support list of monitor ids in Chained Monitor Findings

src/main/kotlin/org/opensearch/commons/alerting/action/IndexWorkflowRequest.kt

@@ -105,19 +105,41 @@ class IndexWorkflowRequest : ActionRequest {
         val monitorIdOrderMap: Map<String, Int> = delegates.associate { it.monitorId to it.order }
         delegates.forEach {
             if (it.chainedMonitorFindings != null) {
-                if (monitorIdOrderMap.containsKey(it.chainedMonitorFindings.monitorId) == false) {
-                    validationException = ValidateActions.addValidationError(
-                        "Chained Findings Monitor ${it.chainedMonitorFindings.monitorId} doesn't exist in sequence",
-                        validationException
-                    )
-                    // Break the flow because next check will generate the NPE
-                    return validationException
-                }
-                if (it.order <= monitorIdOrderMap[it.chainedMonitorFindings.monitorId]!!) {
-                    validationException = ValidateActions.addValidationError(
-                        "Chained Findings Monitor ${it.chainedMonitorFindings.monitorId} should be executed before monitor ${it.monitorId}",
-                        validationException
-                    )
+
+                if (it.chainedMonitorFindings.monitorId != null) {
+                    if (monitorIdOrderMap.containsKey(it.chainedMonitorFindings.monitorId) == false) {
+                        validationException = ValidateActions.addValidationError(
+                            "Chained Findings Monitor ${it.chainedMonitorFindings.monitorId} doesn't exist in sequence",
+                            validationException
+                        )
+                        // Break the flow because next check will generate the NPE
+                        return validationException
+                    }
+                    if (it.order <= monitorIdOrderMap[it.chainedMonitorFindings.monitorId]!!) {
+                        validationException = ValidateActions.addValidationError(
+                            "Chained Findings Monitor ${it.chainedMonitorFindings.monitorId} should be executed before monitor ${it.monitorId}",
+                            validationException
+                        )
+                    }
+                } else {
+                    for (monitorId in it.chainedMonitorFindings.monitorIds) {
+                        if (!monitorIdOrderMap.containsKey(monitorId)) {
+                            validationException = ValidateActions.addValidationError(
+                                "Chained Findings Monitor $monitorId doesn't exist in sequence",
+                                validationException
+                            )
+                            return validationException
+                        } else {
+                            val order = monitorIdOrderMap.get(monitorId)!!
+                            if (order >= it.order) {
+                                return ValidateActions.addValidationError(
+                                    "Chained Findings Monitor ${it.chainedMonitorFindings.monitorId} should be executed before monitor ${it.monitorId}. " +
+                                        "Order of monitor being chained [$order] should be smaller than order of monitor using findings as source data [${it.order}] in sequence",
+                                    validationException
+                                )
+                            }
+                        }
+                    }
                 }
             }
         }

src/main/kotlin/org/opensearch/commons/alerting/model/ChainedMonitorFindings.kt

@@ -9,63 +9,89 @@ import org.opensearch.core.xcontent.XContentBuilder
 import org.opensearch.core.xcontent.XContentParser
 import org.opensearch.core.xcontent.XContentParserUtils
 import java.io.IOException
+import java.util.Collections
 
 /**
- * Context passed in delegate monitor to filter data queried by a monitor based on the findings of the given monitor id.
+ * Context passed in delegate monitor to filter data matched by a list of monitors based on the findings of the given monitor ids.
  */
 // TODO - Remove the class and move the monitorId to Delegate (as a chainedMonitorId property) if this class won't be updated by adding new properties
 data class ChainedMonitorFindings(
-    val monitorId: String
+    val monitorId: String? = null,
+    val monitorIds: List<String> = emptyList(), // if monitorId field is non-null it would be given precendence for BWC
 ) : BaseModel {
 
     init {
-        validateId(monitorId)
+        require(!(monitorId.isNullOrBlank() && monitorIds.isEmpty())) {
+            "at least one of fields, 'monitorIds' and 'monitorId' should be provided"
+        }
+        if (monitorId != null && monitorId.isBlank()) {
+            validateId(monitorId)
+        } else {
+            monitorIds.forEach { validateId(it) }
+        }
     }
 
     @Throws(IOException::class)
     constructor(sin: StreamInput) : this(
-        sin.readString(), // monitorId
+        sin.readOptionalString(), // monitorId
+        Collections.unmodifiableList(sin.readStringList())
     )
 
+    @Suppress("UNCHECKED_CAST")
     fun asTemplateArg(): Map<String, Any> {
         return mapOf(
             MONITOR_ID_FIELD to monitorId,
-        )
+            MONITOR_IDS_FIELD to monitorIds
+        ) as Map<String, Any>
     }
 
     @Throws(IOException::class)
     override fun writeTo(out: StreamOutput) {
-        out.writeString(monitorId)
+        out.writeOptionalString(monitorId)
+        out.writeStringCollection(monitorIds)
     }
 
     override fun toXContent(builder: XContentBuilder, params: ToXContent.Params): XContentBuilder {
         builder.startObject()
             .field(MONITOR_ID_FIELD, monitorId)
+            .field(MONITOR_IDS_FIELD, monitorIds)
             .endObject()
         return builder
     }
 
     companion object {
         const val MONITOR_ID_FIELD = "monitor_id"
+        const val MONITOR_IDS_FIELD = "monitor_ids"
 
         @JvmStatic
         @Throws(IOException::class)
         fun parse(xcp: XContentParser): ChainedMonitorFindings {
-            lateinit var monitorId: String
-
+            var monitorId: String? = null
+            val monitorIds = mutableListOf<String>()
             XContentParserUtils.ensureExpectedToken(XContentParser.Token.START_OBJECT, xcp.currentToken(), xcp)
             while (xcp.nextToken() != XContentParser.Token.END_OBJECT) {
                 val fieldName = xcp.currentName()
                 xcp.nextToken()
 
                 when (fieldName) {
                     MONITOR_ID_FIELD -> {
-                        monitorId = xcp.text()
-                        validateId(monitorId)
+                        if (!xcp.currentToken().equals(XContentParser.Token.VALUE_NULL))
+                            monitorId = xcp.text()
+                    }
+
+                    MONITOR_IDS_FIELD -> {
+                        XContentParserUtils.ensureExpectedToken(
+                            XContentParser.Token.START_ARRAY,
+                            xcp.currentToken(),
+                            xcp
+                        )
+                        while (xcp.nextToken() != XContentParser.Token.END_ARRAY) {
+                            monitorIds.add(xcp.text())
+                        }
                     }
                 }
             }
-            return ChainedMonitorFindings(monitorId)
+            return ChainedMonitorFindings(monitorId, monitorIds)
         }
 
         @JvmStatic

src/test/kotlin/org/opensearch/commons/alerting/TestHelpers.kt

@@ -405,6 +405,11 @@ fun randomClusterMetricsInput(
     return ClusterMetricsInput(path, pathParams, url)
 }
 
+fun ChainedMonitorFindings.toJsonString(): String {
+    val builder = XContentFactory.jsonBuilder()
+    return this.toXContent(builder, ToXContent.EMPTY_PARAMS).string()
+}
+
 fun Workflow.toJsonString(): String {
     val builder = XContentFactory.jsonBuilder()
     return this.toXContentWithUser(builder, ToXContent.EMPTY_PARAMS).string()

src/test/kotlin/org/opensearch/commons/alerting/action/IndexWorkflowRequestTests.kt

@@ -21,6 +21,9 @@ import org.opensearch.search.SearchModule
 import java.lang.Exception
 import java.lang.IllegalArgumentException
 import java.util.UUID
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
 
 class IndexWorkflowRequestTests {
 
@@ -196,6 +199,21 @@ class IndexWorkflowRequestTests {
         delegates = listOf(
             Delegate(1, "monitor-1")
         )
+
+        // Chained finding list of monitors valid
+        delegates = listOf(
+            Delegate(1, "monitor-1"),
+            Delegate(2, "monitor-2"),
+            Delegate(3, "monitor-3", ChainedMonitorFindings(null, listOf("monitor-1", "monitor-2"))),
+
+        )
+        val req7 = IndexWorkflowRequest(
+            "1234", 1L, 2L, WriteRequest.RefreshPolicy.IMMEDIATE, RestRequest.Method.PUT,
+            randomWorkflowWithDelegates(
+                input = listOf(CompositeInput(Sequence(delegates = delegates)))
+            )
+        )
+        assertNull(req7.validate())
         try {
             IndexWorkflowRequest(
                 "1234", 1L, 2L, WriteRequest.RefreshPolicy.IMMEDIATE, RestRequest.Method.PUT,
@@ -207,5 +225,21 @@ class IndexWorkflowRequestTests {
             Assert.assertTrue(ex is IllegalArgumentException)
             Assert.assertTrue(ex.message!!.contains("Workflows can only have 1 search input."))
         }
+
+        // Chained finding list of monitors invalid order and old field null
+        delegates = listOf(
+            Delegate(1, "monitor-1"),
+            Delegate(3, "monitor-2"),
+            Delegate(2, "monitor-3", ChainedMonitorFindings(null, listOf("monitor-1", "monitor-2"))),
+
+        )
+        val req8 = IndexWorkflowRequest(
+            "1234", 1L, 2L, WriteRequest.RefreshPolicy.IMMEDIATE, RestRequest.Method.PUT,
+            randomWorkflowWithDelegates(
+                input = listOf(CompositeInput(Sequence(delegates = delegates)))
+            )
+        )
+        assertNotNull(req8.validate())
+        assertTrue(req8.validate()!!.message!!.contains("should be executed before monitor"))
     }
 }

src/test/kotlin/org/opensearch/commons/alerting/model/CompositeInputTests.kt

@@ -70,10 +70,25 @@ class CompositeInputTests {
     }
 
     @Test
-    fun `test create Chained Findings with illegal monitorId value`() {
+    fun `test create Chained Findings with illegal monitorId value and empty monitorIds list`() {
         try {
             ChainedMonitorFindings("")
             Assertions.fail("Expecting an illegal argument exception")
+        } catch (e: IllegalArgumentException) {
+            e.message?.let {
+                Assertions.assertTrue(
+                    it.contains("at least one of fields, 'monitorIds' and 'monitorId' should be provided")
+
+                )
+            }
+        }
+    }
+
+    @Test
+    fun `test create Chained Findings with null monitorId value and  monitorIds list with blank monitorIds`() {
+        try {
+            ChainedMonitorFindings("", listOf("", ""))
+            Assertions.fail("Expecting an illegal argument exception")
         } catch (e: IllegalArgumentException) {
             e.message?.let {
                 Assertions.assertTrue(

src/test/kotlin/org/opensearch/commons/alerting/model/XContentTests.kt

@@ -267,12 +267,27 @@ class XContentTests {
     @Test
     fun `test workflow parsing`() {
         val workflow = randomWorkflow(monitorIds = listOf("1", "2", "3"))
-
         val monitorString = workflow.toJsonString()
         val parsedWorkflow = Workflow.parse(parser(monitorString))
         Assertions.assertEquals(workflow, parsedWorkflow, "Round tripping workflow failed")
     }
 
+    @Test
+    fun `test chainedMonitorFindings parsing`() {
+        val cmf1 = ChainedMonitorFindings(monitorId = "m1")
+        val cmf1String = cmf1.toJsonString()
+        Assertions.assertEquals(
+            ChainedMonitorFindings.parse(parser(cmf1String)), cmf1,
+            "Round tripping chained monitor findings failed"
+        )
+        val cmf2 = ChainedMonitorFindings(monitorIds = listOf("m1", "m2"))
+        val cmf2String = cmf2.toJsonString()
+        Assertions.assertEquals(
+            ChainedMonitorFindings.parse(parser(cmf2String)), cmf2,
+            "Round tripping chained monitor findings failed"
+        )
+    }
+
     @Test
     fun `test old monitor format parsing`() {
         val monitorString = """