CORAL WIKI
Actors
Getting started
Overview
LookupActor
The LookupActor is a Coral Actor that can enrich data via the lookup table provided in its constructor.
Creating a LookupActor
The creation JSON of the LookupActor actor (see Coral Actor) has "type": "lookup".
The params value contains the following fields:
| field | type | required | description |
|---|---|---|---|
key |
string | yes | name of the key field |
lookup |
JSON object | yes | the lookup table |
function |
string | yes | “enrich”, “filter” or “check” |
match |
string | no | “exact” or “startswith” |
default |
JSON object | no | when there is no match, the default is used when defined |
The function field in the constructor defines the behavior of the LookupActor.
Example
{
"data: {
"type": "actors",
"attributes": {
"type": "lookup",
"params": {
"key": "city",
"lookup": {
"amsterdam": { "country": "netherlands", "population": 800000 },
"vancouver": { "country": "canada", "population": 600000 }
},
"function": "enrich"
}
}
}
}This LookUpActor will now wait for any incoming trigger messages and will look at the “city” field.
It will merge the “country” and “population” fields into the output message since “function” is set to “enrich”.
If this is the input:
{
"city": "amsterdam",
"otherdata": "irrelevant",
"somevalue": 10
}Then enrich will emit this output:
{
"city": "amsterdam",
"otherdata": "irrelevant",
"somevalue": 10,
"country": "netherlands",
"population": 800000
}If the function is set to filter, the output is
{
"city": "amsterdam",
"otherdata": "irrelevant",
"somevalue": 10
}but only if the “city” key is found in the lookup map. If it is not found, the input object is not emitted.
In the case of check, the output is the looked up object if it exists, else, nothing is emitted:
{
"country": "netherlands",
"population": 800000
}The standard behaviour is to use an exact match. When the match is “startswith”, a check is done if the key is a string of which a substring occurs in the lookup map. If there are multiple matches, one of them is used, which one is undefined.
The standard behaviour when there is no match is to do nothing: for check and filter nothing is emitted, for enrich nothing will be added to the output. When a default is given, this is used when there are no matches, so check and filter emit the default and enrich enriches with the default. The default is a template like used by the JsonActor.
Trigger
The LookupActor accepts any JSON as trigger. If a key-field is encountered the fields corresponding to the value in that field will be used to look up additional data (from the lookup table).
Emit
The function of the LookupActor determines what is emitted.
enrich
The function enrich always emits the originig JSON. If lookup values are found these are added to the original JSON.
filter
The function filter emits the unenriched, original JSON when it is found in the lookup table. If it is not found, nothing is emitted.
check
The function check emits the lookup value when it is found, otherwise, nothing is emitted.
State
The LookupActordoes not keep state.
Collect
The LookupActor does not collect state from other actors.
Timer
The LookupActor does not provide timer actions.