[kudu] 01/04: KUDU-2449: "Tablet server addition" best practices

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commit 216dc377c92c983b4693d16ef880f9ec0ebb1d8d
Author: Mitch Barnett <mb...@cloudera.com>
AuthorDate: Tue Apr 9 11:24:18 2019 -0700

    KUDU-2449: "Tablet server addition" best practices
    
    This section will detail the best practices around adding new tablet
    servers to a cluster, specifically around node utilization. The most
    common use-case for adding a tablet server is to reduce load/utilization
    per node, or add additional capacity to the cluster. In either case, the
    newly added tablet server instances won't be utilized unless new tablets are
    created, or if tablets need to be re-homed, which is not the usual expectation
    (I added new tablet servers, Kudu should detect that and use rebalance
    automatically).
    
    Change-Id: I7e44b4a84a8ca8048b8dc930cc1ee228daef6cf9
    Reviewed-on: http://gerrit.cloudera.org:8080/12969
    Reviewed-by: Adar Dembo <ad...@cloudera.com>
    Tested-by: Kudu Jenkins
    Reviewed-by: Grant Henke <gr...@apache.org>
---
 docs/administration.adoc | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/docs/administration.adoc b/docs/administration.adoc
index 2794b40..d4cfe35 100644
--- a/docs/administration.adoc
+++ b/docs/administration.adoc
@@ -797,6 +797,39 @@ INVALIDATE METADATA;
 .. Verify updating the metadata worked by running a simple `SELECT` query on a
 Kudu-backed Impala table.
 
+[[adding_tablet_servers]]
+=== Best Practices When Adding New Tablet Servers
+
+A common workflow when administering a Kudu cluster is adding additional tablet
+server instances, in an effort to increase storage capacity, decrease load or
+utilization on individual hosts, increase compute power, etc.
+
+By default, any newly added tablet servers will not be utilized immediately
+after their addition to the cluster. Instead, newly added tablet servers will
+only be utilized when new tablets are created or when existing tablets need to
+be replicated, which can lead to imbalanced nodes.
+
+To add additional tablet servers to an existing cluster, the
+following steps can be taken to ensure tablets are uniformly distributed
+across the cluster:
+
+1. Ensure that Kudu is installed on the new machines being added to the
+cluster, and that the new instances have been
+link:https://kudu.apache.org/docs/configuration.html#_configuring_tablet_servers[correctly configured]
+to point to the pre-existing cluster. Then, start up the new tablet server instances.
+2. Verify that the new instances check in with the Kudu Master(s)
+successfully. A quick method for veryifying they've successfully checked in
+with the existing Master instances is to view the Kudu Master WebUI,
+specifically the `/tablet-servers` section, and validate that the newly
+added instances are registered, and heartbeating.
+3. Once the tablet server(s) are successfully online and healthy, follow
+the steps to run the
+link:https://kudu.apache.org/docs/administration.html#rebalancer_tool[rebalancing tool]
+which will spread existing tablets to the newly added tablet server
+nodes.
+4. After the balancer has completed, or even during its execution, you can
+check on the health of the cluster using the `ksck` command-line utility.
+
 [[ksck]]
 === Checking Cluster Health with `ksck`