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Batch Data Ingestion

There are two choices for batch data ingestion to your Druid cluster, you can use the Indexing service or you can use the HadoopDruidIndexer.

Which should I use?

The Indexing service is a set of nodes that can run as part of your Druid cluster and can accomplish a number of different types of indexing tasks. Even if all you care about is batch indexing, it provides for the encapsulation of things like the metadata store that is used for segment metadata and other things, so that your indexing tasks do not need to include such information. The indexing service was created such that external systems could programmatically interact with it and run periodic indexing tasks. Long-term, the indexing service is going to be the preferred method of ingesting data.

The HadoopDruidIndexer runs hadoop jobs in order to separate and index data segments. It takes advantage of Hadoop as a job scheduling and distributed job execution platform. It is a simple method if you already have Hadoop running and don’t want to spend the time configuring and deploying the Indexing service just yet.

Batch Ingestion using the HadoopDruidIndexer

The HadoopDruidIndexer can be run like so:

java -Xmx256m -Duser.timezone=UTC -Dfile.encoding=UTF-8 -classpath lib/*:<hadoop_config_path> io.druid.cli.Main index hadoop <spec_file>

Hadoop "specFile"

The spec_file is a path to a file that contains JSON and an example looks like:

{
  "dataSchema" : {
    "dataSource" : "wikipedia",
    "parser" : {
      "type" : "string",
      "parseSpec" : {
        "format" : "json",
        "timestampSpec" : {
          "column" : "timestamp",
          "format" : "auto"
        },
        "dimensionsSpec" : {
          "dimensions": ["page","language","user","unpatrolled","newPage","robot","anonymous","namespace","continent","country","region","city"],
          "dimensionExclusions" : [],
          "spatialDimensions" : []
        }
      }
    },
    "metricsSpec" : [
      {
        "type" : "count",
        "name" : "count"
      },
      {
        "type" : "doubleSum",
        "name" : "added",
        "fieldName" : "added"
      },
      {
        "type" : "doubleSum",
        "name" : "deleted",
        "fieldName" : "deleted"
      },
      {
        "type" : "doubleSum",
        "name" : "delta",
        "fieldName" : "delta"
      }
    ],
    "granularitySpec" : {
      "type" : "uniform",
      "segmentGranularity" : "DAY",
      "queryGranularity" : "NONE",
      "intervals" : [ "2013-08-31/2013-09-01" ]
    }
  },
  "ioConfig" : {
    "type" : "hadoop",
    "inputSpec" : {
      "type" : "static",
      "paths" : "/MyDirectory/examples/indexing/wikipedia_data.json"
    },
    "metadataUpdateSpec" : {
      "type":"metadata",
      "connectURI" : "jdbc:metadata storage://localhost:3306/druid",
      "password" : "diurd",
      "segmentTable" : "druid_segments",
      "user" : "druid"
    },
    "segmentOutputPath" : "/MyDirectory/data/index/output"
  },
  "tuningConfig" : {
    "type" : "hadoop",
    "workingPath": "/tmp",
    "partitionsSpec" : {
      "type" : "dimension",
      "partitionDimension" : null,
      "targetPartitionSize" : 5000000,
      "maxPartitionSize" : 7500000,
      "assumeGrouped" : false,
      "numShards" : -1
    },
    "shardSpecs" : { },
    "leaveIntermediate" : false,
    "cleanupOnFailure" : true,
    "overwriteFiles" : false,
    "ignoreInvalidRows" : false,
    "jobProperties" : { },
    "combineText" : false,
    "persistInHeap" : false,
    "ingestOffheap" : false,
    "bufferSize" : 134217728,
    "aggregationBufferRatio" : 0.5,
    "rowFlushBoundary" : 300000
  }
}

DataSchema

This field is required.

See Ingestion

IOConfig

This field is required.

Field	Type	Description	Required
type	String	This should always be 'hadoop'.	yes
pathSpec	Object	a specification of where to pull the data in from	yes
segmentOutputPath	String	the path to dump segments into.	yes
metadataUpdateSpec	Object	a specification of how to update the metadata for the druid cluster these segments belong to.	yes

Path specification

There are multiple types of path specification:

`static`

Is a type of data loader where a static path to where the data files are located is passed.

Field	Type	Description	Required
paths	Array of String	A String of input paths indicating where the raw data is located.	yes

For example, using the static input paths:

"paths" : "s3n://billy-bucket/the/data/is/here/data.gz, s3n://billy-bucket/the/data/is/here/moredata.gz, s3n://billy-bucket/the/data/is/here/evenmoredata.gz"

`granularity`

Is a type of data loader that expects data to be laid out in a specific path format. Specifically, it expects it to be segregated by day in this directory format y=XXXX/m=XX/d=XX/H=XX/M=XX/S=XX (dates are represented by lowercase, time is represented by uppercase).

Field	Type	Description	Required
dataGranularity	Object	specifies the granularity to expect the data at, e.g. hour means to expect directories `y=XXXX/m=XX/d=XX/H=XX`.	yes
inputPath	String	Base path to append the expected time path to.	yes
filePattern	String	Pattern that files should match to be included.	yes

For example, if the sample config were run with the interval 2012-06-01/2012-06-02, it would expect data at the paths

s3n://billy-bucket/the/data/is/here/y=2012/m=06/d=01/H=00
s3n://billy-bucket/the/data/is/here/y=2012/m=06/d=01/H=01
...
s3n://billy-bucket/the/data/is/here/y=2012/m=06/d=01/H=23

Metadata Update Job Spec

This is a specification of the properties that tell the job how to update metadata such that the Druid cluster will see the output segments and load them.

Field	Type	Description	Required
type	String	"metadata" is the only value available.	yes
connectURI	String	A valid JDBC url to metadata storage.	yes
user	String	Username for db.	yes
password	String	password for db.	yes
segmentTable	String	Table to use in DB.	yes

These properties should parrot what you have configured for your Coordinator.

TuningConfig

The tuningConfig is optional and default parameters will be used if no tuningConfig is specified.

Field	Type	Description	Required
workingPath	String	the working path to use for intermediate results (results between Hadoop jobs).	no (default == '/tmp/druid-indexing')
version	String	The version of created segments.	no (default == datetime that indexing starts at)
leaveIntermediate	leave behind files in the workingPath when job completes or fails (debugging tool).	no (default == false)
partitionsSpec	Object	a specification of how to partition each time bucket into segments, absence of this property means no partitioning will occur.More details below.	no (default == 'hashed'
maxRowsInMemory	Integer	The number of rows to aggregate before persisting. This number is the post-aggregation rows, so it is not equivalent to the number of input events, but the number of aggregated rows that those events result in. This is used to manage the required JVM heap size.	no (default == 5 million)
cleanupOnFailure	Boolean	Cleans up intermediate files when the job fails as opposed to leaving them around for debugging.	no (default == true)
overwriteFiles	Boolean	Override existing files found during indexing.	no (default == false)
ignoreInvalidRows	Boolean	Ignore rows found to have problems.	no (default == false)
jobProperties	Object	a map of properties to add to the Hadoop job configuration.	no (default == null)

Partitioning specification

Segments are always partitioned based on timestamp (according to the granularitySpec) and may be further partitioned in some other way depending on partition type. Druid supports two types of partitioning strategies: "hashed" (based on the hash of all dimensions in each row), and "dimension" (based on ranges of a single dimension).

Hashed partitioning is recommended in most cases, as it will improve indexing performance and create more uniformly sized data segments relative to single-dimension partitioning.

Hash-based partitioning

  "partitionsSpec": {
     "type": "hashed",
     "targetPartitionSize": 5000000
   }

Hashed partitioning works by first selecting a number of segments, and then partitioning rows across those segments according to the hash of all dimensions in each row. The number of segments is determined automatically based on the cardinality of the input set and a target partition size.

The configuration options are:

property	description	required?
type	type of partitionSpec to be used	"hashed"
targetPartitionSize	target number of rows to include in a partition, should be a number that targets segments of 500MB~1GB.	either this or numShards
numShards	specify the number of partitions directly, instead of a target partition size. Ingestion will run faster, since it can skip the step necessary to select a number of partitions automatically.	either this or targetPartitionSize

Single-dimension partitioning

  "partitionsSpec": {
     "type": "dimension",
     "targetPartitionSize": 5000000
   }

Single-dimension partitioning works by first selecting a dimension to partition on, and then separating that dimension into contiguous ranges. Each segment will contain all rows with values of that dimension in that range. For example, your segments may be partitioned on the dimension "host" using the ranges "a.example.com" to "f.example.com" and "f.example.com" to "z.example.com". By default, the dimension to use is determined automatically, although you can override it with a specific dimension.

The configuration options are:

property	description	required?
type	type of partitionSpec to be used	"dimension"
targetPartitionSize	target number of rows to include in a partition, should be a number that targets segments of 500MB~1GB.	yes
maxPartitionSize	maximum number of rows to include in a partition. Defaults to 50% larger than the targetPartitionSize.	no
partitionDimension	the dimension to partition on. Leave blank to select a dimension automatically.	no
assumeGrouped	assume input data has already been grouped on time and dimensions. Ingestion will run faster, but can choose suboptimal partitions if the assumption is violated.	no

Batch Ingestion Using the Indexing Service

Batch ingestion for the indexing service is done by submitting an Index Task (for datasets < 1G) or a Hadoop Index Task. The indexing service can be started by issuing:

java -Xmx2g -Duser.timezone=UTC -Dfile.encoding=UTF-8 -classpath lib/*:config/overlord io.druid.cli.Main server overlord

This will start up a very simple local indexing service. For more complex deployments of the indexing service, see here.

The schema of the Hadoop Index Task contains a task "type" and a Hadoop Index Config. A sample Hadoop index task is shown below:

{
  "type" : "index_hadoop",
  "spec" : {
    "dataSchema" : {
      "dataSource" : "wikipedia",
      "parser" : {
        "type" : "string",
        "parseSpec" : {
          "format" : "json",
          "timestampSpec" : {
            "column" : "timestamp",
            "format" : "auto"
          },
          "dimensionsSpec" : {
            "dimensions": ["page","language","user","unpatrolled","newPage","robot","anonymous","namespace","continent","country","region","city"],
            "dimensionExclusions" : [],
            "spatialDimensions" : []
          }
        }
      },
      "metricsSpec" : [
        {
          "type" : "count",
          "name" : "count"
        },
        {
          "type" : "doubleSum",
          "name" : "added",
          "fieldName" : "added"
        },
        {
          "type" : "doubleSum",
          "name" : "deleted",
          "fieldName" : "deleted"
        },
        {
          "type" : "doubleSum",
          "name" : "delta",
          "fieldName" : "delta"
        }
      ],
      "granularitySpec" : {
        "type" : "uniform",
        "segmentGranularity" : "DAY",
        "queryGranularity" : "NONE",
        "intervals" : [ "2013-08-31/2013-09-01" ]
      }
    },
    "ioConfig" : {
      "type" : "hadoop",
      "inputSpec" : {
        "type" : "static",
        "paths" : "/MyDirectory/examples/indexing/wikipedia_data.json"
      }
    },
    "tuningConfig" : {
      "type": "hadoop"
    }
  }
}

DataSchema

This field is required.

See Ingestion

IOConfig

This field is required.

Field	Type	Description	Required
type	String	This should always be 'hadoop'.	yes
pathSpec	Object	a specification of where to pull the data in from	yes

TuningConfig

The tuningConfig is optional and default parameters will be used if no tuningConfig is specified. This is the same as the tuningConfig for the standalone Hadoop indexer. See above for more details.

Running the Task

The Hadoop Index Config submitted as part of an Hadoop Index Task is identical to the Hadoop Index Config used by the HadoopBatchIndexer except that three fields must be omitted: segmentOutputPath, workingPath, updaterJobSpec. The Indexing Service takes care of setting these fields internally.

To run the task:

curl -X 'POST' -H 'Content-Type:application/json' -d @example_index_hadoop_task.json localhost:8087/druid/indexer/v1/task

If the task succeeds, you should see in the logs of the indexing service:

2013-10-16 16:38:31,945 INFO [pool-6-thread-1] io.druid.indexing.overlord.exec.TaskConsumer - Task SUCCESS: HadoopIndexTask...

Having Problems?

Getting data into Druid can definitely be difficult for first time users. Please don't hesitate to ask questions in our IRC channel or on our google groups page.

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Batch Data Ingestion

Which should I use?

Batch Ingestion using the HadoopDruidIndexer

Hadoop "specFile"

DataSchema

IOConfig

Path specification

static

granularity

Metadata Update Job Spec

TuningConfig

Partitioning specification

Hash-based partitioning

Single-dimension partitioning

Batch Ingestion Using the Indexing Service

DataSchema

IOConfig

TuningConfig

Running the Task

Having Problems?

14 KiB

Raw Blame History

`static`

`granularity`