Improve stability by disabling dynamic leaderboard queries

Due to the extensive computational demand of dynamic queries for various MapRoulette leaderboards — including those for global standings, project-specific, challenge-specific, and country-specific rankings — system stability issues have been observed.

To enhance system reliability, this patch disables the execution of dynamic leaderboard calculations. Requests triggering a dynamic query now result in an HTTP 400 response, encouraging the use of static data.

Affected leaderboards include:
- Project-specific leaderboards
- Challenge-specific leaderboards
- Leaderboards featuring items not currently enabled
- Country-specific leaderboards, excluding the global leaderboard, when multiple countries are selected
- Any use of custom date ranges outside the predefined set of durations

app/org/maproulette/framework/service/LeaderboardService.scala

@@ -8,7 +8,7 @@ package org.maproulette.framework.service
 import javax.inject.{Inject, Singleton}
 import org.joda.time.DateTime
 import org.maproulette.Config
-import org.maproulette.exception.NotFoundException
+import org.maproulette.exception.{InvalidException, NotFoundException}
 import org.maproulette.framework.model.{LeaderboardChallenge, LeaderboardUser, Task, User}
 import org.maproulette.framework.mixins.LeaderboardMixin
 import org.maproulette.framework.repository.{ChallengeRepository, LeaderboardRepository}
@@ -151,11 +151,20 @@ class LeaderboardService @Inject() (
         fetchedUserId => this.getUserTopChallenges(fetchedUserId, params)
       )
 
-      if (result.length > 0) {
-        return result
-      }
+      // NOTE: The result may be an empty list for users who are not in the leaderboard.
+      return result
     }
 
+    // The provided arguments are invalid because the combination cannot query from the pre-built table, throw an error (http 400).
+    throw new InvalidException(
+      "Dynamic queries are disabled. Adjust query parameters for static results."
+    )
+
+    //
+    // TODO(ljdelight): The below needs to be moved to a new endpoint because it CAN CRASH THE SERVER. We MUST always
+    //                  know whether the leaderboard is coming from a pre-built table or not. THUS SEPARATE ENDPOINTS.
+    //
+
     val (startDate, endDate) = this.setupDates(params.monthDuration, params.start, params.end)
 
     val query = this
@@ -220,11 +229,20 @@ class LeaderboardService @Inject() (
         fetchedUserId => this.getUserTopChallenges(fetchedUserId, params)
       )
 
-      if (result.length > 0) {
-        return result
-      }
+      // NOTE: The result may be an empty list for users who are not in the leaderboard.
+      return result
     }
 
+    // The provided arguments are invalid because the combination cannot query from the pre-built table, throw an error (http 400).
+    throw new InvalidException(
+      "Dynamic queries are disabled. Adjust query parameters for static results."
+    )
+
+    //
+    // TODO(ljdelight): The below needs to be moved to a new endpoint because it CAN CRASH THE SERVER. We MUST always
+    //                  know whether the leaderboard is coming from a pre-built table or not. THUS SEPARATE ENDPOINTS.
+    //
+
     val (startDate, endDate) = this.setupDates(params.monthDuration, params.start, params.end)
 
     val rankQuery = this.leaderboardWithRankSQL(
@@ -294,11 +312,20 @@ class LeaderboardService @Inject() (
         )
       )
 
-      if (result.length > 0) {
-        return result
-      }
+      // NOTE: The result may be an empty list for users who are not in the leaderboard.
+      return result
     }
 
+    // The provided arguments are invalid because the combination cannot query from the pre-built table, throw an error (http 400).
+    throw new InvalidException(
+      "Dynamic queries are disabled. Adjust query parameters for static results."
+    )
+
+    //
+    // TODO(ljdelight): The below needs to be moved to a new endpoint because it CAN CRASH THE SERVER. We MUST always
+    //                  know whether the leaderboard is coming from a pre-built table or not. THUS SEPARATE ENDPOINTS.
+    //
+
     val (startDate, endDate)                = setupDates(params.monthDuration, params.start, params.end)
     val (boundingSearch, taskTableIfNeeded) = setupBoundingSearch(params.countryCodeFilter)
 

test/org/maproulette/framework/service/LeaderboardServiceSpec.scala

@@ -30,8 +30,10 @@ class LeaderboardServiceSpec(implicit val application: Application) extends Fram
   var challenge: Challenge        = null
 
   "LeaderboardService" should {
-    "get mapper leaderboard" taggedAs (LeaderboardTag) in {
-      val params  = SearchLeaderboardParameters(onlyEnabled = false)
+    // TODO(ljdelight): Temporarily ignored due to the disabling of dynamic leaderboard queries to improve system stability.
+    //                  This test will be revisited once an alternative approach or solution is implemented.
+    "get mapper leaderboard" taggedAs (LeaderboardTag) ignore {
+      val params  = SearchLeaderboardParameters(onlyEnabled = true)
       val results = this.service.getMapperLeaderboard(params)
       results.size mustEqual 2
 
@@ -85,13 +87,17 @@ class LeaderboardServiceSpec(implicit val application: Application) extends Fram
       ccResults.size mustEqual 2
     }
 
-    "get leaderboard for user" taggedAs (LeaderboardTag) in {
+    // TODO(ljdelight): Temporarily ignored due to the disabling of dynamic leaderboard queries to improve system stability.
+    //                  This test will be revisited once an alternative approach or solution is implemented.
+    "get leaderboard for user" taggedAs (LeaderboardTag) ignore {
       val results = this.service.getLeaderboardForUser(randomUser.id, SearchLeaderboardParameters())
       results.size mustEqual 1
       results.head.userId mustEqual randomUser.id
     }
 
-    "get leaderboard for user with bracketing" taggedAs (LeaderboardTag) in {
+    // TODO(ljdelight): Temporarily ignored due to the disabling of dynamic leaderboard queries to improve system stability.
+    //                  This test will be revisited once an alternative approach or solution is implemented.
+    "get leaderboard for user with bracketing" taggedAs (LeaderboardTag) ignore {
       val results = this.service
         .getLeaderboardForUser(randomUser.id, SearchLeaderboardParameters(), bracket = 1)
       results.size mustEqual 2