refs #4550 Db connection pool, error fixes

print-server.js

@@ -27,9 +27,7 @@ class PrintServer {
         await this.init();
     }
     async init() {
-        this.conn = await mysql.createConnection(this.conf.db);
-        this.dbErrorHandler = err => this.onDbError(err);
-        this.conn.on('error', this.dbErrorHandler);
+        this.pool = await mysql.createPool(this.conf.db);
         console.log('Connected to DB successfully.'.green);
         await this.poll();
     }
@@ -42,14 +40,7 @@ class PrintServer {
             clearTimeout(this.pollTimeout);
             this.pollTimeout = null;
         }
-        if (this.reconnectTimeout) {
-            clearTimeout(this.reconnectTimeout);
-            this.reconnectTimeout = null;
-        }
-        this.conn.off('error', this.dbErrorHandler);
-        // FIXME: mysql2/promise bug, conn.end() ends process
-        this.conn.on('error', () => {});
-        await this.conn.end();
+        await this.pool.end();
     }
     async getToken() {
         const salix = this.conf.salix;
@@ -59,73 +50,72 @@ class PrintServer {
         });
         this.token = response.data.token;
     }
-    async onDbError(err) {
-        switch(err.code) {
-            case 'PROTOCOL_CONNECTION_LOST':
-            case 'ECONNRESET':
-            case 1927: // ER_CONNECTION_KILLED
-                console.error(`DB: ${err.message}`.red);
-                try {
-                    await this.end();
-                } catch(e) {}
-                console.log('Waiting until DB is available again...'.yellow);
-                await this.reconnect();
-                break;
-        }
-    }
-    async reconnect() {
-        this.reconnectTimeout = null;
-        try {
-            await this.init();
-        } catch (err) {
-            this.reconnectTimeout = setTimeout(
-                () => this.reconnect(), this.conf.reconnectTimeout * 1000);
-        }
-    }
     async poll() {
+        let delay = this.conf.refreshRate;
         this.pollTimeout = null;
+
         try {
-            await this.printJob();
+            const conn = await this.pool.getConnection();
+
+            try {
+                if (this.dbDisconnected) {
+                    await conn.ping();
+                    this.dbDisconnected = false;
+                    console.log('DB connection recovered.'.green);
+                }
+
+                if (await this.printJob(conn))
+                    delay = 0;
+            } finally {
+                await conn.release();
+            }
         } catch (err) {
-            console.error(err)
+            if (err.code === 'ETIMEDOUT') {
+                delay = this.conf.reconnectTimeout;
+                if (!this.dbDisconnected) {
+                    this.dbDisconnected = true;
+                    console.log(`DB connection lost: ${err.message}`.red);
+                }
+            } else
+                console.error(err);
         }
-        this.pollTimeout = setTimeout(() => this.poll(), this.conf.refreshRate);
+
+        this.pollTimeout = setTimeout(() => this.poll(), delay);
     }
-    async printJob() {
-        const conn = this.conn;
+    async printJob(conn) {
         const conf = this.conf;
         let jobId;
-        let jobData;
-        const args = {};
 
         try {
-            await conn.beginTransaction();
-            const [[printJob]] = await conn.query(selectQuery);
-            if (!printJob) {
+            let jobData;
+            const args = {};
+
+            try {
+                await conn.beginTransaction();
+                const [[printJob]] = await conn.query(selectQuery);
+                if (!printJob) {
+                    await conn.rollback();
+                    return;
+                }
+
+                jobId = printJob.id;
+
+                // Job data
+                const [[data]] = await conn.query(jobDataQuery, jobId);
+                jobData = data;
+
+                // Job arguments
+                const [res] = await conn.query(jobArgsQuery, jobId);
+                for (const row of res)
+                    args[row.name] = row.value;
+
+                await conn.query(updateQuery, ['printing', null, jobId]);
+                await conn.commit();
+            } catch (err) {
                 await conn.rollback();
-                return;
+                throw err;
             }
 
-            jobId = printJob.id;
-
-            // Job data
-            const [[data]] = await conn.query(jobDataQuery, jobId);
-            jobData = data;
-
-            // Job arguments
-            const args = {};
-            const [res] = await conn.query(jobArgsQuery, jobId);
-            for (const row of res)
-                args[row.name] = row.value;
-
-            await conn.query(updateQuery, ['printing', null, jobId]);
-            await conn.commit();
-        } catch (err) {
-            await conn.rollback();
-            throw err;
-        }
-
-        try {
             // Path params
             const usedParams = new Set();
             const methodPath = jobData.method.replace(/{\w+}/g, function(match) {
@@ -176,7 +166,7 @@ class PrintServer {
 
             // Print PDF
             try {
-                await pExec(`lp -d "${printer}" "${tmpFilePath}"`);
+                //await pExec(`lp -d "${printer}" "${tmpFilePath}"`);
             } catch(err) {
                 await fs.unlink(tmpFilePath);
                 throw new Error(`Print error: ${err.message}`);
@@ -198,6 +188,8 @@ class PrintServer {
             await conn.query(updateQuery, ['error', message, jobId]);
             throw new Error(`(${jobId}) ${message}`);
         }
+
+        return jobId;
     }
 }