Welcome to Livy, the REST Spark Server

Livy is an open source REST interface for interacting with Spark from anywhere. It supports executing snippets of code or programs in a Spark context that runs locally or in YARN.

• Interactive Scala, Python and R shells
• Batch submissions in Scala, Java, Python
• Multi users can share the same server (impersonation support)
• Can be used for submitting jobs from anywhere with REST
• Does not require any code change to your programs

Pull requests are welcomed! But before you begin, please check out the Wiki.

Quick Start

Livy is used for powering the Spark snippets of the Hadoop Notebook of Hue 3.8, which you can see the implementation here.

See the API documentation below and some curl examples:

• Interactive shells
• Batch jobs
• Shared RDDs

Prerequisites

To build/run Livy, you will need:

Debian/Ubuntu:

• mvn (from maven package or maven3 tarball)
• openjdk-7-jdk (or Oracle Java7 jdk)
• spark 1.4+ from (from Apache Spark tarball)
• Python 2.6+
• R 3.x

Redhat/CentOS:

• mvn (from maven package or maven3 tarball)
• java-1.7.0-openjdk (or Oracle Java7 jdk)
• spark 1.4+ (from Apache Spark tarball)
• Python 2.6+
• R 3.x

MacOS:

• Xcode command line tools
• Oracle's JDK 1.7+
• Maven (Homebrew)
• apache-spark 1.5 (Homebrew)
• Python 2.6+
• R 3.x

Building Livy

Livy is built using Apache Maven. To checkout and build Livy, run:

% git clone [email protected]:cloudera/livy.git
% mvn -DskipTests clean package

By default Livy is built with the Cloudera distribution of Spark (currently based off Spark 1.5.0), but it is simple to support other versions, such as Spark 1.4.1, by compiling Livy with:

% mvn -DskipTests -Dspark.version=1.4.1 clean package

Running Tests

In order to run the Livy Tests, first follow the instructions in Building Livy. Then run:

% export SPARK_HOME=/usr/lib/spark
% export HADOOP_CONF_DIR=/etc/hadoop/conf
% mvn test

Running Livy

In order to run Livy with local sessions, first export these variables:

% export SPARK_HOME=/usr/lib/spark
% export HADOOP_CONF_DIR=/etc/hadoop/conf

Then start the server with:

% ./bin/livy-server

Or with YARN sessions by running:

% env \
  LIVY_SERVER_JAVA_OPTS="-Dlivy.server.session.factory=yarn" \
  CLASSPATH=`hadoop classpath` \
  $LIVY_HOME/bin/livy-server

Livy Configuration

The properties of the server can be modified by copying livy-defaults.conf.template and renaming it conf/livy-defaults.conf. The Livy configuration directory can be placed in an alternative directory by defining LIVY_CONF_DIR.

In particular the YARN mode (default is local process for development) can be set with:

livy.server.session.factory = yarn

Spark Configuration

Livy's Spark sessions are configured through two mechanisms. First, is by way of the local Spark configuration. Create, or modify the Spark configuration files as directed, and point Livy at this directory with:

% env \
  SPARK_CONF_DIR=... \
  $LIVY_HOME/bin/livy-server

The second mechanism is by white listing Spark configuration options that can be set by the user creating a Spark session. This list can be created by copying spark-user-configurable-options.template to spark-user-configurable-options and listing the options the user may specify in the conf session field.

warning: Be careful before enabling options. Some options may allow a malicious user to read files that are accessible by the Livy Server process user. Among other things, this might allow a user to access the Livy TLS private key, Kerberos tickets, or more.

Spark Example

Now to see it in action by interacting with it in Python with the Requests library. By default livy runs on port 8998 (which can be changed with the livy_server_port config option). We’ll start off with a Spark session that takes Scala code:

>>> import json, pprint, requests, textwrap
>>> host = 'http://localhost:8998'
>>> data = {'kind': 'spark'}
>>> headers = {'Content-Type': 'application/json'}
>>> r = requests.post(host + '/sessions', data=json.dumps(data), headers=headers)
>>> r.json()
{u'state': u'starting', u'id': 0, u’kind’: u’spark’}

Once the session has completed starting up, it transitions to the idle state:

>>> session_url = host + r.headers['location']
>>> r = requests.get(session_url, headers=headers)
>>> r.json()
{u'state': u'idle', u'id': 0, u’kind’: u’spark’}

Now we can execute Scala by passing in a simple JSON command:

>>> statements_url = session_url + '/statements'
>>> data = {'code': '1 + 1'}
>>> r = requests.post(statements_url, data=json.dumps(data), headers=headers)
>>> r.json()
{u'output': None, u'state': u'running', u'id': 0}

If a statement takes longer than a few milliseconds to execute, Livy returns early and provides a URL that can be polled until it is complete:

>>> statement_url = host + r.headers['location']
>>> r = requests.get(statement_url, headers=headers)
>>> pprint.pprint(r.json())
[{u'id': 0,
  u'output': {u'data': {u'text/plain': u'res0: Int = 2'},
              u'execution_count': 0,
              u'status': u'ok'},
  u'state': u'available'}]

That was a pretty simple example. More interesting is using Spark to estimate PI. This is from the Spark Examples:

>>> data = {
...   'code': textwrap.dedent("""\
...      val NUM_SAMPLES = 100000;
...      val count = sc.parallelize(1 to NUM_SAMPLES).map { i =>
...        val x = Math.random();
...        val y = Math.random();
...        if (x*x + y*y < 1) 1 else 0
...      }.reduce(_ + _);
...      println(\"Pi is roughly \" + 4.0 * count / NUM_SAMPLES)
...      """)
... }
>>> r = requests.post(statements_url, data=json.dumps(data), headers=headers)
>>> pprint.pprint(r.json())
{u'id': 1,
 u'output': {u'data': {u'text/plain': u'Pi is roughly 3.14004\nNUM_SAMPLES: Int = 100000\ncount: Int = 78501'},
             u'execution_count': 1,
             u'status': u'ok'},
 u'state': u'available'}

Finally, lets close our session:

>>> session_url = 'http://localhost:8998/sessions/0'
>>> requests.delete(session_url, headers=headers)
<Response [204]>

PySpark Example

pyspark has the exact same API, just with a different initial command:

>>> data = {'kind': 'pyspark'}
>>> r = requests.post(host + '/sessions', data=json.dumps(data), headers=headers)
>>> r.json()
{u'id': 1, u'state': u'idle'}

The PI example from before then can be run as:

>>> data = {
...   'code': textwrap.dedent("""\
...     import random
...     NUM_SAMPLES = 100000
...     def sample(p):
...       x, y = random.random(), random.random()
...       return 1 if x*x + y*y < 1 else 0
...
...     count = sc.parallelize(xrange(0, NUM_SAMPLES)).map(sample) \
...               .reduce(lambda a, b: a + b)
...     print "Pi is roughly %f" % (4.0 * count / NUM_SAMPLES)
...     """)
... }
>>> r = requests.post(statements_url, data=json.dumps(data), headers=headers)
>>> pprint.pprint(r.json())
{u'id': 12,
 u'output': {u'data': {u'text/plain': u'Pi is roughly 3.136000'},
             u'execution_count': 12,
             u'status': u'ok'},
 u'state': u'running'}

SparkR Example

SparkR also has the same API:

>>> data = {'kind': 'sparkR'}
>>> r = requests.post(host + '/sessions', data=json.dumps(data), headers=headers)
>>> r.json()
{u'id': 1, u'state': u'idle'}

The PI example from before then can be run as:

>>> data = {
...   'code': textwrap.dedent("""\
...      n <- 100000
...      piFunc <- function(elem) {
...        rands <- runif(n = 2, min = -1, max = 1)
...        val <- ifelse((rands[1]^2 + rands[2]^2) < 1, 1.0, 0.0)
...        val
...      }
...      piFuncVec <- function(elems) {
...        message(length(elems))
...        rands1 <- runif(n = length(elems), min = -1, max = 1)
...        rands2 <- runif(n = length(elems), min = -1, max = 1)
...        val <- ifelse((rands1^2 + rands2^2) < 1, 1.0, 0.0)
...        sum(val)
...      }
...      rdd <- parallelize(sc, 1:n, slices)
...      count <- reduce(lapplyPartition(rdd, piFuncVec), sum)
...      cat("Pi is roughly", 4.0 * count / n, "\n")
...     """)
... }
>>> r = requests.post(statements_url, data=json.dumps(data), headers=headers)
>>> pprint.pprint(r.json())
{u'id': 12,
 u'output': {u'data': {u'text/plain': u'Pi is roughly 3.136000'},
             u'execution_count': 12,
             u'status': u'ok'},
 u'state': u'running'}

Community

• User group: http://groups.google.com/a/cloudera.org/group/livy-user
• Dev group: http://groups.google.com/a/cloudera.org/group/livy-dev
• Jira: https://issues.cloudera.org/browse/LIVY
• Pull requests: https://github.com/cloudera/livy/pulls

REST API

GET /sessions

Returns all the active interactive sessions.

Response Body

name	description	type
sessions	session list	list

POST /sessions

Creates a new interative Scala, Python or R shell in the cluster.

Request Body

name	description	type
kind	The session kind (required)	session kind
proxyUser	The user to impersonate that will run this session (e.g. bob)	string
jars	Files to be placed on the java classpath	list of paths
pyFiles	Files to be placed on the PYTHONPATH	list of paths
files	Files to be placed in executor working directory	list of paths
driverMemory	Memory for driver (e.g. 1000M, 2G)	string
driverCores	Number of cores used by driver (YARN mode only)	int
executorMemory	Memory for executor (e.g. 1000M, 2G)	string
executorCores	Number of cores used by executor	int
numExecutors	Number of executors (YARN mode only)	int
archives	Archives to be uncompressed in the executor working directory (YARN mode only)	list of paths
queue	The YARN queue to submit too (YARN mode only)	string
name	Name of the application	string
conf	Spark configuration property	Map of key=val

Response Body

The created Session.

GET /sessions/{sessionId}

Return the session information

Response

The Session.

DELETE /sessions/{sessionId}

Kill the Session job.

GET /sessions/{sessionId}/logs

Get the log lines from this session.

Request Parameters

name	description	type
from	offset	int
size	amount of batches to return	int

Response Body

name	description	type
id	The session id	int
from	offset	int
size	total amount of lines	int
log	The log lines	list of strings

GET /sessions/{sessionId}/statements

Return all the statements in a session.

Response Body

name	description	type
statements	statement list	list

POST /sessions/{sessionId}/statements

Execute a statement in a session.

Request Body

name	description	type
code	The code to execute	string

Response Body

The statement object.

GET /batches

Return all the active batch jobs.

Response Body

name	description	type
batches	batch list	list

POST /batches

Request Body

name	description	type
proxyUser	The user to impersonate that will execute the job	string
file	Archive holding the file	path (required)
args	Command line arguments	list of strings
className	Application's java/spark main class	string
jars	Files to be placed on the java classpath	list of paths
pyFiles	Files to be placed on the PYTHONPATH	list of paths
files	Files to be placed in executor working directory	list of paths
driverMemory	Memory for driver (e.g. 1000M, 2G)	string
driverCores	Number of cores used by driver	int
executorMemory	Memory for executor (e.g. 1000M, 2G)	string
executorCores	Number of cores used by executor	int
numExecutors	Number of executor	int
archives	Archives to be uncompressed (YARN mode only)	list of paths
queue	The YARN queue to submit too (YARN mode only)	string
name	Name of the application	string
conf	Spark configuration property	Map of key=val

Response Body

The created Batch object.

GET /batches/{batchId}

Request Parameters

name	description	type
from	offset	int
size	amount of batches to return	int

Response Body

name	description	type
id	The batch id	int
state	The state of the batch	batch state
log	The output of the batch job	list of strings

DELETE /batches/{batchId}

Kill the Batch job.

GET /batches/{batchId}/logs

Get the log lines from this batch.

Request Parameters

name	description	type
from	offset	int
size	amount of batches to return	int

Response Body

name	description	type
id	The batch id	int
from	offset	int
size	total amount of lines	int
log	The log lines	list of strings

REST Objects

Session

Sessions represent an interactive shell.

name	description	type
id	The session id	int
kind	session kind (spark, pyspark, or sparkr)	session kind (required)
log	The log lines	list of strings
state	The session state	string

Session State

name	description
not_started	session has not been started
starting	session is starting
idle	session is waiting for input
busy	session is executing a statement
error	session errored out
dead	session has exited

Session Kind

name	description
spark	interactive scala/spark session
pyspark	interactive python/spark session
sparkr	interactive R/spark session

Statement

Statements represent the result of an execution statement.

name	description	type
id	The statement id	integer
state	The execution state	statement state
output	The execution output	statement output

Statement State

name	description
running	Statement is currently executing
available	Statement has a ready response
error	Statement failed

Statement Output

name	description	type
status	execution status	string
execution_count	a monotomically increasing number	integer
data	statement output	an object mapping a mime type to the result. If the mime type is application/json, the value will be a JSON value

Batch

name	description	type
id	The session id	int
kind	session kind (spark, pyspark, or sparkr)	session kind (required)
log	The log lines	list of strings
state	The session state	string

License

Apache License, Version 2.0 http://www.apache.org/licenses/LICENSE-2.0