Move symbol table demangling out of SymbolStore into SymbolProvider #5746

mstange · 2026-01-06T09:59:19Z

We have a WASM module for symbol demangling. However, usually we don't actually make any use of it: Usually, we get symbols via the symbolication API, either from the server or from the browser. And in the JSON API response, the symbols are already demangled.

The only time when we need to do the demangling in the front-end is if we fail to get symbols via the API and instead get a full symbol table from the browser. This is a rare case. With modern versions of Firefox (anything newer than Firefox 95), we only hit this case if we capture a profile from Firefox for Android (via about:debugging) and get symbols for native Android libraries. (There's one other case: Sometimes the symbolication API query runs out of memory when you have a local Firefox build with a big symbol table, so then the browser symbolication API fails but getting the symbol table succeeds.)

This PR is an attempt to make it so that we only load the demangling module when we run the symbolication code in a browser context.

Today, symbolicator-cli bundles the unused demangling wasm module. This PR moves the wasm dependency into receive-profile.ts which isn't used by symbolicator-cli, so the symbolicator-cli build will no longer bundle it.

Before:

% yarn build-symbolicator-cli && ls -l dist
[...]
built modules 1.17 MiB (javascript) 511 KiB (webassembly) 1.72 KiB (asset) [built]
[...]
-rw-r--r--@ 1 mstange  staff  522947 Jan  6 10:42 158fdaedb0d7e61a0391.module.wasm
-rw-r--r--@ 1 mstange  staff     842 Jan  6 10:42 1ddbc3ce40af8c7a648b.svg
-rw-r--r--@ 1 mstange  staff    1555 Jan  6 10:42 307.symbolicator-cli.js
-rw-r--r--@ 1 mstange  staff   45110 Jan  6 10:42 461.symbolicator-cli.js
-rw-r--r--@ 1 mstange  staff   31575 Jan  6 10:42 957.symbolicator-cli.js
-rw-r--r--@ 1 mstange  staff     720 Jan  6 10:42 957.symbolicator-cli.js.LICENSE.txt
-rw-r--r--@ 1 mstange  staff     916 Jan  6 10:42 d6df0017c0241dfe86ff.svg
-rw-r--r--@ 1 mstange  staff  142051 Jan  6 10:42 symbolicator-cli.js

After:

% yarn build-symbolicator-cli && ls -l dist
[...]
built modules 1.15 MiB (javascript) 1.72 KiB (asset) [built]
[...]
-rw-r--r--@ 1 mstange  staff     842 Jan  6 10:41 1ddbc3ce40af8c7a648b.svg
-rw-r--r--@ 1 mstange  staff     916 Jan  6 10:41 d6df0017c0241dfe86ff.svg
-rw-r--r--@ 1 mstange  staff  213276 Jan  6 10:41 symbolicator-cli.js

codecov · 2026-01-06T10:02:21Z

Codecov Report

❌ Patch coverage is 84.81013% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.67%. Comparing base (1a808fe) to head (3f43d12).
⚠️ Report is 50 commits behind head on main.

Files with missing lines	Patch %	Lines
src/actions/receive-profile.ts	80.35%	11 Missing ⚠️
src/symbolicator-cli/index.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5746      +/-   ##
==========================================
+ Coverage   85.64%   85.67%   +0.02%     
==========================================
  Files         313      314       +1     
  Lines       31013    31106      +93     
  Branches     8535     8558      +23     
==========================================
+ Hits        26562    26649      +87     
- Misses       4021     4027       +6     
  Partials      430      430

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canova

Looks good to me, thanks!

src/profile-logic/symbol-store.ts

canova · 2026-01-09T10:47:08Z

src/actions/receive-profile.ts

+  // Note, the database name still references the old project name, "perf.html". It was
+  // left the same as to not invalidate user's information.
  const symbolProvider = new RegularSymbolProvider(
+    'perf-html-async-storage',


Ah I was looking at the previous commits and was going to suggest moving the name here, but looks like you already did it :)

canova · 2026-01-09T10:51:34Z

src/actions/receive-profile.ts

+    if (typeof dbNamePrefixOrDB === 'string') {
+      this._symbolDb = new SymbolStoreDB(`${dbNamePrefixOrDB}-symbol-tables`);
+    } else {
+      this._symbolDb = dbNamePrefixOrDB;


Do we ever use this path where we pass a ISymbolStoreDB (or intend to use in the future)? I can't find any use cases for it. So maybe we can convert dbNamePrefixOrDB to a string only and simplify this logic?

Oh, no, we are definitely not intending to use this in the future. I'll add a commit to make it a string.

canova · 2026-01-09T10:52:45Z

src/actions/receive-profile.ts

+  async closeDb() {
+    await this._symbolDb.close();
  }


I can't find any calls to closeDb. Is this expected? Where do we close the DB or do we keep it open all the time?

Hmm, looking at the old code, I can't find any callers to it either. So it's not new at least.

Ah, this was used by tests, but I removed all those tests. Our tests don't really exercise the caching logic any more because I moved it into the RegularSymbolProvider which isn't used in the tests. I'll remove closeDb as well then.

…k cached symbol tables only after API requests come back with no info.

…ses to the SymbolStore it creates.

…'t in the database.

This removes the demangling dependency from symbol-store.ts. It also lets us remove the unused "database" from symbolicator-cli. The cache only exists so that we don't give the browser unnecessary work to recompute the symbol table. So we only need to access the cache if we're about to ask the browser for a full symbol table.

With this and #5746 combined, `yarn build-symbolicator-cli` will only produce a single output file. Without this PR, it also produced two SVG files.

mstange requested a review from canova January 6, 2026 09:59

mstange self-assigned this Jan 6, 2026

mstange force-pushed the move-db-access branch from a1e4db0 to 568be0a Compare January 6, 2026 10:00

mstange force-pushed the move-db-access branch from 568be0a to a66fd2c Compare January 6, 2026 10:03

mstange mentioned this pull request Jan 6, 2026

Remove SVG asset imports from profile-data.ts #5747

Merged

canova approved these changes Jan 9, 2026

View reviewed changes

mstange added 7 commits January 9, 2026 17:20

Change the order in which we consult the various symbol sources: Chec…

b32ae2a

…k cached symbol tables only after API requests come back with no info.

Make option 4 work more like options 1 and 2.

0d48bc0

Create a proper class for the symbol provider that getSymbolStore pas…

9b62de6

…ses to the SymbolStore it creates.

Make SymbolStoreDB.getSymbolTable return null if the symbol table isn…

2b6c486

…'t in the database.

Remove unused ISymbolStoreDB interface.

6cae060

Disable async chunks in the symbolicator-cli build.

3f43d12

mstange force-pushed the move-db-access branch from a66fd2c to 3f43d12 Compare January 9, 2026 16:24

mstange enabled auto-merge January 9, 2026 16:26

mstange merged commit 45bf912 into firefox-devtools:main Jan 9, 2026
19 checks passed

mstange added a commit that referenced this pull request Jan 9, 2026

Remove SVG asset imports from profile-data.ts (#5747)

c70f208

With this and #5746 combined, `yarn build-symbolicator-cli` will only produce a single output file. Without this PR, it also produced two SVG files.

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Move symbol table demangling out of SymbolStore into SymbolProvider #5746

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Move symbol table demangling out of SymbolStore into SymbolProvider #5746

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