Add backend memory usage comparison action for PRs (#16926)

* Initial plan

* Add backend memory usage comparison action

Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

* Fix deprecated serverProcess.killed usage

Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

* Add explicit permissions to save-pr-number job

Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

* Change PR comment text from Japanese to English

Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

* Inline memory measurement script to fix base ref compatibility

Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

* Revert "Inline memory measurement script to fix base ref compatibility"

This reverts commit 6f76a121efd450c257167cce6e298c59936f4e37.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

3 files changed, 359 insertions, 0 deletions

diff --git a/.github/workflows/get-backend-memory.yml b/.github/workflows/get-backend-memory.yml
new file mode 100644
index 0000000000..6f36c088f1
--- /dev/null
+++ b/.github/workflows/get-backend-memory.yml
@@ -0,0 +1,85 @@
+# this name is used in report-backend-memory.yml so be careful when change name
+name: Get backend memory usage
+
+on:
+  pull_request:
+    branches:
+      - master
+      - develop
+    paths:
+      - packages/backend/**
+      - packages/misskey-js/**
+      - .github/workflows/get-backend-memory.yml
+
+jobs:
+  get-memory-usage:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+
+    strategy:
+      matrix:
+        memory-json-name: [memory-base.json, memory-head.json]
+        include:
+          - memory-json-name: memory-base.json
+            ref: ${{ github.base_ref }}
+          - memory-json-name: memory-head.json
+            ref: refs/pull/${{ github.event.number }}/merge
+
+    services:
+      postgres:
+        image: postgres:18
+        ports:
+          - 54312:5432
+        env:
+          POSTGRES_DB: test-misskey
+          POSTGRES_HOST_AUTH_METHOD: trust
+      redis:
+        image: redis:7
+        ports:
+          - 56312:6379
+
+    steps:
+    - uses: actions/checkout@v4.3.0
+      with:
+        ref: ${{ matrix.ref }}
+        submodules: true
+    - name: Setup pnpm
+      uses: pnpm/action-setup@v4.2.0
+    - name: Use Node.js
+      uses: actions/setup-node@v4.4.0
+      with:
+        node-version-file: '.node-version'
+        cache: 'pnpm'
+    - run: pnpm i --frozen-lockfile
+    - name: Check pnpm-lock.yaml
+      run: git diff --exit-code pnpm-lock.yaml
+    - name: Copy Configure
+      run: cp .github/misskey/test.yml .config/default.yml
+    - name: Build
+      run: pnpm build
+    - name: Run migrations
+      run: pnpm --filter backend migrate
+    - name: Measure memory usage
+      run: |
+        # Start the server and measure memory usage
+        node packages/backend/scripts/measure-memory.mjs > ${{ matrix.memory-json-name }}
+    - name: Upload Artifact
+      uses: actions/upload-artifact@v4
+      with:
+        name: memory-artifact-${{ matrix.memory-json-name }}
+        path: ${{ matrix.memory-json-name }}
+
+  save-pr-number:
+    runs-on: ubuntu-latest
+    permissions: {}
+    steps:
+      - name: Save PR number
+        env:
+          PR_NUMBER: ${{ github.event.number }}
+        run: |
+          echo "$PR_NUMBER" > ./pr_number
+      - uses: actions/upload-artifact@v4
+        with:
+          name: memory-artifact-pr-number
+          path: pr_number
diff --git a/.github/workflows/report-backend-memory.yml b/.github/workflows/report-backend-memory.yml
new file mode 100644
index 0000000000..8ae33bc582
--- /dev/null
+++ b/.github/workflows/report-backend-memory.yml
@@ -0,0 +1,122 @@
+name: Report backend memory
+
+on:
+  workflow_run:
+    types: [completed]
+    workflows:
+      - Get backend memory usage # get-backend-memory.yml
+
+jobs:
+  compare-memory:
+    runs-on: ubuntu-latest
+    if: ${{ github.event.workflow_run.conclusion == 'success' }}
+    permissions:
+      pull-requests: write
+
+    steps:
+      - name: Download artifact
+        uses: actions/github-script@v7.1.0
+        with:
+          script: |
+            const fs = require('fs');
+            let allArtifacts = await github.rest.actions.listWorkflowRunArtifacts({
+               owner: context.repo.owner,
+               repo: context.repo.repo,
+               run_id: context.payload.workflow_run.id,
+            });
+            let matchArtifacts = allArtifacts.data.artifacts.filter((artifact) => {
+              return artifact.name.startsWith("memory-artifact-") || artifact.name == "memory-artifact"
+            });
+            await Promise.all(matchArtifacts.map(async (artifact) => {
+              let download = await github.rest.actions.downloadArtifact({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                artifact_id: artifact.id,
+                archive_format: 'zip',
+              });
+              await fs.promises.writeFile(`${process.env.GITHUB_WORKSPACE}/${artifact.name}.zip`, Buffer.from(download.data));
+            }));
+      - name: Extract all artifacts
+        run: |
+          find . -mindepth 1 -maxdepth 1 -type f -name '*.zip' -exec unzip {} -d artifacts ';'
+          ls -la artifacts/
+      - name: Load PR Number
+        id: load-pr-num
+        run: echo "pr-number=$(cat artifacts/pr_number)" >> "$GITHUB_OUTPUT"
+
+      - name: Output base
+        run: cat ./artifacts/memory-base.json
+      - name: Output head
+        run: cat ./artifacts/memory-head.json
+      - name: Compare memory usage
+        id: compare
+        run: |
+          BASE_MEMORY=$(cat ./artifacts/memory-base.json)
+          HEAD_MEMORY=$(cat ./artifacts/memory-head.json)
+
+          BASE_RSS=$(echo "$BASE_MEMORY" | jq -r '.memory.rss // 0')
+          HEAD_RSS=$(echo "$HEAD_MEMORY" | jq -r '.memory.rss // 0')
+
+          # Calculate difference
+          if [ "$BASE_RSS" -gt 0 ] && [ "$HEAD_RSS" -gt 0 ]; then
+            DIFF=$((HEAD_RSS - BASE_RSS))
+            DIFF_PERCENT=$(echo "scale=2; ($DIFF * 100) / $BASE_RSS" | bc)
+            
+            # Convert to MB for readability
+            BASE_MB=$(echo "scale=2; $BASE_RSS / 1048576" | bc)
+            HEAD_MB=$(echo "scale=2; $HEAD_RSS / 1048576" | bc)
+            DIFF_MB=$(echo "scale=2; $DIFF / 1048576" | bc)
+            
+            echo "base_mb=$BASE_MB" >> "$GITHUB_OUTPUT"
+            echo "head_mb=$HEAD_MB" >> "$GITHUB_OUTPUT"
+            echo "diff_mb=$DIFF_MB" >> "$GITHUB_OUTPUT"
+            echo "diff_percent=$DIFF_PERCENT" >> "$GITHUB_OUTPUT"
+            echo "has_data=true" >> "$GITHUB_OUTPUT"
+            
+            # Determine if this is a significant change (more than 5% increase)
+            if [ "$(echo "$DIFF_PERCENT > 5" | bc)" -eq 1 ]; then
+              echo "significant_increase=true" >> "$GITHUB_OUTPUT"
+            else
+              echo "significant_increase=false" >> "$GITHUB_OUTPUT"
+            fi
+          else
+            echo "has_data=false" >> "$GITHUB_OUTPUT"
+          fi
+      - id: build-comment
+        name: Build memory comment
+        run: |
+          HEADER="## Backend Memory Usage Comparison"
+          FOOTER="[See workflow logs for details](https://github.com/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID})"
+
+          echo "$HEADER" > ./output.md
+          echo >> ./output.md
+
+          if [ "${{ steps.compare.outputs.has_data }}" == "true" ]; then
+            echo "| Metric | base | head | Diff |" >> ./output.md
+            echo "|--------|------|------|------|" >> ./output.md
+            echo "| RSS | ${{ steps.compare.outputs.base_mb }} MB | ${{ steps.compare.outputs.head_mb }} MB | ${{ steps.compare.outputs.diff_mb }} MB (${{ steps.compare.outputs.diff_percent }}%) |" >> ./output.md
+            echo >> ./output.md
+
+            if [ "${{ steps.compare.outputs.significant_increase }}" == "true" ]; then
+              echo "⚠️ **Warning**: Memory usage has increased by more than 5%. Please verify this is not an unintended change." >> ./output.md
+              echo >> ./output.md
+            fi
+          else
+            echo "Could not retrieve memory usage data." >> ./output.md
+            echo >> ./output.md
+          fi
+
+          echo "$FOOTER" >> ./output.md
+      - uses: thollander/actions-comment-pull-request@v2
+        with:
+          pr_number: ${{ steps.load-pr-num.outputs.pr-number }}
+          comment_tag: show_memory_diff
+          filePath: ./output.md
+      - name: Tell error to PR
+        uses: thollander/actions-comment-pull-request@v2
+        if: failure() && steps.load-pr-num.outputs.pr-number
+        with:
+          pr_number: ${{ steps.load-pr-num.outputs.pr-number }}
+          comment_tag: show_memory_diff_error
+          message: |
+            An error occurred while comparing backend memory usage. See [workflow logs](https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}) for details.
diff --git a/packages/backend/scripts/measure-memory.mjs b/packages/backend/scripts/measure-memory.mjs
new file mode 100644
index 0000000000..017252d7ec
--- /dev/null
+++ b/packages/backend/scripts/measure-memory.mjs
@@ -0,0 +1,152 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+/**
+ * This script starts the Misskey backend server, waits for it to be ready,
+ * measures memory usage, and outputs the result as JSON.
+ *
+ * Usage: node scripts/measure-memory.mjs
+ */
+
+import { fork } from 'node:child_process';
+import { setTimeout } from 'node:timers/promises';
+import { fileURLToPath } from 'node:url';
+import { dirname, join } from 'node:path';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+const STARTUP_TIMEOUT = 120000; // 120 seconds timeout for server startup
+const MEMORY_SETTLE_TIME = 10000; // Wait 10 seconds after startup for memory to settle
+
+async function measureMemory() {
+	const startTime = Date.now();
+
+	// Start the Misskey backend server using fork to enable IPC
+	const serverProcess = fork(join(__dirname, '../built/boot/entry.js'), [], {
+		cwd: join(__dirname, '..'),
+		env: {
+			...process.env,
+			NODE_ENV: 'test',
+		},
+		stdio: ['pipe', 'pipe', 'pipe', 'ipc'],
+	});
+
+	let serverReady = false;
+
+	// Listen for the 'ok' message from the server indicating it's ready
+	serverProcess.on('message', (message) => {
+		if (message === 'ok') {
+			serverReady = true;
+		}
+	});
+
+	// Handle server output
+	serverProcess.stdout?.on('data', (data) => {
+		process.stderr.write(`[server stdout] ${data}`);
+	});
+
+	serverProcess.stderr?.on('data', (data) => {
+		process.stderr.write(`[server stderr] ${data}`);
+	});
+
+	// Handle server error
+	serverProcess.on('error', (err) => {
+		process.stderr.write(`[server error] ${err}\n`);
+	});
+
+	// Wait for server to be ready or timeout
+	const startupStartTime = Date.now();
+	while (!serverReady) {
+		if (Date.now() - startupStartTime > STARTUP_TIMEOUT) {
+			serverProcess.kill('SIGTERM');
+			throw new Error('Server startup timeout');
+		}
+		await setTimeout(100);
+	}
+
+	const startupTime = Date.now() - startupStartTime;
+	process.stderr.write(`Server started in ${startupTime}ms\n`);
+
+	// Wait for memory to settle
+	await setTimeout(MEMORY_SETTLE_TIME);
+
+	// Get memory usage from the server process via /proc
+	const pid = serverProcess.pid;
+	let memoryInfo;
+
+	try {
+		const fs = await import('node:fs/promises');
+
+		// Read /proc/[pid]/status for detailed memory info
+		const status = await fs.readFile(`/proc/${pid}/status`, 'utf-8');
+		const vmRssMatch = status.match(/VmRSS:\s+(\d+)\s+kB/);
+		const vmDataMatch = status.match(/VmData:\s+(\d+)\s+kB/);
+		const vmSizeMatch = status.match(/VmSize:\s+(\d+)\s+kB/);
+
+		memoryInfo = {
+			rss: vmRssMatch ? parseInt(vmRssMatch[1], 10) * 1024 : null,
+			heapUsed: vmDataMatch ? parseInt(vmDataMatch[1], 10) * 1024 : null,
+			vmSize: vmSizeMatch ? parseInt(vmSizeMatch[1], 10) * 1024 : null,
+		};
+	} catch (err) {
+		// Fallback: use ps command
+		process.stderr.write(`Warning: Could not read /proc/${pid}/status: ${err}\n`);
+
+		const { execSync } = await import('node:child_process');
+		try {
+			const ps = execSync(`ps -o rss= -p ${pid}`, { encoding: 'utf-8' });
+			const rssKb = parseInt(ps.trim(), 10);
+			memoryInfo = {
+				rss: rssKb * 1024,
+				heapUsed: null,
+				vmSize: null,
+			};
+		} catch {
+			memoryInfo = {
+				rss: null,
+				heapUsed: null,
+				vmSize: null,
+				error: 'Could not measure memory',
+			};
+		}
+	}
+
+	// Stop the server
+	serverProcess.kill('SIGTERM');
+
+	// Wait for process to exit
+	let exited = false;
+	await new Promise((resolve) => {
+		serverProcess.on('exit', () => {
+			exited = true;
+			resolve(undefined);
+		});
+		// Force kill after 10 seconds if not exited
+		setTimeout(10000).then(() => {
+			if (!exited) {
+				serverProcess.kill('SIGKILL');
+			}
+			resolve(undefined);
+		});
+	});
+
+	const result = {
+		timestamp: new Date().toISOString(),
+		startupTimeMs: startupTime,
+		memory: memoryInfo,
+	};
+
+	// Output as JSON to stdout
+	console.log(JSON.stringify(result, null, 2));
+}
+
+measureMemory().catch((err) => {
+	console.error(JSON.stringify({
+		error: err.message,
+		timestamp: new Date().toISOString(),
+	}));
+	process.exit(1);
+});