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Production audit – Batch 30 (Migrations: autogenerate wanted to drop full-text search, and a rotated password would have kept the API from booting) - #30
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…would have kept the API from booting
Batch 30. Scope was the one part of the backend no batch had opened: the Alembic
chain and the boot sequence that runs it — the twelve revisions, alembic/env.py,
and the `alembic upgrade head && python -m app.seed && uvicorn ...` chain in
infra/docker-compose.prod.yml. Three findings, all three real, each with a test
that was confirmed to fail before the fix and pass after.
THE NEXT AUTOGENERATED MIGRATION WOULD HAVE DROPPED FULL-TEXT SEARCH.
env.py sets target_metadata = Base.metadata with no include_object filter, so
`alembic revision --autogenerate` diffs the live database against the models and
proposes removing everything the migrations own outright. Measured against a
schema migrated to head, that is five objects: messages.search_tsv (the GENERATED
tsvector column), its GIN index ix_messages_search_tsv, ix_messages_links,
ix_users_org_display_name and ix_message_attachments_message_id. Dropping
search_tsv is not a slow query, it takes the message results out of /api/search
altogether.
This is a known hazard that had outgrown its safeguard. bdbf829f823f's docstring
records deleting exactly this drop out of a generated migration by hand — and at
that point the set was two entries. 4471a6d661d3 added a third and b7e21c4a9d33
two more, while the safeguard stayed "whoever generates the next migration
remembers to re-read it". The five are now declared in one place in models.py and
handed to alembic's include_object hook, so the drops are never proposed.
The drift guard is the more valuable half. Nothing had ever compared the models
to the migrations, and the test harness cannot notice: conftest builds the schema
FROM the migrations, so a column added to models.py and never migrated is simply
absent and the suite stays green until a query selects it in production. Two
tests close both directions — no drift once the migration-owned set is excluded,
and that set is exactly as wide as what autogenerate actually proposes, so it
cannot be widened into a rubber stamp. Both were checked by adding a column to a
model and confirming they fail.
A DATABASE PASSWORD ROTATION WOULD HAVE STOPPED THE API FROM STARTING.
env.py handed the DSN straight to config.set_main_option, and alembic's Config is
a configparser with BasicInterpolation: a bare percent in the value raises
ValueError("invalid interpolation syntax") on that line, before any migration
runs. A percent is not an exotic DSN here, it is what the bootstrap produces —
user_data.sh.tftpl urlencodes the database password on purpose, because an
unencoded '@' or '/' would corrupt the URL, so any password containing one of
+ ! # $ * , ; = & ' ( ) : arrives as %XX. The only reason this is latent today is
terraform's override_special = "-_.~"; it stops being latent the first time
anyone rotates the RDS master password by hand or lets RDS generate one.
The blast radius is the whole API rather than the migration step. Production boots
with `alembic upgrade head && python -m app.seed && uvicorn ...`, so env.py
raising means uvicorn is never reached — and the app itself would have been fine,
since SQLAlchemy unquotes %XX, which is what makes the traceback so hard to read.
Escaped to %% at the single point the DSN enters alembic's config.
THE RETRY PATH OF THE IDEMPOTENCY MIGRATION TOOK THE LOCK IT WAS WRITTEN TO AVOID.
c5d81e37a204 builds its unique index CONCURRENTLY, and drops it first so a retry
after a failed build cannot mistake a leftover INVALID index for a finished one —
but the drop was the plain form. A plain DROP INDEX takes ACCESS EXCLUSIVE on
messages, queueing every read and every write behind it, which is the one lock the
surrounding autocommit block exists to avoid taking on the highest-volume table in
the schema. b7e21c4a9d33 already gets this right and says it is "the same pattern,
and the same reasoning, as c5d81e37a204"; now it is.
The drop is easy to read as the harmless half because it is usually a no-op. The
case it is written for is the retry after a failed concurrent build, which is
exactly when the index IS there, is INVALID, and the table is live — and because
migrations run before uvicorn, blocking there does not stall sends, it stops the
API from coming up. downgrade() is deliberately left plain: it drops the column
immediately after, which takes ACCESS EXCLUSIVE regardless.
Tested by executing the migration's own statements, parsed out of the revision
with ast rather than copied, so the tests cannot drift from what production runs:
re-running upgrade()'s three statements against the migrated schema still lands a
valid index, and the drop is pinned to the concurrent form by the one thing SQL
can observe about it — Postgres refuses CONCURRENTLY inside a transaction block
and accepts the plain form.
Verified: 234 backend tests pass (228 before, six new), ruff check and
ruff format --check clean, `alembic upgrade head` clean against a database built
from scratch with the index landing valid, and scripts/check_contracts.py reports
no drift. No production behaviour changes on the current schema — the chain is
already at head, so the migration edit only alters the retry path.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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📝 WalkthroughWalkthroughAlembic now filters migration-owned schema objects during autogeneration and escapes percent-encoded database URLs. The idempotency migration uses a concurrent index drop during upgrades. Migration tests cover schema drift, startup configuration, and index retry behavior. CI separates Chromium installation from system dependencies. ChangesMigration integrity and CI browser setup
Estimated code review effort: 3 (Moderate) | ~25 minutes Possibly related PRs
Suggested reviewers: 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
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Inline comments:
In `@backend/tests/test_migrations.py`:
- Around line 89-106: Update _percent_encode_password to decode parts.password
with unquote before re-encoding it, then use quote with safe="-._~" so existing
percent escapes are not double-encoded and the resulting DSN preserves the
original credentials.
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_percent_encode_password took urlsplit().password and encoded its first character without decoding what was already there. For the DSN this suite actually runs against that is a no-op — `rxhive` carries no escapes — but for the deployment the test exists to speak for it is not: a password already arriving as `%40secret` came back as `%2540secret`, which is a different password. The subprocess would then have failed on authentication, and the test would have reported the interpolation bug as fixed for the wrong reason, or as broken for one. unquote first, then re-encode the tail with quote(), so the escaped DSN always decodes back to the credentials the run was configured with — which is the only thing that makes a green result mean "the URL survived config parsing". 234 tests pass, ruff check and ruff format --check clean. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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… of dying
Batch 28 bounded the case where a mirror black-holes: azure.archive.ubuntu.com
stopped answering, apt's desktop defaults turned that into 38 minutes in one step,
and short Acquire timeouts brought the fail-over down to about thirty seconds.
That fix is intact and still doing its job. It just does not cover what happened
on run 32270826562, twice in a row on the same commit: the fail-over worked, apt
reached the canonical archive, fetched every InRelease — and then went silent for
eleven and a half minutes until this step's own cap killed it. The run reported
"Install frontend + browsers has timed out after 12 minutes" and nothing else.
Acquire::*::Timeout cannot catch that and never could. It is an INACTIVITY
timeout, so a mirror that trickles bytes never trips it, and Acquire::Retries "3"
makes it worse by doing the whole thing three times. There is no apt setting for
"give up after N seconds of wall clock", which is the bound actually wanted here.
So apt stops being able to fail this job at all:
* The browser BINARY is installed on its own, before any of it. It comes from
Playwright's CDN rather than apt, and it is the half that genuinely cannot be
skipped — it had no business sharing a failure domain with Ubuntu's mirrors.
* The system libraries keep going through apt, but under `timeout` and
non-fatally. ubuntu-24.04 already ships Chromium's dependencies; this run is
belt-and-braces. `sudo timeout`, not `timeout sudo` — timeout signals its
direct child, and with sudo in between it is sudo that gets the TERM rather
than the apt holding the dpkg lock.
* Which makes a launch check the real gate, and a better one than apt's exit
status was: if a library genuinely is missing, chromium fails to launch there,
once, with the reason — rather than every one of the specs failing separately
on a browser that will not start. Same reasoning as the LiveKit readiness
check above it, where a silent skip was worse than a loud failure.
Verified locally: the workflow parses, the step's script is valid bash, the launch
check exits 0 against a working install and 1 when the browser is unusable
(PLAYWRIGHT_BROWSERS_PATH pointed at an empty directory), so the gate fails in the
direction it claims to.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Batch 30. Scope was the one part of the backend no batch had opened: the Alembic chain and the boot sequence that runs it — the twelve revisions,
alembic/env.py, and thealembic upgrade head && python -m app.seed && uvicorn ...chain ininfra/docker-compose.prod.yml.Three findings, all three real. Each has a test that was confirmed to fail before the fix and pass after.
1. The next autogenerated migration would have dropped full-text search
env.pysetstarget_metadata = Base.metadatawith noinclude_objectfilter, soalembic revision --autogeneratediffs the live database against the models and proposes removing everything the migrations own outright. Measured against a schema migrated to head, that is five objects:messages.search_tsv09c892c227fc/api/searchentirelyix_messages_search_tsv09c892c227fcix_messages_links4471a6d661d3ix_users_org_display_nameb7e21c4a9d33ix_message_attachments_message_idb7e21c4a9d33This is a known hazard that had quietly outgrown its safeguard.
bdbf829f823f's docstring records deleting exactly this drop out of a generated migration by hand — and at that point the set was two entries.4471a6d661d3added a third andb7e21c4a9d33two more, while the safeguard stayed "whoever generates the next migration remembers to re-read it".The five are now declared in one place in
app/db/models.pyand handed to alembic'sinclude_objecthook, so the drops are never proposed.The drift guard is the more valuable half. Nothing had ever compared the models to the migrations, and the test harness structurally cannot notice:
conftestbuilds the schema from the migrations, so a column added tomodels.pyand never migrated is simply absent and the suite stays green until a query selects it in production. Two tests close both directions — no drift once the migration-owned set is excluded, and that set is exactly as wide as what autogenerate actually proposes, so it cannot be widened into a rubber stamp. Both were checked by adding a column to a model and confirming they fail.2. A database password rotation would have stopped the API from starting
env.pyhanded the DSN straight toconfig.set_main_option, and alembic'sConfigis aconfigparserwithBasicInterpolation: a bare%in the value raisesValueError: invalid interpolation syntaxon that line, before any migration runs.A percent is not an exotic DSN here — it is what the bootstrap produces.
infra/terraform/user_data.sh.tftpl:144urlencodes the database password on purpose, because an unencoded@or/would corrupt the URL, so any password containing one of+ ! # $ * , ; = & ' ( ) :arrives as%XX. The only reason this is latent today is terraform'soverride_special = "-_.~"; it stops being latent the first time anyone rotates the RDS master password by hand or lets RDS generate one.The blast radius is the whole API rather than the migration step. Production boots with
alembic upgrade head && python -m app.seed && uvicorn ..., soenv.pyraising means uvicorn is never reached — and the app itself would have been fine, since SQLAlchemy unquotes%XX, which is what makes the traceback so hard to read.Escaped to
%%at the single point the DSN enters alembic's config.3. The retry path of the idempotency migration took the lock it was written to avoid
c5d81e37a204builds its unique indexCONCURRENTLY, and drops it first so a retry after a failed build cannot mistake a leftoverINVALIDindex for a finished one — but the drop was the plain form. A plainDROP INDEXtakesACCESS EXCLUSIVEonmessages, queueing every read and every write behind it, which is the one lock the surroundingautocommit_block()exists to avoid taking on the highest-volume table in the schema.b7e21c4a9d33already gets this right and says it is "the same pattern, and the same reasoning, asc5d81e37a204"; now it is.The drop is easy to read as the harmless half because it is usually a no-op. The case it is written for is the retry after a failed concurrent build — exactly when the index IS there, is INVALID, and the table is live. And because migrations run before uvicorn, blocking there does not stall sends, it stops the API from coming up.
downgrade()is deliberately left plain: it drops the column immediately after, which takesACCESS EXCLUSIVEregardless, so a concurrent drop would buy nothing and would cost the function its single transaction.Tested by executing the migration's own statements, parsed out of the revision with
astrather than copied, so the tests cannot drift from what production runs: re-runningupgrade()'s three statements against the migrated schema still lands a valid index, and the drop is pinned to the concurrent form by the one thing SQL can observe about it — Postgres refusesCONCURRENTLYinside a transaction block and accepts the plain form.Verification
ruff check app testsandruff format --check app testscleanalembic upgrade headclean against a database built from scratch, withuq_messages_client_msg_idlandingindisvalid = truescripts/check_contracts.py— no drift (112 web + 57 iOS calls against 105 routes)No production behaviour changes on the current schema: the chain is already at head, so the migration edit only alters the retry path.
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Bug Fixes
Tests