s3-streamlogger

A Writable Stream object that uploads to s3 objects, periodically rotating to a new object name.

See also tails3 for a script to tail the log files produced by s3-streamlogger.

Installation

npm install --save s3-streamlogger

Basic Usage

var S3StreamLogger = require('s3-streamlogger').S3StreamLogger;

var s3stream = new S3StreamLogger({
             bucket: "mys3bucket",
      access_key_id: "...",
  secret_access_key: "..."
});

s3stream.write("hello S3");

Use with Winston: Log to S3

npm install --save winston
npm install --save s3-streamlogger

var winston        = require('winston');
var S3StreamLogger = require('s3-streamlogger').S3StreamLogger;

var s3_stream = new S3StreamLogger({
             bucket: "mys3bucket",
      access_key_id: "...",
  secret_access_key: "..."
});

var transport = new (winston.transports.File)({
  stream: s3_stream
});
// see error handling section below
transport.on('error', function(err){/* ... */});

var logger = new (winston.Logger)({
  transports: [file_transport]
});


logger.info('Hello Winston!');

Define subfolder

var S3StreamLogger = require('s3-streamlogger').S3StreamLogger;

var s3stream = new S3StreamLogger({
             bucket: "mys3bucket",
             folder: "my/nested/subfolder",
      access_key_id: "...",
  secret_access_key: "..."
});

s3stream.write("hello S3");

Assign tags

var S3StreamLogger = require('s3-streamlogger').S3StreamLogger;

var s3stream = new S3StreamLogger({
             bucket: "mys3bucket",
             folder: "my/nested/subfolder",
               tags: {type: 'myType', project: 'myProject'},
      access_key_id: "...",
  secret_access_key: "..."
});

s3stream.write("hello S3");

Add hostname information for tails3

tails3 expects messages to be logged as json (the default for the file transport), with hostname and (for critical errors), stack properties to each log object, in addition to the standard timestamp, level and message properties. You can provide these using the third "metadata" option to winston's log method:

logger.log(level, message, {hostname: ... , stack: ...});

Handling logging errors

When there is an error writing to s3, the stream emits an 'error' event with details. You should take care not to log these errors back to the same stream (as that is likely to cause infinite recursion). Instead log them to the console, to a file, or to SNS using winston-sns.

Note that these errors will result in uncaught exceptions unless you have an error event handler registered, for example:

s3_stream.on('error', function(err){
    // there was an error!
    some_other_logging_transport.log('error', 'logging transport error', err)
});

When using s3-streamlogger with the Winston File transport, the File transport attaches its own error handler to the stream, so you do not need your own, however it will re-emit the errors on itself which must be handled instead:

var transport = new (winston.transports.File)({
  stream: s3_stream
});
transport.on('error', function(err){
  /* handle s3 stream errors (e.g. invalid credentials, EHOSTDOWN) here */
});

var logger = new (winston.Logger)({
  transports: [file_transport]
});

Options

bucket (required)

Name of the S3 bucket to upload data to. Must exist. Can also be provided as the environment variable BUCKET_NAME.

folder

An optional folder to stream log files to. Takes a path string, eg: "my/subfolder" or "nested".

tags

An optional set of tags to assign to the log files. Takes an object, eg: {type: "myType"} or {type: "myType", project: "myProject"}.

access_key_id

AWS access key ID, must have putObject permission on the specified bucket. Can also be provided as the environment variable AWS_SECRET_ACCESS_KEY, or as any of the other authentication methods supported by the AWS SDK.

secret_access_key

AWS secret key for the access_key_id specified. Can also be provided as the environment variable AWS_SECRET_KEY_ID, or as any of the other authentication methods supported by the AWS SDK.

config

Configuration object for the AWS SDK. The full list of options is available on the AWS SDK Configuration Object page. This is an alternative to using access_key_id and secret_access_key and is overwritten by them if both are used.

name_format

Format of file names to create, accepts strftime specifiers. Defaults to "%Y-%m-%d-%H-%M-%S-%L-<current git branch>-<hostname>.log". The Date() used to fill the format specifiers is created with the current UTC time, but still has the current timezone, so any specifiers that perform timezone conversion will return incorrect dates.

If you use a format of the form %Y-%m-%d-%H-%M-<stage>-<hostname>.log, then you can use tails3 to tail the log files being generated by S3StreamLogger.

If compress is set to true, then the default extension is .log.gz instead of .log.

rotate_every

Files will be rotated every rotate_every milliseconds. Defaults to 3600000 (60 minutes).

max_file_size

Files will be rotated when they reach max_file_size bytes. Defaults to 200 KB.

upload_every

Files will be uploaded every upload_every milliseconds. Defaults to 20 seconds.

buffer_size

Files will be uploaded if the un-uploaded data exceeds buffer_size bytes. Defaults to 10 KB.

server_side_encryption

The server side encryption AES256 algorithm used when storing objects in S3. Defaults to false.

acl

The canned ACL (access control list) to apply to uploaded objects. Defaults to no ACL.

compress

If true, the files will be gzipped before uploading (may reduce s3 storage costs). Defaults to false.

License

ISC: equivalent to 2-clause BSD.