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High number of connections due to Mongo health indicator #50734

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2e7f0aa
Run a single hello command in MongoDB health indicators
seonwooj0810 Jun 10, 2026
bc374ae
Use visible Mongo database for health check
seonwooj0810 Jun 10, 2026
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25 changes: 15 additions & 10 deletions ...t-mongodb/src/main/java/org/springframework/boot/mongodb/health/MongoHealthIndicator.java
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Expand Up @@ -17,9 +17,7 @@
package org.springframework.boot.mongodb.health;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import com.mongodb.client.MongoClient;
import org.bson.Document;
Expand All @@ -34,10 +32,13 @@
* MongoDB.
*
* @author Christian Dupuis
* @author Seonwoo Jung
* @since 4.0.0
*/
public class MongoHealthIndicator extends AbstractHealthIndicator {

private static final String ADMIN_DATABASE = "admin";

private static final Document HELLO_COMMAND = Document.parse("{ hello: 1 }");

private final MongoClient mongoClient;
Expand All @@ -50,15 +51,19 @@ public MongoHealthIndicator(MongoClient mongoClient) {

@Override
protected void doHealthCheck(Health.Builder builder) throws Exception {
Map<String, Object> details = new LinkedHashMap<>();
List<String> databases = new ArrayList<>();
details.put("databases", databases);
this.mongoClient.listDatabaseNames().forEach((database) -> {
Document result = this.mongoClient.getDatabase(database).runCommand(HELLO_COMMAND);
databases.add(database);
details.putIfAbsent("maxWireVersion", result.getInteger("maxWireVersion"));
});
builder.up().withDetails(details);
this.mongoClient.listDatabaseNames().forEach(databases::add);
Document result = this.mongoClient.getDatabase(getDatabaseName(databases)).runCommand(HELLO_COMMAND);
builder.up()
.withDetail("databases", databases)
.withDetail("maxWireVersion", result.getInteger("maxWireVersion"));
}

private static String getDatabaseName(List<String> databases) {
if (databases.contains(ADMIN_DATABASE)) {
return ADMIN_DATABASE;
}
return (!databases.isEmpty()) ? databases.get(0) : ADMIN_DATABASE;
}

}
34 changes: 15 additions & 19 deletions ...b/src/main/java/org/springframework/boot/mongodb/health/MongoReactiveHealthIndicator.java
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Expand Up @@ -16,10 +16,7 @@

package org.springframework.boot.mongodb.health;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import com.mongodb.reactivestreams.client.MongoClient;
import org.bson.Document;
Expand All @@ -35,10 +32,13 @@
* A {@link ReactiveHealthIndicator} for Mongo.
*
* @author Yulin Qin
* @author Seonwoo Jung
* @since 4.0.0
*/
public class MongoReactiveHealthIndicator extends AbstractReactiveHealthIndicator {

private static final String ADMIN_DATABASE = "admin";

private static final Document HELLO_COMMAND = Document.parse("{ hello: 1 }");

private final MongoClient mongoClient;
Expand All @@ -51,24 +51,20 @@ public MongoReactiveHealthIndicator(MongoClient mongoClient) {

@Override
protected Mono<Health> doHealthCheck(Health.Builder builder) {
Mono<Map<String, Object>> healthDetails = Flux.from(this.mongoClient.listDatabaseNames())
.flatMap((database) -> Mono.from(this.mongoClient.getDatabase(database).runCommand(HELLO_COMMAND))
.map((document) -> new HelloResponse(database, document)))
.collectList()
.map((responses) -> {
Map<String, Object> databaseDetails = new LinkedHashMap<>();
List<String> databases = new ArrayList<>();
databaseDetails.put("databases", databases);
for (HelloResponse response : responses) {
databases.add(response.database());
databaseDetails.putIfAbsent("maxWireVersion", response.document().getInteger("maxWireVersion"));
}
return databaseDetails;
});
return healthDetails.map((details) -> builder.up().withDetails(details).build());
Mono<List<String>> databases = Flux.from(this.mongoClient.listDatabaseNames()).collectList();
return databases.flatMap((databaseNames) -> Mono
.from(this.mongoClient.getDatabase(getDatabaseName(databaseNames)).runCommand(HELLO_COMMAND))
.map((result) -> builder.up()
.withDetail("databases", databaseNames)
.withDetail("maxWireVersion", result.getInteger("maxWireVersion"))
.build()));
}

private record HelloResponse(String database, Document document) {
private static String getDatabaseName(List<String> databases) {
if (databases.contains(ADMIN_DATABASE)) {
return ADMIN_DATABASE;
}
return (!databases.isEmpty()) ? databases.get(0) : ADMIN_DATABASE;
}

}
38 changes: 33 additions & 5 deletions ...godb/src/test/java/org/springframework/boot/mongodb/health/MongoHealthIndicatorTests.java
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Expand Up @@ -35,12 +35,14 @@
import static org.mockito.BDDMockito.then;
import static org.mockito.BDDMockito.willAnswer;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.never;

/**
* Tests for {@link MongoHealthIndicator}.
*
* @author Christian Dupuis
* @author Andy Wilkinson
* @author Seonwoo Jung
*/
class MongoHealthIndicatorTests {

Expand All @@ -52,19 +54,45 @@ void mongoIsUp() {
MongoClient mongoClient = mock(MongoClient.class);
MongoIterable<String> databaseNames = mock(MongoIterable.class);
willAnswer((invocation) -> {
((Consumer<String>) invocation.getArgument(0)).accept("db");
((Consumer<String>) invocation.getArgument(0)).accept("test");
((Consumer<String>) invocation.getArgument(0)).accept("admin");
return null;
}).given(databaseNames).forEach(any());
given(mongoClient.listDatabaseNames()).willReturn(databaseNames);
MongoDatabase mongoDatabase = mock(MongoDatabase.class);
given(mongoClient.getDatabase("db")).willReturn(mongoDatabase);
given(mongoDatabase.runCommand(Document.parse("{ hello: 1 }"))).willReturn(commandResult);
MongoDatabase adminDatabase = mock(MongoDatabase.class);
given(mongoClient.getDatabase("admin")).willReturn(adminDatabase);
given(adminDatabase.runCommand(Document.parse("{ hello: 1 }"))).willReturn(commandResult);
MongoHealthIndicator healthIndicator = new MongoHealthIndicator(mongoClient);
Health health = healthIndicator.health();
assertThat(health.getStatus()).isEqualTo(Status.UP);
assertThat(health.getDetails()).containsEntry("maxWireVersion", 10);
assertThat(health.getDetails()).containsEntry("databases", List.of("db"));
assertThat(health.getDetails()).containsEntry("databases", List.of("test", "admin"));
then(commandResult).should().getInteger("maxWireVersion");
// the hello command must only be run once, never per listed database
then(mongoClient).should(never()).getDatabase("test");
}

@Test
@SuppressWarnings("unchecked")
void mongoUsesFirstDatabaseWhenAdminIsNotVisible() {
Document commandResult = mock(Document.class);
given(commandResult.getInteger("maxWireVersion")).willReturn(10);
MongoClient mongoClient = mock(MongoClient.class);
MongoIterable<String> databaseNames = mock(MongoIterable.class);
willAnswer((invocation) -> {
((Consumer<String>) invocation.getArgument(0)).accept("test");
return null;
}).given(databaseNames).forEach(any());
given(mongoClient.listDatabaseNames()).willReturn(databaseNames);
MongoDatabase database = mock(MongoDatabase.class);
given(mongoClient.getDatabase("test")).willReturn(database);
given(database.runCommand(Document.parse("{ hello: 1 }"))).willReturn(commandResult);
MongoHealthIndicator healthIndicator = new MongoHealthIndicator(mongoClient);
Health health = healthIndicator.health();
assertThat(health.getStatus()).isEqualTo(Status.UP);
assertThat(health.getDetails()).containsEntry("maxWireVersion", 10);
assertThat(health.getDetails()).containsEntry("databases", List.of("test"));
then(mongoClient).should(never()).getDatabase("admin");
}

@Test
Expand Down
42 changes: 36 additions & 6 deletions .../test/java/org/springframework/boot/mongodb/health/MongoReactiveHealthIndicatorTests.java
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Expand Up @@ -24,6 +24,7 @@
import com.mongodb.reactivestreams.client.MongoDatabase;
import org.bson.Document;
import org.junit.jupiter.api.Test;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.test.StepVerifier;

Expand All @@ -32,38 +33,67 @@

import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.BDDMockito.given;
import static org.mockito.BDDMockito.then;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.never;

/**
* Tests for {@link MongoReactiveHealthIndicator}.
*
* @author Yulin Qin
* @author Seonwoo Jung
*/
class MongoReactiveHealthIndicatorTests {

@Test
void mongoIsUp() {
MongoClient mongoClient = mock(MongoClient.class);
given(mongoClient.listDatabaseNames()).willReturn(Mono.just("db"));
MongoDatabase mongoDatabase = mock(MongoDatabase.class);
given(mongoClient.getDatabase("db")).willReturn(mongoDatabase);
given(mongoClient.listDatabaseNames()).willReturn(Flux.just("test", "admin"));
MongoDatabase adminDatabase = mock(MongoDatabase.class);
given(mongoClient.getDatabase("admin")).willReturn(adminDatabase);
Document commandResult = mock(Document.class);
given(mongoDatabase.runCommand(Document.parse("{ hello: 1 }"))).willReturn(Mono.just(commandResult));
given(adminDatabase.runCommand(Document.parse("{ hello: 1 }"))).willReturn(Mono.just(commandResult));
given(commandResult.getInteger("maxWireVersion")).willReturn(10);
MongoReactiveHealthIndicator mongoReactiveHealthIndicator = new MongoReactiveHealthIndicator(mongoClient);
Mono<Health> health = mongoReactiveHealthIndicator.health();
StepVerifier.create(health).consumeNextWith((h) -> {
assertThat(h.getStatus()).isEqualTo(Status.UP);
assertThat(h.getDetails()).containsOnlyKeys("maxWireVersion", "databases");
assertThat(h.getDetails()).containsEntry("maxWireVersion", 10);
assertThat(h.getDetails()).containsEntry("databases", List.of("db"));
assertThat(h.getDetails()).containsEntry("databases", List.of("test", "admin"));
}).expectComplete().verify(Duration.ofSeconds(30));
// the hello command must only be run once, never per listed database
then(mongoClient).should(never()).getDatabase("test");
}

@Test
void mongoUsesFirstDatabaseWhenAdminIsNotVisible() {
MongoClient mongoClient = mock(MongoClient.class);
given(mongoClient.listDatabaseNames()).willReturn(Flux.just("test"));
MongoDatabase database = mock(MongoDatabase.class);
given(mongoClient.getDatabase("test")).willReturn(database);
Document commandResult = mock(Document.class);
given(database.runCommand(Document.parse("{ hello: 1 }"))).willReturn(Mono.just(commandResult));
given(commandResult.getInteger("maxWireVersion")).willReturn(10);
MongoReactiveHealthIndicator mongoReactiveHealthIndicator = new MongoReactiveHealthIndicator(mongoClient);
Mono<Health> health = mongoReactiveHealthIndicator.health();
StepVerifier.create(health).consumeNextWith((h) -> {
assertThat(h.getStatus()).isEqualTo(Status.UP);
assertThat(h.getDetails()).containsOnlyKeys("maxWireVersion", "databases");
assertThat(h.getDetails()).containsEntry("maxWireVersion", 10);
assertThat(h.getDetails()).containsEntry("databases", List.of("test"));
}).expectComplete().verify(Duration.ofSeconds(30));
then(mongoClient).should(never()).getDatabase("admin");
}

@Test
void mongoIsDown() {
MongoClient mongoClient = mock(MongoClient.class);
given(mongoClient.listDatabaseNames()).willThrow(new MongoException("Connection failed"));
given(mongoClient.listDatabaseNames()).willReturn(Flux.just("admin"));
MongoDatabase adminDatabase = mock(MongoDatabase.class);
given(mongoClient.getDatabase("admin")).willReturn(adminDatabase);
given(adminDatabase.runCommand(Document.parse("{ hello: 1 }")))
.willReturn(Mono.error(new MongoException("Connection failed")));
MongoReactiveHealthIndicator mongoReactiveHealthIndicator = new MongoReactiveHealthIndicator(mongoClient);
Mono<Health> health = mongoReactiveHealthIndicator.health();
StepVerifier.create(health).consumeNextWith((h) -> {
Expand Down