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Full DAX oracle: msmdsrv on three hosts

Status: attach, pump, and model publish landed. The bounded Go evaluator stays the default on every OS. A real Analysis Services process (msmdsrv.exe) is an optional oracle, reached through FABRIC_DAX_URL, never a compose default, and never started by make up / make up-lite. This is the host map for that oracle — the thing 33-pbix-tooling.md proved on windows-latest (Desktop answers bit-identically) and the thing Wine / OrbStack / Rancher Desktop on macOS cannot host.

Same move as Eventhouse (25-rti-kusto.md) and Eventstream (51-eventstream-kafka.md): terminate Fabric’s contract ourselves, relay the compute to a real engine. The difference is the engine. Microsoft ported the SQL database engine to Linux; they did not port Analysis Services. There is no mcr.microsoft.com/.../msmdsrv. So the sidecar is a Windows guest, and the guest is started differently on each OS.

What is in and what is out

Section titled “What is in and what is out”
InOut
Query relay: executeQueries (and the portal runner) POST DAX to a pump in front of msmdsrv when FABRIC_DAX_URL is setPutting dockur/windows on docker compose up or --profile dax for Mac users
Three recipes for a machine you own that actually has a Windows kernelWine, Moonshine, Game Porting Toolkit, OrbStack, Rancher Desktop on macOS
Growing the Go subset against Desktop goldens so every-push CI stays on the in-process engineClaiming “full DAX” because a VM can boot, or because the host recipes exist
Honest 502 when the URL is set and the pump is downSilent fallback to the Go subset (that would hide a dead oracle)
The CI oracle already on windows-latest (e2e/pbix-desktop)UTM on macos-latest, or dockur/windows on ubuntu-latest, as a required CI job

Wine maps user-mode Win32 onto Darwin. msmdsrv is a Windows service (SCM, COM, named pipes, SSPI, VertiPaq). SQL Server on a Mac is the official Linux image, not wine sqlservr.exe. Analysis Services is still listed unsupported on Linux through SQL Server 2025. That is why this page is a host map and not a Wine bottle.

The three hosts

Section titled “The three hosts”

These rows are developer (or self-hosted) machines, not GitHub-hosted runner labels. macos-latest is not “the macOS row.” ubuntu-latest is not “the Linux row.” See Not GitHub-hosted runners.

Host (a machine you own)How Windows runsHow you start msmdsrvWhat the Mac/Linux emulator sets
macOSUTM (or Parallels) on the host, not inside OrbStackInstall Windows in the guest, then Power BI Desktop or SSAS Developer. Desktop hosts msmdsrv as a child; the port is in %LOCALAPPDATA%\Microsoft\Power BI Desktop*\*\Data\msmdsrv.port.txt — the same file e2e/pbix-desktop/desktop.ps1 already polls. Then pwsh e2e/msmdsrv/start.ps1FABRIC_DAX_URL=http://<guest-ip>:8080 from the Mac
LinuxDocker Engine on the metal (or a VM that already has KVM) + dockur/windows with /dev/kvmSame guest install as Windows. Compose file: e2e/msmdsrv/docker-compose.yml. make dax-linux refuses unless uname is Linux and /dev/kvm exists. Pump still starts inside the guestFABRIC_DAX_URL=http://127.0.0.1:8080 (published port)
WindowsNothing. The kernel is already thereDesktop (the path e2e/pbix-desktop already runs in CI) plus FABRIC_DAX_URL (#232). Headless msmdsrv listens with a shoestring parent PID (33 Phase 0c); ROW needs a table, so it is not a ready oracle. Then pwsh e2e/msmdsrv/start.ps1FABRIC_DAX_URL=http://127.0.0.1:8080

dockur/windows is QEMU in a Linux container. It needs /dev/kvm passed in. Their own requirements are Linux+KVM or Docker Desktop on Windows 11 with nested virt. They call out Docker Desktop on macOS as unsupported. OrbStack and Rancher Desktop on a Mac have the same hole: the Linux VM does not expose /dev/kvm. KVM=N (TCG) is software emulation of Windows inside Linux inside macOS — the project itself says that is a major performance loss. Do not use it.

On Apple Silicon, a UTM guest should be Windows 11 ARM. x64 Desktop inside ARM Windows is emulation; prefer the ARM Desktop build when it is the thing that hosts msmdsrv.

Not GitHub-hosted runners

Section titled “Not GitHub-hosted runners”

The host table is how a person reaches msmdsrv without waiting for Monday’s Windows job. It is not how every-push CI gets full DAX.

GitHub-hosted macos-latest and ubuntu-latest are already VMs. Windows inside them is nested virtualization.

  • macos-latest + UTM. GitHub does not support nested virtualization on macOS images. UTM is a GUI hypervisor. There is no Hypervisor.framework for a Windows 11 ARM guest on that runner.
  • ubuntu-latest + dockur/windows. /dev/kvm exists on x64 Linux runners for the Android emulator (small, cached images). GitHub still calls nested VMs experimental and unsupported. dockur/windows is a full Windows 11 install (our compose asks for 8 GB RAM; their docs want ≥32 GB disk). First boot installs Windows. That is not a PR job, and caching a Windows VHD across jobs is a size and licence question. ARM Ubuntu runners do not get KVM.

The CI witness is e2e/pbix-desktop on windows-latest. That kernel is Windows. Desktop hosts msmdsrv as a child. No nested guest.

Every-push tests on ubuntu/mac run the bounded Go subset against Desktop goldens. They do not boot Windows. Empty FABRIC_DAX_URL is what those jobs have, and what they test. A self-hosted runner that really is Linux+KVM or a Mac with UTM on the metal may use the recipes above; that is a human’s machine, not runs-on: ubuntu-latest.

The attach point

Section titled “The attach point”
client  --executeQueries-->  fabric-emulator
                                |  FABRIC_DAX_URL empty → internal/semanticmodel
                                |  FABRIC_DAX_URL set   → POST {url}/v1/deploy
                                |                         POST {url}/v1/dax
                                v
                         pump (AMO + ADOMD.NET)
                                |
                                v
                         msmdsrv.exe

msmdsrv does not speak executeQueries REST. The pump is a thin HTTP front (same job as Microsoft’s own azure-analysis-services-http-sample): ADOMD to localhost:<port>, JSON back. The emulator still does Power BI audience auth, workspace RBAC, and model-id resolution. Only the EVALUATE is forwarded.

Pump contract:

POST {FABRIC_DAX_URL}/v1/deploy
{"tmsl":{"createOrReplace":{"object":{"database":"RetailAnalysis"},"database":{…}}}}


POST {FABRIC_DAX_URL}/v1/dax
{"query":"EVALUATE SUMMARIZECOLUMNS(...)","catalog":"RetailAnalysis"}
{"rows":[{"Customer[Country]":"US","[Revenue]":101.72}]}

Deploy runs once per item definition (sha256 of the TMSL). Import rows from the item’s data.json become DATATABLE calculated partitions — VertiPaq will not read our JSON, and pbix-mcp is not a runtime dependency (33). Direct Lake tables are refused rather than dropped.

Desktop’s workspace instance often rejects CreateOrReplace of a new database (it already has the open .pbix). The pump returns 409 DAXDeployRejected; the emulator then queries whatever catalog is loaded — the Phase 1 hand-open path still works. SSAS Developer / headless msmdsrv accepts the publish.

A 4xx from the pump is a DAXQueryError (400). An unreachable pump is DAXEngineUnreachable (502). The Go subset is not consulted when the URL is set — a dead oracle must be loud.

Empty FABRIC_DAX_URL (the default) keeps today’s evaluator. No 501 on the query path: the subset is a real engine for the rows it pins. GitHub-hosted ubuntu/mac jobs never start msmdsrv; they test this default. See Not GitHub-hosted runners.

Running the pump

Section titled “Running the pump”

The pump is e2e/msmdsrv/pump — a net8.0 Kestrel front that opens a new ADOMD connection per request. It must run inside the Windows guest. ADOMD’s bare localhost:<port> form is Windows-only on .NET Core, and that is the form a loopback msmdsrv answers. Same Microsoft.AnalysisServices.AdomdClient.NetCore.retail.amd64 19.* package as e2e/pbix-desktop/probe (x64-emulated on ARM Windows).

On the guest, start the pump. SSAS / headless msmdsrv needs only a listening engine (MSMDSRV_PORT or MSMDSRV_DATA_SOURCE). Desktop still needs a process hosting msmdsrv — open any .pbix so the port file exists; the emulator then tries CreateOrReplace and falls back to the open catalog if Desktop refuses.

Terminal window
pwsh e2e/msmdsrv/start.ps1

GET /health opens ADOMD and returns {"ok":true,"port":"…"}. Allow inbound TCP 8080 on the guest firewall if the emulator is on another host.

EnvDefaultMeaning
MSMDSRV_PUMP_ADDRhttp://0.0.0.0:8080Kestrel listen URL
MSMDSRV_PORT(Desktop msmdsrv.port.txt)Loopback port. Unset → re-read the newest Desktop port file per request (Desktop can restart and move it)
MSMDSRV_CATALOG(empty)Optional Initial Catalog=
MSMDSRV_DATA_SOURCE(empty)Full ADOMD connection string; skips port discovery (SSAS named instance)

On the emulator host:

Terminal window
export FABRIC_DAX_URL=http://<guest-ip>:8080   # UTM / Parallels
export FABRIC_DAX_URL=http://127.0.0.1:8080    # dockur published port, or native Windows

Phases

Section titled “Phases”

Phase 1 — attach and relay (landed)

Section titled “Phase 1 — attach and relay (landed)”
  • FABRIC_DAX_URL on the config / server / executeQueries path.
  • Unit tests: empty URL uses the Go evaluator; set URL forwards and does not fall back; unreachable pump is 502.
  • Host recipes on this page. make dax-linux is a guard, not a family profile.
  • Pump: e2e/msmdsrv/pump + e2e/msmdsrv/start.ps1, run inside the Windows guest. Compose publishes 8080; it does not start the pump.

Phase 2 — publish the model (landed)

Section titled “Phase 2 — publish the model (landed)”

executeQueries POSTs CreateOrReplace TMSL to /v1/deploy before the first /v1/dax. The pump runs it through AMO Server.Execute. Desktop that will not create a database returns 409 and the query still goes to the open catalog. Opening a .pbix by hand remains valid; it is no longer required on a host that accepts TMSL (SSAS Developer, later headless msmdsrv).

DATATABLE columns must set sourceColumn (the BIM sourceColumn, or the column name). Desktop rejects the omit. The pump also maps that refusal — and empty-partition errors — to 409 so a still-open .pbix stays queryable. If the named catalog is missing on Desktop’s workspace instance, /v1/dax retries without Initial Catalog= and hits the open file.

Phase 3 — grow the Go subset against the oracle

Section titled “Phase 3 — grow the Go subset against the oracle”

Unchanged from 33: every new function is one Desktop agreed about. A developer VM (UTM / dockur on metal) is how a Mac or Linux laptop reaches that oracle without waiting for Monday’s windows-latest job. Every-push CI on ubuntu/mac does not boot that VM; it replays the goldens against Go. That is what keeps those jobs honest: they test the engine those runners actually have.

Pins so far, in e2e/semantic-model/fixtures/desktop_goldens.json, replayed by TestDesktopFunctionGoldens: ACOS, then ABS (BLANK stays BLANK), then ROUND (half away from zero; BLANK number stays BLANK, BLANK digits count as 0), then LOG / LOG10 (default LOG base is 10; BLANK/<=0 and LOG base 1/<=0 error), then INT (floor toward −∞; BLANK stays BLANK), then MIN (BLANK is not a candidate; all-blank is BLANK), then AVERAGE (BLANK is not in the mean), then COUNT (non-blank cells, including text; empty is 0), then POWER (BLANK base is BLANK; BLANK exponent is 0; POWER(0, 0) errors), then SIGN (BLANK stays BLANK; SIGN(0) is 0), then ASIN / ATAN (BLANK stays BLANK; ASIN outside [-1, 1] errors), then PI / SIN / COS / TAN (COS(BLANK()) is 1; SIN/TAN BLANK stays BLANK; TAN of a right angle errors), then DEGREES / RADIANS (BLANK stays BLANK), then DATE / YEAR / MONTH / DAY (two-digit years 0–30 → 2000s, 31–99 → 1900s; month/day overflow; day <=0 errors; YEAR(BLANK()) is BLANK), then TIME / HOUR / MINUTE / SECOND (wraps modulo 24h; BLANK parts are 0; negative total errors), then the rest of the Phase 3 batch: SWITCH (BLANK equals only BLANK), DISTINCTCOUNT / MAX, SQRT, MOD (MOD(-10,3)=2), FLOOR / CEILING (CEILING(n,0)=0), LN, EXP, WEEKDAY / WEEKNUM, EOMONTH / EDATE, TRUNC (toward zero), QUOTIENT (toward zero; BLANK divisor errors), BLANK / ISBLANK (ISBLANK("") is false), then ROW (one-row constructor; keeps a BLANK cell, unlike SUMMARIZECOLUMNS which drops all-blank groups; names must be unique non-empty strings). ATAN2 is not a DAX function. Captured on a UTM Windows 11 ARM guest + Desktop. Clone that guest only while it is stopped (utmctl clone refuses a running VM). Do not treat the live oracle as disposable.

Phase 4 — XMLA write-through (only if demanded)

Section titled “Phase 4 — XMLA write-through (only if demanded)”

executeQueries is the tractable surface. XMLA already terminates on the Go evaluator. Relaying XMLA Execute to msmdsrv is a separate cost and is not a Phase 1 blocker.

What this does not change

Section titled “What this does not change”
  • Parity row Power BI — DAX beyond the bounded subset stays 🟡 until the pump step on e2e/pbix-desktop (windows-latest) has been seen green. That job already opened Desktop; it now also starts e2e/msmdsrv and POSTs /v1/dax. Weekly, continue-on-error, Windows-only. It is not replaced by UTM on macos-latest or dockur/windows on ubuntu-latest.
  • make up / OrbStack / Rancher Desktop on a Mac are unchanged.
  • No Microsoft OSS engine was found to vendor (tmdl-parser is an empty stub; SemPy / TOM / ADOMD are clients). A tabular-emulator remains a clean-room write if we want full DAX without a Windows guest.

Licence

Section titled “Licence”

Same caveat as 33 Phase 0b: Microsoft documents -quiet ACCEPT_EULA=1 for Desktop install. Automated use of Desktop or SSAS in CI is a human decision. This page is the host map, not that reading.

Cost, measured where we have numbers

Section titled “Cost, measured where we have numbers”
PathWhat we know
e2e/pbix-desktop on windows-latest~7–8 min, 698 MB Desktop download, bit-identical on the fixture query (5/5). Same job now starts the DAX pump and POSTs /v1/dax
UTM on Apple SiliconWindows guest: budget 8–16 GB RAM, minutes to boot, plus Desktop inside it
dockur/windows on Linux+KVMImage + Windows install disk (their docs: ≥32 GB free, 2–4 GB RAM for the guest). First boot installs Windows; later boots reuse /storage
Wine / GPTK / OrbStackNot a path. Do not budget it
GitHub macos-latest + UTMNot a path. Nested virt unsupported on those images
GitHub ubuntu-latest + dockur/windowsNot a PR job. Nested Windows install is the wrong size and GitHub does not support it