A java library for parsing valid Syslog IETF RFC 5424 and IETF_RFC_3164 logs. The library provides it's own parser implementations, but also exposes the Antlr generated base classes and interfaces should you want your own implementations.

Simple Syslog provids a Simple class with methods for parsing syslog with the default options and as little configuration as possible.

  Map<String, Object> = Simple.simpleNested5424(syslogLine);
  Map<String, String> = Simple.simpleFlat5424(syslogLine);

Calls exist for using Readers and Consumers with the default options

The default options for RFC 5424:

• No Deviations
• OMIT policy for Nils
• Default KeyProvider

The default options for RFC 3164:

• No Deviations
• Default KeyProvider

In general, there are Simple calls for almost all the SyslogParser interface calls described below.

Simple Syslog aims to provide syslog parsing that allows callers to handle syslog in the least restrictive way.

The syslog parsers do not build objects from syslog string, they call the provided syslog builder with the message parts. This allows for custom object building.

The default syslog builders provided allow specialization of Allowed Deviation, how to produce names for message parts, and how to handle Nils in RFC 5424 messages.

Custom SyslogBuilds can use these or other methods to help build their objects as well. see Default3164MessageHandler, Flat5424MessageHandler, and MapOfMaps5424MessageHandler

Parsing any Syslog with the lower leve (non Simple) apis requires using the SyslogParserBuilder to build a SyslogParser accoring to the SyslogSpecification you desire, and with a SyslogBuilder implemenation you provide, either from the provided classes or your own.

The SyslogParser is generically typed, so you must know the type that any implementation of SyslogBuilder returns.

The SyslogParserBuilder defaults to SyslogSpecification.RFC_5424 so it doesn't have to be explicitly set by .forSpecification().

Please see the ample unit tests for examples of all the options.

 SyslogParser<Map<String, Object>> parser = new SyslogParserBuilder<Map<String, Object>>().withSyslogBuilder(new MapOfMaps5424MessageHandler()).build();
 Map<String,Object> syslogMap = parser.parseLine(syslogLine);

To parse a number of Syslog lines together, say from a file you would create a Reader and all parseLines

  List<Map<String,Object>> syslogMapList = null;
  SyslogParser<Map<String, Object>> parser = new SyslogParserBuilder<Map<String, Object>>().withSyslogBuilder(new MapOfMaps5424MessageHandler()).build();
  try (Reader reader = new BufferedReader(new FileReader(new File(fileName)))) {
      syslogMapList = parser.parseLines(reader);
  }

Both parseLine and parseLines also provide a functional interface if you prefer that style. Just pass a Consumer to the function.

  SyslogParser<Map<String, Object>> parser = new SyslogParserBuilder<Map<String, Object>>().withSyslogBuilder(new MapOfMaps5424MessageHandler()).build();
  syslogMap = parser.parseLine(syslogLine, (syslogMap) -> {
   // do something with map
 });

  SyslogParser<Map<String, Object>> parser = new SyslogParserBuilder<Map<String, Object>>().withSyslogBuilder(new MapOfMaps5424MessageHandler()).build();
  try (Reader reader = new BufferedReader(new FileReader(new File(fileName)))) {
      parser.parseLines(reader, (map) -> {
        // do something with each map
      });
  }

  SyslogParser<Map<String, Object>> parser = new SyslogParserBuilder<Map<String, Object>>().withSyslogBuilder(new MapOfMaps5424MessageHandler()).build();
  try (Reader reader = new BufferedReader(new FileReader(new File(fileName)))) {
      parser.parseLines(reader, (map) -> {
        // do something with each map
      }, (line, throwable) -> {
        // do something for a failed line
      });
  }

A simple, default usage to parser a Syslog RFC 3164 log line is to build a SyslogParser with at least SyslogSpecification and SyslogBuilder.

 SyslogParser<Map<String, String>> parser = new SyslogParserBuilder<Map<String,String>>().forSpecification(SyslogSpecification.RFC_3164).withSyslogBuilder(new Default3164MessageHandler()).build();
 Map<String,Object> syslogMap = parser.parseLine(syslogLine);

To parse a number of Syslog lines together, say from a file you would create a Reader and all parseLines

  List<Map<String,String>> syslogMapList = null;
  SyslogParser<Map<String, String>> parser = new SyslogParserBuilder<Map<String,String>>().forSpecification(SyslogSpecification.RFC_3164).withSyslogBuilder(new Default3164MessageHandler()).build();
  try (Reader reader = new BufferedReader(new FileReader(new File(fileName)))) {
      syslogMapList = parser.parseLines(reader);
  }

Both parseLine and parseLines also provide a functional interface if you prefer that style. Just pass a Consumer to the function.

 SyslogParser<Map<String, String>> parser = new SyslogParserBuilder<Map<String,String>>().forSpecification(SyslogSpecification.RFC_3164).withSyslogBuilder(new Default3164MessageHandler()).build();
 syslogMap = parser.parseLine(syslogLine, (syslogMap) -> {
   // do something with map
 });

  SyslogParser<Map<String, String>> parser = new SyslogParserBuilder<Map<String,String>>().forSpecification(SyslogSpecification.RFC_3164).withSyslogBuilder(new Default3164MessageHandler()).build();
  try (Reader reader = new BufferedReader(new FileReader(new File(fileName)))) {
      parser.parseLines(reader, (map) -> {
        // do something with each map
      });
  }

  SyslogParser<Map<String, String>> parser = new SyslogParserBuilder<Map<String,String>>().forSpecification(SyslogSpecification.RFC_3164).withSyslogBuilder(new Default3164MessageHandler()).build();
  try (Reader reader = new BufferedReader(new FileReader(new File(fileName)))) {
      parser.parseLines(reader, (map) -> {
        // do something with each map
      }, (line, throwable) -> {
        // do something for a failed line
      });
  }

RFC 6587 describe a method of transmitting Syslog messages of either specifications prefixed with octet counts. Simple Syslog supports these messages with explicit specifications available.

Heroku HTTPS Drains An HTTPS encapsulated version of RFC6587 and RFC5424.

SyslogParser parser = new SyslogParserBuilder().forSpecification(SyslogSpecification.HEROKU_HTTPS_LOG_DRAIN).withSyslogBuilder(new MapOfMaps5424MessageHandler()).build();

While the SyslogParserBuilder supports setting SyslogSpecification, the options for changing the AllowableVariations, the SyslogSpecifictation and the KeyProvider are set on the provided SyslogBuilder implemenations.

Callers may or may not use these in their SyslogBuilder implementations as well.

The specifications supported by the library. RFC_5424, RFC_6587_5424, RFC_3164, and RFC_6587_3164.

Allowable deviations from the specifications. This allows for fields required by the specification, but perhaps omitted by convention to be missing, and a line that is by specificiation technically incorrect to still parse.

This is specified by an {@code EnumSet}

/**
   * Properly formed Syslog.
   */
  NONE,
  /**
   * Syslog that does not have PRIORITY.
   */
  PRIORITY,
  /**
   * Syslog that does not have VERSION.
   */
  VERSION

A KeyProvider is used to provide the map keys for the Syslog data. The default KeyProvider : DefaultKeyProvider provides keys using the SyslogKeys:

 MESSAGE("syslog.message"),
   HEADER_APPNAME("syslog.header.appName"),
   HEADER_HOSTNAME("syslog.header.hostName"),
   HEADER_PRI("syslog.header.pri"),
   HEADER_PRI_SEVERITY("syslog.header.severity"),
   HEADER_PRI_FACILITY("syslog.header.facility"),
   HEADER_PROCID("syslog.header.procId"),
   HEADER_TIMESTAMP("syslog.header.timestamp"),
   HEADER_MSGID("syslog.header.msgId"),
   HEADER_VERSION("syslog.header.version"),
   STRUCTURED_BASE("syslog.structuredData."),
   STRUCTURED_ELEMENT_ID_FMT("syslog.structuredData.%s"),
   STRUCTURED_ELEMENT_ID_PNAME_FMT("syslog.structuredData.%s.%s"),
   STRUCTURED_ELEMENT_ID_PNAME_PATTERN("syslog.structuredData\\.(.*)\\.(.*)$");

A custom KeyProvider can be supplied to the provided SyslogBuilder implemenations if there is a different key strategy required. Note that the keys are a superset of the syslog specifications.

The NilPolicy governs how the parser handles nil message parts for SyslogSpecification.RFC_5424. That is message parts that can be nil as part of a valid message;

• HOSTNAME
• APPNAME
• PROCID
• MSGID
• TIMESTAMP

• OMIT : The map will not contain an entry for that field
• NULL : The map will contain a null entry for that field
• DASH : The map will contain a '-' for that field

The default policy is OMIT.

Simple Syslog 5424 uses Antlr 4 to generate the Listener that the parser is based on. The generated Rfc5424Listener and Rfc5424Visitor interfaces, or Rfc5424BaseListener and Rfc5424BaseVisitor classes, may be used to implement new parsers as well in the event that you prefer different handling.

Implementors would then build their own parsers or builders etc. In other words the use of this library would minimally be the Antlr classes alone.

For examples, see the implementations of Rfc3164SyslogParser and Rfc5424SyslogParser for examples of parser implementations as well as the Syslog3164Listener and Syslog5424Listener implementations.

This project uses simple-syslog-grammars You will want to use git clone --recursive and ensure the src/main/antlr4/com/github/palindromicity/syslog/dsl/generated directory is created.

• Why not just use java-grok?

  Though I love java-grok (it is used in Apache Metron and Apache Nifi which I contribute to), and have even submitted PRs to it, it and other Regex based parsers do not handle Syslog 5424 Structured Data. I wanted something that did. I have not found any regex based approach which handles structured data in a single pass. If you find one, let me know!

• Why not fix the groks to handle it? Or create regexes outside of grok?

  I'm not good enough at regex, and couldn't write something that worked single pass.

• Why not write a custom state machine type parser?

  I like Antlr and wanted to try it ;)

<dependency>
  <groupId>com.github.palindromicity</groupId>
  <artifactId>simple-syslog</artifactId>
  <version>1.0.0</version>
  <type>pom</type>
</dependency>