exmdb: make DB_LOCK_TIMEOUT configurable

Author: jengelh

doc/exmdb_provider.4gx

@@ -185,11 +185,20 @@ warning log message. Use 0 to disable.
 Default: \fI10\fP
 .TP
 \fBmbox_contention_reject\fP
-If there are more than this many threads waiting to use a mailbox, refuse the
-particular exmdb RPC that is executing. Use 0 to disable.
+If there are more than this many threads waiting to use a mailbox, refuse new
+exmdb calls to the mailbox. Use 0 to disable. When a call is not rejected
+upfront like this, it will be added to the waiting queue. (mailbox access is
+serialized.)
 .br
 Default: \fI0\fP
 .TP
+\fBmbox_contention_reject_time\fP
+If an exmdb call was queued in the waiting list for too long (cf.
+mbox_contention_reject), the call will be aborted, error E-2207 logged, an
+error returned to the client.
+.br
+Default: \fI60s\fP
+.TP
 \fBnotify_stub_threads_num\fP
 For every remote exmdb server in exmdb_list.txt, establish and keep this many
 number of outbound connections for receiving notification RPCs.

exch/exmdb/db_engine.cpp

@@ -109,7 +109,7 @@ unsigned int g_exmdb_schema_upgrades, g_exmdb_search_pacing;
 unsigned long long g_exmdb_search_pacing_time = 2000000000;
 unsigned int g_exmdb_search_yield, g_exmdb_search_nice;
 unsigned int g_exmdb_pvt_folder_softdel;
-static constexpr auto DB_LOCK_TIMEOUT = std::chrono::seconds(60);
+unsigned long long g_exmdb_lock_timeout = 60000000000ULL;
 
 static bool remove_from_hash(const decltype(g_hash_table)::value_type &, time_t);
 static void dbeng_notify_cttbl_modify_row(DB_ITEM *, uint64_t folder_id, uint64_t message_id);
@@ -213,10 +213,10 @@ db_item_ptr db_engine_get_db(const char *path, const char *parent_func)
 		++pdb->reference;
 		hhold.unlock();
 		auto func_then = znul(pdb->giant_lock_func);
-		if (!pdb->giant_lock.try_lock_for(DB_LOCK_TIMEOUT)) {
+		if (!pdb->giant_lock.try_lock_for(std::chrono::nanoseconds(g_exmdb_lock_timeout))) {
 			--pdb->reference;
-			mlog(LV_ERR, "E-2207: %s: could not obtain exclusive access within %us (mailbox busy with <%s>/<%s>)",
-				path, static_cast<unsigned int>(DB_LOCK_TIMEOUT.count()),
+			mlog(LV_ERR, "E-2207: %s: could not obtain exclusive access within %llu ns (mailbox busy with <%s>/<%s>)",
+				path, g_exmdb_lock_timeout,
 				func_then, znul(pdb->giant_lock_func));
 			return NULL;
 		}
@@ -239,7 +239,7 @@ db_item_ptr db_engine_get_db(const char *path, const char *parent_func)
 	pdb->last_time = time(nullptr);
 	pdb->reference ++;
 	hhold.unlock();
-	if (!pdb->giant_lock.try_lock_for(DB_LOCK_TIMEOUT)) {
+	if (!pdb->giant_lock.try_lock_for(std::chrono::nanoseconds(g_exmdb_lock_timeout))) {
 		pdb->reference --;
 		return NULL;
 	}

exch/exmdb/db_engine.h

@@ -162,7 +162,7 @@ extern BOOL db_engine_enqueue_populating_criteria(const char *dir, cpid_t, uint6
 extern bool db_engine_check_populating(const char *dir, uint64_t folder_id);
 
 extern unsigned int g_exmdb_schema_upgrades, g_exmdb_search_pacing;
-extern unsigned long long g_exmdb_search_pacing_time;
+extern unsigned long long g_exmdb_search_pacing_time, g_exmdb_lock_timeout;
 extern unsigned int g_exmdb_search_yield, g_exmdb_search_nice;
 extern unsigned int g_exmdb_pvt_folder_softdel;
 extern std::string g_exmdb_ics_log_file;

exch/exmdb/main.cpp

@@ -63,6 +63,7 @@ static constexpr cfg_directive exmdb_cfg_defaults[] = {
 	{"max_rule_number", "1000", CFG_SIZE, "1", "2000"},
 	{"max_store_message_count", "0", CFG_SIZE},
 	{"mbox_contention_reject", "0", CFG_SIZE},
+	{"mbox_contention_reject_time", "60s", CFG_TIME_NS},
 	{"mbox_contention_warning", "10", CFG_SIZE},
 	{"notify_stub_threads_num", "4", CFG_SIZE, "0"},
 	{"populating_threads_num", "50", CFG_SIZE, "1", "50"},
@@ -106,6 +107,7 @@ static bool exmdb_provider_reload(std::shared_ptr<config_file> gxcfg = nullptr,
 	exmdb_pf_read_states = pconfig->get_ll("exmdb_pf_read_states");
 	g_exmdb_pvt_folder_softdel = pconfig->get_ll("exmdb_private_folder_softdelete");
 	g_exmdb_search_pacing = pconfig->get_ll("exmdb_search_pacing");
+	g_exmdb_lock_timeout = pconfig->get_ll("mbox_contention_reject_time");
 	g_exmdb_search_yield = pconfig->get_ll("exmdb_search_yield");
 	g_exmdb_search_nice = pconfig->get_ll("exmdb_search_nice");
 	g_exmdb_search_pacing_time = pconfig->get_ll("exmdb_search_pacing_time");