In which I add a custom prompt by making a hack in the PowerShell profile.

As I have mentioned in previous posts, I use Oh My Posh to set the theme in Powershell. While working with Pulumi to create deployment stacks, I thought I could use a way to see which stack is the current one, i.e. to effectively have the output of pulumi stack --show-name appear in the prompt automatically.

Back in the old world, the agnoster theme was the prettiest. In my terminal at least, it looked quite a lot worse after upgrading to Oh-My-Posh 3, so I did exactly what they say in the documentation, I used Get-PoshThemes to look at all of them, exported the one I liked best into a json file and went to work.

Command

The naïve implementation would be to add a new segment in the prompt, using the segment type seemed to be “command”, which does what it says on the tin, it allows you to call a command and display the output, like it works in Bash.

        {
          "type": "command",
          "style": "powerline",
          "foreground": "#000000",
          "background": "#ffff00",
          "properties": {
            "shell": "powershell",
            "command": "pulumi stack --show-name"
          }
        },  

They do warn you that there will be performance implications, and – yes- on my 16 core desktop it still takes forever to start a process in PowerShell, so that didn’t seem to be a workable way forward. The suggested approach is to “abuse environment variables”, so… let’s?

Environment variable

I have previously made hacks to set window titles in cmder to work around iffy built-in support for showing the path as the tab name. The idea was to replace the built-in “cd” alias with a PowerShell function that also does dodgy stuff on the side apart from changing directory. In this case I would test if a pulumi.yaml file exists in the new directory, and in that case set the variable PULUMI_STACK to the output of pulumi stack --show-name, or set the variable to empty.

# --- other stuff
function Change-Directory() {
    param(
        [string]
        $directory
    )
    Set-Location $directory
    $env:PULUMI_STACK = ""
    if (Test-Path "pulumi.yaml") {
        $env:PULUMI_STACK = & pulumi stack --show-name
    }
}
# --- other stuff
Set-Alias -name cd -Value Change-Directory -Option AllScope

I of course don’t want to globally change this variable, I explicitly only care about the current terminal session, so hence I’m not trying to update the registry or anything like that. To read this variable and show a prompt, we then modify the theme json file to leverage the envvar block and to contain the following:

{
    "type": "envvar",
    "style": "powerline",
    "foreground": "#000000",
    "background": "#ffff00",
    "properties": {
       "var_name": "PULUMI_STACK"
    }
},  

After this work, the prompt is much faster, beyond acceptable, maybe even pleasant.

In the beginning of time, Grace Hopper invented business software and Cobol at IBM. This meant that in addition to calculating the trajectory of an intercontinental ballistic missile, large computers could now be installed, literally built into the very lower basement of international enterprises and be used to process payroll and do forecasting, gradually obsoleting armies of calculators and typists.

Earliest business applications

At this point, nobody knew how to actually or maintain write large software systems. I mean, granted, current paradigms like object oriented programming and functional programming were formalised around that time, but still, people had not written as much software back then as you now have to write to make a car set fire to petrol at an opportune time given crank angle, engine speed and temperature (I exaggerate, but not really).

From terminals to personal computers

Eventually Microsoft began it’s journey to global domination in the office by piggybacking onto IBM’s good name and getting installed into offices by default since nobody got fired for buying IBM. Unfortunately, IBM’s own operating system guys that wrote time sharing operating systems for mainframes had no influence over the people that created the CP/M knockoff that was to be PC-DOS (and Microsoft’s MS DOS), so it had no multi-user or networking security features built it as, well you were supposed to have it on your desk, and buy another computer for somebody else’s desk. No need for passwords, amirite? I mean UNIX existed and was fairly wide-spread in the corporate environment at the time, and it had decent security built-in, at least a fundamental understanding that even as a power user, you don’t want to have that power all the time.

The beginnings of Enterprise IT was therefore to maintain and write software for mainframe computers, and that was so alien of work to most organisations that it quickly became outsourced to suppliers that could lower maintenance costs, but overcharged for development work, thus lowering OPEX but moving software to CAPEX. This had one of the first negative incentives driving the business to make fewer changes, making enterprise IT infamously slow to react and become a department of No.

As technology changed, the IT department stayed in the cellars and basements where the business rarely ventured. As mainframes were phased out and replaced with banks of personal computers, the white coats disappeared. Gradually, typing stuff into computers at the IT department stopped being work exclusively for women, and men started taking over; salaries increased (not saying there is a causal relationship, just saying), but still no natural daylight.

Forces conspire to make organisations write and maintain code

There is a syndrome that happens to computer people called “Not Invented Here”, which is a form of exceptionalism that means that no outsider could possibly understand our Very Special Requirements, so we need to write our own X, where X can be anything. While certain pieces of software became standardised, like payroll and accounting for small businesses, there is still big money in helping people shoot themselves in the foot by developing and maintaining their own adaptations of commercial ERP systems like SAP and on a lesser scale Dynamics NAV or GP. Microsoft Excel is the most successful way of combining both, as in letting people buy a commercial off the shelf application but then making excel sheets with bespoke maths that can both be the lifeblood of new business and be its cause of death when the bespoke template turns out to have a bug and nobody knows how to fix it anymore.

An accounting quirk (see the bit about CAPEX above) where you count code written as value created rather than a pure expense, and book development costs as having added capital value to your code base despite, objectively, few if any of your competitors would buy your bespoke mess of a back-office system if you offered it on the open market. Also they most often don’t count the depreciation that comes naturally unless you make the code maintainable and easy to refactor if requirements change in future.

At this point we have an alienated IT department that has only two key metrics, to cut cost and to add features to internal software products, but no real way to directly discuss requirements with those that use the software.

Negative incentives

In the beginning you only have developers. As in, they develop, profess to test and deploy their code without any supervision. Then you have an outage that embarrasses somebody in management but no singular scapegoat could be found and all of a sudden you get ops guys that are there to protect the business from the devs. After another outage that embarrasses the management further, you may get a QA department. You can imagine how IT security comes to exist as a function within an IT department?

You now have one team that’s there to make changes that implement business requirements they have captured some way or another, one side that’s there to make sure those changes are valid and one side that’s there to make sure there are no outages. The incentives become to make few releases so that the QA guys want to be able to make a full regression before they green-light the release, and the QA guys are the ones getting a bollocking when bugs get out in the wild. The ops guys have enough to contend with without f^!£$g developers making changes ON PURPOSE, how are you ever going to maintain a stable system if you keep poking it with new software all the time?! So yea at best one release per month, anything quicker would be irresponsible and you would be working your QA department to the bone.

From a business perspective this means you are never getting your change in. As more things go wrong, process/red tape is added, lead times longer, change freezes are introduced periodically. Longer release cycles and bigger releases cause bigger problems.

Technically speaking, after mainframes people bought servers. At first they were just computers, beige like all the rest of them, and a server room was just a cupboard where they were shoved. You bought a physical computer from a supplier where you got a decent price, and you set it up, installed your OS and then you installed your software one it. Or you bought the computer and shipped it to your software vendor and let them install their software on it. 19″ racks became a thing, and servers became distinct from PCs in that they became loud and flat. You were going to stick them in a room away from humans anyway, so noise was no longer a concern. You did want many computers per rack, and you wanted simple but effective cooling, so you would fit powerful high-RPM fans.

As things progressed, people realised that it is hard to find office space that allows you to fit redundant power, automatic fire suppression and redundant network connections, so instead of trying to fit that into your basement, they would go to a third party that offered co-located datacentres. There you could mount your rack servers and they would give you ways to remotely manage them, so you wouldn’t have to physically interact with the servers to run them. All the patching and other maintenance could be done over the internet, and the data centre would make sure no villains could get at your hardware.

After a while people realised that you could just buy a couple of massively overpowered servers and then divvy up the computer horsepower onto virtual machines, pretend servers that would behave like separate physical machines. Carving out a bit of virtual compute and create a new “server” was a lot faster than buying a physical server and having your colo provider plug it into your rack. You would still have to install the OS and configure the networking, but there would be templates and automation. Heck, you could even write command line scripts to new up new servers.

Point is, in Enterprise IT there is no time to write scripts, and far be it from the mind of any ops person to collaborate with developers to explore things like version control and automated testing, I mean the developers are the enemy, the cause of all our problems, why would we collaborate? VMs are therefore largely artisan creations with very bespoke installs, apart from possibly sharing a raw template with some antivirus or monitoring, not even instance 1 and 2 of a load balanced pair have the same software on them.

As the blows keep coming with outages, bugs in productions and near misses that cause leadership to go on long-term sick leave, decrees can go out to create test environments that are “the same as production”.

Servers are bought (VM hosts, or course) and VMs are configured. Obviously, it is prohibitively expensive to make it exactly the same as production given that the load requirements will be different, so some corners are cut, but, it should be close enough. As the old meme would go – narrator: It was not close enough. Also, since the server operating systems are still hand crafted, there are multiple potential places where differences between production and test can creep in.

Great expectations

In various countries, leaps were made at various times that caused people to adopt electronics at vastly greater rate than before. In Sweden there was a push in the late nineties, early noughties where you would get a quite substantial tax rebate if you bought a modern computer at a certain cost, causing a lot of people to all of a sudden possess a modern computer. With various Covid stimulus cheques it seems a lot of Americans put money straight into a gaming computer (thus worsening the current silicon supply chain constraint situation). There have been similar schemes all over the world at one time or another to encourage adoption of technology to promote familiarity with new technology, I just can’t be bothered to google more examples. Basically, people have used the internet and are able to see what commercial software development can do. Another cause of people becoming aware of the wider world is how various Apple products have had a marked impact on Enterprise IT, and BYOD basically becomes a thing in businesses because the CFO one days comes back to the office with a MacBook Air and stares the IT department down until they “make it work” with their existing corporate software that only runs on a specific type of dell laptop they have imaged two years ago, requiring IE6.

The exposure to what computers can really do and the daily torture of using enterprise software to do their jobs, dissatisfaction among the people on the business side is rife. Eventually, some middle manager just takes their corporate expense account and hires some consultant off the books and builds some quick win software to solve a specific problem. If we are unlucky, this is an all out win. It works, it generates business and was executed in a timely fashion on, or just over, budget. A dangerous precedent is set, another wedge is driven in between the business and the IT department. Shadow IT is born.

Recap

To bring us to the final bit of the story, let’s assess where we are.
Enterprise IT is disgraced, underfunded and distinct from the core business, literally moved away from the rest of the organisation. A troll under a bridge or an ogre in a swamp. Sure, the CTO may report to the Board of Directors, but there is no real correlation between desired business outcomes and the metrics that the IT department measures its services against, and no work is done to ensure that IT services directly benefit the key outcomes that the business as a whole needs to achieve. Control of IT spend is instead largely project based, as in, the business has an idea, it needs some IT support, a project is created with a budget and a final ship date before anybody with technical know-how has even assessed it, and then work commences. Probably contractors are brought in if there is sizeable chunk of development, but normally the department is kept lean. Service desk and “maintenance development” presumably outsourced to a country in a different timezone.

What Enterprise IT wants is to be a force for good within the organisation, but since the beginnings of time IT has often been deemed a non-core support function, and that increased conceptual distance has made it more difficult to effectively be of use to the organisation. Cultural differences between IT and other parts of the organisation, and perhaps ineffective communication between stakeholders and the developer organisation as caused upper management to silo the organisations further apart rather than agree on an effective way of working closer together. In cases where IT is not involved in other aspects of the business, obviously there will be no “osmotic” assimilation of domain knowledge, so the business may be shocked of how little the IT department actually knows about the bread-and-butter business that keeps the lights on.

Roadmap

How do we turn things around? What are the most important things moving forward? I will leave out the Practices bit, because I have rarely seen bad practitioners in organisations I have worked with. People will write automated tests and implement CI and CD if they are given circumstances not directly hostile to professional software development. The bigger lego pieces are usually where the problems lie, and why management buy-in is crucial.

Increase automation

The VMs are not family or even pets, you should delete them all and start over. Not in one go, or to cause another outage, but replace at pace the VMs you are currently running in production with new ones created through automation. When you can automatically deploy your core business application from nothing to a running instance without any manual intervention you are done. Thinking you could replace your running VMs with automation but not actually having proven it has no value. Ideally make the deployment process be some version of “stand up new VMs with an app on them, run tests to make sure it’s working, route traffic to the new instances, destroy the old instances”, so that you can deploy without causing any loss of availability. This is crucial in building trust with the rest of the organisation. When I write VM, I’m not making a dig against containers or containerisation, just saying you can achieve this without moving to kubernetes and a service mesh, you can do it with bog standard VMs and a bit of scripting.

Decouple systems

In order to be able to fearlessly deploy, you will have to decouple systems so that you can deploy small changes often, with small blast radius and short time to recover.

Organise your IT department after what you are supporting. Yes, after business functions but also after the systems that you maintain. If you have a monolith that support all business functions, then you need to split it up. The output of different teams needs to be independently deployable. This is not easy, but it is the only way to enable teams to make predictable progress. Consider it an investment in predictable outcomes.

Maintain products, don’t run projects

When you have finally managed to put together teams that match your customers and your work, then don’t disband them again after you have delivered a certain milestone and the “project is done”. Budget for products rather than projects, so see your own software as a driver to increase profits and reduce cost. Set targets for what you want to achieve and measure outcomes. Let developers prototype things and show the business what’s possible. If you have built the right platform for people, it will be possible to securely bring new ideas to life and test them with real clients and get true feedback. This way you can delight customers faster, and there is lesser risk you get saddled with maintaining some Shadow-IT piece of software that suddenly became core IT after it was successful and the consultant that wrote it moved on to greener pastures.

Goal

By introducing a wider interface between the business and IT, and making teams that have the autonomy and platform support to independently iterate of features quickly, you will both delight the business, delight the customers, make more money and have happier teams. There will be times when you have to organise and coordinate, but the lion’s share of work can be done independently.

Back in the day

You would have one database connection string, and that would be it. “The Database” would live in the darkest corner of the office and you would try not to interact with the physical machine that hosted the relational database management server. The Windows Forms app would open a connection and keep it alive forever with nothing to really threaten it. It would enable Multiple Active Result Sets because there was no grown-up way to query the database, queries were being shoved down the shared connection seemingly randomly depending on what the user was doing and what events forced data to be loaded. You would use the Windows Credentials of the end-user and specifically allow a the user to access the server, which fit with the licensing model where the user paid for accessing SQL Server when buying Office products, whilst pure server deployments needed per CPU core licensing which was hysterically expensive.

Cloud

The cloud revolution came and went, whilst we in the Microsoft / Windows / .NET bubble never really heard about it, until Microsoft decided to try their hand at hosting cloud servers with the Windows Azure project. I genuinely think this was extremely useful for Windows, as the prospect of hosting cloud services was so far beyond the capabilities of the bare OS, and forced some stark introspection and engineering effort to overcome some of the worst designs in the kernel.

For .NET Framework, a lot was too late already, and many misfeatures weren’t fixed until in the .NET Core reboot effort.

One of the things that did change for the average programmer was that database connections became ephemeral, and pooled. You could no longer hog one connection for all of your needs for all eternity – you created a new connection when you needed something and the framework would pool the connections for you, but you had to allow for connections taking longer to get established and also that they can be evicted at any point. Relatively quickly database providers would build in resilience so that you didn’t have to know or care, but in the early days even the happy path Microsoft marketing slides that usually never have error handling or security in them had to feature retry mechanisms – or else people simply couldn’t successfully replicate the early samples.

Security

As people started using the public cloud, eventually people figured out that security was a thing. Maybe we should not have overly powerful credentials lying around in config files on the webserver ready to be exploited by any nefarious visitors? People eventually started using things like Azure KeyVault or AWS Secrets Manager. Sure it’s bad if people break in and nick your stuff, but it’s worse if they also steal your car to carry away the loot.

Once people had all their secrets backed by hardened credentials services, features like autorotating credentials started becoming available. Since you are provided most of your authorisation by the general hosting environment anyway, and only really need credentials for systems that are incompatible with this approach, why don’t you just automatically periodically update the credentials?

Also – back in the day when the server lived back in the office, if somebody got a bit enthusiastic with the UPDATE statements and forgot to add a WHERE, you could send everybody out for coffee (read tea, dear UK readers) whilst the techiest person in the office would Restore to Point in Time and feel like a hero when the database stopped being in recovery mode and everything was back to the way it was before the Incident.

Today a “restore” means you get to create a new database that contains the world as you knew it, before the Incident. You then need to serially rename databases to achieve the effect of having restored the database. Not a big deal, just not what we used to call restore back in my day.

Back to retry mechanisms

For SQL Server running in Azure, you can now tell the Microsoft.Data.SqlClient to connect to the database using the Managed Identity for the app, meaning you are completely free of faff and the KeyVault is managing your access automatically.

With RDS on AWS you need to use legacy usernames and passwords unless you configure an Active Directory domain up there, but … no, but these credentials can be auto-rotated in AWS Secrets Manager. Because of the cost of talking to the Secrets Manager, it’s not something you want to do every request, as that piles up over a month.

One of those retry mechanisms from early Azure days start to make sense again, and is easily implemented as a factory method you can call instead of the await using var cn = new SqlConnection(...) you have littered all throughout the code. I mean you’ll still await using that factory method, but it can do the setting up of the connection and validating the credentials, and only spend the dosh fetching the latest from the vault if you get the error code for invalid credentials. This means your bespoke factory method replaces both new SqlConnection and OpenAsync().

Naïve retry mechanism, featuring goto:

// https://docs.microsoft.com/en-us/sql/relational-databases/errors-events/mssqlserver-18456-database-engine-error?view=sql-server-ver15
// Error code that indicates invalid credentials, meaning we need to bite the bullet and fetch latest settings from Secrets Manager
private const int INVALID_CREDS_ERROR = 18456;
private const int INVALID_DB_NAME = 4060;

public async Task EnsureValidCredentialsAsync(SqlConnection conn, CancellationToken cancellationToken)
{
    var rdsCredential = GetRdsCredential(await _secretsCache.GetCachedSecretAsync(_siteConfiguration.DefaultDatabaseCredentialKey));
    var dbCatalog = await _secretsCache.GetCachedSecretAsync(_siteConfiguration.DefaultCatalogKey);    int reconnectCount = 0;
reconnect:
    var connectionString = GetConnectionString(rdsCredential, dbCatalog);
    conn.ConnectionString = connectionString;
    try
    {
        await conn.OpenAsync(cancellationToken);
        conn.Close(); //  restore to known state
        return;
    }
    catch (SqlException sqlEx) when (sqlEx.Number == INVALID_CREDS_ERROR)
    {
        // Credentials are incorrect, double check with secrets manager to see what's what - potentially creds have been rotated
        rdsCredential = await _secretsCache.GetSecretAsync<AwsSecretsManagerCredential>( _siteConfiguration.DefaultDatabaseCredentialKey );
    }
    catch (SqlException sqlEx) when (sqlEx.Number == INVALID_DB_NAME)
    {
        // Database identifier is not valid, double check with secrets manager to see what's what (potentially restored db, deprecating old db name)
        dbCatalog =
            await _secretsCache.GetSecretAsync(_siteConfiguration.DefaultCatalogKey);
    }
    catch (SqlException sqlEx)
    {
        Log.Error(sqlEx, "Could not open default DB connection. Reattempting");
    }
    if (reconnectCount++ < 3) goto reconnect;
    // surrounding code expects an exception if the open fails 
    throw new InvalidOperationException("Could not open database connection");
}

What about Entity Framework?

Looking at the way you officially configure Entity Framework – it seems you can’t get away from having a known connection string up-front, which again isn’t a problem in Azure as discussed earlier, but for me, I want to only hand credentials to the app that I know have been tested.

In my past life inviting speakers to Oredev I once invited Julie Lerman to speak about Entity Framework and DDD, so I pretend that I know her and that I can call upon her for help in matters of programming, so I sent out a tweet linking to a Hail Mary Stack Overflow question I had created where I asked how I would be able to dynamically handle connection retries in a similar way or at least be able to call out and ask for credentials.

Surprisingly she had time to reply and pointed me to a video where she had addressed this subject and which taught me about something called DbConnectionInterceptors that had all the things I wanted, in addition this also introduced me to the super elegant solution natively supported by Microsoft.Data.SqlClient for handling this situation in Azure that I mentioned earlier.

Basically I therefore created a class that inherits from DbConnectionInterceptor and overrides two methods, one sync and one async version and call something like the above function to test the connection EF Core is about to open.

public override async ValueTask<InterceptionResult> ConnectionOpeningAsync(DbConnection connection, ConnectionEventData eventData, InterceptionResult result,
    CancellationToken cancellationToken = new CancellationToken())
{
    var sqlConnection = (SqlConnection) connection;
    // try opening the connection, if it doesn't work - update its params - close it before returning to achieve same state
    await _dbConnectionFactory.EnsureValidCredentialsAsync(sqlConnection, cancellationToken);
    return await base.ConnectionOpeningAsync(connection, eventData, result, cancellationToken);
}     

Of course – registering this interceptor is easy as well, after I had googled some more. There is a (synchronous) override that allows you access to an instantiated IServiceProvider as follows:

services.AddSingleton<ResilientRdsConnectionInterceptor>();
services.AddDbContext<ADbContext>((provider, options) =>
            {
                var dbConnectionFactory = provider.GetRequiredService<DbConnectionFactory>();
                var connectionString = dbConnectionFactory.GetDefaultConnectionString().GetAwaiter().GetResult(); // So sorry, but there is no async override
                options.AddInterceptors( provider.GetRequiredService<ResilientRdsConnectionInterceptor>());
                options.UseSqlServer(connectionString);
            });

An aside on async/sync. It seems Microsoft will have you rewrite every other line of your codebase to properly support async or your app will fall over. But when you then want to reuse your async code and not have to duplicate everything into similar-but-not-reusable sync and async versions, the tiny changes needed for MS to support async everywhere are all of a sudden “not needed”, line in configuration or DI. It’s laziness, I tell you.

Anyway I have integration tests in place that verify that the mechanism for calling out for updated credentials actually works. Provided the credentials in the secrets manager/key vault actually work, this works like a charm.

Just like that rebrand cycle years ago when RUP consultants transitioned over to scrum masters through staged re-titling on LinkedIn and liberal use of search / replace in their CV, scaled agile frameworks and certified project managers attempt to apply the agile manifesto to large organisations by bringing in processes and tools to manage the individuals and interactions, comprehensive documentation of the working software, to negotiate contracts to manage customer collaboration and make plans for how to respond to changes. You start seeing concepts like the Agile Release Train, which are – well – absurd.

Why? Do they not see what they are doing? Are they Evil?

No – I think it’s simple – and really really hard, at the same time.

You cannot respond to change quickly if you have delays in the system. These delays could be things like manual regression testing due to lack of automated test coverage, insufficient or badly configured tooling around the release or having a test stack that is an inverted pyramid, where you rely on a big stack of UI tests to cover the entire feature set of the application because faster, lower level tests aren’t covering all the features and you have undeniable experience of users finding bugs for you.

Obviously, if these tests are all you have, you need to run them before releasing or you would alienate customers. If your software stack is highly coupled, it would be irresponsible to not coordinate carefully when making changes on shared components with less-than-stellar contract test coverage. You are stuck with this, and it is easy to just give up. The actual solution is to first shorten the time it takes from deciding you have all the features you want to release until the software is actually live. This means automate everything that isn’t automated (the release itself, the necessary tests, et c) which could very well be a “let’s just stop developing features and focus all our attention on this until this is in place” type investment, the gains are so great. After this initial push you need to make an investment into decoupling software components into bits that can be released independently. This can be done incrementally whilst normal business is progressing.

Once you have reached the minimum bar of being able to release whatever you want at any time you want and be confident that each change is small enough that you can roll them back in the unlikely event that the automated tests missed something, then you are in a position to talk about an agile process, because now teams are empowered and independent enough that you only need to coordinate in very special cases, where you can bring in ad hoc product and technical leadership, but in the day to day, product and engineering together will make very quick progress in independent teams without holding each other up.

When you can release small changes, you can all of a sudden see the value in delivering features in smaller chunks with feature flags, because you can understand the value in making 20 small changes in trunk (main for you zoomers) rather than a massive feature branch, as releases go live several times a day, and the benefit of your colleagues seeing your feature flagged changes start appearing from beginning to end, they can work with your massive refactor rather than be surprised when you open a 100 file PR at 16:45 on a Friday.