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Namespaced Lookup

Lookups are an experimental feature.

Make sure to include druid-lookups-cached-global as an extension.

Configuration

Static configuration is no longer supported. Only cluster wide configuration is supported

Cached namespace 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, and are small enough to reasonably populate on a node. This usually means tens to tens of thousands of entries per lookup.

Cached namespace lookups all draw from the same cache pool, allowing each node to have a fixed cache pool that can be used by namespace lookups.

Cached namespace lookups can be specified as part of the cluster wide config for lookups as a type of cachedNamespace

{
   "type": "cachedNamespace",
   "extractionNamespace": {
      "type": "uri",
      "namespace": "some_uri_lookup",
      "uri": "file:/tmp/prefix/",
      "namespaceParseSpec": {
        "format": "csv",
        "columns": [
          "key",
          "value"
        ]
      },
      "pollPeriod": "PT5M"
    },
    "firstCacheTimeout": 0
}

{
   "type": "cachedNamespace",
   "extractionNamespace": {
      "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"
   },
   "firstCacheTimeout": 120000,
   "injective":true
}

The parameters are as follows

Property	Description	Required	Default
`extractionNamespace`	Specifies how to populate the local cache. See below	Yes	-
`firstCacheTimeout`	How long to wait (in ms) for the first run of the cache to populate. 0 indicates to not wait	No	`60000` (1 minute)
`injective`	If the underlying map is injective (keys and values are unique) then optimizations can occur internally by setting this to `true`	No	`false`

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

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.lookup.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.

onHeap uses ConcurrentMaps in the java heap, and thus affects garbage collection and heap sizing. offHeap uses a 10MB on-heap buffer and MapDB using memory-mapped files in the java temporary directory. So if total cachedNamespace lookup size is in excess of 10MB, the extra will be kept in memory as page cache, and paged in and out by general OS tunings.

Supported Lookups

For additional lookups, please see our extensions list.

URI namespace update

The remapping values for each namespaced lookup can be specified by a json object as per the following examples:

{
  "type":"uri",
  "uri": "s3://bucket/some/key/prefix/renames-0003.gz",
  "namespaceParseSpec":{
    "format":"csv",
    "columns":["key","value"]
  },
  "pollPeriod":"PT5M"
}

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

Property	Description	Required	Default
`namespace`	The namespace to define	Yes
`pollPeriod`	Period between polling for updates	No	0 (only once)
`uri`	URI for the file of interest	No	Use `uriPrefix`
`uriPrefix`	A URI which specifies a directory (or other searchable resource) in which to search for files	No	Use `uri`
`fileRegex`	Optional regex for matching the file name under `uriPrefix`. Only used if `uriPrefix` is used	No	`".*"`
`namespaceParseSpec`	How to interpret the data at the URI	Yes

One of either uri xor uriPrefix must be specified.

The pollPeriod value specifies the period in ISO 8601 format between checks for replacement data for the lookup. 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 look for new data later. Whenever an poll occurs, the updating system will look for a file with the most recent timestamp and assume that one with the most recent data set, replacing the local cache of the lookup data.

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.

Only ONE file which matches the search will be used. For most implementations, the discriminator for choosing the URIs is by whichever one reports the most recent timestamp for its modification time.

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`)
`listDelimiter`	The list delimiter in the file	no	(`\u0001`)

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
}

Introspection

Cached namespace lookups have introspection points at /keys and /values which return a complete set of the keys and values (respectively) in the lookup. Introspection to / returns the entire map. Introspection to /version returns the version indicator for the lookup.

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Namespaced Lookup

Configuration

Cache Settings

Supported Lookups

URI namespace update

csv lookupParseSpec

tsv lookupParseSpec

customJson lookupParseSpec

simpleJson lookupParseSpec

JDBC namespaced lookup

Introspection

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