Introduction

The CDAP 4.0 UI is designed to provide operational insights about both - CDAP services as well as other service providers such as YARN, HBase and HDFS. The CDAP platform will need to expose additional APIs to surface this information.

Goals

The operational APIs should surface information for the Management Screen

These designs translate into the following requirements:

CDAP Uptime
- P1: Should indicate the time (number of hours, days?) for which the CDAP Master process has been running.
- P2: In an HA environment, it would be nice to indicate the time of the last master failover.
CDAP System Services:
- P1: Should indicate the current number of instances.
- P1: Should have a way to scale services.
- P1: Should show service logs
- P2: Node name where container started
- P2: Container name
- P2: master.services YARN application name
Middle Drawer:
- CDAP:
  - P1: # of masters, routers, kafka-servers, auth-servers
  - P1: Router requests - # 200s, 404s, 500s
  - P1: # namespaces, artifacts, apps, programs, datasets, streams, views
  - P1: Transaction snapshot summary (invalid, in-progress, committing, committed)
  - P1: Logs/Metrics service lags
  - P2: Last GC pause time
- HDFS:
  - P1: Space metrics: yotal, free, used
  - P1: Nodes: yotal, healthy, decommissioned, decommissionInProgress
  - P1: Blocks: missing, corrupt, under-replicated
- YARN:
  - P1: Nodes: total, new, running, unhealthy, decommissioned, lost, rebooted
  - P1: Apps: total, submitted, accepted, running, failed, killed, new, new_saving
  - P1: Memory: total, used, free
  - P1: Virtual Cores: total, used, free
  - P1: Queues: total, stopped, running, max_capacity, current_capacity
- HBase
  - P1: Nodes: total_regionservers, live_regionservers, dead_regionservers, masters
  - P1: No. of namespaces, tables
  - P2: Last major compaction (time + info)
- Zookeeper: Most of these are from the output of echo mntr | nc localhost 2181
  - P1: Num of alive connections
  - P1: Num of znodes
  - P1: Num of watches
  - P1: Num of ephemeral nodes
  - P1: Data size
  - P1: Open file descriptor count
  - P1: Max file descriptor count
- Kafka
  - JMX Metrics that Kafka exposes: https://kafka.apache.org/documentation#monitoring
  - P1: # of topics
  - P1: Message in rate
  - P1: Request rate
  - P1: # of under replicated partitions
  - P1: Partition counts
- Sentry
  - P1: # of roles
  - P1: # of privileges
  - P1: memory: total, used, available
  - P1: requests per second
  - any more?
- KMS
  - TBD: Having a hard time hitting the JMX endpoint for KMS
Component Overview
- P1: YARN, HDFS, HBase, Zoookeeper, Kafka, Hive
- P1: For each component: version, url, logs_url
- P2: Sentry, KMS
- P2: Distribution info
- P2: Plus button - to store custom components and version, url, logs_url for each.

User Stories

As a CDAP admin, I would like a single place to perform health checks and monitoring for CDAP system services as well as service providers that CDAP depends upon.
As a CDAP admin, I would like to have insights into the health of all CDAP system services including master, log saver, explore container, metrics processor, metrics, streams, transaction server and dataset executor
As a CDAP admin, I would like to know information about my CDAP setup including the version of CDAP
As a CDAP admin, I would like to know the uptime of CDAP including optionally the time since the last failover in an HA scenario
As a CDAP admin, I would like to know the versions and (optionally) links to the web UI and logs if available of the underlying infrastructure components.
As a CDAP admin, I would like to have operational insights including stats such as request rate, node status, available compute as well as storage capacity for the underlying infrastructure components that CDAP relies upon. These insights should help me understand the health of these components as well as help in root cause analysis in case CDAP fails or performs poorly.

Design

Data Sources

Versions

CDAP - co.cask.cdap.common.utils.ProjectInfo
HBase - co.cask.cdap.data2.util.hbase.HBaseVersion
YARN - org.apache.hadoop.yarn.util.YarnVersionInfo
HDFS - org.apache.hadoop.util.VersionInfo
Zookeeper - No client API available. Will have to build a utility around echo stat | nc localhost 2181
Hive - org.apache.hive.common.util.HiveVersionInfo

URL

CDAP - $(dashboard.bind.address) + $(dashboard.bind.port)
YARN - $(yarn.resourcemanager.webapp.address)
HDFS - $(dfs.namenode.http-address)
HBase - hbaseAdmin.getClusterStatus().getMaster().toString()

HDFS

DistributedFileSystem - For HDFS stats

YARN

YarnClient - for YARN stats and info

HBase

HBaseAdmin - for HBase stats and info

Kafka

JMX

Reference: https://github.com/linkedin/kafka-monitor

Zookeeper

Option 1: Four letter commands - mntr. Drawbacks: mntr was introduced in 3.5.0 - users may be running older versions of Zookeeper

Option 2: Zookeeper also exposes JMX - https://zookeeper.apache.org/doc/trunk/zookeeperJMX.html

HiveServer2

TBD

Sentry

JMX

The following is available by enabling the sentry web service (ref: http://www.cloudera.com/documentation/enterprise/latest/topics/sg_sentry_metrics.html) and querying for metrics (API: http://[sentry-service-host]:51000/metrics?pretty=true).

Code Block

language	java
title	Sentry JMX output
collapse	true

{
  "version" : "3.0.0",
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    "buffers.direct.capacity" : {
      "value" : 57344
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      "value" : 5
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      "value" : 0
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      "value" : 0
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      "value" : 0
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  "counters" : { },
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}

KMS

KMS also exposes JMX via the endpoint http://host:16000/kms/jmx.

TODO: CDAP Master Uptime?

Caching

It is not possible to hit HBase/YARN/HDFS for every request from the UI. As a result, the result of the stats API will have to be cached, with a configurable time to live. The cache will be keyed by the service provider name, with the value as the stats for the service provider. In addition to a time-to-live, the cache will also need to be invalidated when:

In the ProgramController and ProgramRuntimeService class hierarchy, so YARN stats can be updated

In the Entity (app, dataset, stream) lifecycle (creation and deletion) when storage stats will need to be updated

P3: In the authorization class hierarchy, when the authorization stats may need to be updated. However, we may choose to not do this, because we eventually want to get out of the business of managing authorization policies in CDAP

TODO: Invalidation for Kafka and Zookeeper

Implementation

The service provider stats fetchers will be implemented as extensions. Each such extension will be installed by CDAP in the master/ext/operations directory as jar files. Each jar file in this directory will be scanned for implementations of the ServiceProviderStatsCollector interface defined below. There will be one implementation of this interface for every service provider. A single jar file may contain multiple implementations of this interface. These classes will be loaded in a separate classloader. However, at this point, there will not be classloader isolation. The classloader that loads these classes will have the CDAP system classloader as the parent.

Code Block

public interface ServiceProviderStatsCollector {
	/**
	 * Returns the name of the service provider for which operational stats will be collected.
	 */
	String getServiceProviderName();
 
	/**
	 * Returns the operational stats for the service provider.
	 */
	Map<String, Object> getServiceProviderStats();
}

TODO: CDAP Master Uptime?

Caching

There will not be any caching in these APIs. Since it is ok for the UI to only poll every 15 seconds or even less frequently, it should be ok to hit the service providers for every request.

API changes

New REST APIs

The following REST APIs will be exposed from app fabric.

Path

Method

Description

Response Code

Response

/v3/system/serviceproviders

GET

Lists all the available service providers and (optionally) minimal info about each (version, url and logs_url)

200 - On success

500 - Any internal errors

Code Block

language	java
title	List Service Providers Response
collapse	true

{
  "hdfs": {
    "version": "2.7.0",
    "url": "http://localhost:50070",
    "url": "http://localhost:50070/logs/"
  },
  "yarn": {
    "version": "2.7.0",
    "url": "http://localhost:8088",
    "logs": "http://localhost:8088/logs/"
  },
  "hbase": {
    "version": "1.0.0",
    "url": "http://localhost:50070",
    "logs": "http://localhost:60010/logs/"
  },
  "hive": {
    "version": 1.2
  },
  "zookeeper": {
    "version": "3.4.2"
  },
  "kafka": {
    "version": "2.10"
  }
}

/v3/system/serviceproviders/{service-provider-name}/stats

GET

Returns stats for the specified service provider

200 OK - stats for the specified service provider were successfully fetched

503 Unavailable - Could not contact the service provider for status

404 Not found - Service provider not found (not in the list returned by the list service providers API)

500 - Any other internal errors

Code Block

language	java
title	CDAP Stats Response
collapse	true

{
    "services": {
      "masters": 2,
      "kafka-servers": 2,
      "routers": 1,
      "auth-servers": 1
    },
    "entities": {
      "namespaces": 10,
      "apps": 46,
      "artifacts": 23,
      "datasets": 68,
      "streams": 34,
      "programs": 78
    }
}

Code Block

language	java
title	HDFS Stats Response
collapse	true

{
    "storage": {
      "total": 3452759234,
      "used": 34525543,
      "available": 3443555345
    },
    "nodes": {
      "total": 40,
      "healthy": 36,
      "decommissioned": 3,
      "decommissionInProgress": 1
    },
    "blocks": {
      "missing": 33,
      "corrupt": 3,
      "underreplicated": 5
    }
}

Code Block

language	java
title	YARN Stats Response
collapse	true

{
    "nodes": {
      "total": 35,
      "new": 0,
      "running": 30,
      "unhealthy": 1,
      "decommissioned": 2,
      "lost": 1,
      "rebooted": 1
    },
    "apps": {
      "total": 30,
      "submitted": 2,
      "accepted": 4,
      "running": 20,
      "failed": 1,
      "killed": 3,
      "new": 0,
      "new_saving": 0
    },
    "memory": {
      "total": 8192,
      "used": 7168,
      "available": 1024
    },
    "virtualCores": {
      "total": 36,
      "used": 12,
      "available": 24
    },
    "queues": {
      "total": 10,
      "stopped": 2,
      "running": 8,
      "maxCapacity": 32,
      "currentCapacity": 21
    }
}

Code Block

language	java
title	HBase Stats Response
collapse	true

{
    "nodes": {
      "totalRegionServers": 37,
      "liveRegionServers": 34,
      "deadRegionServers": 3,
      "masters": 3
    },
    "entities": {
      "tables": 56,
      "namespaces": 43
    }
}

TODO: Add responses for Kafka, Zookeeper, Sentry, KMS

CLI Impact or Changes

New CLI commands will have to be added to front the two new APIs.

List Service Providers

list service providers

Get Service Provider Stats

get stats for service provider <service-provider>

UI Impact or Changes

The Management screen on the CDAP 4.0 UI will have to be implemented using the APIs exposed by this design in addition to existing APIs for getting System Service Status and Logs

Security Impact

Currently CDAP does not enforce authorization for the system services APIs -

Jira Legacy

server	Cask Community Issue Tracker
columns	key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution
serverId	45b48dee-c8d6-34f0-9990-e6367dc2fe4b
key	CDAP-6917

. The APIs in this design should enforce the same authorization policies as will be implemented for the system services APIs. Ideally, only users that have ADMIN privileges on the CDAP instance should be able to execute these APIs successfully.

Impact on Infrastructure Outages

Test Scenarios

Test ID	Test Description	Expected Results
T1	Positive test for list API	Should return all the configured service providers
T2	Positive test for stats of each service provider	Should return the appropriate details for each service provider
T3	Stop a configured storage provider and hit the API to get its stats	Should return 503 with a proper error message
T4	Hit the API to get stats of a non-existent API	Should return 404 with a proper error message
T5	Hit the stats API repeatedly without making any changes that impact the service provider stats	The API should perform well because of caching. Only after the cache entries time out should a call be made to the storage provider to do a refresh
T6	Cache invalidation scenario #1	After a program changes state (start/stop), the stats API should reflect the change immediately.
T7	Cache invalidation scenario #2	After a new entity is created/deleted, the stats APIs for storage providers (HDFS/Hive/HBase) should return updated information

Releases

Release 4.0.0

Ground work for collecting stats from infrastructure components.
Focus on HDFS, YARN, HBase, Hive, Kafka, Zookeeper (in that order)

Release 4.1.0

More components such as Hive, Kafka, Zookeeper, Sentry, KMS (in that order).

Related Work

Monitor APIs

Future work

TBD

Versions Compared

Old Version 38

New Version 39

Key

Introduction

Goals

User Stories

Design

Data Sources

Versions

URL

HDFS

YARN

HBase

Kafka

Zookeeper

HiveServer2

Sentry

KMS

TODO: CDAP Master Uptime?

Caching

Implementation

TODO: CDAP Master Uptime?

Caching

API changes

New REST APIs

CLI Impact or Changes

List Service Providers

Get Service Provider Stats

UI Impact or Changes

Security Impact

Impact on Infrastructure Outages

Test Scenarios

Releases

Release 4.0.0

Release 4.1.0

Related Work

Future work

Page Comparison

Versions Compared

Old Version 38

New Version 39

Key

Introduction

Goals

User Stories

Design

Data Sources

Versions

URL

HDFS

YARN

HBase

Kafka

Zookeeper

HiveServer2

Sentry

KMS

TODO: CDAP Master Uptime?

Caching

Implementation

TODO: CDAP Master Uptime?

Caching

API changes

New REST APIs

CLI Impact or Changes

List Service Providers

Get Service Provider Stats

UI Impact or Changes

Security Impact

Impact on Infrastructure Outages

Test Scenarios

Releases

Release 4.0.0

Release 4.1.0

Related Work

Future work