NAME

Neo4j::Driver - Perl implementation of the Neo4j Driver API

VERSION

version 0.13

SYNOPSIS

 use Neo4j::Driver;
 my $uri = 'http://localhost';
 my $driver = Neo4j::Driver->new($uri)->basic_auth('neo4j', 'password');
 
 sub say_friends_of {
   my $query = 'MATCH (a:Person)-[:KNOWS]->(f) '
             . 'WHERE a.name = {name} RETURN f.name';
   my $records = $driver->session->run($query, name => shift)->list;
   foreach my $record ( @$records ) {
     say $record->get('f.name');
   }
 }
 
 say_friends_of 'Alice';

DESCRIPTION

This is an unofficial Perl implementation of the Neo4j Driver API. It enables interacting with a Neo4j database server using the same classes and method calls as the official Neo4j drivers do.

This driver extends the uniformity across languages, which is a stated goal of the Neo4j Driver API, to Perl. The downside is that this driver doesn't offer fully-fledged object bindings like the existing REST::Neo4p module does. Nor does it offer any DBI integration. However, it avoids the legacy cypher endpoint, assuring compatibility with future Neo4j versions.

As of version 0.13, the interface of this software may be considered stable.

However, bugs may still exist. Also, experimental features may be changed or deprecated at any time. If you find yourself reliant on an experimental feature, please file a new issue requesting that it be made stable.

There is an ongoing effort to clean up the experimental features. For each of them, the goal is to eventually either declare it stable or deprecate it. There is also ongoing work to further improve general stability and reliability of this software. However, there is no schedule for the completion of these efforts.

METHODS

Neo4j::Driver implements the following methods.

basic_auth

 $driver->basic_auth('neo4j', 'password');

Set basic auth credentials with a given user and password. This method returns the modified Neo4j::Driver object, so that method chaining is possible.

 my $session = $driver->basic_auth('neo4j', 'password')->session;

new

 my $driver = Neo4j::Driver->new('http://localhost');

Construct a new Neo4j::Driver object. This object holds the details required to establish connections with a Neo4j database, including server URIs, credentials and other configuration.

The URI passed to this method determines the type of driver created. Only the http URI scheme is currently supported.

If a part of the URI or even the entire URI is missing, suitable default values will be substituted. In particular, the host name localhost will be used as default, along with the default port of the selected protocol.

 # all of these are semantically equal
 my $driver = Neo4j::Driver->new;
 my $driver = Neo4j::Driver->new('localhost');
 my $driver = Neo4j::Driver->new('http://localhost');
 my $driver = Neo4j::Driver->new('http://localhost:7474');

session

 my $session = $driver->session;

Creates and returns a new Session.

EXPERIMENTAL FEATURES

Neo4j::Driver implements the following experimental features. These are subject to unannounced modification or removal in future versions. Expect your code to break if you depend upon these features.

Bolt support

 my $driver = Neo4j::Driver->new('bolt://localhost');

Thanks to Neo4j::Bolt, there is now skeletal support for the Bolt Protocol, which can be used as an alternative to HTTP to connect to the Neo4j server.

The design goal is for this driver to eventually offer equal support for Bolt and HTTP. At this time, using Bolt with this driver is not recommended, although it sorta-kinda works. The biggest issues include: Unicode is not supported in Neo4j::Bolt, libneo4j-client error reporting is unreliable, summary information reported by Neo4j::Bolt is incomplete, and graph meta data supplied by Neo4j::Bolt is unreliable and has a different format than when the HTTP transport is used.

Additionally, there are incompatibilities with other "experimental" features of this driver, and parts of the documentation still assume that HTTP is the only option.

TLS encryption is disabled in early versions of Neo4j::Bolt. If you need remote access, consider using HTTPS instead of Bolt.

HTTPS support

 my $driver = Neo4j::Driver->new('https://localhost');
 $driver->config(ca_file => 'neo4j/certificates/neo4j.cert');

Using HTTPS will result in an encrypted connection. In order to rule out a man-in-the-middle attack, the server's certificate must be verified. By default, this driver may be expected to use operating system default root certificates (not really tested yet). This will fail unless your Neo4j installation uses a key pair that is trusted and verifiable through the global CA infrastructure. For self-signed certificates (such as those automatically provided by some Neo4j versions), you need to specify the location of a local copy of the server certificate. The driver config option ca_file may be used for this; it corresponds to SSL_ca_file in LWP::UserAgent and IO::Socket::SSL.

See also the Neo4j Operations Manual for details on Neo4j network security.

Close method

 $driver->close;  # no-op

All resources opened by this driver are closed automatically once they are no longer required. Explicit calls to close() are neither required nor useful.

HTTP Timeout

 $driver->{http_timeout} = 10;  # seconds

A timeout in seconds for making HTTP connections to the Neo4j server. If a connection cannot be established before timeout, a local error will be triggered by this client.

The default timeout currently is 6 seconds.

Mutability

 my $session1 = $driver->basic_auth('user1', 'password')->session;
 my $session2 = $driver->basic_auth('user2', 'password')->session;
 
 my $session1 = $driver->session;
 $driver->{http_timeout} = 30;
 $driver->{die_on_error} = 0;
 my $session2 = $driver->session;

The official Neo4j drivers are explicitly designed to be immutable. As this driver currently has a much simpler design, it can afford mutability, but applications shouldn't depend upon it.

The modifications will not be picked up by existing sessions. Only sessions that are newly created after making the changes will be affected.

Suppress exceptions

 my $driver = Neo4j::Driver->new;
 $driver->{die_on_error} = 0;
 my $result = $driver->session->run('...');

The default value of the die_on_error attribute is 1. Setting this to 0 causes the driver to no longer die on server errors.

This is much less useful than it sounds. Not only is the StatementResult structure not well-defined for such situations, but also the internal state of the Transaction object may be corrupted. For example, when a minor server error occurs on the first request (which would normally establish the connection), the expected Location header may be missing from the error message and the transaction may therefore be marked as closed, even though it still is open.

Additionally, client errors (such as trying to call single() on a result with multiple result records) currently still will cause the driver to die.

This feature will likely be removed in a future version. Use eval, Try::Tiny or similar instead.

ENVIRONMENT

This software currently targets Neo4j versions 2.3, 3.x and 4.x.

This software requires at least Perl 5.10, though you should consider using Perl 5.16 or newer if you can.

PERFORMANCE

Preliminary testing seems to indicate the two major bottlenecks are the HTTP transport to and from the Neo4j server, and the JSON parsing. Switching to the experimental Bolt protocol support may well increase the speed tenfold. You are encouraged to run your own tests for your specific application.

DIAGNOSTICS

Neo4j::Driver currently dies as soon as an error condition is discovered. Use eval, Try::Tiny or similar to catch this.

Warnings are given when deprecated or ambiguous method calls are used. These warnings may be disabled if desired.

 no warnings 'deprecated';
 no warnings 'ambiguous';

BUGS

See the TODO document and Github for known issues and planned improvements. Please report new issues and other feedback on Github.

Just like the official Neo4j drivers, this driver has been designed to strike a balance between an idiomatic API for Perl and a uniform surface across all languages. Differences between this driver and the official Neo4j drivers in either the API or the behaviour are generally to be regarded as bugs unless there is a compelling reason for a different approach in Perl.

Due to lack of resources, only the Neo4j community edition is targeted by this driver at present.

SEE ALSO

Neo4j::Driver::Session, Neo4j Drivers Manual, Neo4j HTTP API Docs, REST::Neo4p

AUTHOR

Arne Johannessen <ajnn@cpan.org>

COPYRIGHT AND LICENSE

This software is Copyright (c) 2016-2019 by Arne Johannessen.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)