Someone at my old company basically did this and put it into production.
The first problem he encountered was that multiple connections couldn't both be using the database at a time without clobbering each other. "No problem," he thought, this is a good use case for micro services. A service sitting on top would ensure that there was only one operation being performed at a time.
Next, his problem was that the database would get corrupt sometimes when something bad happened in the middle of writing the file. His solution was to put the entire JSON format inside of a JSON string. If it could be parsed successfully, then he knew the whole file was written. Then all he needed were "backup" files for each table, in case the current one was corrupt.
Next, his problem was that querying and iterating through a large table performed badly, since it required parsing the entire thing first. Querying several times required the whole file to be parsed every time. The solution was to move SOME of the tables over to JSON-inside-SQLite.
EDIT: Oh yeah, the next problem was how to structure the data inside of sqlite. He decided to make a single table called "kitchen_sink" that held every JSON value. There was a column that said which "collection" it belonged to. There was another column that represented the row's primary key. So you could quickly query for a collection name, and a primary key, and get the full JSON row.
So the next problem was that you couldn't query quickly for things that weren't the primary key. So new columns had to be added called "opt_key1" and "opt_key2" where certain rows could put key values, and indexes could be added on those columns, so you could quickly query by it's first optional key, or it's second optional key.
> So the next problem was that you couldn't query quickly for things that weren't the primary key. So new columns had to be added called "opt_key1" and "opt_key2" where certain rows could put key values, and indexes could be added on those columns, so you could quickly query by it's first optional key, or it's second optional key.
It's easy to get a little laugh from this, but congrats to the guy for exploring. Now he knows first-hand the inordinate challenge and can describe it in detail, but more importantly avoid these hard-learned patterns later.
> but more importantly avoid these hard-learned patterns later.
Depends, I’ve known people who have gone through similar experiences and still poo-poo all those “unnecessarily bloated” solutions like a proper database.
I worked with someone that was keen to use reductionist logic and arguments...
we ended up with a lot of shitty solutions to problems that were hard to maintain, hard to extend, and hard to use because the more "complex" solution was really just a fancy version of a folder and some text files.
AFAICT (not being Node-fluent) this doesn't even use atomic file writing strategies :| So yeah, all of these are pretty likely to happen with this lib.
Just use SQLite, people. Even JSON-in-SQLite is still likely to be an improvement.
> Next, his problem was that the database would get corrupt sometimes when something bad happened in the middle of writing the file.
I'm not sure i understand how this can happen... unless you try to update JSON in-place (which is a very bad idea for any text-based format), what you do is encode/write the entire JSON from scratch. So either the file is written properly or it isn't written.
Honestly from the entire message it doesn't sound like JSON was a bad idea but that your coworker didn't know what he was doing and if he was doing something else then he'd still be doing big mistakes.
I remember reading quite a bit about the (performance reducing) lengths filesystems go to in order to ensure consistency of directory entries even in case of a crash, and for example how "soft updates" were introduced to accomplish the same consistency with less of a performance degradation.
Looking at it from another angle, if you are running on top of a filesystem that cannot keep itself consistent, then you are SOL, there really isn't anything you can do to mitigate.
Just like we can't guarantee that we will be able to persist data that's in memory to disk if the OS is free to kill us at any time. "Best effort" it is, which means getting the data to disk as quickly as possible and not corrupting what is there.
They are if you perform the correct sequence of fsync operations on both the file and the directories, and use a file system which is correctly implemented.
The article linked above never explains that part, it only assumes that it will happen. From the code it sounds as if the crash can happen in the OS itself (but then the entire kernel will crash). At that point things are completely outside your control and you might as well running on broken hardware.
Oh yeah, so basically had he pushed further, he would have realized to avoid corruption, he would need to implement "write ahead log (WAL)". An for the implementation of WAL and other performance concern, he would have realized that storing the JSON as string is not the way to go, he'd need to implement other binary data structure. Then he'd have realized that he had just invented another NoSQL DB.
Had he pushed further.....
Had he pushed further, he'd have raised funding for the newly invented NoSQL DB, and built a startup company on top of it.
It all sounds funny but the final solution is not far away except the JSON bit. FriendFeed 11 years ago first popularized the concept of storing schema-less data in MySQL: https://qht.co/item?id=496946. Uber did the similar thing a few years ago: https://qht.co/item?id=16251143
I've been building an open-source alternative on mobile that based on similar concept (SQLite + FlatBuffers): https://dflat.io/ SQLite own schema is already awesome, but in this way, you can have sum-types, better schema upgrade guarantees, index building can be asynchronously etc.
Someone at my old company basically did this and put it into production.
The is the mentality that plagues the industry, that anything more than a few years old is obsolete, and therefore experience is worthless, and therefore the wheel must be reinvented every time because those old programmers must have been dumb, why would they use SQL otherwise. Why real engineers don't take "software engineers" very seriously (and in turn why software engineers don't take webdevs seriously).
I used sets of flat JSON files as our "database" in the Wunderlist iOS and macOS clients.
Worked like a charm, never had a problem with it.
It was actually put in as a placeholder until we had time to think about a real storage solution, but it turned out we never needed anything more sophisticated, and were actually the fastest and most reliable clients we had. In fact, every time I encountered a performance problem I was hopeful that I would finally have a good reason to do that real implementation, but it invariably turned out to be a simple bug.
- Cocoa has -writeToFile:atomically:, which writes a new file and then renames, so no write-corruption
- We were lucky that lists had just the right granularity for a single file to be read/written atomically
- We likely wrote (quite) a bit more data than absolutely necessary, but I/O tends to have large fixed overheads so medium files tend to take around the same time as small files
- We did not do anything with the data on disk except read it, so not a DB
- We really did use files, not JSON strings inside SQLite
- We flushed to disk asynchronously, but as quickly as possible
I have built this into some software and the reason is when you are developing, and for very limited use cases outside of development it is extremely convenient. Clone my project and start messing around without provisioning a database. It reduced dependencies by hundreds of modules too because all of the connectivity libraries were abstracted into separate modules you'd only install if you wanted that particular type in production.
This is why I love sqlite. No provisioning required and you have a flat portable file. But you also have the added bonus that it's highly performant and there isn't much work to refactor your SQL from sqlite3 to most other RDBMS.
I tried. I held a meeting to talk about the code. I found the problems hard to predict and hard to describe. It was decided that after the meeting he would work more on making his code less hacky and more production ready.
But the real answer is that our team was very siloed. No one knew what anyone else was doing. The other problem was that he was actually solving real world problems, and he was a very high performer. He got stuff done. Arguing to start over a project that's already working is a difficult position to hold when talking to management.
It's unfortunate that in this industry, on a lot of teams, "high performer" means "sloppy coder who lets his co-workers finish their project."
The problems he encountered with his dumbass solution were EASILY foreseen by an even noob coder. What did he "get done"? How did writing his own shitty version of a database add value to the company? He is good at finishing his own pointless tasks quickly, maybe, but if I was in charge of the team he would be looking for a new job after this stunt.
Sick-to-death of these cowboys. Nothing is ever "done", the majority of expense in software development comes in during maintenance, not during initial implementation.
My interpretation of this as a manager is that this developer was probably a creative thinker with a decent track record who got stuck going down a bad path on this project, and nobody paid attention or intervened until it was too late. They were also probably pretty junior but perhaps had some past accomplishments that made them appear less likely to make this kind of mistake. Once it was in production, the developer very well may have been "stuck" with it (i.e., unable to get permission to scrap it and redo it, since it was technically working and solved some business problem).
Given the team dynamics and lack of involvement from this person's manager, I wouldn't move to fire them. I'd move to rethink the entire team, admonish the manager, and possibly remove them. The team itself wasn't working, and this was a symptom: someone had a bad idea, pursued it for too long, nobody did enough to stop it, and then they couldn't go back.
This is a classic consequence of a manager who has stopped paying attention to their own team. The team was most likely also overburdened with too many tasks, which is why everyone was working on something separate and independent and nobody knew what anyone else was doing. In reality this developer shouldn't have been given a project like this without being paired with a more senior engineer to supervise it, but that would cut down on the number of story points the team could get through and would thus be discouraged in a dysfunctional environment.
If he was in your team it would be your fault. I think you just need a healthy balance of senior/juniors on the same codebase.
As OP said they were siloed from each other and he definitely needed some mentorship. I've seen devs like that turn to incredible coders just after a couple of months of pair programming.
I can sympathize but it seems hard to argue with this developer's approach then. If it met the needs of the company, particularly to the desired level at the times these features were requested, I don't think there's a valid critique of the developer's architecture beyond iT's NoT DoNe CoRrEcTlY. And still, there's a lot to be said for keeping your developer's entertained so they stick around.
> there's a lot to be said for keeping your developer's entertained so they stick around
Really? At the expense of everyone else who has to deal with this monstrosity for the foreseeable future, or worse yet replace it with an actual tool that can be reliably used.
This JSON-inside-sqlite-inside-JSON-inside-a-JSON-string beast should never have seen the light of day.
You're not paid to be entertained, sorry. You're paid to be productive. As productive as you can, and to put the needs of the client and the long-term success of the company hopefully first but certainly before any resemblance of entertainment if you're getting paid
I can certainly say that that's exactly the way I felt complaining about it. I felt like I was an asshole attacking him, and I don't think he liked me very much because of it. The whole thing was very uncomfortable. I didn't throw a fit. I tried to be very understanding and make suggestions.
If it's any consolation, it fell on to me to maintain this code after he moved on to something else, which is why I know so much about how it works.
> it fell on to me to maintain this code after he moved on to something else
This has happened to be before. I disagreed with a technical direction, it was implemented anyways, and then I'm left to maintain it. Very frustrating.
I've dealt with this before, it is a form of gas-lighting. Some people are good at making everyone else into a bully when THEY are the actual bully. Like the kid who keeps splashing you in a pool, but runs off and cries and tells when you splash them back.
Standing up for yourself sometimes makes you look/feel like an asshole. That doesn't mean you are wrong or that you shouldn't do it.
edit: Check out the book "Radical Candor" if you regularly struggle with expressing negative feedback
> If it's any consolation, it fell on to me to maintain this code
That's not any consolation... If anything, it's all the more reason for you to be pissed off. He should have dropped the project, rolled out a future-proof tool and taught to do differently next time.
Anything short of that is just enabling the dude's delusion of grandeur and therefore a mistake on everyone else's part...
If you're maintaining it, then I think you get a fair vote in it's architecture going forward. Things that are plainly problematic now didn't seem that way to a different group of people in a different context before it was even created. Perhaps it was a cascade of poor choices, but regardless, identifying problems with the architecture in the context of today gives a huge advantage over those who were putting it together under who knows what conditions (at work or elsewhere).
Just like the never ending "turn this Excel workbook into an app" stream of work, refactoring older apps will be a constant. Focusing today's conversations on yesterday's mistakes only detracts from the work left to do (which is to say if your architecture change arguments are valid, there should be ways to justify implementing them today outside of "it should've been done this way in the first place because then we wouldn't have had those problems that are now solved anyway")
> If it met the needs of the company, particularly to the desired level at the times these features were requested, I don't think there's a valid critique of the developer's architecture beyond iT's NoT DoNe CoRrEcTlY.
I'm pretty sure the cascading series of "his next problem" sentences implies that there were plenty of problems with the architecture that weren't identified ahead of time, and they had to encounter and then fix as a series of bugs.
> And still, there's a lot to be said for keeping your developer's entertained so they stick around.
There's a difference between keeping your developers entertained and letting them infect production with ill-conceived projects that cause problems for all those that interact with them.
This project is reimplmenting something already solved multiple times. There are many document stores, and JSON interfaces and addon to traditional RDBMS, so what was being solved here, other than letting someone scratch an itch at the expense of the division he's working in. You're better off giving him 20% time for his own projects and calling it a day if you really think entertaining your developers is important enough to warrant it.
There are times when rolling your own is useful. Generally when there's some extreme requirements for space or performance, but even that becomes rare when the area is mature and explored thoroughly. A database, even a JSON document store of some sort, is so mature that to make it worth while for one person to roll their own when it seems to need all the common features (locking, remote access, different clients), that to actually recoup the cost of building our own (much less the future cost of troubleshooting and bug fixing) is almost impossible unless you're somehow hired a genius workaholic for peanuts.
I would say operator friendliness is actually the best reason to roll your own (was clearly not the case here). If you have a system that is less complex, because it meets your use case only and not the competing use cases of every damn engineering outfit that can pay overpaid and underqualified devs to commit to an open sourced codebase, and as a result requires less labor to manage (for example, not using kubernetes for a 3 person startup), you should roll your own.
Sure, but there are different levels of "roll your own". Mysql or Pestresql + a text field and a microservice front end for access control and JSON validation (if you don't want to use the included components from those respective projects that handle those for you) is easier and friendlier most of the time than a microservice on top of sqlite on a local disk, which is friendlier than replacing sqlite with BDB, which is probably friendlier than rolling your own storage format.
Once you've abstacted it to a service, your API is what you and your client (should) care about, and many of the arguments for more specialized implementations no longer apply. Personally, I think the only reason I would go with something like sqlite instead of Postgres/Mysql behind a microservice is if I was baking the date into it with each release, so the sqlite data files are shipped with the version released. Even then, I'm not sure there's any reason I would do anything other than sqlite though. Even if I had need of lots of JSON files, I would probably have my build procedure process them into an sqlite file I tested and shipped with, if only because I would then avoid having to deal with all the problems this guy encountered by trying to make his own database.
Oh yeah. Unless you're actually in the database biz, Don't roll you own database. Those things are rock solid, usually easy (well postgres and mysql/maria are anyways) and state is hard.
Rolling something yourself has the benefit that you don't need to teach yourself how the system works because you built it but once you want someone else to join the team this fires back because that person needs to be taught how your database works. If the database in question was widely used then spending time on learning a new database would be worth the investment but if it is only used internally then it's just a waste of time.
I left my last company because one of my co-devs would always do crazy hack-job things, and when I complained to them or higher-ups, the excuse was:
< "Well all the work was already developed, and it would take too much time to rewrite it. You should have said something earlier"
> "When?" I asked, considering she had just put up the (big) PR's and PR's ARE the time to review...
< "Check her commits as she pushes them to the repo" - as in her bugfix/feature branches, not master...
My jaw dropped. Especially since I was hired on as "Lead" and had all the accountability but no actual power.
It's incredibly frustrating because during code reviews I will request changes so it's not such a broken hack job, and the response will basically be "No, it's not worth changing". At which point I'm the one "holding up development". We wasted hundreds of development hours during the last project because of this persons "inventive" code, and nobody seems to understand what's going on.
It's hard to get more strength to push back with out of thin air. I'd encourage you to try pushing for more detailed post-mortems (if you don't already have them) and just keep an eye out on how much curtailed reviews cost the company. You also really want an advocate for code maintenance and if you don't have one of these with a loud voice there isn't a really feasible way to solve it except becoming it yourself and earning the trust of those above you.
Two pieces of actual useful advice I can offer are:
1. A review style I picked up based off of RFC 2119[1] basically the reviewing software we use allows us to mark particular comments as blocking of non-blocking and I pair that with the usage of MAY/SHOULD/MUST within the comment language i.e. "We're using the old `array()` syntax here instead of `[]` we MAY wish to use the more modern syntax" this allows me some room to elevate necessary change while keeping in the nitpicks I really want to throw in (and I do try and minimize them) without lowering the power of the strong comments. I've used MUST maybe three times always for something incredibly terrible like pages not loading or migrations to the DB that are unsafe and cause data loss.
2. Agree on syntax and style rules and enforce them. It's easier to get people to agree to rules once than try and argue for them on each PR - anything like brace placement or line limit shouldn't come up repeatedly since it wastes everyone time and makes folks feel belittled.
This is great advice. Just have some minor thoughts to tack on.
Post-mortems are great for many reasons. For the case of GP, one particular advantage is that they align senior peoples' understanding: we shouldn't do X again. If you have a strong narrative for why a project failed, post-mortems are a formal setting in which you can present this narrative with concrete evidence to higher-ups.
In the future, when you see warning signs that a mistake is approaching repetition, you can raise the concern up the chain, invoking the memory of the post-mortem to motivate their intervention.
I also totally agree that a sincere and high-quality code review process is required for high quality code. Your 2119 recommendation is excellent. I'd also recommend doing some reading on commit message templates that smart people follow, they've improved my commit game, big-time.
At our company no commits get into the trunk without going by another set of eyes. We're probably creeping up to mid-sized right now so those eyes can vary in stringency and reliability more so than they would have when it was just a handful of devs, but I think mandatory code reviews are a good habit to get into - so long as you empower every reviewer to be critical and make it clear that both the reviewer and dev are owning the code and must ensure it is acceptable during the process.
We've had that process on for quite a while, and while there are some big weaknesses and holes in it we've also adopted a principle to keep PRs as small as possible[1] with those two tools we've had some pretty reasonable success with a lot of our biggest incidents being related to times when we've made large changes or a review was skimped on.
1. Even if that isn't measure in LoC - moving a dependency and updating references to it is something I'd count as a single action - but one I'd want isolated from any logic changes.
Many good companies enforce a no-origin-branches policy, with rare and well-justified exceptions. Because, used as you describe, a "feature branch" is just a future massive diff in disguise (when it's eventually merged), and massive diffs are a big no-no because they're a huge pain to iterate on via code review.
Doesn't every git repo have an origin branch? What is the alternative to creating a feature branch for developing something you don't want in production until it's ready?
Yep! Sorry, I meant that the only developed branch on origin is `master` (or whatever it’s called at your org). You can create branches locally, but pushing a local branch is strongly discouraged.
At this point, you submit the code for review, and upon approval the branch is merged into master and pushed. It’s not possible to push a commit hash to master that has not been reviewed.
If you have a feature that’s composed of many steps, you can “stack” multiple commits, and review/merge them in order.
If you want to develop the entire stack at once, you’re most likely doing something wrong (according to this culture). You can incrementally merge pieces of code to master in such a way that’s impossible for it to be deployed, and your final diff can be what makes it deployable.
Encouraging smaller changes isn't nearly as useful if those changes aren't isolated - if it's just half the picture then you can't accurately review it.
I hit a similar sort of issue recently - I've been incrementally developing a complex data migration, each change to the migration has worked on its own and been reviewed separately but I'm still going to go in and request a full review once the piece of logic is fully assembled. This is also happening on an integration branch on origin - we do try and keep these to a minimum but we're making a backwards incompatible change that would be quite expensive to do in a fully backwards compatible manner.
There are things that are infeasible to reasonably do without an integration branch (nothing is impossible technically, but it might be a huge waste of time) but even those things are pretty few and far between. If integration branches are common place at your company it might be good to examine coding practices and see if you can slice up tickets to be smaller.
Yeah, organizing work in such a way that you can make isolated, incremental change requires a nontrivial amount creativity and discipline, and that takes time like you say.
But, I do believe it pays off in the form of a higher quality end-product (fewer bugs, more testable/legible components, more extensible), which saves you time in the long run.
I disagree. It's coder malpractice. There is something to be said for a quick solution that just gets the job done. But each one of the updates described would take more work than just implementing SQLite or similar. Sure, on the outset, do something quick and dirty. By the second or third iteration, any legitimate developer should have switched to a database solution. Creating technical debt for no reason or invalid reasons is just a good way to setup your company for failure.
On the other hand, other sorts of devs would probably not be entertained having to maintain a in-house database some unchained dev decided to introduce into the stack one day for "reasons." That tech debt will compound until it becomes more of a liability.. hopefully the product brings in enough money so that the in-house database can continue to be supported or removed.
This sort of stuff is what deters me from being a developer sometimes. Fuck the salary, get me out of here.
It's not very agile friendly, but emphasizing design early in the process and having some "gate-keeping" protocol such as design review or code review can greatly reduce the chance of something going off the rails like this as it forces everyone to acknowledge what done looks like, as well as what the "missing" pieces will be.
The GateKeeper process isn't something you want to index on too heavily - but you also need a mechanism to counter-balance the possibility of a dev saying "I built a prototype last week that does 95% of the things we want" and 3 months of iteration later identifying that it only did 5%, and that getting the remaining use cases will require a re-write.
> Next, his problem was that the database would get corrupt sometimes when something bad happened in the middle of writing the file. His solution was to ...
As others have mentioned, there are a ton of off-the-shelf solutions that would have been more than adequate for this.
My question is, why didn't he go for any of the existing solutions when setting them up would've still been faster than rolling his own DB-in-a-JSON-file solution?
How did you go about porting the database code to something more sane? (just assuming you did)
I imagine if this database system is contained well enough, it shouldn't be so difficult to swap its internals with something else. Especially if it's all just JSON-like.
Maybe because it was tempting: JSON is fairly easy to handle, very portable, and when you look at a JSON document, it's straightforward to think about querying it, and thus DB, although JSON is structured, and DBs are relational.
The first problem he encountered was that multiple connections couldn't both be using the database at a time without clobbering each other. "No problem," he thought, this is a good use case for micro services. A service sitting on top would ensure that there was only one operation being performed at a time.
Next, his problem was that the database would get corrupt sometimes when something bad happened in the middle of writing the file. His solution was to put the entire JSON format inside of a JSON string. If it could be parsed successfully, then he knew the whole file was written. Then all he needed were "backup" files for each table, in case the current one was corrupt.
Next, his problem was that querying and iterating through a large table performed badly, since it required parsing the entire thing first. Querying several times required the whole file to be parsed every time. The solution was to move SOME of the tables over to JSON-inside-SQLite.
EDIT: Oh yeah, the next problem was how to structure the data inside of sqlite. He decided to make a single table called "kitchen_sink" that held every JSON value. There was a column that said which "collection" it belonged to. There was another column that represented the row's primary key. So you could quickly query for a collection name, and a primary key, and get the full JSON row.
So the next problem was that you couldn't query quickly for things that weren't the primary key. So new columns had to be added called "opt_key1" and "opt_key2" where certain rows could put key values, and indexes could be added on those columns, so you could quickly query by it's first optional key, or it's second optional key.