feat(logger): optional subcontext

This adds an optional subcontext for loggers to print on every log
statement. This is used in place of wrapping the log methods for the lnd
loggers to display currency, but can also be reused in a generic fashion
going forward.

Before:

```
19/06/2019 15:44:43.634 [LND] info: BTC: trying to verify connection...
```

After:

```
19/06/2019 15:44:43.634 [LND-BTC] info: trying to verify connection...
```

lib/Logger.ts

@@ -50,15 +50,26 @@ class Logger {
 
   private level: string;
   private context: Context;
+  private subcontext?: string;
   private logger?: winston.Logger;
+  private filename?: string;
   private instanceId: number;
-
-  constructor({ level, filename, context, instanceId, disabled, dateFormat }:
-    {instanceId?: number, level?: string, filename?: string, context?: Context, disabled?: boolean, dateFormat?: string}) {
-
-    this.level = level || Level.Trace;
-    this.context = context || Context.Global;
-    this.instanceId = instanceId || 0;
+  private dateFormat?: string;
+
+  constructor({ level = Level.Trace, filename, context = Context.Global, subcontext, instanceId = 0, disabled, dateFormat }: {
+    instanceId?: number,
+    level?: string,
+    filename?: string,
+    context?: Context,
+    subcontext?: string,
+    disabled?: boolean,
+    dateFormat?: string,
+  }) {
+    this.level = level;
+    this.context = context;
+    this.subcontext = subcontext;
+    this.instanceId = instanceId;
+    this.dateFormat = dateFormat;
 
     if (disabled) {
       return;
@@ -71,7 +82,8 @@ class Logger {
       }),
     ];
 
-    if (filename !== '') {
+    if (filename) {
+      this.filename = filename;
       transports.push(new winston.transports.File({
         filename,
         level: this.level,
@@ -100,14 +112,27 @@ class Logger {
     };
   }
 
+  public createSubLogger = (subcontext: string) => {
+    return new Logger({
+      subcontext,
+      instanceId: this.instanceId,
+      level: this.level,
+      filename: this.filename,
+      context: this.context,
+      disabled: this.logger === undefined,
+      dateFormat: this.dateFormat,
+    });
+  }
+
   private getLogFormat = (colorize: boolean, dateFormat?: string) => {
     const { format } = winston;
 
+    const context = this.subcontext ? `${this.context}-${this.subcontext}` : this.context;
     if (this.instanceId > 0) {
-      return format.printf(info => `${getTsString(dateFormat)} [${this.context}][${this.instanceId}] ` +
+      return format.printf(info => `${getTsString(dateFormat)} [${context}][${this.instanceId}] ` +
         `${this.getLevel(info.level, colorize)}: ${info.message}`);
     } else {
-      return format.printf(info => `${getTsString(dateFormat)} [${this.context}] ${this.getLevel(info.level, colorize)}: ${info.message}`);
+      return format.printf(info => `${getTsString(dateFormat)} [${context}] ${this.getLevel(info.level, colorize)}: ${info.message}`);
     }
   }
 

lib/lndclient/types.ts

@@ -30,12 +30,3 @@ export type Chain = {
   network: string,
   chain: string,
 };
-
-export type LndLogger = {
-  error: Function,
-  warn: Function,
-  info: Function,
-  verbose: Function,
-  debug: Function,
-  trace: Function,
-};

lib/swaps/SwapClientManager.ts

@@ -1,9 +1,9 @@
 import Config from '../Config';
 import SwapClient from './SwapClient';
 import LndClient from '../lndclient/LndClient';
-import { LndLogger, LndInfo } from '../lndclient/types';
+import { LndInfo } from '../lndclient/types';
 import RaidenClient from '../raidenclient/RaidenClient';
-import Logger, { Loggers } from '../Logger';
+import { Loggers } from '../Logger';
 import { errors } from './errors';
 import { Currency } from '../orderbook/types';
 import { Models } from '../db/DB';
@@ -41,21 +41,6 @@ class SwapClientManager extends EventEmitter {
     this.raidenClient = new RaidenClient(config.raiden, loggers.raiden);
   }
 
-  /**
-   * Wraps each lnd logger call with currency.
-   * @returns A wrapped lnd logger object.
-   */
-  private static wrapLndLogger = (logger: Logger, currency: string): LndLogger => {
-    return {
-      error: (msg: string) => logger.error(`${currency}: ${msg}`),
-      warn: (msg: string) => logger.warn(`${currency}: ${msg}`),
-      info: (msg: string) => logger.info(`${currency}: ${msg}`),
-      verbose: (msg: string) => logger.verbose(`${currency}: ${msg}`),
-      debug: (msg: string) => logger.debug(`${currency}: ${msg}`),
-      trace: (msg: string) => logger.trace(`${currency}: ${msg}`),
-    };
-  }
-
   /**
    * Starts all swap clients, binds event listeners
    * and waits for the swap clients to initialize.
@@ -70,7 +55,7 @@ class SwapClientManager extends EventEmitter {
         const lndClient = new LndClient(
           lndConfig,
           currency,
-          (SwapClientManager.wrapLndLogger(this.loggers.lnd, currency) as Logger),
+          this.loggers.lnd.createSubLogger(currency),
         );
         this.swapClients.set(currency, lndClient);
         initPromises.push(lndClient.init());

test/jest/SwapClientManager.spec.ts

@@ -16,7 +16,13 @@ jest.mock('../../lib/db/DB', () => {
   });
 });
 jest.mock('../../lib/Config');
-jest.mock('../../lib/Logger');
+jest.mock('../../lib/Logger', () => {
+  return jest.fn().mockImplementation(() => {
+    return {
+      createSubLogger: () => {},
+    };
+  });
+});
 jest.mock('../../lib/nodekey/NodeKey');
 const mockLndPubKey = 1;
 const lndInfoMock = jest.fn(() => Promise.resolve());