Make sure to include druid-lookups-cached-global as an extension.
Globally cached 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.
Globally cached lookups all draw from the same cache pool, allowing each node to have a fixed cache pool that can be used by cached lookups.
Globally cached lookups can be specified as part of the cluster wide config for lookups as a type of cachedNamespace
{ "type": "cachedNamespace", "extractionNamespace": { "type": "uri", "uri": "file:/tmp/prefix/", "namespaceParseSpec": { "format": "csv", "columns": [ "key", "value" ] }, "pollPeriod": "PT5M" }, "firstCacheTimeout": 0 }
{ "type": "cachedNamespace", "extractionNamespace": { "type": "jdbc", "connectorConfig": { "createTables": true, "connectURI": "jdbc:mysql:\/\/localhost:3306\/druid", "user": "druid", "password": "diurd" }, "table": "lookupTable", "keyColumn": "mykeyColumn", "valueColumn": "myValueColumn", "filter" : "myFilterSQL (Where clause statement e.g LOOKUPTYPE=1)", "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 | 0 (do not wait) |
injective | If the underlying map is injective (keys and values are unique) then optimizations can occur internally by setting this to true | No | false |
If firstCacheTimeout is set to a non-zero value, it should be less than druid.manager.lookups.hostUpdateTimeout. If firstCacheTimeout is NOT set, then management is essentially asynchronous and does not know if a lookup succeeded or failed in starting. In such a case logs from the lookup nodes should be monitored for repeated failures.
Proper functionality of globally cached lookups requires the following extension to be loaded on the broker, peon, and historical nodes: druid-lookups-cached-global
In a simple case where only one tier exists (realtime_customer2) with one cachedNamespace lookup called country_code, the resulting configuration json looks similar to the following:
{ "realtime_customer2": { "country_code": { "version": "v0", "lookupExtractorFactory": { "type": "cachedNamespace", "extractionNamespace": { "type": "jdbc", "connectorConfig": { "createTables": true, "connectURI": "jdbc:mysql:\/\/localhost:3306\/druid", "user": "druid", "password": "diurd" }, "table": "lookupValues", "keyColumn": "value_id", "valueColumn": "value_text", "filter": "value_type='country'", "tsColumn": "timeColumn" }, "firstCacheTimeout": 120000, "injective": true } } } }
Where the coordinator endpoint /druid/coordinator/v1/lookups/realtime_customer2/country_code should return
{ "version": "v0", "lookupExtractorFactory": { "type": "cachedNamespace", "extractionNamespace": { "type": "jdbc", "connectorConfig": { "createTables": true, "connectURI": "jdbc:mysql://localhost:3306/druid", "user": "druid", "password": "diurd" }, "table": "lookupValues", "keyColumn": "value_id", "valueColumn": "value_text", "filter": "value_type='country'", "tsColumn": "timeColumn" }, "firstCacheTimeout": 120000, "injective": true } }
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 |
druid.lookup.namespace.numExtractionThreads | The number of threads in the thread pool dedicated for lookup extraction and updates. This number may need to be scaled up, if you have a lot of lookups and they take long time to extract, to avoid timeouts. | 2 |
druid.lookup.namespace.numBufferedEntries | If using offHeap caching, the number of records to be stored on an on-heap buffer. | 100,000 |
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 an on-heap buffer and MapDB using memory-mapped files in the java temporary directory. So if total number of entries in the cachedNamespace is in excess of the buffer‘s configured capacity, the extra will be kept in memory as page cache, and paged in and out by general OS tunings. It’s highly recommended that druid.lookup.namespace.numBufferedEntries is set when using offHeap, the value should be chosen from the range between 10% and 50% of the number of entries in the lookup.
For additional lookups, please see our extensions list.
The remapping values for each globally cached 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 |
|---|---|---|---|
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.
| Parameter | Description | Required | Default |
|---|---|---|---|
columns | The list of columns in the csv file | no if hasHeaderRow is set | 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 |
hasHeaderRow | A flag to indicate that column information can be extracted from the input files' header row | no | false |
skipHeaderRows | Number of header rows to be skipped | no | 0 |
If both skipHeaderRows and hasHeaderRow options are set, skipHeaderRows is first applied. For example, if you set skipHeaderRows to 2 and hasHeaderRow to true, Druid will skip the first two lines and then extract column information from the third line.
example input
bar,something,foo bat,something2,baz truck,something3,buck
example namespaceParseSpec
"namespaceParseSpec": { "format": "csv", "columns": ["value","somethingElse","key"], "keyColumn": "key", "valueColumn": "value" }
| Parameter | Description | Required | Default |
|---|---|---|---|
columns | The list of columns in the tsv 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) |
hasHeaderRow | A flag to indicate that column information can be extracted from the input files' header row | no | false |
skipHeaderRows | Number of header rows to be skipped | no | 0 |
If both skipHeaderRows and hasHeaderRow options are set, skipHeaderRows is first applied. For example, if you set skipHeaderRows to 2 and hasHeaderRow to true, Druid will skip the first two lines and then extract column information from the third line.
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": "|" }
| 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" }
With customJson parsing, if the value field for a particular row is missing or null then that line will be skipped, and will not be included in the lookup.
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" }
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 | |
filter | The filter to use when selecting lookups, this is used to create a where clause on lookup population | No | No Filter |
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 }
Globally cached 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.