druid/docs/content/development/extensions-core/namespaced-lookup.md

layout
doc_page

Namespaced Lookup

Lookups are an experimental feature.

Make sure to include druid-namespace-lookup as an extension.

Configuration

Namespaced lookups are appropriate for lookups which are not possible to pass at query time due to their size, or are not desired to be passed at query time because the data is to reside in and be handled by the Druid servers. Namespaced lookups can be specified as part of the runtime properties file. The property is a list of the namespaces described as per the sections on this page. For example:

druid.query.extraction.namespace.lookups=
  [
    {
      "type": "uri",
      "namespace": "some_uri_lookup",
      "uri": "file:/tmp/prefix/",
      "namespaceParseSpec": {
        "format": "csv",
        "columns": [
          "key",
          "value"
        ]
      },
      "pollPeriod": "PT5M"
    },
    {
      "type": "jdbc",
      "namespace": "some_jdbc_lookup",
      "connectorConfig": {
        "createTables": true,
        "connectURI": "jdbc:mysql:\/\/localhost:3306\/druid",
        "user": "druid",
        "password": "diurd"
      },
      "table": "lookupTable",
      "keyColumn": "mykeyColumn",
      "valueColumn": "MyValueColumn",
      "tsColumn": "timeColumn"
    }
  ]

Proper functionality of Namespaced lookups requires the following extension to be loaded on the broker, peon, and historical nodes: druid-namespace-lookup

Cache Settings

Lookups are cached locally on historical nodes. The following are settings used by the nodes which service queries when setting namespaces (broker, peon, historical)

Property	Description	Default
druid.query.extraction.namespace.cache.type	Specifies the type of caching to be used by the namespaces. May be one of [offHeap, onHeap]. offHeap uses a temporary file for off-heap storage of the namespace (memory mapped files). onHeap stores all cache on the heap in standard java map types.	onHeap

The cache is populated in different ways depending on the settings below. In general, most namespaces employ a pollPeriod at the end of which time they poll the remote resource of interest for updates.

Supported Lookups

For additional lookups, please see our extensions list.

URI namespace update

The remapping values for each namespaced lookup can be specified by json as per

{
  "type":"uri",
  "namespace":"some_lookup",
  "uri": "s3://bucket/some/key/prefix/",
  "namespaceParseSpec":{
    "format":"csv",
    "columns":["key","value"]
  },
  "pollPeriod":"PT5M",
  "versionRegex": "renames-[0-9]*\\.gz"
}

Property	Description	Required	Default
namespace	The namespace to define	Yes
pollPeriod	Period between polling for updates	No	0 (only once)
versionRegex	Regex to help find newer versions of the namespace data	Yes
namespaceParseSpec	How to interpret the data at the URI	Yes

The pollPeriod value specifies the period in ISO 8601 format between checks for updates. If the source of the lookup is capable of providing a timestamp, the lookup will only be updated if it has changed since the prior tick of pollPeriod. A value of 0, an absent parameter, or null all mean populate once and do not attempt to update. Whenever an update occurs, the updating system will look for a file with the most recent timestamp and assume that one with the most recent data.

The versionRegex value specifies a regex to use to determine if a filename in the parent path of the uri should be considered when trying to find the latest version. Omitting this setting or setting it equal to null will match to all files it can find (equivalent to using ".*"). The search occurs in the most significant "directory" of the uri.

The namespaceParseSpec can be one of a number of values. Each of the examples below would rename foo to bar, baz to bat, and buck to truck. All parseSpec types assumes each input is delimited by a new line. See below for the types of parseSpec supported.

csv lookupParseSpec

Parameter	Description	Required	Default
columns	The list of columns in the csv file	yes	null
keyColumn	The name of the column containing the key	no	The first column
valueColumn	The name of the column containing the value	no	The second column

example input

bar,something,foo
bat,something2,baz
truck,something3,buck

example namespaceParseSpec

"namespaceParseSpec": {
  "format": "csv",
  "columns": ["value","somethingElse","key"],
  "keyColumn": "key",
  "valueColumn": "value"
}

tsv lookupParseSpec

Parameter	Description	Required	Default
columns	The list of columns in the csv file	yes	null
keyColumn	The name of the column containing the key	no	The first column
valueColumn	The name of the column containing the value	no	The second column
delimiter	The delimiter in the file	no	tab (\t)

example input

bar|something,1|foo
bat|something,2|baz
truck|something,3|buck

example namespaceParseSpec

"namespaceParseSpec": {
  "format": "tsv",
  "columns": ["value","somethingElse","key"],
  "keyColumn": "key",
  "valueColumn": "value",
  "delimiter": "|"
}

customJson lookupParseSpec

Parameter	Description	Required	Default
keyFieldName	The field name of the key	yes	null
valueFieldName	The field name of the value	yes	null

example input

{"key": "foo", "value": "bar", "somethingElse" : "something"}
{"key": "baz", "value": "bat", "somethingElse" : "something"}
{"key": "buck", "somethingElse": "something", "value": "truck"}

example namespaceParseSpec

"namespaceParseSpec": {
  "format": "customJson",
  "keyFieldName": "key",
  "valueFieldName": "value"
}

simpleJson lookupParseSpec

The simpleJson lookupParseSpec does not take any parameters. It is simply a line delimited json file where the field is the key, and the field's value is the value.

example input

{"foo": "bar"}
{"baz": "bat"}
{"buck": "truck"}

example namespaceParseSpec

"namespaceParseSpec":{
  "format": "simpleJson"
}

JDBC namespaced lookup

The JDBC lookups will poll a database to populate its local cache. If the tsColumn is set it must be able to accept comparisons in the format '2015-01-01 00:00:00'. For example, the following must be valid sql for the table SELECT * FROM some_lookup_table WHERE timestamp_column > '2015-01-01 00:00:00'. If tsColumn is set, the caching service will attempt to only poll values that were written after the last sync. If tsColumn is not set, the entire table is pulled every time.

Parameter	Description	Required	Default
namespace	The namespace to define	Yes
connectorConfig	The connector config to use	Yes
table	The table which contains the key value pairs	Yes
keyColumn	The column in table which contains the keys	Yes
valueColumn	The column in table which contains the values	Yes
tsColumn	The column in table which contains when the key was updated	No	Not used
pollPeriod	How often to poll the DB	No	0 (only once)

{
  "type":"jdbc",
  "namespace":"some_lookup",
  "connectorConfig":{
    "createTables":true,
    "connectURI":"jdbc:mysql://localhost:3306/druid",
    "user":"druid",
    "password":"diurd"
  },
  "table":"some_lookup_table",
  "keyColumn":"the_old_dim_value",
  "valueColumn":"the_new_dim_value",
  "tsColumn":"timestamp_column",
  "pollPeriod":600000
}