log4js-cloudwatch-appender

Simple appender for log4js to submit logs to AWS cloudwatch based on the lawgs module.

Installation

This module is installed via npm:

npm install --save log4js-cloudwatch-appender

Usage

Add aws appender to the log4js config file:

1const config = {

2    appenders: {

3        aws: {

4              type: "log4js-cloudwatch-appender",

5              accessKeyId: '<accessKeyId>',

6              secretAccessKey: '<secretAccessKey>',

7              region: 'eu-central-1',

8              logGroup: 'prod',

9              logStream: 'apps',

10              layout: '<custom layout object>',

11              lawgsConfig: '<optional alwgs config object>'
12            }
13    },

14    categories: {

15        default: {appenders: ['aws'], level: 'info'}
16    }
17}

This will cause logs to be sent to AWS CloudWatch with the specified group and stream.

Configuration

If you are using roles, you will need the following roles:

• logs:DescribeLogGroups
• logs:DescribeLogStreams
• logs:CreateLogGroup
• logs:CreateLogStream
• logs:PutLogEvents

mandatory

• region - The CloudWatch region
• logGroup - The log group to send the metrics to
• logStream - The log stream of the group to send the metrics to

optional

• accessKeyId - Optional if credentials are set in ~/.aws/credentials
• secretAccessKey - Optional if credentials are set in ~/.aws/credentials
• layout - Custom layout. See suggested layout
• lawgsConfig - Optional vonfig object for lawgs:
  • showDebugLogs - Show debug logs. Default: false.
  • uploadMaxTimer - After this ms timeout, flush to server. Default: 5000.
  • uploadBatchSize - After this amount of logs, flush to server. Default: 500.

Suggested json layout

Logs are easier to query whn they are formatted as json. Following is a suggested json layout to set for this appender. The logging style should be:

1const uuid = require('node-uuid');
2const corr = uuid.v4();
3const logger = logFactory.getLogger('category');
4
5logger.info(corr, 'methodName()','part1','part2');

Which will output:

1{
2  "timestamp": "2017-06-10T11:55:38.251Z",
3  "corr": "2e2c99aa-7eee-4fd2-ae36-cd9dc9533816",
4  "app": "<appName>",
5  "host": "<ip>",
6  "pid": 24532,
7  "level": "INFO",
8  "category": "category",
9  "method": "methodName()",
10  "message": "part1 part2"
11}

The layout:

1const util = require('util');
2const _ = require('underscore');
3
4let processName = path.basename(process.argv[1]);
5processName = processName.substring(0, processName.length - 3);
6
7const publicIp = require('public-ip').v4;
8let ip = '';
9publicIp()
10  .then(function (_ip) {
11    ip = _ip;
12  })
13  .catch(function (e) {
14    console.log(e);
15    ip = 'unknown';
16  });
17
18const jsonLayout = {
19  "type": "pattern",
20  "pattern": '{"timestamp": "%d{yyyy-MM-ddThh:mm:ss.SSSZ}", "app": "' + processName + '", "ip": "%x{my_ip}", "host": "%h", "pid": %z, "level": "%p", "category": "%c"%x{corr}%x{method}, "message": "%x{message}"}',
21  "tokens": {
22    "my_ip": function () {
23      return ip;
24    },
25   "corr": function (logEvent) {
26      logEvent.__data__ = _.map(logEvent.data, _.clone);
27      if (logEvent.__data__) {
28        let corr = logEvent.__data__[0];
29        if (Array.isArray(corr) && corr.length === 2) {
30          corr = corr[0];
31          if (typeof corr === 'string' && corr.length === 36 && corr.split("-").length === 5) {
32            logEvent.__data__[0] = logEvent.__data__[0][1];
33            return ', "corr": "' + corr + '"';
34          }
35        }
36        if (logEvent.__data__.length > 1 && corr && typeof corr === 'string' && corr.length === 36 && corr.split("-").length === 5) {
37          logEvent.__data__.shift();
38          return ', "corr": "' + corr + '"';
39        }
40      }
41      return '';
42    },
43    "method": function (logEvent) {
44      if (logEvent.__data__) {
45        const method = logEvent.__data__[0];
46        if (logEvent.__data__.length > 1 && method && typeof method === 'string' && method.indexOf("()", method.length - 2) !== -1) {
47          logEvent.__data__.shift();
48          return ', "method": "' + method + '"';
49        }
50      }
51      return '';
52    },
53    "message": function (logEvent) {
54      if (logEvent.__data__) {
55        let data = logEvent.__data__;
56        data = util.format.apply(util, wrapErrorsWithInspect(data));
57        data = escapedStringify(data);
58        logEvent.__data__ = undefined;
59        return data;
60      }
61      return '';
62    }
63  }
64};
65
66function wrapErrorsWithInspect(items) {
67  return items.map(function (item) {
68    if ((item instanceof Error) && item.stack) {
69      return {
70        inspect: function () {
71          return util.format(item) + '\n' + item.stack;
72        }
73      };
74    } else {
75      return item;
76    }
77  });
78}
79
80function escapedStringify(json) {
81  return json
82    .replace(/[\\]/g, '\\\\')
83    .replace(/[\"]/g, '\\\"')
84    .replace(/[\/]/g, '\\/')
85    .replace(/[\b]/g, '\\b')
86    .replace(/[\f]/g, '\\f')
87    .replace(/[\n]/g, '\\n')
88    .replace(/[\r]/g, '\\r')
89    .replace(/[\t]/g, '\\t');
90}

Contributing

Please make all pull requests to the master branch and ensure tests pass locally.