Overview

docs
tests
package

The ultimate rotation and windows friendly log tailer plus a lot more...

• backfills rotated files
• handles gz and bz2 files
• handles multi line records
• doesn't break windows rotating log handlers
• easy to extend
• Free software: BSD license
• other than six pure Python stdlib.

Installation

pip install tailchaser

Thsi will install the tailchaser library in your site-packages and it will also add the script tailchase to your Scripts directory.

Usage

$ tailchase /where/my/logs/*.log

$ tailchase -h

usage: tailchase [-h] [--only-backfill] [--dont-backfill]
               [--clear-checkpoint] [--read-period READ_PERIOD]
               [--read-pause READ_PAUSE] [--reading-from {unix,win}]
               [--temp-dir TEMP_DIR]
               [--logging {DEBUG,INFO,WARN,ERROR,CRITICAL}]
               file-pattern


positional arguments:
  file-pattern          The file pattern to tail, such as /var/log/access.*

optional arguments:
  -h, --help            show this help message and exit
  --only-backfill       dont't tail, default: False
  --dont-backfill       basically only tail, default: False
  --clear-checkpoint    start form the begining, default: False
  --read-period READ_PERIOD
                    how long you read before you pause. If zero you don't
                    pause, default: 1
  --read-pause READ_PAUSE
                    how long you pause between reads, default: 0
  --reading-from PLATFORM
                    sets how long you read and then pause can be one of {unix,win}, default: win
  --temp-dir TEMP_DIR   on back fill files are copied to a temp directory.Use
                    this to set this directory, default: None
  --logging LEVEL
                    logging level it can be one of  DEBUG,INFO,WARN,ERROR,CRITICAL, default: ERROR

In its simplest form

In its simplest form tailchase works like a combination of cat and tail -f except it will start with the oldest rotated file. So if you were to have

/var/log/opendirectoryd.log
/var/log/opendirectoryd.log.0
/var/log/opendirectoryd.log.1
/var/log/opendirectoryd.log.2
/var/log/opendirectoryd.log.3
/var/log/opendirectoryd.log.4

it would first output the text of /var/log/opendirectoryd.log.4, then /var/log/opendirectoryd.log.3, etc. until it reached the newest file then when it has reached the end of /var/log/opendirectoryd.log revert to a "tail -f" behaviour.

So if you were to do

tailchase 'tests/logs/opendirectoryd.*'

"note: In bash you need to quote the wildcard otherwise it will be expanded into the scripts argv array."

you would get something like

2015-12-24 15:39:56.733754 EST - AID: 0x0000000000000000 - Registered node with name '/Contacts'
2015-12-24 15:39:56.733933 EST - AID: 0x0000000000000000 - Registered node with name '/LDAPv3' as hidden
2015-12-24 15:39:56.736154 EST - AID: 0x0000000000000000 - Registered node with name '/Local' as hidden
2015-12-24 15:39:56.736868 EST - AID: 0x0000000000000000 - Registered node with name '/NIS' as hidden
2015-12-24 15:39:56.737134 EST - AID: 0x0000000000000000 - Discovered configuration for node name '/Search' at path '       2015-12-24 15:39:56.737151 EST - AID: 0x0000000000000000 - Registered node with name '/Search'
2015-12-24 15:39:56.738794 EST - AID: 0x0000000000000000 - Loaded bundle at path '/System/Library/OpenDirectory/Modules     2015-12-24 15:39:56.740509 EST - AID: 0x0000000000000000 - Loaded bundle at path '/System/Library/OpenDirectory/Modules/

Coding with tailchaser

Using the tailchaser library in a project is probably best done by example.

Example 1 - Tailchase to a REST service.

#
# Example 1 - Tail to Elastic
#

import requests

import tailchaser

class TailToElastic(tailchaser.Tailer):
    def handoff(self, file_tailed, checkpoint, record):
        """ Expect a record like:

        20160204 10:28:15,525 INFO PropertiesLoaderSupport - Loading properties file from URL [file:C:/WaterWorks/Broken/BSE//config/lme-market.properties]
        20160204 10:28:15,541 INFO PropertiesLoaderSupport - Loading properties file from URL [file:C:/WaterWorks/Broken/BSE//config/default-database.properties]
        20160204 10:28:15,541 INFO PropertiesLoaderSupport - Loading properties file from URL [file:C:/WaterWorks/Broken/BSE//config/default-hibernate.properties]
        """

        date, time, level, source, _, message = record.split(5)
        result = requests.json("http://someelacticserver.com:9200/myindex/log", json={
                        'timestamp': '{}T{}'.format(date, time)
                        'level': level,
                        'source': source,
                        'message': message
                        })
        return result.status_code == requests.codes.ok

Example 2 - Tailchase to Kafka

#
# Example 2 - Tail to Kafka - shows how to add your own arguments and then send messages to kafka.
#

from kafka import KafkaProducer
rom tailchaser.tailer import Tailer


class TailToKafka(Tailer):
    def add_arguments(cls, parser=None):
        parser = super(TailToKafka, cls).add_arguments(parser)

    HOSTS = 'localhost:1234'
    TOPIC = b'log'
    def startup(self):
        self.kafka_producer = KafkaProducer(bootstrap_servers=self.HOSTS,value_serializer=msgpack.dumps)


    def handoff(self, file_tailed, checkpoint, record):
        """ Expect a record like:

        20160204 10:28:15,525 INFO PropertiesLoaderSupport - Loading properties file from URL [file:C:/WaterWorks/Broken/BSE//config/lme-market.properties]
        20160204 10:28:15,541 INFO PropertiesLoaderSupport - Loading properties file from URL [file:C:/WaterWorks/Broken/BSE//config/default-database.properties]
        20160204 10:28:15,541 INFO PropertiesLoaderSupport - Loading properties file from URL [file:C:/WaterWorks/Broken/BSE//config/default-hibernate.properties]
        """
        self.kafka_producer.send(self.TOPIC, record).get(timeout=10)
        return True

Example 3 - Saving and Loading last Offset from Zookeeper

#
# Example 3 - Saving and Loading last Offset from Zookeeper
#
import platform
import pickle
import six
from kazoo.client import KazooClient
from tailchaser.tailer import Tailer

class TailToElastic(Tailer):
    def start(self):
        self.zk = KazooClient(hosts=self.config.zookeeper_host)
        self.zk.start()


    def stop():
        self.zk.stop()

    def load_checkpoint(self):
        zk_path = self.config.checkpoint_filename
        try:
            checkpoint = pickle.loads(self.zk.get(zk_path))
            log.debug('loaded: %s %s', zk_path, checkpoint)
            return checkpoint
        except (IOError, EOFError):
            log.debug('failed to load: %s', zk_path)
            return self.INIT_CHECKPOINT

    def save_checkpoint(self, checkpoint):
        log.debug('dumping %s %s', self.config.checkpoint_filename, checkpoint)
        return self.zk.set(self.config.checkpoint_filename, six.b(pickle.dumps(checkpoint)))


    @staticmethod
    def make_checkpoint_filename(source_pattern, path=None):
        zk_path =  '/'.join(['tailchase', platform.node(), slugify(source_pattern)]
        self.zk.ensure_path(zk_path)
        return zk_path

Documentation

https://tailchaser.readthedocs.org/

Development

To run the all tests run:

tox

Note, to combine the coverage data from all the tox environments run:

set PYTEST_ADDOPTS=--cov-append
tox

PYTEST_ADDOPTS=--cov-append tox