tesseract worker restart to aviod memory leak

src/utils/tesseract.ts

@@ -5,8 +5,12 @@ import {
 } from 'tesseract.js'
 
 import logger from './logger'
+import utils from './utils'
 import { isMainThread, workerData } from 'worker_threads'
 
+let recognizeCount = 0
+const MAX_ALLOWED_RECOGNIZE_COUNT = 100
+
 // https://github.com/naptha/tesseract.js/blob/master/docs/api.md
 let tesseractWorker: TesseractWorker = null
 export async function initTesseractWorker(): Promise<TesseractWorker> {
@@ -17,17 +21,6 @@ export async function initTesseractWorker(): Promise<TesseractWorker> {
     await worker.load()
     await worker.loadLanguage('hun+eng')
     await worker.initialize('hun+eng')
-    return worker
-    // await worker.terminate();
-}
-
-let resolveLoaded: () => void = null
-export const tesseractLoaded: Promise<void> = new Promise((resolve) => {
-    resolveLoaded = resolve
-})
-
-initTesseractWorker().then((worker) => {
-    tesseractWorker = worker
 
     if (isMainThread) {
         logger.Log('Tesseract loaded on main thread')
@@ -35,14 +28,70 @@ initTesseractWorker().then((worker) => {
         const { workerIndex }: { workerIndex: number } = workerData
         logger.Log(`[THREAD #${workerIndex}]: Tesseract loaded`)
     }
+
+    return worker
+}
+
+let resolveLoaded: () => void = null
+export let tesseractLoaded: Promise<void> = new Promise((resolve) => {
+    resolveLoaded = resolve
+})
+
+export async function restartTesseractWorker(): Promise<void> {
+    tesseractLoaded = new Promise((resolve) => {
+        resolveLoaded = resolve
+    })
+
+    await tesseractWorker.terminate()
+    tesseractWorker = await initTesseractWorker()
+    resolveLoaded()
+}
+
+initTesseractWorker().then((worker) => {
+    tesseractWorker = worker
     resolveLoaded()
 })
 
-export async function recognizeTextFromBase64(base64: string): Promise<string> {
-    const {
-        data: { text },
-    } = await tesseractWorker.recognize(base64)
-    return text
+export async function recognizeTextFromBase64(
+    base64: string
+): Promise<string | null> {
+    await tesseractLoaded
+    try {
+        // TODO: somehow integrate confidence
+        const {
+            data: { text /*, confidence */ },
+        } = await tesseractWorker.recognize(base64)
+
+        recognizeCount += 1
+        restartIfNecesarry()
+        return text
+    } catch (e) {
+        logger.Log(
+            'Error happened during recognizing base64 text!',
+            logger.GetColor('redbg')
+        )
+        console.error(e)
+
+        await restartTesseractWorker()
+
+        return null
+    }
+}
+
+async function restartIfNecesarry() {
+    if (recognizeCount > MAX_ALLOWED_RECOGNIZE_COUNT) {
+        logger.Log('Restarting Tesseract worker')
+
+        const memBefore = process.memoryUsage().rss
+
+        await restartTesseractWorker()
+
+        const memAfter = process.memoryUsage().rss
+        const freed = utils.formatBytes(memBefore - memAfter)
+        logger.Log(`Restarted tesseract worker, freed up ${freed} memory`)
+
+        recognizeCount = 0
+    }
 }
 
 export async function terminateWorker(): Promise<void | ConfigResult> {