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What is a document? An object is equivalent to a record record of mysql

[document]

What is a document?

Most entities or objects in the program can be serialized into JSON objects that contain key-value pairs. Key is the name of a field (field) or property. A value can be a string, a number, a Boolean type, another object, an array of values, or other special types, such as a string that represents a date or an object that represents a geographic location.

{"name": "John Smith", "age": 42, "confirmed": true, "join_date": "2014-06-01", "home": {"lat": 51.5, "lon": 0.1}, "accounts": [{"type": "facebook" "id": "johnsmith"}, {"type": "twitter", "id": "johnsmith"}]}

In general, we can assume that objects (object) and documents (document) are equivalent. However, there are differences: an object (Object) is a JSON structure-- similar to a hash, hashmap, dictionary, or associative array; an object (Object) may also contain other objects (Object). In Elasticsearch, the term document has a special meaning. It specifically refers to the JSON data serialized into the topmost structure or root object (root object) (identified by a unique ID and stored in Elasticsearch).

Document metadata

A document contains more than just data. It also contains metadata (metadata)-information about the document. The three required metadata nodes are:

Node description

_ where index documents are stored

Class of the object represented by the _ type document

Unique identification of _ id document

_ index

An index is similar to a "database" in a relational database-- it is where we store and index associated data.

Tip:

In fact, our data is stored and indexed in shards, which is just a logical space that groups one or more shards together. However, these are just internal details-our program doesn't care about fragmentation at all. For our program, the document is stored in the index. The remaining details can be taken care of by Elasticsearch.

We will discuss how to create and manage indexes in the "Index Management" section, but for now, we will have Elasticsearch create indexes for us. The only thing we need to do is choose an index name. The name must be all lowercase, cannot begin with an underscore, or contain a comma. Let's use website as the index name.

_ type

In applications, we use objects to represent "things", such as a user, a blog, a comment, or an email. Each object belongs to a class (class) that defines attributes or data associated with the object. Objects of the user class may contain name, gender, age, and Email address.

In relational databases, we often store similar objects in a table because they have the same structure. Similarly, in Elasticsearch, we use documents of the same type (type) to represent the same "things" because their data structures are the same. +

Each type (type) has its own mapping or structure definition, just like columns in traditional database tables. Documents under all types are stored under the same index, but the type mapping (mapping) tells Elasticsearch how different documents are indexed. We will discuss how to define and manage mappings in the "Mapping" section, but for now we will rely on Elasticsearch to automatically handle data structures.

The name of _ type can be uppercase or lowercase and cannot contain an underscore or comma. We will use blog as the type name.

_ id

Id is simply a string that, when combined with _ index and _ type, uniquely identifies a document in Elasticsearch. When creating a document, you can customize _ id, or you can have Elasticsearch automatically generate it for you.

Other metadata

There is also some other metadata, which we will discuss in the "Mapping" section. Using the elements mentioned above, we can already store documents in Elasticsearch and retrieve them through ID-in other words, using Elasticsearch as a document store.

[index] based on the HTTP protocol, RESTful API with JSON as the data exchange format, all other programming languages can use RESTful API, communicate with Elasticsearch through port 9200, you can use your favorite WEB client, in fact, as you can see, you can even communicate with Elasticsearch through the curl command.

NOTE

Elasticsearch officially provides clients in multiple programming languages-Groovy,Javascript, .NET, PHP,Perl,Python, and Ruby---as well as many community-provided clients and plug-ins, all of which can be found in the documentation.

The components of a request to Elasticsearch are the same as other normal HTTP requests:

Curl-X': / /: /?'- d''

VERB HTTP method: GET, POST, PUT, HEAD, DELETE

PROTOCOL http or https protocol (available only if there is a https agent in front of Elasticsearch)

The hostname of any node in the HOST Elasticsearch cluster, if it is a local node, is called localhost

The port on which the PORT Elasticsearch HTTP service is located. Default is 9200.

PATH API path (for example, _ count will return the number of documents in the cluster), PATH can contain multiple components, such as _ cluster/stats or _ nodes/stats/jvm

QUERY_STRING some optional query request parameters, such as? pretty parameter, will make the request return more beautiful and readable JSON data

BODY a request body in JSON format (if the request is required)

For example, to calculate the number of documents in a cluster, we can do this:

Curl-XGET 'http://localhost:9200/_count?pretty'-d' {"query": {"match_all": {}'

For example, return the jvm information of all nodes

Curl-I 127.0.0.1:9200/_nodes/stats/jvm?pretty

[API-RESTful API]

Reference:

Http://www.learnes.net/data/README.html

Curl 192.168.100.10:9200?preetycurl 192.168.100.10:9200/_count?pretty

The usage of curl in shell

-X specifies that the request method defaults to-XGET

-I when the data is returned, the request result is also returned

-d sent data

View the status of elk:

Curl 192.168.100.10:9200/_cluster/health?pretty

This return value means that our index request has been successfully created, which also contains metadata for _ index, _ type, and _ id, as well as a new element _ version

The noun _ index is the equivalent of a library in a database.

_ type is equivalent to a table in a database

_ id is id (can be specified or incremented by yourself)

_ index and _ type and _ id constitute the uniqueness of the data in elasticsearch storage.

Create a

Curl-XPUT 192.168.100.10:9200/website/blog/123-d'{"title": "My first blog entry", "text": "Just trying this out...", "date": "2016-01-01"}'

You can see that the document created at that time was found by search.

[root@master ~] # curl 192.168.100.10:9200/website/blog/123?pretty {"_ index": "website", "_ type": "blog", "_ id": "123"," _ version ": 1," found ": true," _ source ": {" title ":" My first blog entry "," text ":" Just trying this out... " "date": "2014-01-01"}

For every situation found:

[root@master ~] # curl 192.168.100.10:9200/website/blog/1235?pretty {"_ index": "website", "_ type": "blog", "_ id": "1235", "found": false}

_ source is the content of the document. You can specify a value to return the field specified by the document

[root@master] # curl-I-XGET "192.168.100.10 HTTP/1.1 9200 OKContent-Type OKContent-Type: application/json Charset=UTF-8Content-Length: 185 {"_ index": "logstash-2016.05.12", "_ type": "syslog", "_ id": "AVSlIBy3bzztddJUaGzh", "_ version": 1, "found": true, "_ source": {"file": "/ var/log/messages"}}

Get more than one document at a time _ mget

[root@master ~] # curl-I-XGET 192.168.100.10:9200/logstash-2016.05.12/syslog/_mget?pretty-d'{"ids": ["2", "1"]} 'HTTP/1.1 200 OKContent-Type: application/json Charset=UTF-8Content-Length: 230 {"docs": [{"_ index": "logstash-2016.05.12", "_ type": "syslog", "_ id": "2", "found": false}, {"_ index": "logstash-2016.05.12", "_ type": "syslog", "_ id": "1" "found": false}]}

Too many indexes will accumulate and need to be deleted regularly, such as those a month ago. (you cannot use rm-rf to delete the index directory under data, because elk is distributed, and the replication shards of other nodes will be synchronized.)

# Delete indices

Curl-XDELETE "http://localhost:9200/access-log-2016.12.02/"

# Delete multiple indices

Curl-XDELETE "http://localhost:9200/access-log-2015.12.*/"

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