diff --git a/hadoop-project/src/site/site.xml b/hadoop-project/src/site/site.xml index 6fc3cf993f..8cb57c833c 100644 --- a/hadoop-project/src/site/site.xml +++ b/hadoop-project/src/site/site.xml @@ -154,7 +154,12 @@ - + + + + + + diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/native-services/NativeServicesDiscovery.md b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/native-services/NativeServicesDiscovery.md new file mode 100644 index 0000000000..4a048afeb7 --- /dev/null +++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/native-services/NativeServicesDiscovery.md @@ -0,0 +1,127 @@ +# YARN DNS Server +## Introduction + +The YARN DNS Server provides a standard DNS interface to the information posted into the YARN Registry by deployed applications. The DNS service serves the following functions: + +1. **Exposing existing service­ discovery information via DNS**​­ - Information provided in +the current YARN service registry’s records will be converted into DNS entries, thus +allowing users to discover information about YARN applications using standard DNS +client mechanisms (for e.g. a DNS SRV Record specifying the hostname and port +number for services). +2. **Enabling Container to IP mappings​­** - Enables discovery of the IPs of containers via +standard DNS lookups. Given the availability of the records via DNS, container +name­based communication will be facilitated (e.g. ‘curl +http://myContainer.myDomain.com/endpoint’). + +## Service Properties + +The existing YARN Service Registry is leveraged as the source of information for the DNS Service. + +The following core functions are supported by the DNS­ Server: + +###Functional properties + +1. Supports creation of DNS records for end­points of the deployed YARN applications +2. Record names remain unchanged during restart of containers and/or applications +3. Supports reverse lookups (name based on IP). +4. Supports security using the standards defined by The Domain Name System Security +Extensions (DNSSEC) +5. Highly available +6. Scalable ­- The service provides the responsiveness (e.g. low­ latency) required to +respond to DNS queries (timeouts yield attempts to invoke other configured name +servers). + +###Deployment properties + +1. Supports integration with existing DNS assets (e.g. a corporate DNS server) by acting as +a DNS server for a Hadoop cluster zone/domain. The server is not intended to act as a +primary DNS server and does not forward requests to other servers. +2. The DNS Server exposes a port that can receive both TCP and UDP requests per +DNS standards. The default port for DNS protocols is in a restricted, administrative port +range (53), so the port is configurable for deployments in which the service may +not be managed via an administrative account. + +##DNS Record Name Structure + +The DNS names of generated records are composed from the following elements (labels). Note that these elements must be compatible with DNS conventions (see “Preferred Name Syntax” in RFC 1035): + +* **domain** -​­ the name of the cluster DNS domain. This name is provided as a +configuration property. In addition, it is this name that is configured at a parent DNS +server as the zone name for the defined yDNS zone (the zone for which the parent DNS +server will forward requests to yDNS). E.g. yarncluster.com +* **user­name**​ -­ the name of the application deployer. This name is the simple short­name (for +e.g. the primary component of the Kerberos principal) associated with the user launching +the application. As the user­name is one of the elements of DNS names, it is expected +that this also confirms DNS name conventions (RFC 1035 linked above) ­ so special translation is performed for names with special characters like hyphens and spaces. +* **application ­name** -​­ the name of the deployed YARN application. This name is inferred +from the YARN registry path to the application's node. Application­ name, rather thn application­ id, was chosen as a way of making it easy for users to refer to human­-readable DNS +names. This obviously mandates certain uniqueness properties on application­ names. +* **container id** -​­ the YARN assigned ID to a container (e.g. +container_e3741_1454001598828_01_000004) +* **component ­name** -​­ the name assigned to the deployed component (for e.g. a master +component). A component is a distributed element of an application or service that is +launched in a YARN container (e.g. an HBase master). One can imagine multiple +components within an application. A component­ name is not yet a first­ class concept in +YARN, but is a very useful one that we are introducing here for the sake of yDNS +entries. Many frameworks like MapReduce, Slider already have component ­names +(though, as mentioned, they are not yet supported in YARN in a first­ class fashion). +* **api** -​­ the api designation for the exposed endpoint + +###Notes about DNS Names + +* In most instances, the DNS names can be easily distinguished by the number of +elements/labels that compose the name. The cluster’s domain name is always the last +element. After that element is parsed out, reading from right to left, the first element +maps to the application ­user and so on. Wherever it is not easily distinguishable, naming conventions are used to disambiguate the name ­using a prefix such as +“container­” or suffix such as “api”. For example, an endpoint published as a +management endpoint will be referenced with the name *management­-api.griduser.yarncluster.com​*. +* Unique application ­name (per user) is not currently supported/guaranteed by YARN, but +it is supported by frameworks such as Apache Slider. The yDNS service currently +leverages the last element of the ZK path entry for the application as an +application­ name. These application­ names have to be unique for a given user.​ + +##DNS Server Functionality + +The primary functions of the DNS service are illustrated in the following diagram: + + +![DNS Functional Overview](../images/dns_overview.png "DNS Functional Overview") + +###DNS record creation +The following figure illustrates at slightly greater detail the DNS record creation and registration sequence (NOTE: service record updates would follow a similar sequence of steps, +distinguished only by the different event type): + +![DNS Functional Overview](../images/dns_record_creation.jpeg "DNS Functional Overview") + +###DNS record removal +Similarly, record removal follows a similar sequence + +![DNS Functional Overview](../images/dns_record_removal.jpeg "DNS Functional Overview") + +(NOTE: The DNS Zone requires a record as an argument for the deletion method, thus +requiring similar parsing logic to identify the specific records that should be removed). + +###DNS Service initialization +* The DNS service initializes both UDP and TCP listeners on a configured port. As +noted above, the default port of 53 is in a restricted range that is only accessible to an +account with administrative privileges. +* Subsequently, the DNS service listens for inbound DNS requests. Those requests are +standard DNS requests from users or other DNS servers (for example, DNS servers that have the +YARN DNS service configured as a forwarder). + +## Configuration +The YARN DNS server reads its configuration properties from the yarn­site.xml file. The following are the DNS associated configuration properties: + +| Name | Description | +| ------------ | ------------- | +| hadoop.registry.dns.enabled | The DNS functionality is enabled for the cluster. Default is false. | +| hadoop.registry.dns.domain-­name | The domain name for Hadoop cluster associated records. | +| hadoop.registry.dns.bind­-address | Address associated with the network interface to which the DNS listener should bind. | +| hadoop.registry.dns.bind-­port | The port number for the DNS listener. The default port is 53. However, since that port falls in a administrator­only range, typical deployments may need to specify an alternate port. | +| hadoop.registry.dns.dnssec.enabled | Indicates whether the DNSSEC support is enabled. Default is false. | +| hadoop.registry.dns.public­-key | The base64 representation of the server’s public key. Leveraged for creating the DNSKEY Record provided for DNSSEC client requests. | +| hadoop.registry.dns.private-­key-­file | The path to the standard DNSSEC private key file. Must only be readable by the DNS launching identity. See [dnssec­-keygen](https://ftp.isc.org/isc/bind/cur/9.9/doc/arm/man.dnssec-keygen.html) documentation. | +| hadoop.registry.dns­-ttl | The default TTL value to associate with DNS records. The default value is set to 1 (a value of 0 has undefined behavior). A typical value should be approximate to the time it takes YARN to restart a failed container. | +| hadoop.registry.dns.zone-­subnet | An indicator of the IP range associated with the cluster containers. The setting is utilized for the generation of the reverse zone name. | +| hadoop.registry.dns.zone-­mask | The network mask associated with the zone IP range. If specified, it is utilized to ascertain the IP range possible and come up with an appropriate reverse zone name. | +| hadoop.registry.dns.zones­-dir | A directory containing zone configuration files to read during zone initialization. This directory can contain zone master files named *zone-name.zone*. See [here](http://www.zytrax.com/books/dns/ch6/mydomain.html) for zone master file documentation.| diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/native-services/NativeServicesIntro.md b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/native-services/NativeServicesIntro.md new file mode 100644 index 0000000000..e69de29bb2 diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/resources/images/dns_overview.png b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/resources/images/dns_overview.png new file mode 100644 index 0000000000..b9e80b9327 Binary files /dev/null and b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/resources/images/dns_overview.png differ diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/resources/images/dns_record_creation.jpeg b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/resources/images/dns_record_creation.jpeg new file mode 100644 index 0000000000..63b2599f7c Binary files /dev/null and b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/resources/images/dns_record_creation.jpeg differ diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/resources/images/dns_record_removal.jpeg b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/resources/images/dns_record_removal.jpeg new file mode 100644 index 0000000000..40d870c5a4 Binary files /dev/null and b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/resources/images/dns_record_removal.jpeg differ