diff options
Diffstat (limited to 'modules/watchdog/watchdog.lua')
| -rw-r--r-- | modules/watchdog/watchdog.lua | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/modules/watchdog/watchdog.lua b/modules/watchdog/watchdog.lua new file mode 100644 index 0000000..6d50be2 --- /dev/null +++ b/modules/watchdog/watchdog.lua @@ -0,0 +1,129 @@ +-- SPDX-License-Identifier: GPL-3.0-or-later +local ffi = require('ffi') + +ffi.cdef([[ + int sd_watchdog_enabled(int unset_environment, uint64_t *usec); + int sd_notify(int unset_environment, const char *state); + void abort(void); +]]) + +local watchdog = {} +local private = {} + +local function sd_signal_ok() + ffi.C.sd_notify(0, 'WATCHDOG=1') +end + +function private.fail_callback() + log_error(ffi.C.LOG_GRP_WATCHDOG, 'ABORTING resolver, supervisor is expected to restart it') + ffi.C.abort() +end + +-- logging +local function add_tracer(logbuf) + return function (req) + local function qrylogger(_, msg) + jit.off(true, true) -- JIT for (C -> lua)^2 nesting isn't allowed + table.insert(logbuf, ffi.string(msg)) + end + req.trace_log = ffi.cast('trace_log_f', qrylogger) + end +end + +local function check_answer(logbuf) + return function (pkt, req) + req.trace_log:free() + if pkt ~= nil and (pkt:rcode() == kres.rcode.NOERROR + or pkt:rcode() == kres.rcode.NXDOMAIN) then + private.ok_callback() + return + end + log_info(ffi.C.LOG_GRP_WATCHDOG, 'watchdog query returned unexpected answer! query log:') + log_info(ffi.C.LOG_GRP_WATCHDOG, table.concat(logbuf, '')) + if pkt ~= nil then + log_info(ffi.C.LOG_GRP_WATCHDOG, 'problematic answer:\n%s', pkt) + else + log_info(ffi.C.LOG_GRP_WATCHDOG, 'answer was dropped') + end + -- failure! quit immediately to allow process supervisor to restart us + private.fail_callback() + end +end +private.check_answer_callback = check_answer + +local function timer() + local logbuf = {} + -- fire watchdog query + if private.qname and private.qtype then + log_info(ffi.C.LOG_GRP_WATCHDOG, 'starting watchdog query %s %s', private.qname, private.qtype) + resolve(private.qname, + private.qtype, + kres.class.IN, + {'TRACE'}, + private.check_answer_callback(logbuf), + add_tracer(logbuf)) + else + private.ok_callback() + end +end + +function watchdog.config(cfg) + -- read only + if not cfg then + return private + end + + local interval = tonumber(cfg.interval or private.interval or 10000) + if not interval or interval < 1 then + error('[watchdog] interval must be >= 1 ms') + end + private.interval = interval + + -- qname = nil will disable DNS queries + private.qname = cfg.qname + private.qtype = cfg.qtype or kres.type.A + + -- restart timers + watchdog.deinit() + private.event = event.recurrent(private.interval, timer) + return private +end + +-- automatically enable watchdog if it is configured in systemd +function watchdog.init() + if private.event then + error('[watchdog] module is already loaded') + end + local timeoutptr = ffi.new('uint64_t[1]') + local systemd_present, ret = pcall(function() return ffi.C.sd_watchdog_enabled(0, timeoutptr) end) + if not systemd_present then + log_info(ffi.C.LOG_GRP_WATCHDOG, 'systemd library not detected') + return + end + private.ok_callback = sd_signal_ok + if ret < 0 then + error('[watchdog] %s', ffi.string(ffi.C.knot_strerror(math.abs(ret)))) + return + elseif ret == 0 then + log_info(ffi.C.LOG_GRP_WATCHDOG, 'disabled in systemd (WatchdogSec= not specified)') + return + end + local timeout = tonumber(timeoutptr[0]) / 1000 -- convert to ms + local interval = timeout / 2 -- halve interval to make sure we are never late + if interval < 1 then + log_error(ffi.C.LOG_GRP_WATCHDOG, 'error: WatchdogSec= must be at least 2ms! (got %d usec)', + tonumber(timeoutptr[0])) + end + watchdog.config({ interval = interval }) + log_info(ffi.C.LOG_GRP_WATCHDOG, 'systemd watchdog enabled (check interval: %s ms, timeout: %s ms)', + private.interval, timeout) +end + +function watchdog.deinit() + if private.event then + event.cancel(private.event) + private.event = nil + end +end + +return watchdog |