kardianos
commented
6 years ago The current Get Instances function uses UDP port 1434 to port to the SQL Server Browser. This network service lists available SQL Servers and how they can be connected to.
This AlwaysOn connector appears to be describing something else. Here is how we can work on this:
- We need a problem statement along with docs.
- In your PR you mentioned a link to MS docs. That's great. It looks like this talks TCP and does something different.
- I'm uncertain if @denisenkom is familiar with AlwaysOn or similar, but I'm very much in the dark about what it is and when it is used. Can you provide a summary?
- We need a proposal of how this code would work and what it would do.
- Ideally we would know how to setup a test environment for this, but I understand that this may be difficult.
GnatorX
Right now getInstance in tds.go only checks the first resolved address from dialer.DialContext. This means that if the AlwaysOn connector has subnets where the app can't reach, the driver will fail to create any connections. https://github.com/denisenkom/go-mssqldb/blob/master/tds.go#L58.
The solution already exist in the code in dialConnection https://github.com/denisenkom/go-mssqldb/blob/master/tds.go#L1115. This code will go through all resolution of the connector and pick one that works before proceeding. This allows the driver to work with AlwaysOn connectors with unreachable unsubnets. PR created: https://github.com/denisenkom/go-mssqldb/pull/422