Marten projection distribution fails to start agents when using a unix socket connection

[RonTamG]

Describe the bug
When using Marten with wolverine projection distribution and a PostgreSQL connection string with a Unix socket we started seeing the error "Failed to start requested agent" with an IndexOutOfRangeException from JasperFx.Descriptors.DatabaseId.Parse. We encountered this after trying to update to the new versions of Marten and Wolverine in GCP Cloud Run with GCP Cloud SQL.

This happens because DatabaseId (derived from the connection string Host) contains slashes (e.g., /cloudsql/...), which causes the Uri used in EventSubscriptionAgentFamily to be parsed into multiple segments. This shifts the expected segment index for DatabaseId in BuildAgentAsync and splits the ID, preventing DatabaseId.Parse from receiving the correct full string.

To Reproduce
Steps to reproduce the behavior:

1. Configure Marten with a connection string pointing to a Unix socket (e.g., Host=/tmp/postgresql;Database=mydb) and wolverine projection distribution.
2. Run the application.
3. See error IndexOutOfRangeException at JasperFx.Descriptors.DatabaseId.Parse.

Expected behavior
Wolverine should correctly parse the DatabaseId and start agents when the connection string uses a Unix socket path containing slashes.

Additional context
Stack Trace:

System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at JasperFx.Descriptors.DatabaseId.Parse(String text) in /_/src/JasperFx/Descriptors/DatabaseId.cs:line 12
   at Wolverine.Marten.Distribution.EventSubscriptionAgentFamily.BuildAgentAsync(Uri uri, IWolverineRuntime wolverineRuntime) in /home/runner/work/wolverine/wolverine/src/Persistence/Wolverine.Marten/Distribution/EventSubscriptionAgentFamily.cs:line 50
   at Wolverine.Runtime.Agents.NodeAgentController.StartAgentAsync(Uri agentUri) in /home/runner/work/wolverine/wolverine/src/Wolverine/Runtime/Agents/NodeAgentController.cs:line 164
   at Wolverine.Runtime.Agents.StartAgents.ExecuteAsync(IWolverineRuntime runtime, CancellationToken cancellationToken) in /home/runner/work/wolverine/wolverine/src/Wolverine/Runtime/Agents/StartAgents.cs:line 71

Analysis:
The EventSubscriptionAgentFamily.UriFor method constructs a URI by directly embedding the DatabaseId string into the path. If databaseId contains / (which is required when using a unix socket connection), the Uri class parses it as multiple path segments. BuildAgentAsync hardcodes retrieving Segments[2], which is incorrect when the ID spans multiple segments.

Minimal Reproduction:

using JasperFx.Descriptors; // Assuming reference

public void Run()
{
    var host = "/tmp/postgresql";
    var database = "mydb";
    var databaseId = $"{host}.{database}";
            
    // Emulating EventSubscriptionAgentFamily.UriFor logic
    // URI becomes: event-subscriptions://marten/main//tmp/postgresql.mydb/some/shard
    var uriString = $"event-subscriptions://marten/main/{databaseId}/some/shard";
    var uri = new Uri(uriString);

    // Emulating BuildAgentAsync logic
    // Fails here because Segments[2] is just "/" (due to double slash)
    // instead of the full "/tmp/postgresql.mydb"
    var databaseIdPart = uri.Segments[2].Trim('/'); 
    
    // Throws IndexOutOfRangeException because databaseIdPart does not contain '.'
    var id = DatabaseId.Parse(databaseIdPart); 
}

[jeremydmiller]

@RonTamG TBH, I'm going to ask you for a PR to address this. Or throw in a failing test in a PR and I'll turn it around quickly

[jeremydmiller]

@RonTamG Can't even begin to tell you how not proud I am of the intended fix for this. Changing DatabaseId in JasperFx so it escapes the "slash" in the Host name with a ~ character.

[RonTamG]

Sorry for the very late response, I tried to upgrade again after the changes and I am still encountering an error when trying to use a unix socket to connect to postgres.

This time it's from the creation of the url at this point
https://github.com/JasperFx/jasperfx/blob/57c178af5db500193a592a261816264717b0869a/src/JasperFx/Descriptors/DatabaseDescriptor.cs#L57

The exception is System.UriFormatException: Invalid URI: The hostname could not be parsed.

From what I can see at this point the server name is still in it's original form without the changes to the slashes.

I can open a pull request to adjust this as well using the same method from your fix.

[jeremydmiller]

@RonTamG Hey man, I'm thinking you've got some special sauce going on. I'm happy to take pull requests for whatever it is that's different in your world. I can't be everywhere, and I don't work w/ *nix, so I don't have any context for any of the things you're hitting. But I'd get the PR in quickly if you want to step in and deal with your issue here.