All Products
Search

This Product

    ApsaraDB for MongoDB:Stress test maximum connections for replica set instances

    Document Center

    ApsaraDB for MongoDB:Stress test maximum connections for replica set instances

    Last Updated:Jun 02, 2026

    Verify that ApsaraDB for MongoDB replica set instances of different specifications can reach their maximum connections by running stress tests from an ECS instance that accesses the ApsaraDB for MongoDB instances in the same VPC.

    Test environment

    Create an ECS instance and an ApsaraDB for MongoDB replica set instance. Create a replica set instance and Create an ECS instance.

    The following table lists the instance configurations used in this test.

    Configuration item

    ECS Instance

    ApsaraDB for MongoDB instance that uses cloud disks

    ApsaraDB for MongoDB instance that uses local disks

    Region and zone

    Beijing Zone H

    Beijing Zone H

    Beijing Zone H

    Network type

    Virtual Private Cloud (VPC)

    VPC

    VPC

    Instance category

    c6e, compute-optimized instance family with enhanced performance

    General-purpose and dedicated

    General-purpose and dedicated

    Instance type

    ecs.c6e.2xlarge

    Three instance types tested. Test results.

    Two instance types tested. Test results.

    Storage type

    Enterprise SSD (ESSD) AutoPL disks

    ESSDs

    Local SSDs

    Image or engine version

    Alibaba Cloud Linux 3.2104 LTS 64-bit

    4.19.91-26.al7.x86_64

    3.10.0-327.ali2017.alios7.x86_64

    Kernel version

    N/A

    • Major version: MongoDB 4.4

    • Baseline of minor version: 4.4.28

    • Major version: MongoDB 4.2

    • Baseline of minor version: 4.2.23

    • The ApsaraDB for MongoDB instance uses a three-node architecture: primary, secondary, and hidden.

    • The ECS and ApsaraDB for MongoDB instances are in the same zone, with an average RTT of 0.103 ms.

    Test tool

    Test method

    1. Add the primary private IP address of the ECS instance to a whitelist of the ApsaraDB for MongoDB instance. For more information, see Modify a whitelist.

      Note

      You can log on to the ECS console and view the Primary Private IP Address of the ECS instance in the Configuration Information section of the Instance Details page.

    2. Connect to the ECS instance. For more information, see Create and manage an ECS instance by using the ECS console (express version).

    3. Use the YCSB tool to load test data. 

      ./bin/ycsb.sh load mongodb -s -p workload=site.ycsb.workloads.CoreWorkload -p recordcount=10000000 -p mongodb.url="mongodb://test:****@dds-bp13e84d11****.mongodb.rds.aliyuncs.com:3717/admin" -p table=test -threads 8

      Modify the following settings:

      • recordcount=1000000: total records loaded into the ApsaraDB for MongoDB instance.

      • mongodb.url="mongodb://test:****@dds-bp13e84d11****.mongodb.rds.aliyuncs.com:3717/admin": connection string of the ApsaraDB for MongoDB instance. Account: test, database: admin.

        Note

        Log on to the ApsaraDB for MongoDB console. On the Database Connection page, find the connection string in the Internal Connections - VPC section.

      • threads 8: number of concurrent client threads.

    4. Run the stress test:

      ./bin/ycsb.sh run mongodb -s -p workload=site.ycsb.workloads.CoreWorkload -p recordcount=10000000 -p operationcount=5000000 -p readproportion=50 -p updateproportion=50 -p requestdistribution=zipfian -p mongodb.url="mongodb://test:****@dds-bp13e84d11****.mongodb.rds.aliyuncs.com:3717/admin&maxPoolSize=8000" -p table=test -threads 8000

      Modify the following settings:

      • recordcount=1000000: total records loaded into the ApsaraDB for MongoDB instance.

      • operationcount=5000000: total read and write operations.

      • insertproportion=0: insert ratio.

      • readproportion=50: read ratio.

      • updateproportion=50: update ratio.

      • mongodb.url="mongodb://test:****@dds-bp13e84d11****.mongodb.rds.aliyuncs.com:3717/admin": connection string of the ApsaraDB for MongoDB instance. Account: test, database: admin.

        Note

        • Log on to the ApsaraDB for MongoDB console. On the Database Connection page, find the connection string in the Internal Connections - VPC section.

        • You must specify the maxPoolSize parameter. Otherwise, the default value of 100 applies, which can cause MongoWaitQueueFullException errors and prevent the test from reaching the target maximum connections.

    5. View monitoring data. Node monitoring (previously basic monitoring).

      On the Node Monitoring tab, select the time range for the test and view the CPU Utilization, Memory Usage, QPS, Connections, and Connection Usage metrics.

    Additional information about a stress test for 96,000 connections

    YCSB depends on Java. The JVM heap memory is limited, so tests with more than 20,000 concurrent threads return the Cannot allocate memory error.image

    Increasing JAVA_OPTS does not resolve this. Use a custom stress testing program instead: it cyclically generates threads, each creating a MongoClient that performs a query and holds the connection open without releasing it.

    A single stress-test client has limited ports and cannot reach 96,000 connections (required for 32-core 128 GB specs). Run the same program on multiple machines.

    Query the current port range:

    sysctl net.ipv4.ip_local_port_range

    Example output:

    net.ipv4.ip_local_port_range = 40000    65535

    Expand the port range before testing:

    sudo sysctl -w net.ipv4.ip_local_port_range="10240 65535"

    Test results

    Instance that uses ESSDs

    Dedicated instance that has 4 cores and 8 GB of memory

    Maximum number of connections: 8,000

    QPS

    Connections

    Connection utilization

    CPU utilization

    Memory usage

    image.png

    image.png

    image.png

    image.png

    image.png
    Note

    Minute-level granularity on the Node Monitoring tab may not display the peak connections. The actual connections reached 8,000, verifiable through granular monitoring or the connections sub-document in the serverStatus output.image

    Dedicated instance that has 32 cores and 128 GB of memory

    Maximum number of connections: 96,000

    QPS

    Connections

    Connection utilization

    CPU utilization

    Memory usage

    image.png

    image.png

    image.png

    image.png

    image.png
    Note

    The 96,000-connection test uses a different tool than the 8,000 and 16,000 tests, so QPS, CPU, and memory metrics are not directly comparable.

    General-purpose instance that has 8 cores and 32 GB of memory

    Maximum number of connections: 16,000

    QPS

    Connections

    Connection utilization

    CPU utilization

    Memory usage

    image.png

    image.png

    image.png

    image.png

    image.png

    Instances that use local disks

    General-purpose instance that has 16 cores and 64 GB of memory

    Maximum number of connections: 32,000

    QPS

    Connections

    Connection utilization

    CPU utilization

    Memory usage

    image.png

    image.png

    image.png

    image.png

    image.png
    Note

    With minute-level granularity, some data points show gaps for the 16-core 64 GB instance because collection commands timed out at 100% CPU. The actual connections at those points remained 32,000.

    Dedicated instance that has 2 cores and 16 GB of memory

    Maximum number of connections: 8,000

    QPS

    Connections

    Connection utilization

    CPU utilization

    Memory usage

    image.png

    image.png

    image.png

    image.png

    image.png

    Summary

    • ApsaraDB for MongoDB replica set instances of all tested specifications and storage types reached their maximum connections.

    • After reaching the maximum, subsequent connections are rejected. Applications experience high latency or stuck requests due to connection failures.

    • More concurrent connections consume more CPU and memory. Adjust the connection count based on your business requirements.