Cannot connect to MSSQL service container from self-hosted agents

Question

Cannot connect to MSSQL service container from self-hosted agents

devops engineer 0

Running a pipeline on a self-hosted agent with custom ubuntu sql image that was built based on

mcr.microsoft.com/mssql/server:2022-latest

anyways, running the above image on the ms-hosted ubuntu agent is working fine but when we try to run it on our self-hosted machine it's throwing the error below.

Microsoft.Data.SqlClient.SqlException : A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 40 - Could not open a connection to SQL Server)`

our pipeline yaml looks like below, it seems like the mssql agent service is not starting? or shutting down?

      pool:
        name: selfhostedpool
      container:
        image: test.azurecr.io/mssql:2202image
        endpoint: ACR-serviceconnection
        env:
          ACCEPT_EULA: Y
          MSSQL_SA_PASSWORD: SomePassword
        ports:
          - 1433:1433

PratikLad 960 Reputation points Microsoft External Staff

2025-05-01T12:45:09.57+00:00
Hi devops engineer,

Your pipeline is trying to connect to the SQL Server container but can't reach it. Since it works on the Microsoft-hosted agent, but fails on the self-hosted agent, this likely points to differences in networking on the self-hosted machine.

The SQL container might be starting asynchronously, and your test begins before SQL Server is ready to accept connections.

Add a script step that waits until SQL Server is up before running your test:

- script: | echo "Waiting for SQL Server to be ready..." for i in {1..30}; do /opt/mssql-tools/bin/sqlcmd -S localhost -U SA -P 'SomePassword' -Q "SELECT 1" && break echo "SQL Server is still starting..." sleep 2 done displayName: Wait for SQL Server

Make sure mssql-tools is available in the container or install it via package manager in the wait script step.
PratikLad 960 Reputation points Microsoft External Staff

2025-05-02T11:36:45.57+00:00

Hi devops engineer, We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution

please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

Your answer

PratikLad 960 Reputation points Microsoft External Staff

2025-05-01T12:45:09.57+00:00

Hi devops engineer,

Your pipeline is trying to connect to the SQL Server container but can't reach it. Since it works on the Microsoft-hosted agent, but fails on the self-hosted agent, this likely points to differences in networking on the self-hosted machine.

The SQL container might be starting asynchronously, and your test begins before SQL Server is ready to accept connections.

Add a script step that waits until SQL Server is up before running your test:

- script: | echo "Waiting for SQL Server to be ready..." for i in {1..30}; do /opt/mssql-tools/bin/sqlcmd -S localhost -U SA -P 'SomePassword' -Q "SELECT 1" && break echo "SQL Server is still starting..." sleep 2 done displayName: Wait for SQL Server

Make sure mssql-tools is available in the container or install it via package manager in the wait script step.
PratikLad 960 Reputation points Microsoft External Staff

2025-05-02T11:36:45.57+00:00

Hi devops engineer, We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution

please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

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Cannot connect to MSSQL service container from self-hosted agents

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