handler_base.hpp

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#pragma once
 
/// @file userver/server/handlers/handler_base.hpp
/// @brief @copybrief server::handlers::HandlerBase
 
#include <userver/components/component_base.hpp>
#include <userver/server/handlers/exceptions.hpp>
#include <userver/server/handlers/handler_config.hpp>
#include <userver/server/request/request_base.hpp>
#include <userver/server/request/request_context.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace server::handlers {
 
// clang-format off
 
/// @brief Base class for the request handlers.
///
/// Each handler has an associated path and invoked only for the requests for
/// that path.
///
/// ## Static options:
/// Name | Description | Default value
/// ---- | ----------- | -------------
/// path | if a request matches this path wildcard then process it by handler | -
/// as_fallback | set to "implicit-http-options" and do not specify a path if this handler processes the OPTIONS requests for paths that do not process OPTIONS method | -
/// task_processor | a task processor to execute the requests | -
/// method | comma-separated list of allowed HTTP methods. HEAD method is implicitly enabled if GET method is enabled | -
/// max_request_size | max size of the whole request | 1024 * 1024
/// max_headers_size | max request headers size | 65536
/// parse_args_from_body | optional field to parse request according to x-www-form-urlencoded rules and make parameters accessible as query parameters | false
/// auth | server::handlers::auth::HandlerAuthConfig authorization config | -
/// url_trailing_slash | 'both' to treat URLs with and without a trailing slash as equal, 'strict-match' otherwise | 'both'
/// max_requests_in_flight | integer to limit max pending requests to this handler | <no limit>
/// request_body_size_log_limit | trim request to this size before logging | 512
/// request_headers_size_log_limit | limit on the total length of logged headers | 512
/// response_data_size_log_limit | trim responses to this size before logging | 512
/// max_requests_per_second | integer to limit RPS to this handler | <no limit>
/// decompress_request | allow decompression of the requests | true
/// throttling_enabled | allow throttling of the requests by components::Server , for more info see its `max_response_size_in_flight` and `requests_queue_size_threshold` options | true
/// set-response-server-hostname | set to true to add the `X-YaTaxi-Server-Hostname` header with instance name, set to false to not add the header | <takes the value from components::Server config>
/// monitor-handler | Overrides the in-code `is_monitor` flag that makes the handler run either on `server.listener` or on `server.listener-monitor` | --
/// set_tracing_headers | whether to set http tracing headers (X-YaTraceId, X-YaSpanId, X-RequestId) | true
/// deadline_propagation_enabled | when `false`, disables HTTP handler @ref scripts/docs/en/userver/deadline_propagation.md "deadline propagation" | true
/// deadline_expired_status_code | the HTTP status code to return if the request @ref scripts/docs/en/userver/deadline_propagation.md "deadline expires" | 498
 
// clang-format on
class HandlerBase : public components::ComponentBase {
public:
    HandlerBase(
        const components::ComponentConfig& config,
        const components::ComponentContext& component_context,
        bool is_monitor = false
    );
    ~HandlerBase() noexcept override = default;
 
    /// Parses request, executes processing routines, and fills response
    /// accordingly. Does not throw.
    virtual void HandleRequest(request::RequestBase& request, request::RequestContext& context) const = 0;
 
    /// Produces response to a request unrecognized by the protocol based on
    /// provided generic response. Does not throw.
    virtual void ReportMalformedRequest(request::RequestBase&) const {}
 
    /// Returns whether this is a monitoring handler.
    bool IsMonitor() const { return is_monitor_; }
 
    /// Returns handler config.
    const HandlerConfig& GetConfig() const;
 
    static yaml_config::Schema GetStaticConfigSchema();
 
protected:
    // Pull the type names in the handler's scope to shorten throwing code
    using HandlerErrorCode = handlers::HandlerErrorCode;
    using InternalMessage = handlers::InternalMessage;
    using ExternalBody = handlers::ExternalBody;
 
    using ClientError = handlers::ClientError;
    using InternalServerError = handlers::InternalServerError;
 
private:
    bool is_monitor_;
    HandlerConfig config_;
};
 
}  // namespace server::handlers
 
USERVER_NAMESPACE_END