Elastijk - A specialized Elasticsearch client.
use Elastijk;
my ($status, $response) = Elastijk::request({
host => "localhost",
port => "9200",
method => "GET",
index => "blog",
type => "article",
command => "_search",
uri_param => { search_type => "dfs_query_then_fetch" },
body => {
query => { match => { "body" => "cpan" } }
}
});
if ($status eq "200") {
for my $hit (@{ $response->{hits}{hits} }) {
say $hit->{url};
}
}
Elastijk is a Elasticsearch client library. It uses Hijk, a HTTP client that implements a tiny subset of HTTP/1.1 just enough to talk to Elasticsearch via HTTP.
Elastijk provided low-level functions that are almost identical as using HTTP client, and an object-oriented sugar layer to make it a little bit easier to use. The following documentation describe the low-level function first.
Making a request to the Elasticsearch server specified in $args
. It returns 2
values. $status
is the HTTP status code of the response, and the $response
decoded as HashRef. Elasticsearch API always respond a single HashRef as JSON
text, this might or might not be changed in the future, if it is changed then
this function will be adjusted accordingly.
The $args
is a HashRef takes contains the following key-value pairs:
host => Str
port => Str
index => Str
type => Str
id => Str
command => Str
uri_param => HashRef
body => HashRef | ArrayRef | Str
method => "GET" | "POST" | "HEAD" | "PUT" | "DELETE"
The 4 values of index
, type
, id
, command
are used to form the URI
path following Elasticsearch's routing convention:
/${index}/${type}/${id}/${command}
All these path parts are optional, when that is the case, Elstaijk properly
remove /
in between to form the URL that makes sense, for example:
/${index}/${type}/${id}
/${index}/${command}
The value of uri_param
is used to form the query_string part in the URI, some
common ones for Elasticsearch are q
, search_type
, and timeout
. But the
accepted list is different for different commands.
The value of method
corresponds to HTTP verbs, and is hard-coded to match
Elasticsearch API. Users generally do not need to provide this value, unless you
are calling request
directly, in which case, the default value is 'GET'.
For all cases, Elastijk simply bypass the value it receive to the server without doing any parameter validation. If that generates some errors, it'll be on server side.
Making a request to the Elasticsearch server specified in $args
. The main
difference between this function and Elastijk::request
is that
$args-
{body}> s expected to be a String scalar, rather then a HashRef. And
the $response is not decoded from JSON. This function can be used if users wish
to use their own JSON parser to parse response, or if they wish to delay the
parsing to be done latter in some bulk-processing pipeline.
An Elastijk object is constructed like this:
my $es = Elastijk->new(
host => "es1.example.com",
port => "9200"
);
Under the hood, it is only a blessed hash, while all key-value pairs in the hash are the properties. Users could break the packaging and modify those values, but it is fine. All key-value pairs are shallow-copied from `new` method.
Here's a full list of key-value pairs that are consumed:
host => Str "localhost"
port => Str "9200"
index => Str (optional)
type => Str (optional)
The values for index
and type
act like a "default" value and they are only
used in methods that could use them. Which is handy to save some extra typing.
Given objects constructed with different default of index
attribute:
$es0 = Elastijk->new();
$es1 = Elastijk->new( index => "foo" );
... calling the same search
method with the same arguments will generate
different request:
my @args = (uri_param => { q => "nihao" });
$es0->search( @args ); # GET /_search?q=nihao
$es1->search( @args ); # GET /foo/_search?q=nihao
This behavior is consistent for all methods.
All methods takes the same key-value pair HashRef as
Elastijk::request
function, and returns 2 values that are HTTP
status code, and the body hashref. The boilerplate of checking the
return values is something like:
my ($status, $res) = $es->search(...);
if (substr($status,0,1) eq '2') { # 2xx = successful
... $res->{hits} ...
}
The $res
contains the parsed response and it should be always a
HashRef, but it may be an ArrayRef. Elasticsearch server mostly
respond with a HTTP Body that is a valid JSON document -- but some
past version of Elasticsearch does not always follow that convention in
some APIs. Please consult the Elasticsearch API document link for the
hints of value type. Elastijk is a thin client, and that means itself
only assumes Elasticsearch servers response back with a valid JSON
document, and it decodes it to a perl data structure. Elastijk does as
little data transformation as possible to keep it a stupid, thin
client.
Due to how Perl handles multiple return values, you can omit the status check and just do:
my $res = $es->search(...);
... $res->{hits} ...
This style is by design for the convenience of developers, who can either worry about error checking latter, or throw the program away if it's just a one-timer.
Many of of methods are named after an server command. For example, the command
_search
corresponds to method search
, the command _bulk
corresponds to
method bulk
.
The status code is used for error-checking purposes. Elasticsearch should respond with status 4XX when the relevant thing is missing, and 5XX when there are some sort of errors. To check if a request is successful, test if it is 200 or 201.
Due to the fact the value of a lists is the last value of element, it is a little bit shorter if status check could be ignored:
my $res = $es->search(...);
for (@{ $res->{hits}{hits} }) {
...
}
count
and exists
method modified $res
to be a scalar (instead of
HashRef) to allow these intuitive use cases:
if ($es->exists(...)) { ... }
if ($es->count(...) > 10) { ... }
... the original response body are discarded.
This is a low-level method that just bypass things, but it is useful when, say,
newer Elasticsearch version introduce a new command, and there are no
corresponding method in the Client yet. The only difference between using this
method and calling Elasijk::request
directly, is that the values of
host
,port
,index
, and <type> ind the object context are consumed.
Shorthands for the HTTP verbs. All these are just direct delegate to request
method.
This method invokes the search api.
The arguments are key-value pairs from the API documents.
This method corresponds to the search count api
Check if the given thing exists. Which can be a document, a type, and an index. Due to the nature of their dependency, here's the combination you would need to check the existence of different things:
document: index => "foo", type => "bar", id => "beer"
type: index => "foo", type => "bar"
index: index => "foo"
A way to perform scan and scroll.
The boilerplate to use it is something like:
$es->scan_scroll(
index => "tweet",
body => { query => { match_all => {} }, size => 1000 },
on_response => sub {
my ($status,$res) = @_;
for my $hit (@{ $res->{hits}{hits} }) {
...
}
}
);
The "search_type" is forced to be "scan" in this method.
The very last value to the on_response
key is a callback subroutine that is
called after each HTTP request. The arguments are HTTP status code and response
body hash just like other methods.
The bulk
method is for doing commands via Elasticsearch bulk API
https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-bulk.html.
Unlike other methods, The bulk
method requires the value to the
body
key to be an ArrayRef. The elements of such ArrayRef are
HashRef that correspond to the request content described in the bulk
API document.
Notice that the request body of bulk API is not a valid JSON document as a whole, but just a naive concatenation of multiple JSON documents.
Kang-min Liu gugod@gugod.org and Borislav Nikolov jack@sofialondonmoskva.com
Copyright (c) 2013-2016 Kang-min Liu <gugod@gugod.org>
.
The MIT License
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