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1 | [[chapter_pmgcm]] |
2 | ifdef::manvolnum[] | |
3 | pmgcm(1) | |
4 | ======== | |
5 | :pmg-toplevel: | |
6 | ||
7 | NAME | |
8 | ---- | |
9 | ||
10 | pmgcm - Proxmox Mail Gateway Cluster Management Toolkit | |
11 | ||
12 | ||
13 | SYNOPSIS | |
14 | -------- | |
15 | ||
16 | include::pmgcm.1-synopsis.adoc[] | |
17 | ||
18 | ||
19 | DESCRIPTION | |
20 | ----------- | |
21 | endif::manvolnum[] | |
22 | ifndef::manvolnum[] | |
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23 | Cluster Management |
24 | ================== | |
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25 | :pmg-toplevel: |
26 | endif::manvolnum[] | |
27 | ||
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28 | We are living in a world where email becomes more and more important - |
29 | failures in email systems are just not acceptable. To meet these | |
30 | requirements we developed the Proxmox HA (High Availability) Cluster. | |
31 | ||
32 | The {pmg} HA Cluster consists of a master and several slave nodes | |
33 | (minimum one node). Configuration is done on the master. Configuration | |
34 | and data is synchronized to all cluster nodes over a VPN tunnel. This | |
35 | provides the following advantages: | |
36 | ||
37 | * centralized configuration management | |
38 | ||
39 | * fully redundant data storage | |
40 | ||
41 | * high availability | |
42 | ||
43 | * high performance | |
44 | ||
45 | We use a unique application level clustering scheme, which provides | |
46 | extremely good performance. Special considerations where taken to make | |
47 | management as easy as possible. Complete Cluster setup is done within | |
48 | minutes, and nodes automatically reintegrate after temporary failures | |
49 | without any operator interaction. | |
50 | ||
51 | image::images/pmg-ha-cluster.png[] | |
52 | ||
53 | ||
54 | Hardware requirements | |
55 | --------------------- | |
56 | ||
57 | There are no special hardware requirements, although it is highly | |
58 | recommended to use fast and reliable server with redundant disks on | |
59 | all cluster nodes (Hardware RAID with BBU and write cache enabled). | |
60 | ||
61 | The HA Cluster can also run in virtualized environments. | |
62 | ||
63 | ||
64 | Subscriptions | |
65 | ------------- | |
66 | ||
67 | Each host in a cluster has its own subscription. If you want support | |
68 | for a cluster, each cluster node needs to have a valid | |
69 | subscription. All nodes must have the same subscription level. | |
70 | ||
71 | ||
72 | Load balancing | |
73 | -------------- | |
74 | ||
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75 | It is usually advisable to distribute mail traffic among all cluster |
76 | nodes. Please note that this is not always required, because it is | |
77 | also reasonable to use only one node to handle SMTP traffic. The | |
78 | second node is used as quarantine host, and only provides the web | |
79 | interface to the user quarantine. | |
80 | ||
81 | The normal mail delivery process looks up DNS Mail Exchange (`MX`) | |
82 | records to determine the destination host. A `MX` record tells the | |
83 | sending system where to deliver mail for a certain domain. It is also | |
84 | possible to have several `MX` records for a single domain, they can have | |
85 | different priorities. For example, our `MX` record looks like that: | |
86 | ||
87 | ---- | |
88 | # dig -t mx proxmox.com | |
89 | ||
90 | ;; ANSWER SECTION: | |
91 | proxmox.com. 22879 IN MX 10 mail.proxmox.com. | |
92 | ||
93 | ;; ADDITIONAL SECTION: | |
94 | mail.proxmox.com. 22879 IN A 213.129.239.114 | |
95 | ---- | |
96 | ||
97 | Please notice that there is one single `MX` record for the Domain | |
98 | `proxmox.com`, pointing to `mail.proxmox.com`. The `dig` command | |
99 | automatically puts out the corresponding address record if it | |
100 | exists. In our case it points to `213.129.239.114`. The priority of | |
101 | our `MX` record is set to 10 (preferred default value). | |
102 | ||
103 | ||
104 | Hot standby with backup `MX` records | |
105 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
106 | ||
107 | Many people do not want to install two redundant mail proxies, instead | |
108 | they use the mail proxy of their ISP as fall-back. This is simply done | |
109 | by adding an additional `MX` Record with a lower priority (higher | |
110 | number). With the example above this looks like that: | |
111 | ||
112 | ---- | |
113 | proxmox.com. 22879 IN MX 100 mail.provider.tld. | |
114 | ---- | |
115 | ||
116 | Sure, your provider must accept mails for your domain and forward | |
117 | received mails to you. Please note that such setup is not really | |
118 | advisable, because spam detection needs to be done by that backup `MX` | |
119 | server also, and external servers provided by ISPs usually don't do | |
120 | that. | |
121 | ||
122 | You will never lose mails with such a setup, because the sending Mail | |
123 | Transport Agent (MTA) will simply deliver the mail to the backup | |
124 | server (mail.provider.tld) if the primary server (mail.proxmox.com) is | |
125 | not available. | |
126 | ||
127 | NOTE: Any resononable mail server retries mail devivery if the target | |
128 | server is not available, i.e. {pmg} stores mail and retries delivery | |
129 | for up to one week. So you will not loose mail if you mail server is | |
130 | down, even if you run a single server setup. | |
131 | ||
132 | ||
133 | Load balancing with `MX` records | |
134 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
135 | ||
136 | Using your ISPs mail server is not always a good idea, because many | |
137 | ISPs do not use advanced spam prevention techniques, or do not filter | |
138 | SPAM at all. It is often better to run a second server yourself to | |
139 | avoid lower spam detection rates. | |
140 | ||
141 | Anyways, it’s quite simple to set up a high performance load balanced | |
142 | mail cluster using `MX` records. You just need to define two `MX` records | |
143 | with the same priority. I will explain this using a complete example | |
144 | to make it clearer. | |
145 | ||
146 | First, you need to have at least 2 working {pmg} servers | |
147 | (mail1.example.com and mail2.example.com) configured as cluster (see | |
148 | section xref:pmg_cluster_administration[Cluster administration] | |
149 | below), each having its own IP address. Let us assume the following | |
150 | addresses (DNS address records): | |
151 | ||
152 | ---- | |
153 | mail1.example.com. 22879 IN A 1.2.3.4 | |
154 | mail2.example.com. 22879 IN A 1.2.3.5 | |
155 | ---- | |
156 | ||
157 | Btw, it is always a good idea to add reverse lookup entries (PTR | |
158 | records) for those hosts. Many email systems nowadays reject mails | |
159 | from hosts without valid PTR records. Then you need to define your `MX` | |
160 | records: | |
161 | ||
162 | ---- | |
163 | example.com. 22879 IN MX 10 mail1.example.com. | |
164 | example.com. 22879 IN MX 10 mail2.example.com. | |
165 | ---- | |
166 | ||
167 | This is all you need. You will receive mails on both hosts, more or | |
168 | less load-balanced using round-robin scheduling. If one host fails the | |
169 | other is used. | |
170 | ||
171 | ||
172 | Other ways | |
173 | ~~~~~~~~~~ | |
174 | ||
175 | Multiple address records | |
176 | ^^^^^^^^^^^^^^^^^^^^^^^^ | |
177 | ||
178 | Using several DNS `MX` record is sometime clumsy if you have many | |
179 | domains. It is also possible to use one `MX` record per domain, but | |
180 | multiple address records: | |
181 | ||
182 | ---- | |
183 | example.com. 22879 IN MX 10 mail.example.com. | |
184 | mail.example.com. 22879 IN A 1.2.3.4 | |
185 | mail.example.com. 22879 IN A 1.2.3.5 | |
186 | ---- | |
187 | ||
188 | ||
189 | Using firewall features | |
190 | ^^^^^^^^^^^^^^^^^^^^^^^ | |
191 | ||
192 | Many firewalls can do some kind of RR-Scheduling (round-robin) when | |
193 | using DNAT. See your firewall manual for more details. | |
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194 | |
195 | ||
9aaf2a8c | 196 | [[pmg_cluster_administration]] |
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197 | Cluster administration |
198 | ---------------------- | |
199 | ||
200 | Cluster administration is done with a single command line utility | |
201 | called `pmgcm'. So you need to login via ssh to manage the cluster | |
202 | setup. | |
203 | ||
204 | NOTE: Always setup the IP configuration before adding a node to the | |
205 | cluster. IP address, network mask, gateway address and hostname can’t | |
206 | be changed later. | |
207 | ||
208 | ||
209 | Creating a Cluster | |
210 | ~~~~~~~~~~~~~~~~~~ | |
211 | ||
212 | You can create a cluster from any existing Proxmox host. All data is | |
213 | preserved. | |
214 | ||
215 | * make sure you have the right IP configuration | |
216 | (IP/MASK/GATEWAY/HOSTNAME), because you cannot changed that later | |
217 | ||
218 | * run the cluster creation command: | |
219 | + | |
220 | ---- | |
221 | pmgcm create | |
222 | ---- | |
223 | ||
224 | ||
225 | List Cluster Status | |
226 | ~~~~~~~~~~~~~~~~~~~ | |
227 | ||
228 | ---- | |
229 | pmgcm status | |
230 | --NAME(CID)--------------IPADDRESS----ROLE-STATE---------UPTIME---LOAD----MEM---DISK | |
231 | pmg5(1) 192.168.2.127 master A 1 day 21:18 0.30 80% 41% | |
232 | ---- | |
233 | ||
234 | ||
235 | Adding Cluster Nodes | |
236 | ~~~~~~~~~~~~~~~~~~~~ | |
237 | ||
238 | When you add a new node to a cluster (join) all data on that node is | |
239 | destroyed. The whole database is initialized with cluster data from | |
240 | the master. | |
241 | ||
242 | * make sure you have the right IP configuration | |
243 | ||
244 | * run the cluster join command (on the new node): | |
245 | + | |
246 | ---- | |
247 | pmgcm join <master_ip> | |
248 | ---- | |
249 | ||
250 | You need to enter the root password of the master host when asked for | |
251 | a password. | |
252 | ||
253 | CAUTION: Node initialization deletes all existing databases, stops and | |
254 | then restarts all services accessing the database. So do not add nodes | |
255 | which are already active and receive mails. | |
256 | ||
257 | Also, joining a cluster can take several minutes, because the new node | |
258 | needs to synchronize all data from the master (although this is done | |
259 | in the background). | |
260 | ||
261 | NOTE: If you join a new node, existing quarantined items from the other nodes are not synchronized to the new node. | |
262 | ||
263 | ||
264 | Deleting Nodes | |
265 | ~~~~~~~~~~~~~~ | |
266 | ||
267 | Please detach nodes from the cluster network before removing them | |
268 | from the cluster configuration. Then run the following command on | |
269 | the master node: | |
270 | ||
271 | ---- | |
272 | pmgcm delete <cid> | |
273 | ---- | |
274 | ||
275 | Parameter `<cid>` is the unique cluster node ID, as listed with `pmgcm status`. | |
276 | ||
277 | ||
278 | Disaster Recovery | |
279 | ~~~~~~~~~~~~~~~~~ | |
280 | ||
281 | It is highly recommended to use redundant disks on all cluster nodes | |
282 | (RAID). So in almost any circumstances you just need to replace the | |
283 | damaged hardware or disk. {pmg} uses an asynchronous | |
284 | clustering algorithm, so you just need to reboot the repaired node, | |
285 | and everything will work again transparently. | |
286 | ||
287 | The following scenarios only apply when you really loose the contents | |
288 | of the hard disk. | |
289 | ||
290 | ||
291 | Single Node Failure | |
292 | ^^^^^^^^^^^^^^^^^^^ | |
293 | ||
294 | * delete failed node on master | |
295 | + | |
296 | ---- | |
297 | pmgcm delete <cid> | |
298 | ---- | |
299 | ||
300 | * add (re-join) a new node | |
301 | + | |
302 | ---- | |
303 | pmgcm join <master_ip> | |
304 | ---- | |
305 | ||
306 | ||
307 | Master Failure | |
308 | ^^^^^^^^^^^^^^ | |
309 | ||
310 | * force another node to be master | |
311 | + | |
312 | ----- | |
313 | pmgcm promote | |
314 | ----- | |
315 | ||
316 | * tell other nodes that master has changed | |
317 | + | |
318 | ---- | |
319 | pmgcm sync --master_ip <master_ip> | |
320 | ---- | |
321 | ||
322 | ||
323 | Total Cluster Failure | |
324 | ^^^^^^^^^^^^^^^^^^^^^ | |
325 | ||
326 | * restore backup (Cluster and node information is not restored, you | |
327 | have to recreate master and nodes) | |
328 | ||
329 | * tell it to become master | |
330 | + | |
331 | ---- | |
332 | pmgcm create | |
333 | ---- | |
334 | ||
335 | * install new nodes | |
336 | ||
337 | * add those new nodes to the cluster | |
338 | + | |
339 | ---- | |
340 | pmgcm join <master_ip> | |
341 | ---- | |
342 | ||
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343 | |
344 | ifdef::manvolnum[] | |
345 | include::pmg-copyright.adoc[] | |
346 | endif::manvolnum[] |