfile missing *) | ||
| | Unix.Unix_error (Unix.EAGAIN, _, _) -> debug "Caught EAGAIN (xenvmd running)"; true (* Locked by xenvmd *) | ||
| | Unix.Unix_error (Unix.EACCES, _, _) -> debug "Caught EACCESS (xenvmd running)"; true (* Locked by xenvmd *) | ||
| | e -> raise e | ||
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| (* Verify that xenvmd is running for a particular SR. If xenvmd is not | ||
| running and a suitable config file exists, we'll start it. This | ||
| function is idempotent. *) | ||
| let start sr = | ||
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| (* Here we _actually_ start the xenvmd process *) | ||
| let really_start sr = | ||
| assert_config_present sr; | ||
| try | ||
| let output, stderr = Forkhelpers.execute_command_get_output !Xapi_globs.xenvmd_path | ||
| [ "--daemon"; "--config"; configfile_path sr ] in | ||
| (* Note that xenvmd will detect multiple copies of itself for the same VG. | ||
| it will write an error message to the stdout/stderr but exit with code | ||
| 0 *) | ||
| debug "Xenvmd started for SR %s. output='%s' stderr='%s'" sr output stderr | ||
| with | ||
| | Forkhelpers.Spawn_internal_error(log, output, x) -> | ||
| debug "Failed to execute xenvmd. log='%s' output='%s'" log output; | ||
| raise (XenvmdFailed (log, output)) | ||
| in | ||
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| let rec retry n = | ||
| try | ||
| if not (is_running sr) | ||
| then really_start sr | ||
| with | ||
| | XenvmdFailed _ as e -> | ||
| if n = 0 then raise e; | ||
| Thread.delay 5.0; | ||
| retry (n-1) | ||
| | NoConfigFile -> | ||
| debug "No config file for SR=%s - assuming not thin-lvhd" sr; | ||
| in | ||
| retry 5 | ||
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| (* Let's try _really hard_ and _really carefully_ to kill xenvmd. First we read the | ||
| pidfile to find the pid, then we check to see that that pid corresponds to xenvmd. | ||
| Then we try once to sigterm it, and 5 more times to sigkill it. *) | ||
| let stop sr = | ||
| let open Opt.Monad in | ||
| let rec inner signal n = | ||
| try | ||
| info "Stopping xenvmd for SR uuid: %s" sr; | ||
| Unixext.pidfile_read (lockfile_path sr) >>= fun pid -> | ||
| get_cmdname pid >>= | ||
| check_is "xenvmd" >>= fun _ -> | ||
| Unixext.kill_and_wait ~signal pid; | ||
| None | ||
| with | ||
| | Unixext.Process_still_alive -> | ||
| if n=0 then begin | ||
| error "Failed to kill xenvm process for sr '%s' despite repeated attempts. Giving up." sr; | ||
| None | ||
| end else begin | ||
| warn "xenvmd is still alive. Trying to kill it again (with sigkill this time)."; | ||
| inner Sys.sigkill (n-1) | ||
| end | ||
| in | ||
| ignore (inner Sys.sigterm 5) | ||
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| (* The following functions are used on master transition *) | ||
|
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| let operate_on_shared_srs op = | ||
| let attached_srs = SM.SR.list ~dbg:"xapi_xenvmd" in | ||
| Server_helpers.exec_with_new_task "Xapi_xenvmd: Managing xenvmd instances" (fun __context -> | ||
| let shared_srs = List.filter (fun uuid -> | ||
| let self = Db.SR.get_by_uuid ~__context ~uuid in | ||
| Db.SR.get_shared ~__context ~self) attached_srs in | ||
| List.iter op shared_srs) | ||
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| (* Called on transition to slave, on the way down *) | ||
| (* We must assume we're a slave, so not the SR master for any shared SRs *) | ||
| let kill_non_sr_master_xenvmds () = operate_on_shared_srs stop | ||
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| (* Start xenvmd for shared SRs *) | ||
| let start_xenvmds_for_shared_srs () = operate_on_shared_srs start | ||
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|