closes gh-969: introduces new section `[Thread]` and option `stacksize` to configure default stack-size of the threads running in fail2ban. Example:

```ini
[Thread]
stacksize = 32
```

config/fail2ban.conf

@@ -67,3 +67,11 @@ dbfile = /var/lib/fail2ban/fail2ban.sqlite3
 # Notes.: Sets age at which bans should be purged from the database
 # Values: [ SECONDS ] Default: 86400 (24hours)
 dbpurgeage = 1d
+
+[Thread]
+
+# Options: stacksize
+# Notes.: Specifies the stack size (in KiB) to be used for subsequently created threads,
+#         and must be 0 or a positive integer value of at least 32.
+# Values: [ SIZE ] Default: 0 (use platform or configured default)
+#stacksize = 0

fail2ban/client/configreader.py

@@ -239,8 +239,10 @@ class ConfigReaderUnshared(SafeConfigParserWithIncludes):
 			try:
 				if opttype == "bool":
 					v = self.getboolean(sec, optname)
+					if v is None: continue
 				elif opttype == "int":
 					v = self.getint(sec, optname)
+					if v is None: continue
 				else:
 					v = self.get(sec, optname, vars=pOptions)
 				values[optname] = v

fail2ban/client/fail2banreader.py

@@ -24,7 +24,7 @@ __author__ = "Cyril Jaquier"
 __copyright__ = "Copyright (c) 2004 Cyril Jaquier"
 __license__ = "GPL"
 
-from .configreader import ConfigReader
+from .configreader import ConfigReader, NoSectionError
 from ..helpers import getLogger, str2LogLevel
 
 # Gets the instance of the logger.
@@ -60,12 +60,19 @@ class Fail2banReader(ConfigReader):
 			self.__opts.update(updateMainOpt)
 		# check given log-level:
 		str2LogLevel(self.__opts.get('loglevel', 0))
-	
+		# thread options:
+		opts = [["int", "stacksize", ],
+		]
+		if ConfigReader.has_section(self, "Thread"):
+			thopt = ConfigReader.getOptions(self, "Thread", opts)
+			if thopt:
+				self.__opts['thread'] = thopt
+
 	def convert(self):
 		# Ensure logtarget/level set first so any db errors are captured
 		# Also dbfile should be set before all other database options.
 		# So adding order indices into items, to be stripped after sorting, upon return
-		order = {"syslogsocket":0, "loglevel":1, "logtarget":2,
+		order = {"thread":0, "syslogsocket":11, "loglevel":12, "logtarget":13,
 			"dbfile":50, "dbpurgeage":51}
 		stream = list()
 		for opt in self.__opts:

fail2ban/server/server.py

@@ -709,6 +709,16 @@ class Server:
 				logSys.info("flush performed on %s" % self.__logTarget)
 			return "flushed"
 			
+	def setThreadOptions(self, value):
+		for o, v in value.iteritems():
+			if o == 'stacksize':
+				threading.stack_size(int(v)*1024)
+			else: # pragma: no cover
+				raise KeyError("unknown option %r" % o)
+
+	def getThreadOptions(self):
+		return {'stacksize': threading.stack_size() / 1024}
+
 	def setDatabase(self, filename):
 		# if not changed - nothing to do
 		if self.__db and self.__db.filename == filename:

fail2ban/server/transmitter.py

@@ -170,6 +170,10 @@ class Transmitter:
 				return self.__server.getSyslogSocket()
 			else:
 				raise Exception("Failed to change syslog socket")
+		#Thread
+		elif name == "thread":
+			value = command[1]
+			return self.__server.setThreadOptions(value)
 		#Database
 		elif name == "dbfile":
 			self.__server.setDatabase(command[1])
@@ -384,6 +388,9 @@ class Transmitter:
 			return self.__server.getLogTarget()
 		elif name == "syslogsocket":
 			return self.__server.getSyslogSocket()
+		#Thread
+		elif name == "thread":
+			return self.__server.getThreadOptions()
 		#Database
 		elif name == "dbfile":
 			db = self.__server.getDatabase()

fail2ban/tests/fail2banclienttestcase.py

@@ -478,6 +478,12 @@ class Fail2banClientTest(Fail2banClientServerBase):
 	def testClientStartBackgroundInside(self, tmp):
 		# use once the stock configuration (to test starting also)
 		startparams = _start_params(tmp, True)
+		# test additional options:
+		_write_file(pjoin(tmp, "config", "fail2ban.conf"), "a",
+			"[Thread]",
+			"stacksize = 32"
+			"",
+		)
 		# start:
 		self.execCmd(SUCCESS, ("-b",) + startparams, "start")
 		# wait for server (socket and ready):
@@ -485,10 +491,16 @@ class Fail2banClientTest(Fail2banClientServerBase):
 		self.assertLogged("Server ready")
 		self.assertLogged("Exit with code 0")
 		try:
+			# check thread options were set:
+			self.pruneLog()
+			self.execCmd(SUCCESS, startparams, "get", "thread")
+			self.assertLogged("{'stacksize': 32}")
+			# several:
+			self.pruneLog()
 			self.execCmd(SUCCESS, startparams, "echo", "TEST-ECHO")
 			self.execCmd(FAILED, startparams, "~~unknown~cmd~failed~~")
-			self.pruneLog()
 			# start again (should fail):
+			self.pruneLog()
 			self.execCmd(FAILED, ("-b",) + startparams, "start")
 			self.assertLogged("Server already running")
 		finally:

man/jail.conf.5

@@ -127,9 +127,7 @@ Comments: use '#' for comment lines and '; ' (space is important) for inline com
 
 .SH "FAIL2BAN CONFIGURATION FILE(S) (\fIfail2ban.conf\fB)"
 
-These files have one section, [Definition].
-
-The items that can be set are:
+The items that can be set in section [Definition] are:
 .TP
 .B loglevel
 verbosity level of log output: CRITICAL, ERROR, WARNING, NOTICE, INFO, DEBUG, TRACEDEBUG, HEAVYDEBUG or corresponding numeric value (50-5). Default: ERROR (equal 40)
@@ -163,6 +161,15 @@ Database purge age in seconds. Default: 86400 (24hours)
 .br
 This sets the age at which bans should be purged from the database.
 
+.RE
+The config parameters of section [Thread] are:
+
+.TP
+.B stacksize
+Stack size of each thread in fail2ban. Default: 0 (platform or configured default)
+.br
+This specifies the stack size (in KiB) to be used for subsequently created threads, and must be 0 or a positive integer value of at least 32.
+
 .SH "JAIL CONFIGURATION FILE(S) (\fIjail.conf\fB)"
 The following options are applicable to any jail. They appear in a section specifying the jail name or in the \fI[DEFAULT]\fR section which defines default values to be used if not specified in the individual section.
 .TP