Why (Not) Reverse Interop with Clojure

Written by J. David Smith
Published on 01 May 2021

One of the killer features of Clojure(Script) is that it is extremely easy to use code from the host ecosystem. While it has historically been annoyingly difficult to use npm packages with ClojureScript, Shadow CLJS has made that blessedly simple. This has been hugely beneficial—and not just in the abstact sense that having access to more code is obviously useful. I recently needed to add support for reporting COVID Vaccinations to our software, was able to simply import a Java library to get the job done. This is part of the Clojure sales pitch: it is a pragmatic language, for people that want to get work done.

In that same vein, I would call myself a pragmatic developer: my priority is getting work done, not necessarily in using the "perfect" tool or language to do it. However, that pragmatism extends to the post-deploy lifecycle of the software I write: it is not about building new features, it is about never getting panicked messages about broken websites or inaccurate reporting. As a dynamically typed language, I do not believe that Clojure is well-suited for my brand of pragmatism. Alas: it is what I am stuck with.

Or is it?

Clojure makes it easy to interoperate with code from the host language, but both the JVM and JavaScript ecosystems have multiple choices for language that can all co-exist in the same bundle. Why not build new features in one of those languages? One with things like type inference?

tl;dr - Map<Any, Any>. Clojure code uses a ton of plain-old map literals. Using and producing Clojure values from Scala or Java with the intent of processing the contents is frustrating and unwieldy. Using TypeScript or Elm on the frontend is still something I plan to explore due to their excellent support for this model (and the clj->js family of methods), but I haven't had a reason to do so yet.

The Task

This is the question that I found myself asking recently as I was faced with improving the reliability of one of our core systems: health insurance claim processing. Our software communicates with claim processors, submitting claims on behalf of pharmacists and handling the responses. This is a critical feature: if it doesn't work reliably, then nothing else about the software matters.

Unfortunately, the codebase I inherited was, ahem, under-tested. 118 lines of test code, as compared to over 20,000 lines of application code. Perhaps not the best metric, but enough to establish that test coverage was not good. This made it difficult to guarantee the reliability of this feature. Anything to do with health insurance is black magic as far as I'm concerned, so I'd been putting off dealing with the core code in the vain hope that I'd be able to effectively write a "safe" wrapper for the existing claim processing methods. It recently became obvious to me that this was not going to be possible—that the issues ran too deep, and I would need to dive in.

Given the critical importance of this subsystem, there were two options that I seriously entertained:

Writing tests is, of course, non-negotiable. However, it is easier to guarantee reliability in strongly-typed systems due to the ability to exclude large error classes, so the test suite for a Scala or Java implementation would (in theory) be smaller.

Wrapping Up the JMP Gladiator League

Written by J. David Smith
Published on 19 August 2020

Recently, I wrote a bit about the Gladiator League and how it came to be. Last week, the inaugural Jumpstart (JMP) league ended, with the Amonkhet Remastered (AKR) league taking its place on Thursday. I wanted to take a moment to look back at the league, the results, and the evolution of the bot during the almost-month of the first league.

League Results

Let me begin by setting the stage. The JMP League ran from July 16th until late on August 12th—a day shy of a full 4 weeks. During that time, 166 players completed 416 league runs totalling 1,305 matches. An average of 48 matches and 15 completed runs per day. Not bad for the first run, and—honestly—much higher than expected. The Gladiator community embraced the Sharktocrab with open arms.

Unsurprisingly, In natural systems, count data tends to be exponentially distributed, with a few individuals having large counts and the rest having very small counts.

Those of you more familiar with statistics will note that the chart is flipped from a typical presentation of count distribution that would make this more obvious.
the number of league completions each player has is pretty heavily skewed. The typical player that completed at least one run completed 2 runs, but 13 players completed at least 10 runs and two players completed over 20!

Number of matches played during each hour of the day. This chart automatically uses your computer's local time.

The times at which people play are fairly Amero-centric, but not to the level that I was expecting. This is a bit surprising: the original Gladiator player pool largely came from Wheeler's community, and he is on Pacific Time (GMT-7/GMT-8). The peak hours are much more spread than one would expect if there were only players in North America—which I'd guess is due to a pretty sizable contingent of European players.

In the same vein, we can see a HUGE spike in matches played in the first 3 days of the League. That tapered off, remained fairly stable until the final week of the League. I am curious if that last week of low play is due more to AKR's impending release or tiredness of the League. To answer that, we'll need to wait until we have a bit longer between set releases.

Breakdown of color representation in each week of the league. A deck is listed as having a color if it has at least 5 cards of that color, and each deck can contribute to multiple colors (so each box does not necessarily sum to 1). All decks that completed all 5 matches are included. Decks are assigned to a week based on registration date.

I tried doing all color pairings, but it was honestly illegible.

One of the hot topics during the league's run was, put simply, Green. Many players (myself included) are of the opinion that Green cards were massively pushed relative to other colors in recent standard sets. People are—understandably—concerned that this may translate to a similar level of relative strength in Gladiator.

Breakdown of color representation in each week of the league, filtered to only include decks with at least 3 wins.

Before going further, I want to stress that League data is not a good source for win rates. While it is appealing as one of the only sources of structured match data on Gladiator, there are a couple of reasons to be very careful when looking at League winrates. First: the League is very deliberatly not competitive. Many players are not trying to play the best deck, only the best version of their deck. This has major implications because power is meta-dependent and the League is very unlikely to have a meta developed around pure power in the same way that Standard may.

Second–and this is crucial—we do not have enough data to draw serious conclusions for all but the most egregious outliers. 1,300 matches may sound like a lot, but with a high-variance format in a high-variance game in a meta that isn't centered on trying to win at all costs this data just isn't sufficient to draw strong conclusions. I am not saying that we should abandon hope, just that we should be careful.

This league is actually a great example of how metas evolve and change—and why we shouldn't be too quick to draw conclusions. We can see above that in the first two weeks of the League, decks with Green scored 3+ wins at a much higher rate than any other color. Many of these decks are built on Craterhoof Behemoth, one of the hottest cards from Jumpstart. A great example of this is Roseface's hoof list—the very first 5-0 of the league.

Hoof decks are explosive, and will run over anyone trying to durdle around without interacting. Later in the league, we saw an uptick in the amount of interaction played Check out DemonDrinkingTea's Mardu list for a good interaction-heavy example from later in the league. Note that on top of the removal package, it plays 4 board wipes (not counting Ugin).—especially board wipes, which are incredibly difficult for hoof decks to deal with. While SupremePhantom's (multiple) Bant lists all play Green, they also play (most of) the on-color board wipes. Interaction is valuable across the board, and board wipes happen to be very good in a format built from several years of creature-centric Standard sets. These factors combined with hoof no longer being the hot new toy to bring Green back in line with other colors.

A Combo 5-0

There is one deck in particular that I want to shout out, because I believe it is a first for the format. UFO6300 5-0'd the league with a dedicated combo deck. Historically, No pun intended. we haven't had access to actually good combos in this format. Pre-Ikoria, the only combos that I know of involved 3 card loops with either Teshar or Naru Meha that were expensive, hard to assemble, and easy to disrupt.

UFO's list uses Emergent Ultimatum Emergent Ultimatum to assemble something just shy of a 1-card combo. You find Omniscience, Peer into the Abyss, and Ob Nixilis, Hate Twisted. If the opponent chooses to shuffle Omniscience, you cast Ob Nixilis and then Peer into the Abyss and dome your opponent for 40-50 with Ob's static ability. If the opponent chooses to shuffle one of the other pieces, then you use Omniscience to dig for it—if you have a tutor in hand you can guarantee that you'll find it and win immediately. They killed me on stream with this list. I definitely picked the wrong option the first time.

This is the first combo I've seen do well I don't count "ramp into Omniscience and then durdle for 15 minutes" as a combo., and I'll be interesting to see how it and other combo decks evolve in the format.

Changes & Updates

As much of the bot JMP card-identifier issues notwithstanding. had been built prior to the start of the JMP league, I was able to focus on adding new features during the League. Below, I want to highlight a couple of them. You can check out the complete changeset for the JMP league here.

The API

The first addition I made was the introduction of a GraphQL API. While I still have more improvements to do to this on the technical end, It still dispatches far, far too many SQL queries for my liking. it is relatively complete—and I actually used it to obtain all of the data used in this post!

Deck Viewer Improvements

One of the oft-understated maxims of computing is that names are hard. In that vein, displaying cards in the deck viewer has been a fairly consistent pain point. During the JMP League, I made rendering more consistent (it will now always show the front face of a card). Additionally, I added a decklist export button! This seemingly-simple change actually had huge ramifications, because you can only access the modern clipboard API when connected over SSL. As a result, I had to update the League site to use SSL. This feature still needs improvement, as it currently relies on the oft-flaky TappedOut card tooltips to rename card entries.

Color Indicators on the Standings Page

One of my favorite things about the Penny Dreadful Standings page is their gorgeous color indicators for each deck, giving you an immediate look at what colors the list contains. This league, I implemented a nigh-copy of it for the Gladiator league. When I say nigh-copy, I mean it. The implementation on the front-end is very similar, and I shamelessly stole their colors, which happen to work well with the existing site colors.

Screenshot of color indicators on standings page.
Screenshot of color indicators on standings page.

Upcoming Change: League Start & End Time

One thing that I'm not happy with from the current League is how the rollover from JMP to AKR worked. Internally, I use UTC (GMT+0) dates for everything—including League start and end dates. This meant that the JMP League ended at 5pm on August 12th for players on the West Coast of North America. Rather awkward, I think.

For the next League, this will be changed to be more inline with Arena's update schedule. We haven't worked out the exact time-frame yet, but you can expect the AKR league to end late the night before Zendikar Rising releases and for the ZNR League to start shortly after Arena downtime.

Wrapping Up

On the whole, I'm very happy with how the JMP League went. I have more improvements to the League bot planned for this month, and am looking forward to seeing how the league and the format evolves over time.

If you have any questions, feel free to reach out to me on Discord. The code for the charts contained in this post can be viewed here.

A History of the Gladiator LeagueBot

Written by J. David Smith
Published on 25 July 2020

A bit over one week ago—July 16th—we launched the inaugural Gladiator league using my LeagueBot. Despite some initial difficulties with JMP quirks, Arena exports multiple cards with the same set code and collector number. For example: and Goblin Oriflamme and Rhox Faithmender both get exported as 1 ..... (JMP) 130. the launch was fairly smooth. In this short time we've had 251 league completions, Only decks with the full 5 matches played are counted here. which has been very gratifying for me. You see: while the LeagueBot may appear to have sprung into existence fully formed, this couldn't be further from the truth.

I want to take this opportunity to walk through the history of the bot. Its history is closely tied to my own involvement in singleton formats on Arena, and so at the same time I'm going to cover some Gladiator pre-history.

In the Beginning...

The first Singleton event I can find record of on MTG Arena took place from September 27th–October 1st, 2018. Cards in Format: 1,006 The event offered a play queue for 60-card no-banlist singleton games. Wizards would repeat this event later that year from December 3rd–7th and again two months later from February 14th–18th, 2019. This is where my involvement begins.

I created a Discord server for Singleton shortly after Valentine's Day event ended and posted about it on the MagicArena subreddit. At this point in time, I stuck with the 60-card format due to the small number of cards in the format. Cards in Format: 1,526 Given that Petitioners and Rats were the two most popular (and most annoying) decks in each Singleton event, I might have also banned them to try to encourage people to give it a chance—but I honestly don't remember.

This discord never really took off, and while I will never know for sure why that happened, I do know one reason. This is also the point at which I built the precursor to the LeagueBot we all know and love: the Sharktocrab Bot. I'd intended to build it out into a LeagueBot inspired by Penny Dreadful, but ended up being overrun with work shortly after and never quite got around to it. At this point in time, I had initial plans for how to record matches in a safe manner, but hadn't figured out some details like deck submission (would we use the rising star AetherHub? the old guard Goldfish?). However, I also made a fatal mistake with this bot.

Those of you that've used Discord for a while have probably seen the "React to get speaking permissions" gatekeeping bots. That is one of the few features I got implemented into Sharktocrab—and it worked! Except I would occasionally get DMs about how it didn't—DMs that I could never reproduce. Later, I realized the likely culprit was my use of Heroku's free hosting—which, though free, comes with the caveat that your app may be put to sleep if there is no activity. While I can't know for sure, I believe that this is the cause of those unreproducible bug reports.

Enter: Arena Highlander

Between my own lack of time and the obvious failure to start, the server rotted away for the better part of the year. Then, on September 28th, 2019 corporat created the Historic Canadian Highlander discord, and advertised it on reddit a short time later. Cards in Format: 2,038
Petitioners and Rats were both on the initial points list, effectively banning those decks for much the same reason that I had previously.
The first tournament ran that weekend, a round-robin with 6 participants that was won by Oogablast with a 4-1. Tournament Results:
4-1 Oogablast
3-2 Roseface
3-2 Jesse
2-3 Corporat
2-3 Bertxav
1-4 Yuin

Within two weeks, a pool of regulars was already forming. You'll likely recognize some of them, like Roseface and GoblinMatron, from Gladiator discord. Wheeler joined fairly early on, but wasn't an active participant in the format til much later. I joined about 3 weeks into the format, and won a tournament for the first (and only) time playing Abzan Field of the Mythics. The deck wasn't actually very good, but it and tournament results around this time highlight the problems with 100-card singleton with a small card pool: at some point you just need good stuff to put in your deck. Midrange was clearly very good, with a couple of aggro decks with good top-ends (Gruul, Boros, Mono-Black) also putting up results.

Anyway, this core of players formed the bulk of tournament participation over the next few months. Participation ebbed and flowed, but never really took off. To corporat's credit, he was actively trying to generate & maintain interest in the format with both weekly tournaments and periodic posts about said tournaments on reddit. While the weekly tournaments certainly helped maintain interest, there was a chronic lack of pick-up games during the week that, in my opinion, were both a cause for and caused by the limited number of players.

The Wheeler Effect and the Birth of the LeagueBot

All that changed on April 19th, 2020, Cards in format 2,622 when Wheeler streamed Arena Highlander (then called Historic Highlander) for the first time. The format exploded. The discord gained hundreds of users basically overnight. At the same time, I had just graduated, COVID-19 had frustrated my job search, and I suddenly found myself with copious free time. With the sudden influx of players, I decided to finally finish what I'd started more than a year prior and build the LeagueBot.

During that year, designs for the bot had been in the back of my mind with some regularity. I had mapped out the flows for match reporting, and had ideas for the registration process. Putting those designs into practice was mostly straightforward, with Discord itself giving me the ultimate assist by making uploads so seamless that I could use them for deck registration. One week later, the week-long April 2020 Test League went live—but not before the format split.

I was not involved in many of the conversations preceding the split between Arena Highlander and Gladiator, so I'll refrain from commenting on it. I will say, though, that the timing was incredibly frustrating. I began work on the bot on April 20th, and had made substantial progress on it by the time that the split happened on the 22nd. While I'd hoped that the launch of the League on the 26th would help drive continued interest in Arena Highlander, it became apparent within about a month that the bulk of the new blood had followed Wheeler to Gladiator. To his credit: there was a clear effort to accomodate the existing Arena Highlander format. For example, Gladiator tournaments were deliberately not run at the same time as the existing weekly Arena Highlander tournament, despite Saturday afternoon being an excellent time for tournaments across time zones.

From the League FAQ: an attempt to encourage Gladiator players to participate in the Arena Highlander League.
Can you use your Gladiator Deck in the Arena Highlander League? Yes!

Transitioning to Gladiator

Around this time, I took a break. I found work, played other games, and let my frustration with the failure of the league and with Magic in general WAR–IKO was an awful time to be playing Magic. subside. I popped into the Gladiator discord in early June when there was discussion of starting a league, but aside from that was largely uninvolved.

Then, on July 7th I (finally) reached out to Roseface about moving the LeagueBot over to Gladiator. The only thing that really needed changing was a few names that read "Arena Highlander" and the domain name it used. Two days later, I heard back: 👍. The plan was to launch on July 16th to coincide with the release of Jumpstart—giving just over a week to switch things over. Cards in Format: 3,109

This was plenty of time, and I had the opportunity to add in a couple of new features like the API. Aside from the previously mentioned issues with Jumpstart card exports, launch went smoothly. Seeing the Gladiator community jump into the league and play more than I'd ever expected was…nice. I'll take it.

Postscript

You might have noticed that throughout this I've tracked the number of cards in the format. In just over a year, the number of cards on Arena has doubled. With remastered Pioneer sets, it may well double again by next year.

I think this is relevant to understanding the evolution of the greater Arena-singleton format. For instance: prior to ELD, a 100-card singleton deck would include anywhere from 3-5% of all cards on Arena, 60/2,038 is about 3%, 100/2,038 is about 5%. A typically Gladiator deck has around 60 non-lands, and 3c decks may legitimately play 90+ nonbasic cards. which means you would often dip into borderline (or even outright) draft chaff for playables, especially in mono-colored decks. This means that your card quality was relatively low compared to now (when one plays 2-3% of all cards), and led to an abundance of 2-3c Goodstuff decks along with legitimate concerns that the consistency of Petitioners / Rats decks could be problematic despite the obviously low card quality. I'm glad those days are behind us, and am looking forward to seeing how the increasing card pool lets the format further diversify.

Missing the ASONAM'19 Deadline

Written by J. David Smith
Published on 07 May 2019

In late January, I started working on a new research project. Without getting into too much detail, it involves network analysis on blockchain-based systems. My opinion on blockchain tech has not noticeably improved.After some initial results, my advisor & I decided to target ASONAM 2019 for publication, which has submissions in mid-late April. The exact, final deadline fell on the 28th this year.

I didn't make it.

I would like to briefly explore the reasons that I missed the deadline. Like prior deadlines I've missed, there is some element of research being simply unpredictable. However, there are larger errors that I made that would be valuable to not repeat.

I Was Indecisive

The first, and in my opinion largest, mistake boils down to indecision. While the project started in late January, I never committed to a single research question. Rather, I continued with various bits of exploratory analysis up until very shortly before the deadline.

While much of this exploratory analysis holds small bits of value, it doesn't come together as a cohesive whole. It isn't a paper. I knew this, experientially, from the project I spent most of last year on. In that project, I did a lot of initial analysis that never ended up in the paper despite informing my understanding of the problem space. Some of that will be going back in as I finish dealing with revisions for journal publication in the next couple of weeks. Despite knowing that much of my exploratory work would find its final resting place on the cutting room floor, I persisted with it up until about 12 days before the submission deadline.

Some of these results were quite strong, One of our key results is that prior network analysis had missed a key behavior native to Bitcoin (one-time-use change addresses), which skew the "user" network substantially unless corrected for. which gave me hope that I'd still be able to put together something compelling. Had the small extension I spent several of those 12 days on panned out, I might be writing a different post. However: it didn't, and I'm writing this post because those results were not enough, and I didn't commit to this idea until it was too late to fully realize it.

I Was Passive

As I worked through my analysis and began forming the project, it became clear (to me) that the initial direction that I'd worked out with Dr. Thai wasn't going to be viable. There were several alternatives, and earlier in the semester I suggested each of them in turn to Dr. Thai in our meetings.

However, I didn't do so forcefully. I'm saying now that the direction was inviable, but in early March I was not nearly so clear. I danced around the point, and when she pushed back against it I wilted. Had I been clear, I could've easily been spending six-to-eight weeks fleshing out one of these more promising alternatives. It may still not have panned out, but it at least wouldn't have felt like as much of a waste.

I Did Not Understand the Limitations of My Tools

Over the past year, I have spent a lot of time working within the pandas ecosystem. It's been great! Pandas is a great library for many tasks, with a flexible API that has allowed me to do a lot of analysis much more quickly than I would've been able to otherwise—especially when paired with plotnine to quickly generate complex visualizations. However, pandas has a bit of a problem with large data.

Specifically: pandas' memory usage is highly variable, difficult to predict, and impossible to control. An operation may have minimal memory overhead and take less than a second to compute—but a small modification to it may instead take hours to run and result in a deep copy of some or all of the data. When the first copy of the data clocks in at 120GB, doing a deep copy automatically slows things to a crawl, and very quickly led to OOMing the server. The most common culprit was the .groupby(...) method, though I had issues with some chained aggregations via .apply(...) as well. Unfortunately, groupby(...) is a fundamental operation necessary for my work, so many of attempts to finalize results in the final days before the deadline simply fell apart.

Long nights and wasted hours could've been recovered if I'd realized the cause of these memory issues. While I'd encountered performance issues with pandas before, I had largely attributed them to hitting slow paths in what is ultimately a Python library. During this project, I stumbled upon this post by Pandas creator Wes McKinney that hits on the reasons for many of the issues I've faced. As useful as Pandas is, it became clear to me that it currently isn't going to be a viable option for analysis of this particular dataset. Not that I'm giving up on Pandas. In fact, I still use it heavily. Rather, I now am better-equipped to identify which problems it is ill-suited for. This one in particular has (a) a large memory footprint, and (b) a heavy reliance on groupby(...) operations for reasons intrinsic to the data. The combination of these two means that pandas is simply not the right tool

Ultimately, I ended up rewriting many of these bits of analysis in Rust and doing the aggregations manually, then loading and plotting the results. These simple Rust programs took were not too difficult to write thanks to the hdf5 and csv libraries, and even with repeated data loading they are substantially faster than my Python/pandas code. This let me complete part of my analysis, but ultimately I lost too much time to struggling with MemoryErrors to be able to complete all of it.

Wrapping Up

Despite this failure, I'm not particularly upset. I am frustrated, but am trying to channel this frustration into dealing with the problems I faced productively. I am particularly glad that I have had an excuse to basically ignore research work for the past week, between grading exams and preparing to teach a summer class. It has given me time to reflect on the factors that led to this failure and realize that—even though it is my fault—it is something that I can learn from and improve on subsequent papers.

Brewmaster: Legion in Review & BfA Wishlist

Written by J. David Smith
Published on 12 February 2018

I rerolled from my Hunter (MM lyfe) to a Brewmaster shortly after the Nighthold released, and holy hell I didn't expect this ride. I was going to just play my already-110 BDK, but our other tank was a BDK and after the incident with Cenarius A bug/weird interaction on Cenarius removed Marrowrend stacks much faster than they could be applied. This made tanking Cenarius pre-fix on a BDK really awkward and more difficult than necessary. the raid team was kind of sketchy on having two of the same tank. So, I powerleveled my formerly-Windwalker Monk from 88 to 110 over a weekend and started tanking.

Since then, I've become active in the #brewlounge and #brewcraft channels in the Peak of Serenity Discord, tanked a bit of Mythic 5/9M T20. Less than I'd have liked., and picked up maintenance of the WoWAnalyzer modules for Brewmaster. All in the space of less than a year. Whew.

Now BfA has been announced and changes are rolling out on the alpha. Since Brewmasters have received no super noteworthy changes yet, it's the perfect time for a wishlist! Before we get to that, however, I'd like to break down what the Brewmaster kit looks like right now so we have some context for my BfA wishlist.

What We Have

Stagger & Mastery

While meatballs Guardian Druids have held the title of "Dodge Tank" in the past, it now firmly belongs to Brewmasters. It is not uncommon to see people reach 70% or more dodge rates in practice thanks to our Mastery: Elusive Brawler. EB provides a stacking bonus to our dodge chance each time we either fail to dodge a dodgeable ability or cast certain spells. The current list is Blackout Strike, Breath of Fire, and (with Blackout Combo and rarely used) Blackout Strike + Purifying Brew. This mastery performs three functions: first, it boosts our overall dodge percentage; second, it allows use to consistently deal with dodgeable mechanics through proactive play (banking EB-generating abilities); third, it mitigates downsides of randomness-driven mitigation.

That last point is fundamental. Historically, dodge-based mitigation has been much inferior to reduction-based mitigation due to shear randomness: if you fail dodge several hits in a row, you can simply die. Those more familiar with pre-MoP tanking may be confused by this. Dodge was a good stat! It is more useful to compare Dodge for brewmasters with Defense prior to its removal: defense capping prevented crushing blows from randomly spiking you. Reaching the defense cap was considered mandatory. Brewmasters (along with VDH) have by far the least armor of any tank (I have 2,940 armor without trinkets, while a similarly geared DK has 5k+ and a Paladin has 7k+), meaning that pre-Stagger melee hits are much larger. Mastery prevents this from happening altogether. At current gear levels, many BrMs are guaranteed to dodge at least every 3rd hit without taking any actions. With the low cooldown of Blackout Strike, this gets close to a guaranteed every-other-hit dodge rate.

While Elusive Brawler significantly smooths our damage intake from melees, without further mitigation we would still be extremely spikey. Smooth damage intake can be healed much more efficiently, lowering the strain on your healer's mana and reaction times. Stagger, our second "mitigation" method not only addresses this, but in fact has led us to be the smoothest tank in terms of damage-intake despite our reliance on the inherently random nature of dodge. Stagger causes every hit to be partially absorbed (currently 75% with Ironskin Brew up and no specific talents or gear), with the absorbed damage spread over the next ten seconds. The exact mechanics of it aren't quite straightforward. emptyrivers has an excellent overview of how it works on the Peak of Serenity. Functionally, this means that every would-be spike of damage instead is translated into a much lower damage-taken-per-second effect.

Despite not reducing total damage taken, Stagger enabled ludicrous cheesing Creative strategies that make otherwise-difficult mechanics nearly non-existant. early in the expansion. A cap on the total staggered damage (at most 10x player HP) was patched in after Tier 19 ended. Though it doesn't affect normal gameplay, it does mean that previous cases of stagger cheesing were much riskier if not impractical.

On the whole, Elusive Brawler and Stagger together give Brewmasters a unique way of smoothing damage taken – turning what would otherwise be the spikiest tank into the smoothest. In particular, Elusive Brawler gives rise to gameplay that no other tank presently has. If you haven't known the joy of tanking Tyrannical Blackrook Hold as a BrM: Smashspite's charge can be dodged. It still applies stacks, and will rapidly reach the point of one-shotting you through any and all cooldowns. This leads to an intense do-or-die minigame.

Brews & CDR

The second, active, half of Brewmasters' mitigation toolkit comes in the form of Ironskin Brew & Purifying Brew. Ironskin Brew increases the amount of damage absorbed by Stagger from 40% to 75%. Note again that this does not mitigate anything. Our active mitigation is instead packed into Purifying Brew, which removes 40% (without traits or talents) the damage that has been absorbed by Stagger but not yet dealt over time. These two abilities share 3 charges with a cooldown of 21 seconds each (reduced by haste). However, Ironskin Brew only lasts for 8 seconds, meaning that based on these charges alone we are not capable of maintaining the buff – let alone Purifying.

However, this cooldown is reduced significantly by correctly performing the conventional rotation since key rotational abilities (Tiger Palm and Keg Smash) reduce the cooldown of brews by a significant amount. This situation is further helped by the presence of the (mandatory) Black Ox Brew talent, which restores all 3 charges on use, on an effective 40-45 second cooldown. BoB benefits from the cooldown reduction of TP and KS. Combined, this gives each Brew charge an effective cooldown of around 6-7 seconds. Or, put another way: exactly enough to keep Ironskin Brew up 100% of the time and have occasional charges to spend on Purification.

This system sounds great. It leaves us with manageable DTPS over the course of a fight, while allowing us to mitigate large spikes such as Fel Claws with Purifying Brew. Unfortunately, it suffers from a fundamental flaw: prior to Tier 20, there was no cap on the duration of the Ironskin Brew buff. This led to effective BrMs ending fights with several minutes of time remaining on the buff, while still having plentiful brews to spend on-demand for Purification. In response to this, Blizzard implemented a cap of three times the buff duration (24 seconds with traits). This turned the previously-comfortable Brew system into one with an annoying buff to maintain and another button you rarely use. And when I say rarely, I mean rarely: pre-Mythic it is possible to go entire fights without needing to Purify due to low damage intake, and on Mythic bosses Purification may only occur a couple of times a minute. This leads to an unsatisfying situation where we have to jump through a bunch of hoops to hit 100% ISB uptime – which is nearly mandatory to avoid being DK- or DH-levels of spikey without the self-sustain, cooldowns, or utility to compensate – but then have excess charges that we worked to generate but can't use effectively.

On the whole, I like the Brew/CDR system. However, its flaws are noticeable and have no easy solutions. In conjunction with this system, Stagger has been on the razor's edge between hopelessly busted and borderline useless since its value fundamentally scales with the amount of incoming damage. On high damage fights, Purifying Brew provides excellent mitigation while Ironskin Brew keeps our damage intake smooth and easily healable. Below that point, Purifying Brew becomes worthless because we cannot reach a high enough level of staggered damage for purifying to be worth more than pressing Ironskin Brew again.

The UI

I won't spend long on this, but the current UI situation for Brewmasters is preeeeettty bad. The maintenance buff of Ironskin Brew is difficult to track on the default UI – a situation made worse by the fact that dropping it can lead to a quick, untimely demise. Worse: the Stagger bar caps out at 100% of your HP, which is quite frankly nothing. It is common for experienced brewmasters on #brew_questions to recommend not purifying at less than 100% of your HP staggered.

In Summary...

...Brewmasters are really good. They're a strong tank class for challenging content, fun to play, and have a distinct playstyle not shared with other classes. While flaws exist, the spec works despite them. There is still room for improvement, however, so now we get on to the part you're really reading this for: what I want in Battle for Azeroth.

What I Want

1. Death to Ironskin

The biggest complaint I have with the playstyle of BrM is the annoyance that is ISB. It is only interactive insofar as it requires not pressing Purify too much and executing your rotation well. Pressing the ISB button is merely an annoyance that is necessary to confirm you've done the other two things.

As we saw in Nighthold, we clearly can't leave it uncapped either. So, what do we do? An oft-suggested option is to make ISB baseline and reduce the CDR available for Purifying Brew. However, this seems unlikely to be effective either given how infrequently we have to Purify. It is clear from the Legion Beta posts that they intended for Ironskin Brew to be used as an active mitigation ability like Shield Block, but doing so left Brewmasters uncomfortably spikey in the interim.

My main issue with ISB as it stands is the needlessness of pressing that extra button during an already high-APM rotation. I have logs with negative overall downtime since brews are off the GCD. What if Ironskin Brew were just removed, an equivalent and appropriately-themed buff given to Tiger Palm / Keg Smash, and Purifying Brew's cooldown reduced to compensate? While clearly not a perfect solution (it doesn't solve the fundamental balance issues with Stagger, for example), it does eliminate my major annoyance with current Brewmastery.

2. Better Utility

You might notice that in the What We Have segment I never once mentioned utility. While we have some unique utility currently, it mostly boils down to (a) cheesing fights with Dodge & Stagger, and (b) Ring of Peace – both of which are highly situational. This is in stark contrast to Meatball's Savage Roar, Protadin's Healing & Bubbles, and Blood DKs. My wish for BfA here is just to have a bit to set us apart from other tanks.

On the BfA Alpha, we're getting a bit of "extra" utility in the form of Leg Sweep being made baseline. This is supported by AoE stuns being stripped from other classes, which means that the presence of Leg Sweep in our kit becomes more noticeable – especially if we are allowed to go into BfA with both Ring of Peace and Leg Sweep available together.

3. Revisiting Dead Talents

On the whole, Brewmasters don't have many talents that are just totally completely unusable garbage. Even Chi Wave, which is used in neither dungeons nor raid content, can be a decent talent out in the world. I've used every talent we have at some point for a reason beyond just trying it out – every talent, that is, except for the Level 45 Row.

The Level 45 row has exactly 1 talent in it: Black Ox Brew. Don't @ me. I will fight you. BoB is better, both empirically and in feelycraft, than either of the alternatives in every feasible situation. Going into BfA, I'd like to see that change. That may mean buffing the alternatives, I'd love to have access to proper self-sustain through a buffed GotM but more realistically it means that BoB just needs to get hit. The cooldown reduction it provides is simply too high – it is both immensively powerful at smoothing an entire fight due to its low cooldown, and excellent for dealing with specific mechanics like KJ's Fel Claws.

4. (Just for Me) Better Transparancy

As I mentioned in the intro, I maintain the WoWAnalyzer modules for Brewmaster. This has been a lot of fun: the dev team is fantastic, #brewcraft has been super helpful in filling in the gaps in my knowledge, and the codebase is generally nice to work with. That said, it has not been without frustrations. Stagger in particular has been an immense nuisance. I rewrote what the previous maintainer (WOPR) had done so that I could add some extra features that were infeasible before, but that implementation sometimes breaks down for no apparent reason.

In BfA, I'd like to see the amount of staggered damage reported in the logs. There is already a classResources field that records things like energy, runes, mana, etc. While there may be technical limitations to adding Stagger to that list, I'd very much like to see it happen. It'd make my job significantly easier.

Wrapping It Up

Playing Brewmaster during Legion has been one of the highlights of my WoW career, and I'm excited to see where we end up in BfA. Although I'm obviously hoping that not much changes since BrM is currently a lot of fun, I am hopeful that we can have some wrinkles ironed out in the transition to the next expansion.