1COROSYNC-QDEVICE(8) System Manager's Manual COROSYNC-QDEVICE(8)
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6 corosync-qdevice - QDevice daemon
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9 corosync-qdevice [-dfh] [-S option=value[,option2=value2,...]]
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13 corosync-qdevice is a daemon running on each node of a cluster. It pro‐
14 vides a configured number of votes to the quorum subsystem based on a
15 third-party arbitrator's decision. Its primary use is to allow a clus‐
16 ter to sustain more node failures than standard quorum rules allow. It
17 is recommended for clusters with an even number of nodes and highly
18 recommended for 2 node clusters.
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21 -d Forcefully turn on debug information without the need to change
22 corosync.conf.
23 -f Do not daemonize, run in the foreground.
25 -h Show short help text
27 -S Set advanced settings described in its own section below. This
29 option shouldn't be generally used because most of the options
30 are not safe to change.
31
33 corosync-qdevice reads its configuration from corosync.conf file.
34 The main configuration is within quorum.device sub-key. Each model also
36 has its own configuration within a similarly named sub-key.
37 model Specifies the model to be used. This parameter is required.
39 corosync-qdevice is modular and is able to support multiple dif‐
40 ferent models. The model basically defines what type of arbitra‐
41 tor is used. Currently only net is supported.
42 timeout
44 Specifies how often corosync-qdevice should call the votequo‐
45 rum_poll function. It is also used by the net model to adjust
46 its hearbeat timeout. It is recommended that you don't change
47 this value. Default is 10000.
48 sync_timeout
50 Specifies how often corosync-qdevice should call the votequo‐
51 rum_poll function during a sync phase. It is recommended that
52 you don't change this value. Default is 30000.
53 votes The number of votes provided to the cluster by qdevice. Default
55 is (number_of_nodes - 1) or generally sum(votes_per_node) - 1.
56 quorum.device.heuristics subkey holds the configuration of the heuris‐
59 tics. Heuristics are set of commands executed locally on startup, clus‐
60 ter membership change, successful connect to corosync-qnetd and option‐
61 ally also at regular times. When all commands finish successfully
62 (their return error code is zero) on time, heuristics have passed, oth‐
63 erwise they have failed. The heuristics result is sent to corosync-
64 qnetd and there it's used in calculations to determine which partition
65 should be quorate.
66 timeout
68 Specifies maximum time in milliseconds how long corosync-qdevice
69 waits till the heuristics commands finish. If some command
70 doesn't finish before the timeout, it's killed and heuristics
71 fail. This timeout is used for heuristics executed at regular
72 times. Default value is half of the quorum.device.timeout, so
73 5000.
74 sync_timeout
76 Similar to quorum.device.heuristics.timeout but used during mem‐
77 bership changes. Default value is half of the quo‐
78 rum.device.sync_timeout, so 15000.
79 interval
81 Specifies interval between two regular heuristics execution.
82 Default value is 3 * quorum.device.timeout, so 30000.
83 mode Can be on of on, sync or off and specifies mode of operation of
85 heuristics. Default is off what means heuristics are disabled.
86 When sync is set, heuristics are executed only during startup,
87 membership change and when connection to corosync-qnetd is
88 established. When heuristics should be running also on regular
89 basis, this option should be set to on value.
90 exec_NAME
92 defines executables. NAME can be arbitrary valid cmap key name
93 string and it has no special meaning. The value of this vari‐
94 able must contain a command to execute. The alue is parsed
95 (split) into arguments similarly as Bourne shell would do. Quot‐
96 ing is possible by using backslash and double quotes.
97 quorum.device.net subkey holds the configuration for model 'net'.
100 tls Can be one of on, off or required and specifies if tls should be
102 used. on means a connection with TLS is attempted first, but if
103 the server doesn't advertise TLS support then non-TLS will be
104 used. off is used then TLS is not required and it's then not
105 even tried. This mode is the only one which doesn't need a prop‐
106 erly initialized NSS database. required means TLS is required
107 and if the server doesn't support TLS, qdevice will exit with
108 error message. Default is on.
109 host Specifies the IP address or host name of the qnetd server to be
111 used. This parameter is required.
112 port Specifies TCP port of qnetd server. Default is 5403.
114 algorithm
116 Decision algorithm. Can be one of the ffsplit or lms. (actually
117 there are also test and 2nodelms , both of which are mainly for
118 developers and shouldn't be used for production clusters). For a
119 description of what each algorithm means and how the algorithms
120 differ see their individual sections. Default value is ffsplit.
121 tie_breaker
123 can be one of lowest, highest or valid_node_id (number) values.
124 It's used as a fallback if qdevice has to decide between two or
125 more equal partitions. lowest means the partition with the low‐
126 est node id is chosen. highest means the partition with highest
127 node id is chosen. And valid_node_id means that the partition
128 containing the node with the given node id is chosen. Default
129 is 'lowest'.
130 connect_timeout
132 Timeout when corosync-qdevice is trying to connect to corosync-
133 qnetd host. Default is 0.8 * quorum.sync_timeout.
134 force_ip_version
136 can be one of 0|4|6 and forces the software to use the given IP
137 version. 0 (default value) means IPv6 is prefered and IPv4
138 should be used as a fallback.
139 Logging configuration is within the logging directive. corosync-qde‐
142 vice parses and supports most of the options with exception of to_log‐
143 file, logfile and logfile_priority. The logger_subsys sub-directive
144 can be also used if subsys is set to QDEVICE.
145 For corosync-qdevice to work correctly, the nodelist directive has to
148 be used and properly configured. Also the net model requires that
149 totem.cluster_name option is set.
150
153 For model net to work using TLS, it's necessary to create the NSS data‐
154 base, import Qnetd CA certificate, and get/distribute a valid client
155 certificate.
156 If pcs is used (recommended) the following steps are not needed because
158 pcs does them automatically.
159 corosync-qdevice-net-certutil is the tool to perform required actions
161 semi-automatically. Please consult the help output of it and its man
162 page. For a first time configuration it may make sense to start with
163 the -Q option.
164 If TLS is not required just edit corosync.conf file and set quo‐
166 rum.device.net.tls to off.
167
170 Algorithms are used to change behavior of how corosync-qnetd provides
171 votes to a given node/partition. Currently there are two algorithms
172 supported.
173 ffsplit
175 This one makes sense only for clusters with an even number of
176 nodes. It provides exactly one vote to the partition with the
177 highest number of active nodes. If there are two exactly similar
178 partitions, it provides its vote to the partition with higher
179 score. The score is computed as (number_of_connected_nodes +
180 number_of_connected_nodes_with_passed_heuristics - num‐
181 ber_of_connected_nodes_with_failed_heuristics) If the scores are
182 equal, the vote is provided to partition with the most clients
183 connected to the qnetd server. If this number is also equal,
184 then the tie_breaker is used. It is able to transition its vote
185 if the currently active partition becomes partitioned and a non-
186 active partition still has at least 50% of the active nodes.
187 Because of this, a vote is not provided if the qnetd connection
188 is not active.
189 To use this algorithm it's required to set the number of votes
191 per node to 1 (default) and the qdevice number of votes has to
192 be also 1. This is achieved by setting quorum.device.votes key
193 in corosync.conf file to 1.
194 lms Last-man-standing. If the node is the only one left in the clus‐
196 ter that can see the qnetd server then we return a vote.
197 If more than one node can see the qnetd server but some nodes
199 can't see each other then the cluster is divided up into 'parti‐
200 tions' based on their ring_id and this algorithm returns a vote
201 to the partition with highest heuristics score (computed the
202 same way as for the ffsplit algorithm), or if there is more than
203 1 partition with equal scores, the largest active partition or,
204 if there is more than 1 equal partition, the partition that con‐
205 tains the tie_breaker node (lowest, highest, etc). For LMS to
206 work, the number of qdevice votes has to be set to default (so
207 just delete quorum.device.votes key from corosync.conf).
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211 Set by using -S option. The default value is shown in parentheses)
212 Options beginning with net_ prefix are specific to model net.
213 lock_file
215 Lock file location. (/var/run/corosync-qdevice/corosync-qde‐
216 vice.pid)
217 local_socket_file
219 Internal IPC socket file location. (/var/run/corosync-qde‐
220 vice/corosync-qdevice.sock)
221 local_socket_backlog
223 Parameter passed to listen syscall. (10)
224 max_cs_try_again
226 How many times to retry the call to a corosync function which
227 has returned CS_ERR_TRY_AGAIN. (10)
228 votequorum_device_name
230 Name used for qdevice registration. (Qdevice)
231 ipc_max_clients
233 Maximum allowed simultaneous IPC clients. (10)
234 ipc_max_receive_size
236 Maximum size of a message received by IPC client. (4096)
237 ipc_max_send_size
239 Maximum size of a message allowed to be sent to an IPC client.
240 (65536)
241 master_wins
243 Force enable/disable master wins. (default is model)
244 heuristics_ipc_max_send_buffers
246 Maximum number of heuristics worker send buffers. (128)
247 heuristics_ipc_max_send_receive_size
249 Maximum size of a message allowed to be send to, or received
250 from heuristics worker. (4096)
251 heuristics_min_timeout
253 Minimum heuristics timeout accepted by client in ms. (1000)
254 heuristics_max_timeout
256 Maximum heuristics timeout accepted by client in ms. (120000)
257 heuristics_min_interval
259 Minimum heuristics interval accepted by client in ms. (1000)
260 heuristics_max_interval
262 Maximum heuristics interval accepted by client in ms. (3600000)
263 heuristics_max_execs
265 Maximum number of exec_ commands. (32)
266 heuristics_use_execvp
268 Use execvp instead of execv for executing commands. (off)
269 heuristics_max_processes
271 Maximum number of processes running at one time. (160) heuris‐
272 tics_kill_list_interval Interval between status is gathered and
273 eventually signal is sent to processes which didn't finished on
274 time in ms. (5000)
275 net_nss_db_dir
277 NSS database directory. (/etc/corosync/qdevice/net/nssdb)
278 net_initial_msg_receive_size
280 Initial (used during connection parameters negotiation) maximum
281 size of the receive buffer for message (maximum allowed message
282 size received from qnetd). (32768)
283 net_initial_msg_send_size
285 Initial (used during connection parameter negotiation) maximum
286 size of one send buffer (message) to be sent to server. (32768)
287 net_min_msg_send_size
289 Minimum required size of one send buffer (message) to be sent to
290 server. (32768)
291 net_max_msg_receive_size
293 Maximum allowed size of receive buffer for a message sent by
294 server. (16777216)
295 net_max_send_buffers
297 Maximum number of send buffers. (10)
298 net_nss_qnetd_cn
300 Canonical name of qnetd server certificate. (Qnetd Server)
301 net_nss_client_cert_nickname
303 NSS nickname of qdevice client certificate. (Cluster Cert)
304 net_heartbeat_interval_min
306 Minimum heartbeat timeout accepted by client in ms. (1000)
307 net_heartbeat_interval_max
309 Maximum heartbeat timeout accepted by client in ms. (120000)
310 net_min_connect_timeout
312 Minimum connection timeout accepted by client in ms. (1000)
313 net_max_connect_timeout
315 Maximum connection timeout accepted by client in ms. (120000)
316 net_test_algorithm_enabled
318 Enable test algorithm. (if built with --enable-debug on, other‐
319 wise off)
320
323 Define qdevice with net model connecting to qnetd running on
324 qnetd.example.org host, using ffsplit algorithm. Heuristics is set to
325 sync mode and executes two commands.
326 quorum {
328 provider: corosync_votequorum
329 device {
330 votes: 1
331 model: net
332 net {
333 tls: on
334 host: qnetd.example.org
335 algorithm: ffsplit
336 }
337 heuristics {
338 mode: sync
339 exec_ping: /bin/ping -q -c 1 "www.example.org"
340 exec_test_txt_exists: /usr/bin/test -f /tmp/test.txt
341 }
342 }
343
345 corosync-qdevice-tool(8) corosync-qdevice-net-certutil(8) corosync-
346 qnetd(8) corosync.conf(5)
347
349 Jan Friesse
350 2017-10-17 COROSYNC-QDEVICE(8)