/ 
Net-Z3950-FOLIO-1.4
River stage zero No dependents
/ Net::Z3950::FOLIO::Config

NAME

Net::Z3950::FOLIO::Config - configuration file for the FOLIO Z39.50 gateway

SYNOPSIS

  {
    "okapi": {
      "url": "https://folio-snapshot-okapi.dev.folio.org",
      "tenant": "${OKAPI_TENANT-indexdata}"
    },
    "login": {
      "username": "diku_admin",
      "password": "${OKAPI_PASSWORD}"
    },
    "indexMap": {
      "1": "author",
      "7": "identifiers/@value/@identifierTypeId=\"8261054f-be78-422d-bd51-4ed9f33c3422\"",
      "4": "title",
      "12": {
        "cql": "hrid",
        "relation": "==",
        "omitSortIndexModifiers": [ "missing", "case" ]
      },
      "21": "subject",
      "1016": "author,title,hrid,subject"
    },
    "queryFilter": "source=marc",
    "graphqlQuery": "instances.graphql-query",
    "chunkSize": 5
    "postProcessing": {
      "marc": {
	"008": { "op": "regsub", "pattern": "([13579])", "replacement": "[$1]", "flags": "g" },
	"245$a": [
	  { "op": "stripDiacritics" },
	  { "op": "regsub", "pattern": "[abc]", "replacement": "*", "flags": "g" }
	]
      }
    }
  }

DESCRIPTION

The FOLIO Z39.50 gateway z2folio is configured by a stacking set of JSON files whose basename is specified on the command-line. These files specify how to connect to FOLIO, how to log in, and how to search.

The structure of each of these file is the same, and the mechanism by which they are stacked is described below. The shared format is simple. There are several top-level sections, each described in its own section below, and each of them is an object with several keys that can exist in it.

If any string value contains sequences of the form ${NAME}, they are each replaced by the values of the corresponding environment variables $NAME, providing a mechanism for injecting values into the configuration. This is useful if, for example, it is necessary to avoid embedding authentication secrets in the configuration file.

When substituting environment variables, the bash-like fallback syntax ${NAME-VALUE} is recognised. This evaluates to the value of the environment variable $NAME when defined, falling back to the constant value VALUE otherwise. In this way, the configuration can include default values which may be overridden with environment variables.

okapi

Contains three elements (two mandatory, one optional), all with string values:

url

The full URL to the Okapi server that provides the gateway to the FOLIO installation.

graphqlUrl (optional)

Usually, the main Okapi URL is used for all interaction with FOLIO: logging in, searching, retrieving records, etc. When the optional graphqlUrl configuration entry is provided, it is used for GraphQL queries only. This provides a way of "side-loading" mod-graphql, which is useful in at least two situations: when the FOLIO snapshot services are unavailable (since the production services do not presently included mod-graphql); and when you need to run against a development version of mod-graphql so you can make changes to its behaviour.

tenant

The name of the tenant within that FOLIO installation whose inventory model should be queried.

login

Contains two elements, both with string values:

username

The name of the user to log in as, unless overridden by authentication information in the Z39.50 init request.

password

The corresponding password, unless overridden by authentication information in the Z39.50 init request.

indexMap

Contains any number of elements. The keys are the numbers of BIB-1 use attributes, and the corresponding values contain instructions about the indexes in the FOLIO instance record to map those access-points to. The key default is special, and is used for terms where no BIB-1 use attribute is specified.

Each value may be either a string, in which case it is interpreted as a CQL index to map to (see below for details), or an object. When the object version is used, that object's cql member contains the CQL index mapping (see below), and any of the following additional members may also be included:

omitSortIndexModifiers

A bug in FOLIO's CQL query interpreter means that for some indexes, query translation will fail if a sort-specification is provided that requests certain valid behaviours, e.g. a case-sensitive search on the HRID index. To work around this until it's fixed, an index's omitSortIndexModifiers allows you to specify a list of the index-modifier types that they do not support, so that the server can omit those qualifiers when creating sort-specifications. The valid index-modifier types are missing, relation and case.

relation

If specified, the value is the relation that should be used instead of = by default when searching in this index. This is useful mostly for defaulting to the strict-equality relation == for indexes whose values are atomic, such as identifiers.

Each cql value (or string value when the object form is not used) may be a comma-separated list of multiple CQL indexes to be queried.

Each CQL index specified as a value, or as one of the comma-separated components of a value, may contain a forward slash. If it does, then the part before the slash is used as the actual index name, and the part after the slash as a CQL relation modifier. For example, if the index map contains

"999": "foo/bar=quux"

Then a search for @attr 1=9 thrick will be translated to the CQL query foo =/bar=quux thrick.

queryFilter

If specified, this is a CQL query which is automatically anded with every query submitted by the client, so it acts as a filter allowing through only records that satisfy it. This might be used, for example, to specify source=marc to limit search result to only to those FOLIO instance records that were translated from MARC imports.

graphqlQuery

The name of a file, in the same directory as the main configuration file, which contains the text of the GraphQL query to be used to obtain the instance, holdings and item data pertaining to the records identified by the CQL query.

chunkSize

An integer specifying how many records to fetch from FOLIO with each search. This can be tweaked to tune performance. Setting it too low will result in many requests with small numbers of records returned each time; setting it too high will result in fetching and decoding more records than are actually wanted.

postProcessing

Specifies sets of transformations to be applied to the values of fields retrieved from the back-end. At present, the only supported key is marc, which specifies transformations to be applied to MARC records (either standalone or as part of OPAC records); in the future, post-processing for JSON and XML records may also be supported.

Within the marc sections, keys are the names of simple MARC fields, such as 008; or of complex field$subfield combinations, such as 245$a. The corresponding values specify the transformations that should be applied to the values of these fields and subfields.

Transformations are represented by objects with an op key whose values specifies the required operation. Either single transformation or an array of transformations may be provided.

The following transformation operations are supported:

stripDiacritics

All diacritics are stripped from the value in the relevant field: for example, délétère becomes deletere.

regsub

A regular expression substitution is performed on the value in the relevant field, as specified by the parameters in the transformation object:

pattern

A regular expression intended to matching some part of the field value. This is Perl regular expression, as overviewed in perlretut and fully documented in perlre and as such supports advanced facilities such as back-references.

replacement

The string with which to replace the part of the field value that matches the pattern. This may include numbered references $1, $2, etc., to parenthesized sub-expressions in the pattern. (If this statement means nothing to you, you need to go and read about regular expressions.)

flags

Optionally, a set of flags such as g for global replacement, i for case-insensitivity, etc. See Using regular expressions in Perl.

For example, the MARC post-processing directive

"245$a": [
  { "op": "stripDiacritics" },
  { "op": "regsub", "pattern": "[abc]", "replacement": "*", "flags": "g" }
]

Says first to remove all diacritics from the 245$a (title) field of the MARC record (so that for example é becomes e), then to replace all vowels with asterisks.

CONFIGURATION STACKING

To implement both multi-tenancy and per-database output tweaks that may be required for specific Z39.50 client application, it is necessary to allow flexibility in the configuration of the server, based both on Z39.50 database name and on further specifications. Three levels of configuration are therefore supported.

  1. A base configuration file is always used, and will typically provide the bulk of the configuration that is the same for all supported databases. Its base name is specified when the server is invoked -- for example, as the argument to the -c command-line option of z2folio: when the server is invoked as z2folio -c etc/config the base configuration file is found at etc/config.json.

  2. The Z39.50 database name provided in a search is used as a name of a sub-configuration specific to that database. So for example, if a Z39.50 search request come in for the database theo, then the additional database-specific configuration file etc/config.theo.json is also consulted. Often this file will specify the FOLIO tenant to be used for this database.

    Values provided in a database-specific configuration are added to those of the base configuration, overriding the base values when the same item is provided at both levels.

  3. One or more filters may also be used to specify additional configuration. These are specified as part of the Z39.50 database name, separated from the main part of the name by pipe characters (|). For example, if the database name theo|foo|bar is used, then two additional filter-specific configuration files are also read, etc/config.foo.json and etc/config.bar.json. The values of filter-specific configurations override those of the base or database-specific configuration, and those of later filters override those of earlier filters.

In the example used here, then, a server launched with z2folio -c etc/config and serving a search against the Z39.50 database theo|foo|bar will consult four configuration files: etc/config.json, etc/config.theo.json (if present), etc/config.foo.json and etc/config.bar.json.

This scheme allows us to handle several scenarios in a uniform way:

  • Basic configuration all in one place

  • Database-specific overrides, such as the FOLIO tenant and any customer-specific definition of ISBN searching (see issue ZF-24) in the database configuration, leaving the standard definition to apply to other tenants.

  • Application-specific overrides, such as those needed by the ABLE client (see issue ZF-25), specified only in a filter that is not used except when explicitly requested.

SEE ALSO

The z2folio script conveniently launches the server.
Net::Z3950::FOLIO is the library that consumes this configuration.
The Net::Z3950::SimpleServer handles the Z39.50 service.

AUTHOR

Mike Taylor, <mike@indexdata.com>

COPYRIGHT AND LICENSE

Copyright (C) 2018 The Open Library Foundation

This software is distributed under the terms of the Apache License, Version 2.0. See the file "LICENSE" for more information.