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HADOOP-13190. Mention LoadBalancingKMSClientProvider in KMS HA documentation. Contributed by Wei-Chiu Chuang.

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Wei-Chiu Chuang 2016-08-11 12:27:09 -07:00
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hadoop-common-project/hadoop-kms/src/site/markdown/index.md.vm
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@ -19,6 +19,8 @@
Hadoop Key Management Server (KMS) - Documentation Sets
=======================================================
<!-- MACRO{toc|fromDepth=0|toDepth=3} -->
Hadoop KMS is a cryptographic key management server based on Hadoop's **KeyProvider** API.
It provides a client and a server components which communicate over HTTP using a REST API.
@ -34,6 +36,18 @@ KMS Client Configuration
The KMS client `KeyProvider` uses the **kms** scheme, and the embedded URL must be the URL of the KMS. For example, for a KMS running on `http://localhost:9600/kms`, the KeyProvider URI is `kms://http@localhost:9600/kms`. And, for a KMS running on `https://localhost:9600/kms`, the KeyProvider URI is `kms://https@localhost:9600/kms`
The following is an example to configure HDFS NameNode as a KMS client in
`hdfs-site.xml`:
<property>
<name>dfs.encryption.key.provider.uri</name>
<value>kms://http@localhost:9600/kms</value>
<description>
The KeyProvider to use when interacting with encryption keys used
when reading and writing to an encryption zone.
</description>
</property>
KMS
---
@ -623,13 +637,51 @@ Additionally, KMS delegation token secret manager can be configured with the fol
</property>
```
$H3 Using Multiple Instances of KMS Behind a Load-Balancer or VIP
$H3 High Availability
KMS supports multiple KMS instances behind a load-balancer or VIP for scalability and for HA purposes.
Multiple KMS instances may be used to provide high availability and scalability.
Currently there are two approaches to supporting multiple KMS instances:
running KMS instances behind a load-balancer/VIP,
or using LoadBalancingKMSClientProvider.
When using multiple KMS instances behind a load-balancer or VIP, requests from the same user may be handled by different KMS instances.
In both approaches, KMS instances must be specially configured to work properly
as a single logical service, because requests from the same client may be
handled by different KMS instances. In particular,
Kerberos Principals Configuration, HTTP Authentication Signature and Delegation
Tokens require special attention.
KMS instances behind a load-balancer or VIP must be specially configured to work properly as a single logical service.
$H4 Behind a Load-Balancer or VIP
Because KMS clients and servers communicate via a REST API over HTTP,
Load-balancer or VIP may be used to distribute incoming traffic to achieve
scalability and HA. In this mode, clients are unaware of multiple KMS instances
at the server-side.
$H4 Using LoadBalancingKMSClientProvider
An alternative to running multiple KMS instances behind a load-balancer or VIP,
is to use LoadBalancingKMSClientProvider. Using this approach, a KMS client
(for example, a HDFS NameNode) is aware of multiple KMS instances, and it sends
requests to them in a round-robin fashion. LoadBalancingKMSClientProvider is
implicitly used when more than one URI is specified in
`dfs.encryption.key.provider.uri`.
The following example in `hdfs-site.xml` configures two KMS
instances, `kms01.example.com` and `kms02.example.com`.
The hostnames are separated by semi-colons, and all KMS instances must run
on the same port.
<property>
<name>dfs.encryption.key.provider.uri</name>
<value>kms://https@kms01.example.com;kms02.example.com:9600/kms</value>
<description>
The KeyProvider to use when interacting with encryption keys used
when reading and writing to an encryption zone.
</description>
</property>
If a request to a KMS instance fails, clients retry with the next instance. The
request is returned as failure only if all instances fail.
$H4 HTTP Kerberos Principals Configuration