central-services-logger

Common shared Logging lib for Mojaloop components

Configuration

Edit the file in ./config/default.json to configure the logger, or set the following Environment variables:

Environment variable	Description	Default	Available Values
LOG_LEVEL	Also CSL_LOG_LEVEL	info	error, warn, audit, trace, info, perf, verbose, debug, silly
CSL_LOG_LEVEL	Sets the log level	info	error, warn, audit, trace, info, perf, verbose, debug, silly
LOG_FILTER	Also CSL_LOG_FILTER	""	e.g. `"error, trace, verbose"
CSL_LOG_FILTER	Applies a log filter. Specify a comma separated list of individual log levels to be included instead of specifying a LOG_LEVEL	""	e.g. `"error, trace, verbose"
CSL_LOG_TRANSPORT	Selects the transport method. Either console, file or a map for multiple transports. Uses the same transport for errors and standard logs	console	console, file, {}
CSL_TRANSPORT_FILE_OPTIONS	Optional. Required if LOG_TRANSPORT=file. Configures the winston file transport	See default.json	See the Winston Docs
CSL_JSON_STRINGIFY_SPACING	Optional. A number that's used to insert white space into the output JSON string for readability purposes.	2	integer

Configuring multiple transports

The CSL_LOG_TRANSPORT environment variable can be set to a JSON object to configure multiple transports. The key names can be any string, and the values should be objects that contain the transport type and configuration, e.g.:

{
  "stdout": {
    "type": "console"
  },
  "fluentbit": {
    "type": "udp",
    "host": "fluentbit"
  },
  "combined": {
    "type": "file",
    "filename": "combined.log"
  }
}

UDP Transport

The udp transport is a custom transport that sends logs to a remote server via UDP. The following configuration options are available:

Option	Description	Default	Required
host	The hostname or IP address of the remote server	localhost	No
port	The port number of the remote server	5170	No
mtu	The maximum size of a single packet in bytes	1400	No
max	The maximum size of logged message	4096	No
id	Optional id to put in front of each packet	false	No

• Messages above the max size will not be sent.
• id is useful for identifying the source of the logs on the remote server. It can be set to true to generate a random id, or a hex string to use a specific id.
• mtu should be set to the maximum packet size that the network can handle. Messages that are too large will be split into multiple network packets.

Usage

Logger

To use the shared Logger class, you only need to require it in the file you want to perform logging in:

const Logger = require('@mojaloop/central-services-logger')

Then you simply need to call the appropriate method for the logging level you desire:

Logger.debug('this is only a debug statement')
Logger.info('this is some info')
Logger.warn('warning')
Logger.error('an error has occurred')

The Logger class is backed by Winston, which allows you to do things like string interpolation:

Logger.info('test message %s', 'my string');

You can also call the Logger.log method which directly calls the Winston log method and gives even more flexibility.

By default, the Logger class is setup to log to the console only, with timestamps and colorized output.

Auditing Dependencies

We use audit-ci along with npm audit to check dependencies for node vulnerabilities, and keep track of resolved dependencies with an audit-ci.jsonc file.

To start a new resolution process, run:

npm run audit:fix

You can then check to see if the CI will pass based on the current dependencies with:

npm run audit:check

The audit-ci.jsonc contains any audit-exceptions that cannot be fixed to ensure that CircleCI will build correctly.

Contextual Logging

If you need contextual logging, an context object can be passed using Logger.child({'context': {a:1}}).info("Message").

Output: timestamp - info: {
  a: 1,
  message: 'Message'
}

Automated Releases

As part of our CI/CD process, we use a combination of CircleCI, standard-version npm package and github-release CircleCI orb to automatically trigger our releases and image builds. This process essentially mimics a manual tag and release.

On a merge to master, CircleCI is configured to use the mojaloopci github account to push the latest generated CHANGELOG and package version number.

Once those changes are pushed, CircleCI will pull the updated master, tag and push a release triggering another subsequent build that also publishes a docker image.

Potential problems

• There is a case where the merge to master workflow will resolve successfully, triggering a release. Then that tagged release workflow subsequently failing due to the image scan, audit check, vulnerability check or other "live" checks.

  This will leave master without an associated published build. Fixes that require a new merge will essentially cause a skip in version number or require a clean up of the master branch to the commit before the CHANGELOG and bump.

  This may be resolved by relying solely on the previous checks of the merge to master workflow to assume that our tagged release is of sound quality. We are still mulling over this solution since catching bugs/vulnerabilities/etc earlier is a boon.

• It is unknown if a race condition might occur with multiple merges with master in quick succession, but this is a suspected edge case.