Elasticsearch C++ Client: Complete Guide to Working with the Search Engine

Elasticsearch C++ Client: A Powerful Tool for High-Performance Search

Elasticsearch is a distributed search engine based on Apache Lucene, widely used for full-text search, log analysis, and processing large volumes of data. Although there is no official client for C++, developers can effectively interact with Elasticsearch via the REST API using the elasticlient library — a lightweight C++ client specifically created for working with Elasticsearch.

The elasticlient library provides a convenient interface for performing all basic operations: indexing documents, searching, updating, deleting, and cluster management. It is built on top of the libcurl library for HTTP requests and nlohmann/json for working with JSON, ensuring high performance and compatibility with modern C++17/20 standards.

Key Features of elasticlient

• Full support for the Elasticsearch REST API (versions 6.x, 7.x, and 8.x)
• Asynchronous and synchronous requests
• Automatic JSON serialization/deserialization via nlohmann/json
• Support for bulk operations for mass data loading
• Index management (creation, deletion, mapping configuration)
• Working with search queries (match, term, range, bool, etc.)
• Error handling and connection retries

Installation and Configuration

To install elasticlient, you can use CMake and vcpkg or build it manually. The recommended method is via vcpkg:

# Installation via vcpkgvcpkg install elasticlient

# Integration in CMakeLists.txtfind_package(elasticlient REQUIRED)target_link_libraries(my_app PRIVATE elasticlient::elasticlient)

Dependencies are also required:

• libcurl (with HTTPS support)
• nlohmann/json (version 3.9+)
• C++ compiler with C++17 support (GCC 8+, Clang 7+, MSVC 2019+)

Basic Usage Examples

Connecting to Elasticsearch

#include <elasticlient/client.h>

int main() {    // Creating a client connected to a local instance    elasticlient::Client client("http://localhost:9200");        // Checking the connection    auto status = client.get("/");    if (status.statusCode() == 200) {        std::cout << "Connected to Elasticsearch!" << std::endl;    }    return 0;}

Indexing a Document

#include <elasticlient/client.h>#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main() {    elasticlient::Client client("http://localhost:9200");        // Creating a document    json document = {        {"title", "Introduction to C++"},        {"author", "Ivan Petrov"},        {"year", 2023},        {"tags", {"programming", "C++", "textbook"}}    };        // Indexing into the "books" index with ID "1"    auto response = client.index("books", "_doc", "1", document.dump());        if (response.statusCode() == 201) {        std::cout << "Document indexed successfully!" << std::endl;    }    return 0;}

Searching Documents

#include <elasticlient/client.h>#include <iostream>

int main() {    elasticlient::Client client("http://localhost:9200");        // Search query    json query = {        {"query", {            {"match", {                {"title", "C++"}            }}        }}    };        auto response = client.search("books", "_search", query.dump());        if (response.statusCode() == 200) {        auto results = json::parse(response.body());        for (const auto& hit : results["hits"]["hits"]) {            std::cout << "Found: " << hit["_source"]["title"] << std::endl;        }    }    retu