Logging Application Behavior to MongoDB
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Logging Application Behavior to MongoDB

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Presentation given at Mongo SV conference in Mountain View on December 3, 2010. Covers reasons for logging to MongoDB, logging library basics and library options for Java, Python, Ruby, PHP and C#. ...

Presentation given at Mongo SV conference in Mountain View on December 3, 2010. Covers reasons for logging to MongoDB, logging library basics and library options for Java, Python, Ruby, PHP and C#. Updated 1/1/2012 with more info on logging in Ruby and tailable cursors.

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Logging Application Behavior to MongoDB Logging Application Behavior to MongoDB Presentation Transcript

  • Logging ApplicationBehavior to MongoDB Robert Stewart @wombatnation 1/1/2012
  • TOC •  Why Log to MongoDB? •  Logging Library Basics •  Logging by Language •  Other Ways to Distribute Your Logging
  • Why Log to MongoDB? •  Centralized application logging •  Easy remote access, compared to files •  Log events good fit for document model •  Flexible schema •  Indexes for frequent queries •  Capped collections are very efficient •  Analyze data in-place with JavaScript MapReduce
  • Event Storage •  Create a database for your app •  Create a capped collection to store log events •  Time-based eviction more natural, but less efficient •  Capped collection reduces chance of filling up disk
  • Log Analysis •  Compared to files, easier to analyze app behavior across servers and days •  Log values to custom keys where possible •  JavaScript MapReduce
  • Miscellaneous Free Advice •  Take advantage of separating storage from presentation •  Be aware of which classes your Mongo driver knows how to BSONify •  If logging from multiple languages, sticking to Log4Lang family can help
  • Logging Library Basics •  Some provide API with pluggable implementation •  Configuration •  Programmatic •  Declarative •  Dynamic
  • Logging Concepts •  Named, Hierarchical Logger Objects •  Identify a class or an area of an app •  Log Level, e.g., error, warn, info, debug •  Thresholds determine if event is logged •  Logging Event •  The message •  Metadata, e.g., time, level, class, method, line
  • Logging Concepts •  Handler - determines event destination •  File, console, socket, email, syslog, MongoDB, etc. •  Handler level threshold •  Async vs. sync •  Filter - for logger and/or handler •  Formatter - event and message •  Pattern with placeholder tokens
  • Common Flow for Logging App calls For each handler: logger.info( freak out ) Is handler info No Is logger enabled? infoNo enabled? Yes Passes Yes No filter, if Passes any? filter, if Yes Yes any? Format and store event No
  • Polyglotism •  Good news - lots of client language bindings and logging libraries for MongoDB •  Mostly good news - Log4J very influential •  Sort of bad news - default log event formats can be very different
  • Logging by Language •  Java •  Python •  Ruby •  PHP •  C#
  • Java •  APIs •  Apache Commons Logging •  SLF4J •  java.util.logging, a.k.a., JUL •  Limited feature set •  Destinations - console, file, socket, memory •  JVM-level config
  • Log4J •  Apache Log4J is dominant logging library •  Logback is potential successor •  Logger - usually, represents class logging the event •  LoggingEvent - message and metadata •  Appender - sends LoggingEvent to destination •  Layout - formats the event •  Converter - convert placeholder to value
  • Log4mongo-java •  Set of Log4J Appenders for MongoDB •  log4mongo.org •  Open source project on GitHub •  I m a committer with Peter Monks and Jozef Šev ík •  I used it at Voxify with speech reco applications and infrastructure services •  Peter has used it at Alfresco
  • MongoDbAppender •  Stores a Log4J LoggingEvent object as a document in a collection •  Format is very similar to structure of LoggingEvent Java class •  Where possible, data is stored as appropriate BSON objects, rather than just strings
  • MongoDbPatternLayoutAppender •  Stores log event based on user-specified pattern •  Standard Log4J pattern layout, parser and converter functionality •  Very flexible formatting at cost of additional config •  Values stored as strings or arrays •  Custom values determined at time event is logged
  • BsonAppender •  Custom log format by extending BsonAppender •  Can use it to log BSON objects to other data stores •  Includes code for BSONifying Java exceptions
  • Enabling log4mongo-java • Associate a name with an appender implementation log4j.appender.MongoDB = org.log4mongo.MongoDbAppender!• Specify host (optional port, username and password). For replica set, specify all active hosts. log4j.appender.MongoDB.hostname = localhost • Specify database and collection log4j.appender.MongoDB.databaseName = app_name log4j.appender.MongoDB.collectionName = log • Add named appender to rootLogger list log4j.rootLogger = INFO, file, MongoDB
  • Using Pattern Layout Appender • Specify pattern layout appender log4j.appender.MongoDB = org.log4mongo.MongoDbPatternLayoutAppender • Specify  your  custom  Pa2ernLayout  class   log4j.appender.MongoDB.layout = com.voxify.log.log4j.MongoDBPatternLayout• Specify a conversion pattern •  Must be a valid JSON document •  Can have sub-documents •  Values can be strings or arrays log4j.appender.MongoDB.layout.ConversionPattern = {"ts":"%d{yyyy-MM-dd HH:mm:ss,SSS}","level":"%p","class":"%c{1}","message":"%m"}
  • Shell and Tail
  • In the Shell > use app_nameswitched to db app_name> db.log.findOne(){ "_id" : ObjectId("4c200c4d28cf037460e82363"), "ts" : "2010-10-21 18:05:17,237", "level" : "INFO", "class" : "NodeFlagGenerator", "message" : "Generating me some node flags”}
  • Recent Log Events If using mongo 1.9.1+, put useful functions like this in .mongorc.js> function last(count) { if (count==null) count = 1; return db.log.find({}, {_id:0}).sort({ts:-1}).limit(count); }> last(2){ "ts" : "2010-10-28 23:49:14,567", "level" : "INFO", "session" :"122", "class" : "Site", "message" : "uninformative message" }{ "ts" : "2010-10-28 23:49:14,566", "level" : "INFO", "session" :"122", "class" : "Site", "message" : "some info kind of message" }
  • Tailing Logs •  You’ll really miss ability to tail logfiles •  Or, ... will you? •  MongoDB offers tailable cursors •  Specify cursor, e.g., from find, as tailable •  While cursor alive, print new docs then sleep
  • Python Tailing Example from pymongo import Connectionimport timedb = Connection().my_dbcoll = db.my_collectioncursor = coll.find(tailable=True)while cursor.alive: try: doc = cursor.next() print doc except StopIteration: time.sleep(1)
  • Python •  Feature-rich logging module in Python 2.3 •  Influenced by Log4J
  • Components •  Logger - represents area of library or project •  LogRecord •  Handler •  Filter •  Formatter •  LoggerAdapter (2.6) - add contextual info
  • mongodb-log •  Python logging handler to log to MongoDB •  Stores dictionary directly as BSON doc •  https://github.com/andreisavu/mongodb-log
  • log4mongo-python • Similar design to log4mongo PHP and .NET appenders • Example programmatic handler config and usage: import loggingfrom log4mongo.handlers import MongoHandlerlogger = logging.getLogger(test)logger.addHandler(MongoHandler(host=localhost))logger.warning(test) • http://log4mongo.org/display/PUB/Log4mongo+for+Python • https://github.com/log4mongo/log4mongo-python
  • Ruby •  Built-in Logger library •  Limited feature set •  Console and file outputs •  Message format is fixed •  Datetime format is configurable
  • Log4r •  Influenced by Log4J •  Logger •  Outputter •  Formatter •  Configurator •  http://log4r.rubyforge.org •  Code for using Log4r with MongoMapper •  http://gist.github.com/207347
  • Logging •  Similar to Log4r with a few enhancements •  Supports JSON as output format •  http://logging.rubyforge.org/
  • mongo_db_logger •  Rails plugin which uses Rails Logger, which can use Ruby Logger, Log4r, etc. •  Logs a single document per request •  IP address, time, etc. •  All messages logged during request •  Custom request data •  Configure via database.yml •  http://github.com/peburrows/mongo_db_logger
  • Central Logger •  Forked from mongo_db_logger •  Added Rails 3 support and gemified •  Web UI for searching, filtering and analyzing logs •  Configure via database.yml (or mongoid.yml or central_logger.yml) •  http://www.slideshare.net/leopard_me/logging-rails-application-behavior-to-mongodb •  http://files.meetup.com/1742411/Logging%20With%20MongoDB.pdf •  https://github.com/customink/central_logger
  • MongodbLogger •  Based on central_logger •  Different web UI for searching, filtering and analyzing logs •  Configure via database.yml mongodb_logger.yml) (or mongoid.yml or•  http://mongodb-logger.catware.org/
  • PHP •  error_log() logs to file, email address or system logger (e.g., syslog or NT EventLog) •  Log4PHP - heavily influenced by Log4J •  PEAR Log - PHP-specific logging library •  Zend_Log - Logging for Zend Framework
  • Log4mongo-php •  Log4PHP appender •  Programmatic & declarative config •  Timestamp stored as Mongo Date •  Exception stored as array - msg, code, stacktrace •  Inner exception stored if available •  https://github.com/log4mongo/log4mongo-php
  • PEAR Log •  PEAR Log class - lots of handlers (Firebug!), but none yet for MongoDB •  Programmatic config •  Specify handler when creating logger object •  Composite handler for multiple destinations •  http://pear.php.net/package/Log/
  • Log Writer for Zend •  Project -> Recordshelf_Log_Writer_MongoDb •  Described as a prototypesque implementation •  Standard Zend tools to config and init •  Zend log event is associative array •  Project has code for accessing & filtering events •  http://raphaelstolt.blogspot.com/2009/09/logging-to-mongodb-and-accessing-log.html
  • C#/.NET •  Log4net •  Heavily influenced by Log4J •  http://logging.apache.org/log4net/
  • Log4mongo-net •  Uses community developed C# driver, but may move to official driver •  Tested with .NET 3.5+ and Mono 2.8 •  Standard App.config/Web.config or programmatic •  http://log4mongo.org/display/PUB/Log4mongo+for+.NET
  • Other Options •  Destinations include MongoDB •  Flume, logstash, Fluentd •  Primary Destination is HDFS •  Chukwa and Scribe •  Commercial Hosted •  Loggly •  Commercial On-Premise •  Splunk
  • Flume •  If you can t change the source of logs ... •  Can aggregate files, syslog, etc. •  Agent --> Collector --> Storage •  Storage plugins for HDFS, MongoDB, etc. •  Decorators transform data & extract metadata •  https://github.com/cloudera/flume •  https://github.com/mongodb/mongo-hadoop •  Chukwa, Honu and Scribe more HDFS-centric
  • logstash •  Log event storage, search and graphing •  Read from file, syslog, AMQP, tcp, etc. •  Store to ElasticSearch, AMQP queue, websockets, MongoDB, etc. •  http://logstash.net/ •  http://code.google.com/p/logstash
  • Fluentd •  Ruby-based open source log collector •  Input, output and buffer plug-ins •  For example, plug-ins for tailing Apache log files and storing log events to MongoDB •  http://blog.treasure-data.com/post/13766262632/real-time-log-collection-with- fluentd-and-mongodb •  http://fluentd.org/doc/ •  https://github.com/fluent/fluentd
  • Questions? •  Photo/Image Credits •  Log analysis - ww.flickr.com/photos/linuxtuxguy/2579295702 •  Don’t Stop Believing - www.flickr.com/photos/loozrboy/3908830690/ •  Homeland Security Advisory System - www.theonion.com/articles/iraq-adopts-terror-alert-system,1258/ •  Advice - www.flickr.com/photos/wurzle/659315/ •  Shell - http://www.flickr.com/photos/geishaboy500/305555652/ •  Tail - http://www.flickr.com/photos/autumnsonata/2632194442/ •  Log flume - www.flickr.com/photos/halloweenjack/1330806722/ •  Cufflinks - www.flickr.com/photos/oberazzi/318947873/