Traject

Tools for indexing MARC records to Solr.

Generalizable to tools for configuring mapping records to associative array data structures, and sending them somewhere.

Currently under development, not production ready

Background/Goals

Existing tools for indexing Marc to Solr exist, and have served us well for many years, and have many useful things about them -- which I've tried to preserve in traject. But I was having more and more difficulty working with the existing tools, including difficulty providing the custom logic I needed in a maintainable way. I realized that for me, to create a tool with the flexibility, maintainability, and performance I wanted, I would need to do it in jruby (ruby on the JVM).

Some goals:

• Aim to be accessible even to non-rubyists
• Concise and maintainable local configuration -- including an only gradual increase in difficulty to write your own simple logic.
• Support reusable and shareable mapping logic routines.
• Built of modular and composable elements: If you want to change part of what traject does, you should be able to do so without having to reimplement other things you don't want to change.
• A maintainable internal architecture, well-factored with seperated concerns and DRY logic. Aim to be comprehensible to newcomer developers, and well-covered by tests.
• High performance, using multi-threaded concurrency where appropriate to maximize throughput. Actual throughput can depend on complexity of your mapping rules and capacity of your server(s), but I am getting throughput 2-5x greater than previous solutions.
• Cooperate well in unix batch/pipeline, with control over output/logging of errors, proper exit codes, use of stdin/stdout, etc.

Installation

Traject runs under jruby (ruby on the JVM). I recommend chruby and ruby-install for installing and managing ruby installations. (traject is tested and supported for ruby 1.9 -- recent versions of jruby should run under 1.9 mode by default).

Then just gem install traject.

( Note: We may later provide an all-in-one .jar distribution, which does not require you to install jruby or use on your system. This is hypothetically possible. Is it a good idea?)

Usage

Configuration file format

The traject command-line utility requires you to supply it with a configuration file. So let's start by describing the configuration file.

Configuration files are actually just ruby -- so by convention they end in .rb.

Don't worry, you don't neccesarily need to know ruby well to write them, they give you a subset of ruby to work with. But the full power of ruby is available to you.

rubyist tip: Technically, config files are executed with instance_eval in a Traject::Indexer instance, so the special commands you see are just methods on Traject::Indexer (or mixed into it). But you can call ordinary ruby require in config files, etc., too, to load external functionality. See more at Extending Logic below.

There are two main categories of directives in your configuration files: Settings, and Indexing Rules.

Settings

Settings are a flat list of key/value pairs, where the keys are always strings and the values usually are. They look like this in a config file:

# configuration_file.rb
# Note that "#" is a comment, cause it's just ruby

settings do
  # Where to find solr server to write to
  provide "solr.url", "http://example.org/solr"

  # If you are connecting to Solr 1.x, you need to set
  # for SolrJ compatibility:
  # provide "solrj_writer.parser_class_name", "XMLResponseParser"

  # solr.version doesn't currently do anything, but set it
  # anyway, in the future it will warn you if you have settings
  # that may not work with your version.
  provide "solr.version", "4.3.0"

  # default source type is binary, traject can't guess
  # you have to tell it.
  provide "marc_source.type", "xml"

  # settings can be set on command line instead of
  # config file too.

  # various others...
  provide "solrj_writer.commit_on_close", "true"

  # By default, we use the Traject::Marc4JReader, which
  # can read marc8 and ISO8859_1 -- if your records are all in UTF8,
  # the pure-ruby MarcReader may be faster...
  # provide "reader_class_name", "Traject::MarcReader"
  # If you ARE using the Marc4JReader, it defaults to "BESTGUESS"
  # as to encoding when reading binary, you may want to tell it instead
  provide "marc4j_reader.source_encoding", "MARC8" # or UTF-8 or ISO8859_1
end

provide will only set the key if it was previously unset, so first setting wins, and command-line comes first of all and overrides everything. You can also use store if you want to force-set, last set wins.

See, docs page on Settings for list of all standardized settings.

Indexing Rules

You can keep your settings and indexing rules in one config file, or split them accross multiple config files however you like. (Connection details vs indexing? Common things vs environmental specific things?)

The main tool for indexing rules is the to_field command. Which can be used with a few standard functions.

# configuration.rb

# The first arguent, 'source' in this case, is what Solr field we're
# sending to. And the 'literal' function supplies a hard-coded
# constant string literal.
to_field "source", literal("LIB_CATALOG")

# you can call 'to_field' multiple times, additional values
# are concatenated
to_field "source", literal("ANOTHER ONE")

# Serialize the marc record back out and
# put it in a solr field.
to_field "marc_record", serialized_marc(:format => "xml")

# or :format => "json" for marc-in-json
# or :format => "binary", by default Base64-encoded for Solr
# 'binary' field, or, for more like what SolrMarc did, without
# escaping:
to_field "marc_record_raw", serialized_marc(:format => "binary", :binary_escape => false)

# Take ALL of the text from the marc record, useful for
# a catch-all field. Actually by default only takes
# from tags 100 to 899.
to_field "text", extract_all_marc_values

# Now we have a simple example of the general utility function
# `extract_marc`
to_field "id", extract_marc("001", :first => true)

extract_marc takes a marc tag/subfield specification, and optional arguments. :first => true means if the specification returned multiple values, ignore all bet the first. It is wise to use this whenever you have a non-multi-valued solr field even if you think "There should only be one 001 field anyway!", to deal with unexpected data properly.

Other examples of the specification string, which can include multiple tag mentions, as well as subfields and indicators:

  # 245 subfields a, p, and s. 130, all subfields.
  # built-in punctuation trimming routine.
  to_field "title_t", extract_marc("245nps:130", :trim_punctuation => true)

  # Can limit to certain indicators with || chars.
  # "*" is a wildcard in indicator spec.  So
  # 856 with first indicator '0', subfield u.
  to_field "email_addresses", extract_marc("856|0*|u")

  # Instead of joining subfields from the same field
  # into one string, joined by spaces, leave them
  # each in seperate strings:
  to_field "isbn", extract_marc("020az", :seperator => nil)

The extract_marc function by default includes any linked MARC 880 fields with alternate-script versions. Another reason to use the :first option if you really only want one.

For MARC control (aka 'fixed') fields, you can use square brackets to take a slice by byte offset.

to_field "langauge_code", extract_marc("008[35-37]")

extract_marc also supports translation maps similar to SolrMarc's. There will be some translation maps built in, and you can provide your own. translation maps can be supplied in yaml or ruby. Translation maps are especially useful for mapping form MARC codes to user-displayable strings. See Traject::TranslationMap for more info:

# "translation_map" will be passed to Traject::TranslationMap.new
# and the created map used to translate all values
to_field "language", extract_marc("008[35-37]:041a:041d", :translation_map => "marc_language_code")

Direct indexing logic vs. Macros

It turns out all those functions we saw above used with to_field -- literal, serialized_marc, extract_all_marc_values, and extract_marc -- are what Traject calls 'macros'.

They are all actually built based upon a more basic element of indexing functionality, which you can always drop down to, and which is used to build the macros. The basic use of to_field, with directly specified logic instead of using a macro, looks like this:

to_field "source" do |record, accumulator, context|
   accumulator << "LIB CATALOG"
end

That's actually equivalent to the macro we used earlier: to_field("source"), literal("LIB_CATALOG").

This direct use of to_field happens to be a ruby "block", which is used to define a block of logic that can be stored and executed later. When the block is called, first argument (record above) is the marc_record being indexed (a ruby-marc MARC::Record object), and the second argument (accumulator) is a ruby array used to accumulate output values.

The third argument is a Traject::Indexer::Context object that can be used for more advanced functionality, including caching expensive per-record calculations, writing out to more than one output field at a time, or taking account of current Traject Settings in your logic. The third argument is optional, you can supply a two-argument block too.

You can always drop out to this basic direct use whenever you need special purpose logic, directly in the config file, writing in ruby:

# this is more or less nonsense, just an example
to_field "weird_title" do |record, accumlator, context|
   field = record['245']
   title = field['a']
   title.upcase! if field.indicator1 = '1'
   accumulator << title
end

# To make use of marc extraction by specification, just like
# marc_extract does, you may want to use the Traject::MarcExtractor
# class
to_field "weirdo" do |record, accumulator, context|
   # use MarcExtractor.cached for performance, globally
   # caching the MarcExtractor we create. See docs
   # at MarcExtractor.
   list = MarcExtractor.cached("700a").extract(record)

   # combine all the 700a's in ONE string, cause we're weird
   list = list.join(" ")

   accumulator << list
end

You can also combine a macro and a direct block for some post-processing. In this case, the accumulator parameter in our block will start out with the values left by the extract_marc:

to_field "subjects", extract_marc("600:650:610") do |record, accumulator, context|
  # for some reason we want to uppercase all our subjects
  accumulator.collect! {|s| s.upcase }
end

If you find yourself repeating code a lot in direct blocks, you can supply your own macros, for local use, or even to share with others in a ruby gem. See docs Macros

each_record

There is also a method each_record, which is like to_field, but without a specific field. It can be used for other side-effects of your choice, or even for writing to multiple fields.

  each_record do |record, context|
    # example of writing to two fields at once.
    (x, y) = Something.do_stuff
    (context["one_field"] ||= [])     << x
    (context["another_field"] ||= []) << y
  end

You could write or use macros for each_record too. It's suggested that such a macro take the field names it will effect as arguments (example?)

each_record and to_field calls will be processed in one big order, guaranteed in order.

  to_field("foo") {...}  # will be called first on each record
  each_record {...}      # will always be called AFTER above has potentially added values
  to_field("foo") {...}  # and will be called after each of the preceding for each record

Sample config

A fairly complex sample config file can be found at ./test/test_support/demo_config.rb

Built-in MARC21 Semantics

There is another package of 'macros' that comes with Traject for extracting semantics from Marc21. These are sometimes 'opinionated', using heuristics or algorithms that are not inherently part of Marc21, but have proven useful in actual practice.

It's not loaded by default, you can use straight ruby require and extend to load the macros into the indexer.

# in a traject config file, extend so we can use methods from...
require 'traject/macros/marc21_semantics'
extend Traject::Macros::Marc21Semantics

to_field "date",        marc_publication_date
to_field "author_sort", marc_sortable_author
to_field "inst_facet",  marc_instrumentation_humanized

See documented list of macros available in Marc21Semantics

Command Line

The simplest invocation is:

traject -c conf_file.rb marc_file.mrc

Traject assumes marc files are in ISO 2709 binary format; it is not currently able to guess marc format type from filenames. If you are reading marc files in another format, you need to tell traject either with the marc_source.type or the command-line shortcut:

traject -c conf.rb -t xml marc_file.xml

You can supply more than one conf file with repeated -c arguments.

traject -c connection_conf.rb -c indexing_conf.rb marc_file.mrc

If you supply a --stdin argument, traject will try to read from stdin. You can only supply one marc file at a time, but we can take advantage of stdin to get around this:

cat some/dir/*.marc | traject -c conf_file.rb --stdin

You can set any setting on the command line with -s key=value. This will over-ride any settings set with provide in conf files.

traject -c conf_file.rb marc_file -s solr.url=http://somehere/solr -s solr.url=http://example.com/solr -s solrj_writer.commit_on_close=true

There are some built-in command-line option shortcuts for useful settings:

Use -j to output as pretty-printed JSON hashes, instead of sending to solr. Useful for debugging or sanity checking.

traject -j -c conf_file.rb marc_file

Use -u as a shortcut for s solr.url=X

traject -c conf_file.rb -u http://example.com/solr marc_file.mrc

Also see -I load_path and -G Gemfile options under Extending With Your Own Code.

See also Hints for batch and cronjob use of traject.

Extending With Your Own Code

Traject config files are full live ruby files, where you can do anything, including declaring new classes, etc.

However, beyond limited trivial logic, you'll want to organize your code reasonably into seperate files, not jam everything into config files.

Traject wants to make sure it makes it convenient for you to do so, whether project-specific logic in files local to the traject project, or in ruby gems that can be shared between projects.

There are standard ruby mechanisms you can use to do this, and traject provides a couple features to make sure this remains convenient with the traject command line.

For more information, see documentation page on Extending With Your Own Code

Expert summary :

• Traject -I argument command line can be used to list directories to add to the load path, similar to the ruby -I argument. You can then 'require' local project files from the load path.
  • translation map files found on the load path or in a "./translation_maps" subdir on the load path will be found for Traject translation maps.
• Traject -G command line can be used to tell traject to use bundler with a Gemfile located at current working dirctory (or give an argument to -G ./some/myGemfile)

More

• Other traject commands including marcout, and commit
• Hints for batch and cronjob use of traject.

Development

Run tests with rake test or just rake. Tests are written using Minitest (please, no rspec). We use the spec-style describe/it to list the tests -- but generally prefer unit-style "assert_*" methods to make actual assertions, for clarity.

Some tests need to run against a solr instance. Currently no solr instance is baked in. You can provide your own solr instance to test against and set shell ENV variable "solr_url", and the tests will use it. Otherwise, tests will use a mocked up Solr instance.

To make a pull request, please make a feature branch created from the master branch, not from an existing feature branch. (If you need to do a feature branch dependent on an existing not-yet merged feature branch... discuss this with other developers first!)

Pull requests should come with tests, as well as docs where applicable. Docs can be inline rdoc-style, edits to this README, and/or extra files in ./docs -- as appropriate for what needs to be docs.

TODO

• Unicode normalization. Has to normalize to NFKC on way out to index. Except for serialized marc field and other exceptions? Except maybe don't have to, rely on solr analyzer to do it?

  • Should it normalize to NFC on the way in, to make sure translation maps and other string comparisons match properly?
  • Either way, all optional/configurable of course. based on Settings.

• CommandLine class isn't covered by tests -- it's written using functionality from Indexer and other classes taht are well-covered, but the CommandLine itself probably needs some tests -- especially covering error handling, which probably needs a bit more attention and using exceptions instead of exits, etc.

• Optional built-in jetty stop/start to allow indexing to Solr that wasn't running before. maybe https://github.com/projecthydra/jettywrapper ?