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well people are always asking me about uh mainframe modernization and and well let me think about this

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always is that true yeah it very frequently comes up i think especially like i was i was realizing

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uh in this past year i don't know if you've experienced this but in this past year people i

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talked with for years have always been talking about like moving to the cloud and modernizing

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their stuff they really wanted to do it but i've noticed in the past year people actually have

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numbers around it like like goals and kpis they're supposed to reach which seems like it's it's uh

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it's happening more and more so you wrote a uh you wrote a blog post this is actually last year from

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may of 2022 when i was uh when i was looking over i don't know well i don't even remember what i was

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reading about legacy applications and i came across this on our blog and you had a pretty uh what i

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think is a a great in the sense that it's brief and just deep enough to make sense like

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overview of of uh i'm sure along with many people like you worked on um helping modernize uh uh you

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know a mainframe application uh and it was a good overview of a lot of the practices i've heard we

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do in swift and things like that with some uh with some nice diagrams so i thought it'd be fun to uh

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to talk to you about that why don't you introduce yourself first so i am i am fwad and i am working

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uh in tonsu r&d uh today and uh since a few months ago and before that i was working in tonsu labs

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uh in france in paris and i was involved in many engagements where we used to modernize legacy

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applications and mainframes are uh some of the kinds of application that that we we are used to

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modernize there do you see a lot of this out there like mainframe applications that people

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want to and then actually are modernizing or you know does it happen rarely so personally it started

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like uh i think i was involved in that kind of engagement like uh in 2019 like already three

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or four years ago and and at that time there was not really many mainframe uh engagements going on

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but since a couple of years it's i've seen in labs uh uh that there are more and more customers asking

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to to to dig into that and to help them modernizing the mainframe so give a give us an overview of like

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um both both the example as you say engagement here but like i think it's pretty representative of what

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what you see let's call it the business motivations for modernizing a mainframe you actually cover it

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yeah pretty well right from the beginning like it's a 30 year old system with 12 000 programs that's

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relied on by 3 million users you get into like what the business motivations for doing it are and i

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think i think going over this is always very important because like you know for as much as mainframe

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people used to call us distributed people might sort of poke fun at mainframes and have them be old

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like the thing about a mainframe that's been running 30 years is it works right and it's it's worked very

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well for 30 years to survive through all of that when companies have mainframes they usually work fine

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uh but but for for this example one of the main issues that the customer had was the that they

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the lack of knowledge to maintain and to make the mainframe so that was one of the key key cornerstone

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basically that they they they wanted to get rid of to be able to have people who who developers new new

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teams that uh who could handle the business that is implemented in the mainframe but using modern modern

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technologies uh so that was that was one one of the aspects and and uh the second big one was uh to

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reduce infrastructure costs basically because having a mainframe processors running cost them millions of

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euros uh and and being able just to move some transactions that were running uh into the mainframe

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into new application would make them save a lot of money so they wanted to start to do that the goal

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was not to get rid of the whole mainframe like uh uh as fast as possible it was more like to start

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extract few a few things step by step and and being able to do like to have quick wins and a quick

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money savings by just doing that i wrote this little booklet last year with with our colleague mark

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zottner about uh you know about the swift method and and like more broadly like uh we called it the

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legacy trap that was our clever name for but more broadly like from a for lack of a better phrase a

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business perspective like what the deal with modernization is in doing it like we went over

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like what makes software legacy software and i mean you you i think you hit on one of the to kind of

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summarize the two of them like with mainframes especially there's the like you it's you've forgotten

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about it like you lack knowledge about how to do it and you know i think i think the how that manifests

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itself and like something that the organization cares about is that you can no longer really change or add

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to the functionality of it or and and sometimes it's also performance right like if you've forgotten how

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a system works sometimes when you have different performance needs like you have to serve a whole

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bunch of different people or you have to do it in a different medium like you have to go from a desktop

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app to like a mobile app or something like it's kind of no longer fit but i think i would imagine the one

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that people encounter a lot more is like you just have different features that you want to add and

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it's kind of not possible right and because because no one really remembers not only like in this case

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like how to program in cobalt and also not only just like how the programming works but like one that's

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especially like terrible is like no one remembers how to test it yes to make sure it doesn't break things

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which is terrible yeah that's true so so uh they also have to rely on external companies to to maintain

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this this knowledge and and that's a big a big danger for for such companies like they move the

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the business loader they externalize the externalize that business knowledge that knowledge to external

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companies they don't have much more control about on it rather than uh uh in the past they were able to

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control the their business inside the company so so that's why that's one issue for for this company

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and and uh i saw another thing that uh then another issue that they have is the development life cycle

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like you mentioned uh the capability to to deploy new features or to fix existing features uh also takes a

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lot of time uh just to deploy new things uh it's a they have heavy process they had heavy processes they

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had to set up downtime periods like to to stop the user the users using the application to be able to

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deploy your simple feature that was very painful for them their tech debt finally caught up with them

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so you mentioned one thing i'm interested in in hearing more about which is um and this is part of

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like the the the method that you know tonsu labs and pivotal labs people have developed not only in

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legacy modernization but just in apps and platform engineering like in general which is like starting

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small basically is is the way i think of it right instead of oh we're going to modernize and move

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everything on the mainframe like more so it sounds how you all started was like let's start with one

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thing let's start by just to use a word that's common like little slices and slicing away at it was like

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the the customer comfortable with that often there's just like well why wouldn't we do everything at

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once but i think there's also often like an overly ambitious business case they have to deliver on

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like if we're going to take on all this risk and like spend some money on this we need to have a big

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payoff at the end of the year whereas when we go again with this start small and slice thing we're

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kind of like saying yeah there's not going to be a big payoff for like three to 12 months did you encounter

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in this case where you kind of had to sell people on starting small and slices what what was that like

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yeah that that's usually uh hard to convince people uh companies about that customers about this but

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but in that case for example they already tried it in the past so they already tried to rewrite and

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they they and they felt the failure the the pain to do so and and that they they were not happy with

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the result so that's why they wanted like uh to experiment our our approach and actually before

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before working on the mainframe we had past engagements with them where they trusted us yeah

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basically we built a trust relationship with them and and that's why they involve us in try helping

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them modernizing the mainframe it was a kind of some kind of challenge right like uh okay uh prove us

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that you can use your practices to to start modernize you something in the in the mainframe and see and

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see and check if it's better than what we did in the past or is it worse or oh yeah and then to can

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to kind of beat some comparison charts between uh uh our approach i guess this is what like you know

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labs thinking would say is like well let's let's do a small project or a slice to see if we can also do

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this with mainframe stuff right let's prove that that we can do this out uh in kind of like uh it's

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not risk-free but a lower risk way when you're looking at the application like how do you start with

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that like how do you how do you start like comprehending what this application is kind of like figuring out

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what little slice to do kind of kind of walk us through that process yeah sure um so basically we

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we we use one of the tools in our swift uh swift uh swift box swift methodology box

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that is called event storming basically and and what we do uh is a we run a workshop with uh

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uh every everybody uh all the people that are who are involved in the mainframe

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who have knowledge on the mainframes and and that can uh imply having people that are

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at a high level of the hierarchy of the company who often uh were developers in the company and know

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and know about the mainframes but now they've changed their position there are no more developers and

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they and are actively promoted and they and they have but they have knowledge of this so

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we have to involve those people in in this workshop uh until the develop and also the developers and the

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testers we have to gather everybody uh in the same room and and basically build a visual representation of

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all the of the events that are flowing through the system like basically like uh uh everyone brings

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bringing uh his or her piece of knowledge uh regarding all the things work in the system in the mainframe

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and we have to to merge all of this uh uh so it's a sticky notes exercise basically we have gathered in a

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piece in the room and we put stickies and people put stickies and then we have to merge all of this to

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make sense of all the the flows that are uh that we have in the system and and from them and from there we

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we can we start to to draw boundaries like uh identify subdomains like uh the comp the like uh okay this

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makes sense to gather those events together and to call that uh i don't know like the the accountability

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subdomain and together and and and build that kind of uh um identify that kind of subdomains and and

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from there we can also we also uh we can also have a an exercise where we with the uh where the people

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in the room can uh set the value uh of each of these demands right right sort of like the business

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value like how much does this matter exactly how important is it exactly and also try to identify

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the pain points where where they have the most the pain points maybe we we would like to start there

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or not depending on the context because uh depending on where you are in your mainframe modernization

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modernization journey maybe you want to start with something that is small not too hard to implement

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to validate the the process that you have in place but it has some some business rules so so the selection

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itself depends i would say depends on the context but the tools uh that we are using as are basically

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the same put some values on the thing uh identify the complexity identify the the business value and try to

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and prioritize based on the context where you are working what what are you looking what what is your

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goal with your modernization and then right select the appropriate uh let's say context or subdomain

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context and then and then from there identify uh user journeys and and the slices that we could start with

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and so so that gives you a list of just as you're saying like here are technically feasible and important

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enough like components we could work on modernizing because again that as you're saying the goal is to

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let's let's find something we can modernize that takes i mean i think the standard is like 12 weeks or

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whatever but that takes a small amount of time yes uh so that we can as you know just to summarize again that that

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we can figure out if we can do this right and at the same time actually do some of it and and also like

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learn how it's done i'm interested to like test out some of my theories uh you know with you about

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that is i feel like that exercise that you went over the kind of like you know the event storming

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doing like the the finding the domains all of that workshopping stuff like well i mean there's

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not not an assumption but the kind of the unstated thing in doing that exercise is that it doesn't

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that that that system view doesn't exist right like that like like while while each of those individuals

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might like have their own view of what their part of the system does that very often especially with

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like in this case like a 30 year old application um no one really knows the whole let alone everyone

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knowing the whole and like what the handoffs are between them um so i imagine that's a huge part

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of it it's just like as as mark will call it it's like architectural uh archaeology yes like discovering

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the system exactly yeah that's a huge outcome of the of this workshop indeed like uh having

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this view that probably nobody's at the beginning of the workshop had in mind and and align also all the

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stakeholders on the on this knowledge so of course the what we get at the end is not exhaustive like

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we sure you know we don't go deep very deep in the details of every demand but at least big picture

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everyone has a view of the big picture and that is uh that is very i'd say people when they they after

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this this workshop they felt like wow i understand what i'm working on now like yeah well i didn't

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imagine that there was so much complexity in this part oh like uh there are many uh that cannot we had a

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a lot of feedback like this like after the it must it must feel nice on both sides to actually like

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i mean you know in our trade learning is always fun and so like like like to have helped you know the

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the group as a whole to like have learned some new things especially about something you're so close

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to like your own systems right and you know the the other thing that like i think and and you know in

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general this this methodology i've i i shouldn't say seen because i just record things and make slides

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but like you know i've i've i've heard secondhand from labs people that whether it's new applications

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or existing ones right like the other i think the other thing that's valuable about it and and to your

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point of not to your point but like the positive side about of it not being too detailed is that

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that's by design because the purpose is also to capture like again to use the phrase like the

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the business flow of it like the purpose of this application right which is often like

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not fully reflected in all the technical systems like you know and and i think by by doing that

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event storming where there's like one event that you trace through the entire system like

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i don't know just to pick something like uh you know authorizing that something happens whether

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you're authorizing a prescription or authorizing like some forms being filled out like that whole

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authorization thing is an event that goes through the whole system and like i always joke that like

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everyone most people know the boxes but it's those arrows that people lose out on like like the

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connection between the two of them is like where a lot of lost uh knowledge uh typically is so you get

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the slices in front of you and so like what uh like like what slice do y'all pick like how what do you

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start with as you document in the uh in the blog post in the in this example we started by uh uh using

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like uh by working on a a slice uh a simple slice basically to to to be able to build something very

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very fast and see if we could deploy it in production uh very quick and evaluate um and identify all the

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trouble that we could have uh as fast as as quick as possible instead of waiting to build something

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more more more much more ready for the for the users the goal uh so so basically we we use the read

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read transaction written actually even before that sorry even before that what we did is we wanted to

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to start uh uh experimenting on what we call strangling the the mainframe legacy system to be to be sure

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that um so the strangling uh an application is one pattern uh where we try to basically to capture the

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calls like the requests that are done to the legacy system we try to capture them in our new the new

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system that we want to build to see if we can then uh if we could then uh rewrite them like uh modernize

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them in our right system and so basically it's kind of uh adding a proxy a gateway between yeah legacy

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system and our system uh so we we had to start with that because because there were a lot of uncertainty

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about the architecture uh at our customers because our uh so if you if you look into the article there was

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this schema where we have a like a front end a system and then the back end system and then the bus

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that that redirects the calls from the back end to the mainframe and we want i don't know if you

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remember that part and we wanted to to basically to integrate a proxy gateway uh between the bus system

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and the mainframe basically like uh uh we wanted to see if we could capture the calls from the bus to our

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gateway and then redirect the the calls coming to our gateway to the bus again that would call

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the mainframe just basically to see if we could capture things there and yeah i mean it's essentially

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a uh like a yeah i guess you could call it a person in the middle right like exactly you just add a layer

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there and then at that point well i guess one like you experiment with like we can actually connect to a

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mainframe and just be a pipe right exactly and and just getting to that point with authorization and

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figuring out how to do that like and making sure you have the right character and coding and all that

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stuff is probably plenty of work basically to do quote unquote nothing right exactly and it is very

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important also to it was very important to do it first because uh because we realized that it failed

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basically we were not able we were able to build the gateway and to to think but but the thing is that

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the bus the bus uh configuration was was maintained by another team uh all right yeah we didn't have the

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the bandwidth to work with us basically to to configure things to road direct to our gateway because

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um if they had to do that we would have to write like specification and it would take six months to

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implement this just to reconfigure the bus uh to so so that was a uh a very important experimentation to

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have to to validate that to be sure that we could not do that so uh and it forced us to pivot and to

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and to find another way to to stronger the mainframe and basically we uh i think i explained it in the

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article basically we there there was a ldap in this architecture that that is used to to to uh by the

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backend to to know where uh to know the routes that can to call on the on the bus when they want to

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call a mainframe transaction so we changed these routes to rather yeah let's get it to to a new uh to our

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system let's say to simply yeah it was it was fortunate that that but the that bus was in place right like

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that that that was kind of already a uh uh uh sort of already as you're saying a proxy or a gateway or

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whatever that you could have been so we were lucky that's why the context where you are modernizing

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the application is very important because yeah something that works in one context might not work

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in another one and uh and uh yeah we don't try to come with uh at labs at least we don't try to come

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with already keyed solutions like okay we're going to to do in your context and study the problems that we're going to meet

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to face by doing the things uh rather than just diagramming things so you so you start off so

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basically you're fortunate that there's a like call it an enterprise bus but a bus in place that's

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already like and and was that like was that like web sphere connected to the mainframe or like what what

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was the the bus i forget i think the bus was oracle esb and yeah the front-end and backend stuff were

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deployed on weblogic if i remember yeah yeah that would make sense good old j2ee stuff back when there

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was a two yeah and and so so essentially you put that uh you put that gateway in there we'll call it

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that is again putting it kind of sarcastically does nothing like like all it is is to make sure

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that you can have this pass through and then i imagine you know the goal of that is that as you

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have new applications or applications that that want to talk with the mainframe or existing ones you just

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shift them over to using that gateway right exactly and which should more or less be the same so what

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what's like the next step after that you get the gateway in place and then and then how do you uh how

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do you do further slicing so the next step was the next step sorry was to um to to work on the one of the

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uh one of the business transactions that was um responsible of reading information from from the uh

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mainframe databases from db2 and dl1 databases and so basically we start to we started to write

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uh a new a new microservice let's say let's call it like this because it's a fancy word that contained uh

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an endpoint to to read basically uh information from the legacy database and and so uh if i try to describe

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the flow so the front end will call the the back end that will code our getaway and our getaway will

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call our new uh yeah new endpoints and return the result to the front end instead of calling the back

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the the mainframe to our to our uh application new application the other thing that i think is worth

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pointing out or i mean you said it but calling out even more is that it was just a read-only operation

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so it's like again minimal risk right like like like most risk comes from writing or changing the data

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versus just like yeah seeing what it is is not that big of a deal yeah yeah and uh it also helped to

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build confidence within the team like uh right because we didn't have much knowledge on mainframe

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stuff and that's what to learn to have learnings because for example uh uh in the they were using

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db2 as a database but they are they were also using another database that is called dl1 which is quite

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old and it that uh uh that is a hierarchical database uh not a relational database and that uh

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there was no no tool to access the database for modern applications like to be able to read uh okay

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directly in this kind of database actually it's not really true there was one tool uh uh not open

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sourced like and and there was a uh a team who were studying the ability of this tool to to be used in

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modern application to read in this legacy database so so uh that allowed us to learn things like that even even a

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a simple a simple slice like this was very beneficial for for the team so then you know uh eventually

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you want to actually like change the data and write to it so what what how do you all get to that

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so uh so this is yeah this was the moment where we introduced this is the moment where we introduced

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a new database for our new application to give it the responsibility to be the owner of its own data let's

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say and and basically it started the same way than the read slices like we we we configured the ldap to

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route uh to the new to a new one endpoint that is responsible to write uh yeah that in the database

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and and what we did first is to um so is to to set up this new database and to and to basically to trigger

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to uh to to to parallelize the the function the fit let's say the functionality i mean by that like we

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we are saving the data in the new system but we are also saving the data in the old system we also

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calling the the all the transaction that we are rewriting in the old system so it's about it's a

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parallel right like uh we are writing in uh both in the old and the new system uh why we did that is

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because uh uh we wanted to um because there are a lot of data that are that have to be written let's say

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and uh and a lot of business rules uh in the old system that are used to to write data and we wanted

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to implement those business rules incrementally because they are uh this is the way we usually work

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we don't want to to do a big big bang rewriting uh and and so uh basically the the source of truth

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remains the old database while we build uh while we incrementally build uh implement the new the

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business rules to write that time right going back to the beginning you've got 30 years of business

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rules yes and and like and like you know who knows what they are really yes yes there we find surprises

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we have surprises when we dig into those things that are not used think that nobody knows what they

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are for and that can happen yeah yeah and and then essentially with that that uh like that comparator

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pattern you have i mean well you are like testing in production which is always a scary phrase to use

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with people but like you're you're making you know as long as you're really good at accounting for this

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as you implement those new business rules um like in your new database you actually can track if your

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assumptions about them are correct by like what the the comparison looks like and and then also i would

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imagine you also i mean it's annoying to have two copies of the same data like eventually i imagine

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you have to consolidate them but then also ongoing uh other systems that are using that data that have

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not been modernized they can go on functioning right like they they can use that old data which which

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again it fixed into this notion of like let's do the smallest amount possible without without without

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without uh having to mess with the rest of the system you are right you're right um totally um

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so yeah this comparator that we built uh to to validate that what we are writing in the new system

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is the same as the same meaning that what we are right than what we are writing the old system

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uh also helps build a lot of confidence uh um in the team but that's when the whole company because

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is a very sensitive subject to touch to modernize mainframes there uh because we are touching 30 years

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of yeah like you said business rules and yeah things might break and and and having this comparator

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mechanism even if it's complexify a bit the architecture uh helps to build that confidence in

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the company that we are not uh doing uh we are not introducing uh too many i want to say i don't want to

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say no bug because they are they can bugs can happen anytime but it's just the risk of things the risk

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exactly yeah and and like you said after this step when this confidence is built the next step would

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be like to to check to swap the the the source of truth for the data yeah to to give the the source of

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truth to the new application and then to to synchronize the whole system database with the new one to make

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the other application that use the same data still more and that would be the next step after building

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that the confidence path how long do you think that takes like do you think that's like like three

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months or is it like two years that that you kind of just like let let those two databases kind of like

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simmer and merge together yeah i think it take months uh and years just for this example it took two

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years for them to rewrite the transactions like and to have this coffee and to be able to

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to move things to change the source of truth so it depends on yeah the complexity of the transaction and

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uh but uh yeah it can i will not evaluate that in weeks that's really interesting to me because i

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haven't thought about i haven't thought about like this kind of scenario but in general the other thing

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like when i talk with large organizations about modernizing or doing anything is one of the other

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first things in addition is starting small that that i try to emphasize is like however long you think

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this is going to take you should probably double it and and it's it's not just the usual like

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programmers can't estimate and it takes a long time but it's it's more of i think a lot of the best

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practices and knowledge we have about programming comes from organizations that are building new

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applications or at least very young applications right like and especially like consumer applications all

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the social media applications and things like that versus like one of the things that that's different

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at a large older organization is like you're saying or we're saying is they have a 30 year old application

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and just migrating all those business rules is going to take a long time and so you have to have

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this realistic expectation of like yeah it's going to take like two years and that's not bad it's fine

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and in fact it's good to be slow and steady and careful when you're doing this because it's important

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right like it's not like i don't know i'm just making something up if you're doing like a photo management

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app like it is a bummer if you lose someone's photos but it's not that big of a deal in the grand scheme

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of the thing where like for these kind of applications across like you know banks and governments and

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other things like that like it is a big deal if you if you like mess up the business rules like it causes

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like the scale of problems it can cause is much more than like yeah we lost photos from when my kid was

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six which is a big bummer for me personally but it doesn't like bring down the banking system

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yeah you're right you're right that was uh that was indeed the case that was working on that kind

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of modernization is always sensitive i would say like uh compared to more classical legacy system

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uh right because they are yeah they are we are touching the core of the of the company but yeah

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like for example for the concerning this example like it was very important to do it because they

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outsourced a lot of things and and right they still did they were not controlling this corn anymore now

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uh but that's it it's a long journey so then finally so like uh well as as i always joke it worked

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otherwise you probably wouldn't have written it up like like what were the results the outcomes at the

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end a big outcome but that is not really technical it's more like the trust like people people are not

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sure that it will work often we are used to to try to anticipate a lot of things uh beforehand

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and and that can be that can feel very scary to try to discover things uh little by little and solve

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problems as soon as when when they arrive rather than trying to solve problems that maybe we will not

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have and and maybe that yeah that so so building this trust this uh um giving confidence that our

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approach can help them modernizing uh demand frames was one of the big outcomes uh for this engagement

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another one was like uh also uh but we also have in other engagements not specific to mainframe but

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mainframe but uh the capability to deploy new features very fast like building a pipeline and and being

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able to to deploy new features without downtime and stuff like that that was a key learning for them

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of course uh our practices they left like uh being able to to pair to do tdd and and uh having a lean

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approach to order the way they are working was also very very key to come back to the pipeline and to

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give some numbers that i have in mind i think uh before like i said that it was taking weekends to

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deploy new features uh now you just take 30 minutes like to deploy a new feature so that's that's a big

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huge that's basically uh the bigger comes that we had you know i i don't really know what sociotechnical

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systems means i should learn that phrase one day i think i think as with all academic things it's

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probably too precise for me to use correctly and and fully know one of the things that you know you've

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gotten over several times is like when you're when you're looking at modernizing something like this

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you have to not only think about the application or even like no this the hardware system or whatever

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involved but you've got to like treat the whole organization as the application right the way that

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people work together the knowledge that they have and then and then also like it's well it's easy to say

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and maybe a little weird to think of but like your your trust and confidence in the process is part of

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it as well right like it's almost like a form of qa or quality that like you have to maintain

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confidence in it and and instill that before you people can execute all right and uh yeah regarding

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also the you mentioned the the and indirectly the conway conway's law like about the organization

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communication structures yeah that was also uh something that we bring uh like uh building these

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teams that who has uh don't know the capability to take decisions regarding where they want to go to

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implement the things that was also something uh uh very a bit new for the for the team because there

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uh it's hard it can be hard when you you you have said you are responsible of the decision you are

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going to take as a team uh it's not someone else who will take will explain to you what you have to do

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anymore uh and and building that kind of mindset also is a it's part of the of the engagement it was uh

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it's very important to to to instill uh to to adopt another culture let's say you know yeah

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such companies yeah yeah well great well i that was fun talking through that and i think um you know

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i'll definitely put a link to the blog overview overview the the blog uh which which i think like

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it'll definitely it has a lot of visuals about each step uh that that y'all went through and i think uh

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i think it'll help people flesh out the details there do you do you have any any like uh any

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websites or places you would send people if they're interested in uh following you seeing what else

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you're up to yeah there's my blog uh my blog i had in a little bit but i i'm going to do that soon

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yeah so my blog for them d.com basically but it's in french i might try to post some english

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articles as well well good well i'll i'll put a link to that as well and uh yeah it was it was it

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was fun uh talking with you about this as always this has been tanzu talk if you're listening to

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the podcast version of this and you want to get the the show notes you can go to tanzu talk.com and uh

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find them and hopefully if you've listened this far and you don't subscribe to the podcast you should

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definitely subscribe for for interviews and news in the space and things like that and you can also find

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out how to see watch the videos of interviews that we do uh for things like this if you go to tanzu

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talk.com videos and with that we'll see everyone next time bye bye