From bc4b5ccd48029855d562aca69d47be808919600e Mon Sep 17 00:00:00 2001 From: Armon Dadgar Date: Tue, 1 Jul 2014 15:02:42 -0700 Subject: [PATCH] website: Keep old bootstrapping docs --- .../guides/manual-bootstrap.html.markdown | 83 +++++++++++++++++++ 1 file changed, 83 insertions(+) create mode 100644 website/source/docs/guides/manual-bootstrap.html.markdown diff --git a/website/source/docs/guides/manual-bootstrap.html.markdown b/website/source/docs/guides/manual-bootstrap.html.markdown new file mode 100644 index 0000000000..f1375031ee --- /dev/null +++ b/website/source/docs/guides/manual-bootstrap.html.markdown @@ -0,0 +1,83 @@ +--- +layout: "docs" +page_title: "Manual Bootstrapping" +sidebar_current: "docs-guides-bootstrapping" +--- + +# Manually Bootstrapping a Datacenter + +When deploying Consul to a datacenter for the first time, there is an initial bootstrapping that +must be done. As of Consul 0.4, an [automatic bootstrapping](/docs/guides/bootstrapping.html) is +available and is the recommended approach. However, older versions only support a manual bootstrap +that is documented here. + +Generally, the first nodes that are started are the server nodes. Remember that an +agent can run in both client and server mode. Server nodes are responsible for running +the [consensus protocol](/docs/internals/consensus.html), and storing the cluster state. +The client nodes are mostly stateless and rely on the server nodes, so they can be started easily. + +Manual bootstrapping requires that the first server that is deployed in a new datacenter provide +the `-bootstrap` [configuration option](/docs/agent/options.html). This option allows the server to +assert leadership of the cluster without agreement from any other server. This is necessary because +at this point, there are no other servers running in the datacenter! Lets call this first server `Node A`. +When starting `Node A` something like the following will be logged: + + 2014/02/22 19:23:32 [INFO] consul: cluster leadership acquired + +Once `Node A` is running, we can start the next set of servers. There is a [deployment table](/docs/internals/consensus.html#toc_3) +that covers various options, but it is recommended to have 3 or 5 total servers per data center. +A single server deployment is _**highly**_ discouraged as data loss is inevitable in a failure scenario. +We start the next servers **without** specifying `-bootstrap`. This is critical, since only one server +should ever be running in bootstrap mode*. Once `Node B` and `Node C` are started, you should see a +message to the effect of: + + [WARN] raft: EnableSingleNode disabled, and no known peers. Aborting election. + +This indicates that the node is not in bootstrap mode, and it will not elect itself as leader. +We can now join these machines together. Since a join operation is symmetric it does not matter +which node initiates it. From `Node B` and `Node C` you can do the following: + + $ consul join + Successfully joined cluster by contacting 1 nodes. + +Alternatively, from `Node A` you can do the following: + + $ consul join + Successfully joined cluster by contacting 2 nodes. + +Once the join is successful, `Node A` should output something like: + + [INFO] raft: Added peer 127.0.0.2:8300, starting replication + .... + [INFO] raft: Added peer 127.0.0.3:8300, starting replication + +As a sanity check, the `consul info` command is a useful tool. It can be used to +verify `raft.num_peers` is now 2, and you can view the latest log index under `raft.last_log_index`. +When running `consul info` on the followers, you should see `raft.last_log_index` +converge to the same value as the leader begins replication. That value represents the last +log entry that has been stored on disk. + +This indicates that `Node B` and `Node C` have been added as peers. At this point, +all three nodes see each other as peers, `Node A` is the leader, and replication +should be working. + +The final step is to remove the `-bootstrap` flag. This is important since we don't +want the node to be able to make unilateral decisions in the case of a failure of the +other two nodes. To do this, we send a `SIGINT` to `Node A` to allow it to perform +a graceful leave. Then we remove the `-bootstrap` flag and restart the node. The node +will need to rejoin the cluster, since the graceful exit leaves the cluster. Any transactions +that took place while `Node A` was offline will be replicated and the node will catch up. + +Now that the servers are all started and replicating to each other, all the remaining +clients can be joined. Clients are much easier, as they can be started and perform +a `join` against any existing node. All nodes participate in a gossip protocol to +perform basic discovery, so clients will automatically find the servers and register +themselves. + +
+* If you accidentally start another server with the flag set, do not fret. +Shutdown the node, and remove the `raft/` folder from the data directory. This will +remove the bad state caused by being in `-bootstrap` mode. Then restart the +node and join the cluster normally. +
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