### Execute KrakenD with Flexible Configuration

Source: https://www.krakend.io/docs/throttling/cluster

This example demonstrates how to start KrakenD with Flexible Configuration enabled, specifying an output file for the compiled configuration and setting the `NUM_PODS` environment variable. This allows the `max_rate` in the configuration to be dynamically calculated.

```bash
$FC_ENABLE=1 \
FC_OUT=compiled.json \
NUM_PODS=3 krakend check -c krakend.json
```

--------------------------------

### Install KrakenD Integration Tests Tool

Source: https://www.krakend.io/docs/developer/integration-tests

Installs the KrakenD integration test tool using Go. Ensure you have Go installed on your machine or in a Docker container.

```bash
$go install github.com/krakend/krakend-ce/v2/cmd/krakend-integration@v2.13.7

```

--------------------------------

### Initialize Go Module and Create Project Directory

Source: https://www.krakend.io/docs/enterprise/extending/http-server-plugins

Sets up a new Go project for a KrakenD server plugin.

```bash
mkdir krakend-server-example
cd krakend-server-example
go mod init krakend-server-example

```

--------------------------------

### Install KrakenD on CentOS/Oracle/Redhat (yum)

Source: https://www.krakend.io/docs/overview/installing

Install KrakenD on yum-based Linux distributions. This involves adding the repository, installing the package, and starting the service.

```bash
$rpm -Uvh https://repo.krakend.io/rpm/krakend-repo-0.2-0.x86_64.rpm
yum install -y krakend
systemctl start krakend
```

--------------------------------

### Install KrakenD Enterprise on Fedora

Source: https://www.krakend.io/docs/enterprise/overview/installing

Installs KrakenD Enterprise using DNF. This involves adding the repository, installing the package, and starting the service.

```bash
$rpm -Uvh https://download.krakend.io/rpm/krakend-ee-repo-2.1-0.x86_64.rpm
dnf install -y krakend-ee
systemctl start krakend-ee
```

--------------------------------

### Create Go Project for Krakend Server Example

Source: https://www.krakend.io/docs/extending/http-server-plugins

Initializes a new Go project for developing a KrakenD server plugin.

```bash
mkdir krakend-server-example
cd krakend-server-example
go mod init krakend-server-example
```

--------------------------------

### Install KrakenD Enterprise on CentOS/Rocky/Redhat

Source: https://www.krakend.io/docs/enterprise/overview/installing

Installs KrakenD Enterprise using Yum. This involves adding the repository, installing the package, and starting the service.

```bash
$rpm -Uvh https://download.krakend.io/rpm/krakend-ee-repo-2.1-0.x86_64.rpm
yum install -y krakend-ee
systemctl start krakend-ee
```

--------------------------------

### Configuration File Structure Example

Source: https://www.krakend.io/docs/configuration/templates

Illustrates a basic directory structure for organizing KrakenD configuration files when using the flexible configuration system.

```bash
.
├── krakend.tmpl
├── partials
│   └── all_backends_extra_config.json
└── settings
    ├── endpoint.json
    └── service.json

```

--------------------------------

### Install KrakenD on Fedora (dnf)

Source: https://www.krakend.io/docs/overview/installing

Install KrakenD on Fedora using the dnf package manager. This process includes adding the repository, installing the package, and starting the service.

```bash
$rpm -Uvh https://repo.krakend.io/rpm/krakend-repo-0.2-0.x86_64.rpm
dnf install -y krakend
systemctl start krakend
```

--------------------------------

### cURL Request for GET Mutation

Source: https://www.krakend.io/docs/backends/graphql

Example cURL command to send a GET request to KrakenD, triggering a GraphQL mutation with variables passed in the URL.

```bash
$curl -d '' -G http://krakend/review/5

```

--------------------------------

### Initialize Go Project for Client Plugin

Source: https://www.krakend.io/docs/enterprise/extending/http-client-plugins

Sets up a new Go project and initializes its module for developing a Krakend HTTP client plugin.

```bash
mkdir krakend-client-example
cd krakend-client-example
go mod init krakend-client-example

```

--------------------------------

### MCP Entrypoint Configuration Example

Source: https://www.krakend.io/docs/enterprise/ai-gateway/mcp-server

This example shows how to define endpoints that act as entrypoints for MCP servers. Ensure the 'server_name' matches the MCP server definition.

```json
{
  "version": 3,
  "endpoints": [
    {
      "endpoint": "/mcp",
      "method": "POST",
      "timeout": "10s",
      "backend": [
        {
          "url_pattern": "/ignore",
          "host": [
            "ignore"
          ]
        }
      ],
      "extra_config": {
        "ai/mcp": {
          "server_name": "webcam-status"
        }
      }
    },
    {
      "endpoint": "/mcp",
      "method": "DELETE",
      "@comment": "Allows the client to mark the session as deleted to free up memory",
      "backend": [
        {
          "url_pattern": "/ignore",
          "host": [
            "ignore"
          ]
        }
      ],
      "extra_config": {
        "ai/mcp": {
          "server_name": "webcam-status"
        }
      }
    }
  ]
}
```

--------------------------------

### GET + Mutation Example

Source: https://www.krakend.io/docs/enterprise/backends/graphql

Configure KrakenD for GET requests when performing mutations. Variables are passed as URL parameters, and the mutation is still sourced from an external file.

```json
{
    "endpoint": "/review/{stars}",
    "method": "GET",
    "backend": [
        {
            "timeout": "4100ms",
            "url_pattern": "/graphql?timeout=4s",
            "extra_config": {
                "backend/graphql": {
                    "type":  "mutation",
                    "query_path": "./graphql/mutations/review.graphql",
                    "variables": {
                        "review": {
                            "stars": "{stars}"
                        },
                        "ep": "JEDI",
                        "id_show": "1500"
                    },
                    "operationName": "CreateReviewForEpisode"
                }
            }
        }
    ]
}

```

```bash
$curl -d '' -G http://krakend/review/5
```

--------------------------------

### Plugin init command help

Source: https://www.krakend.io/docs/enterprise/extending/generating-plugins

Displays the help message for the `krakend plugin init` command, outlining its usage, available flags, and examples.

```bash
$krakend plugin init -h
```

--------------------------------

### URL Rewrite Configuration Example

Source: https://www.krakend.io/docs/enterprise/endpoints/url-rewrite

This example demonstrates how to configure the url-rewrite plugin within the extra_config section of your KrakenD setup. It includes both literal and regexp rewrites.

```json
{
    "version": 3,
    "plugin": {
        "pattern":".so",
        "folder": "/opt/krakend/plugins/"
    },
    "extra_config": {
      "plugin/http-server": {
        "name": ["url-rewrite", "some-other-plugin-here" ],
        "url-rewrite": {
          "literal": {
            "/hi-there": "/hello",
            "/whatsup": "/hello"
          },
          "regexp": [
            ["^/hi-there/([\w\d\s]+)/bar$", "/hello/${1}"],
            ["^/whats/up/([\w\d\s]+)$", "/hey/${1}/whatsup"]
          ]
        }
      }
    }
}


```

--------------------------------

### New Static Filesystem Configuration Example

Source: https://www.krakend.io/docs/enterprise/endpoints/serve-static-content

The equivalent KrakenD configuration after upgrading to the new static-filesystem namespace.

```json
{
    "version": 3,
    "extra_config": {
        "server/static-filesystem": {
            "prefix": "/media/",
            "path": "./../../assets",
            "skip": [
                "/media/ignore/this/directory",
                "/media/file.json"
            ],
        }
    }
}

```

--------------------------------

### Get the day of the month (0-indexed)

Source: https://www.krakend.io/docs/enterprise/security-policies/built-in-functions

The `getDayOfMonth` function returns the day of the month from a timestamp. The index starts at 0.

```go
// Given it's February 1st
timestamp(now).getDayOfMonth() // returns 0
```

--------------------------------

### Get the day of the month from a timestamp

Source: https://www.krakend.io/docs/enterprise/security-policies/built-in-functions

The `getDate` function extracts the day of the month from a timestamp. The index starts at 1.

```go
// Given it's February 1st
timestamp(now).getDate() // returns 1
```

--------------------------------

### Hello World HTTP Client Plugin Example

Source: https://www.krakend.io/docs/enterprise/extending/http-client-plugins

A basic 'Hello World' HTTP client plugin that intercepts requests to a specific path and returns a custom JSON response. It demonstrates the plugin structure, logger integration, and custom request handling.

```go
// SPDX-License-Identifier: Apache-2.0

package main

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"html"
	"io"
	"net/http"
)

// ClientRegisterer is the symbol the plugin loader will try to load. It must implement the RegisterClient interface
var ClientRegisterer = registerer("krakend-client-example")

type registerer string

var logger Logger = nil

func (registerer) RegisterLogger(v interface{}) {
	l, ok := v.(Logger)
	if !ok {
		return
	}
	logger = l
	logger.Debug(fmt.Sprintf("[PLUGIN: %s] Logger loaded", ClientRegisterer))
}

func (r registerer) RegisterClients(f func(
	name string,
	handler func(context.Context, map[string]interface{}) (http.Handler, error),
)) {
	f(string(r), r.registerClients)
}

func (r registerer) registerClients(_ context.Context, extra map[string]interface{}) (http.Handler, error) {
	// check the passed configuration and initialize the plugin
	name, ok := extra["name"].(string)
	if !ok {
		return nil, errors.New("wrong config")
	}
	if name != string(r) {
		return nil, fmt.Errorf("unknown register %s", name)
	}

	// check the cfg. If the modifier requires some configuration, 
	// it should be under the name of the plugin. E.g.:
	/*
	   "extra_config":{
	       "plugin/http-client":{
	           "name":"krakend-client-example",
	           "krakend-client-example":{
	               "path": "/some-path"
	           }
	       }
	   }
	*/

	// The config variable contains all the keys you have defined in the configuration:
	config, _ := extra["krakend-client-example"].(map[string]interface{})

	// The plugin will look for this path:
	path, _ := config["path"].(string)
	logger.Debug(fmt.Sprintf("The plugin is now hijacking the path %s", path))

	// return the actual handler wrapping or your custom logic so it can be used as a replacement for the default http handler
	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {

		// The path matches, it has to be hijacked and no call to the backend happens.
		// The path is the the call to the backend, not the original request by the user.
		if req.URL.Path == path {
			w.Header().Add("Content-Type", "application/json")
			// Return a custom JSON object:
			res := map[string]string{"message": html.EscapeString(req.URL.Path)}
			b, _ := json.Marshal(res)
			w.Write(b)
			logger.Debug("request:", html.EscapeString(req.URL.Path))

			return
		}

		// If the requested path is not what we defined, continue.
		resp, err := http.DefaultClient.Do(req)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}

		// Copy headers, status codes, and body from the backend to the response writer
		for k, hs := range resp.Header {
			for _, h := range hs {
				w.Header().Add(k, h)
			}
		}
		w.WriteHeader(resp.StatusCode)
		if resp.Body == nil {
			return
		}
		io.Copy(w, resp.Body)
		resp.Body.Close()

	}), nil
}

func main() {}

type Logger interface {
	Debug(v ...interface{})
	Info(v ...interface{})
	Warning(v ...interface{})
	Error(v ...interface{})
	Critical(v ...interface{})
	Fatal(v ...interface{})
}

```

--------------------------------

### OpenAPI Documentation for GET /users

Source: https://www.krakend.io/docs/enterprise/endpoints/openapi

This snippet demonstrates how to configure OpenAPI documentation for a GET endpoint. It includes a description, summary, operation ID, tags, audience, query parameter definition with a description, and a full example response.

```json
{
  "version": 3,
  "$schema": "https://www.krakend.io/schema/krakend.json",
  "host": [
    "http://localhost:8080"
  ],
  "debug_endpoint": true,
  "echo_endpoint": true,
  "endpoints": [
    {
      "endpoint": "/users",
      "method": "GET",
      "extra_config": {
        "documentation/openapi": {
          "description": "Lists all user in the system, paginated in blocks of 50 users",
          "summary": "List all users",
          "operation_id": "GET/users/id_user",
          "tags": [
            "users"
          ],
          "audience": [
            "internal"
          ],
          "query_definition": [
            {
              "name": "page",
              "required": false,
              "description": "Pass a ?page= if you want to use the pagination"
            }
          ],
          "response_definition": {
            "200": {
              "content_type": "application/json",
              "example": {
                "users": [
                  {
                    "id": 1,
                    "first_name": "Juliana",
                    "last_name": "Claire",
                    "email": "jclaire0@livejournal.com"
                  },
                  {
                    "id": 2,
                    "first_name": "Jeannette",
                    "last_name": "Hugonneau",
                    "email": "jhugonneau1@gmpg.org"
                  }
                ]
              }
            }
          }
        }
      },
      "backend": [
        {
          "url_pattern": "/api/1.0/users/list"
        }
      ]
    },
    {
      "endpoint": "/users/{id_user}",
      "method": "PUT",
      "extra_config": {
        "documentation/openapi": {
          "description": "The PUT method updates the data for the given id_user. You only need to pass the fields you want to update.",
          "summary": "Updates the user data",
          "operation_id": "PUT/users/id_user",
          "tags": [
            "users"
          ],
          "audience": [
            "internal"
          ],
          "request_definition": [
            {
              "content_type": "application/json",
              "description": "Updates provided fields. All fields are optional, id_user taken from the URL",
              "example": {
                "address": "Suite 543 907 Green Forks, Wavamouth, CT 10807-8479",
                "first_name": "Felix",
                "last_name": "Richardson"
              }
            }
          ],
          "response_definition": {
            "200": {
              "content_type": "application/json",
              "example": {
                "id_user": 33007,
                "status": "success"
              }
            }
          }
        }
      },
      "backend": [
        {
          "url_pattern": "/api/1.0/users/update/{id_user}"
        }
      ]
    }
  ]
}
```

--------------------------------

### Command-line Check for Flexible Configuration

Source: https://www.krakend.io/docs/configuration/flexible-config

This command-line example demonstrates how to check the syntax of flexible configuration files when not using Docker Compose. It utilizes environment variables to specify configuration paths and settings.

```bash
$FC_ENABLE=1 \
FC_SETTINGS="$PWD/config/settings" \
FC_PARTIALS="$PWD/config/partials" \
FC_TEMPLATES="$PWD/config/templates" \
FC_OUT=out.json \
krakend check -t -d -c "$PWD/config/krakend.json"

```

--------------------------------

### Check Plugin Command Example

Source: https://www.krakend.io/docs/extending/check-plugin

This example demonstrates how to use the `krakend check-plugin` command with flags to check for incompatibilities. It specifies the Go version, libc version, and the path to the go.sum file.

```bash
$krakend check-plugin --go 1.17.7 --libc MUSL-1.2.2 --sum ../plugin-tools/go.sum
15 incompatibility(ies) found...
go
    have: 1.17.0
    want: 1.16.4
libc
    have: MUSL-1.2.2
    want: GLIBC-2.31
github.com/gin-gonic/gin
    have: v1.6.3
    want: v1.7.7
github.com/go-playground/locales
    have: v0.13.0
    want: v0.14.0
github.com/go-playground/universal-translator
    have: v0.17.0
    want: v0.18.0
github.com/go-playground/validator/v10
    have: v10.2.0
    want: v10.9.0
github.com/golang/protobuf
    have: v1.3.3
    want: v1.5.2
github.com/json-iterator/go
    have: v1.1.9
    want: v1.1.12
github.com/leodido/go-urn
    have: v1.2.0
    want: v1.2.1
github.com/mattn/go-isatty
    have: v0.0.12
    want: v0.0.14
github.com/modern-go/concurrent
    have: v0.0.0-20180228061459-e0a39a4cb421
    want: v0.0.0-20180306012644-bacd9c7ef1dd
github.com/modern-go/reflect2
    have: v0.0.0-20180701023420-4b7aa43c6742
    want: v1.0.2
github.com/ugorji/go/codec
    have: v1.1.7
    want: v1.2.6
golang.org/x/sys
    have: v0.0.0-20200116001909-b77594299b42
    want: v0.0.0-20211004093028-2c5d950f24ef
golang.org/x/text
    have: v0.3.2
    want: v0.3.7
```

--------------------------------

### Get the day of the week from a timestamp

Source: https://www.krakend.io/docs/enterprise/security-policies/built-in-functions

The `getDayOfWeek` function returns the day of the week from a timestamp, starting with Sunday at index 0.

```go
timestamp(now).getDayOfWeek() // returns 0 on Sunday
timestamp(now).getDayOfWeek() // returns 1 on Monday
timestamp(now).getDayOfWeek() // returns 6 on Saturday
(timestamp(now).getDayOfWeek() + 6) % 7 <= 4 // returns false on weekend (Sat-Sun)
(timestamp(now).getDayOfWeek() + 6) % 7 <= 4 // returns true on weekdays (Mon-Fri)
```

--------------------------------

### Old Static Filesystem Configuration Example

Source: https://www.krakend.io/docs/enterprise/endpoints/serve-static-content

An example of a KrakenD configuration using the older static-filesystem plugin structure.

```json
{
    "version": 3,
    "plugin": {
        "pattern":".so",
        "folder": "/opt/krakend/plugins/"
    },
    "extra_config": {
        "plugin/http-server": {
            "name": ["static-filesystem", "another-plugin-maybe" ],
            "static-filesystem": {
                "prefix": "/media/",
                "path": "./../../assets",
                "skip": [
                    "/media/ignore/this/directory",
                    "/media/file.json"
                ],
            }
        }
    }
}
```

--------------------------------

### Get the day of the year from a timestamp

Source: https://www.krakend.io/docs/enterprise/security-policies/built-in-functions

The `getDayOfYear` function returns the day of the year from a timestamp, starting with index 0 for January 1st.

```go
timestamp(now).getDayOfYear() // returns 0 on January 1st
timestamp(now).getDayOfYear() // returns 10 on January 11th
```

--------------------------------

### gRPC Client Configuration Example

Source: https://www.krakend.io/docs/enterprise/backends/grpc

This example demonstrates the service-level 'grpc' catalog definition and a backend-level 'backend/grpc' configuration for connecting to a gRPC service. It shows how to load protocol buffer definitions and specify the backend host and URL pattern.

```json
{
  "version": 3,
  "extra_config": {
    "grpc": {
      "@comment": "The catalog loads all .pb files passed or contained in directories",
      "catalog": [
        "grpcatalog/flights/fligths.pb",
        "grpcatalog/known_types",
        "grpcatalog/third_parties"
      ]
    }
  },
  "endpoints": [
    {
      "@comment": "Feature: GRPC",
      "endpoint": "/flights",
      "input_query_strings": ["*"],
      "backend": [
        {
          "host": ["localhost:4242"],
          "url_pattern": "/flight_finder.Flights/FindFlight",
          "extra_config": {
            "backend/grpc": {}
          }
        }
      ]
    }
  ]
}
```

--------------------------------

### Get the month from a timestamp

Source: https://www.krakend.io/docs/enterprise/security-policies/built-in-functions

The `getMonth` function returns the month from a timestamp. The index starts at 0 for January and ends at 11 for December.

```go
timestamp(now).getMonth() // returns 2 on March
```

--------------------------------

### Listen IP Configuration Examples

Source: https://www.krakend.io/docs/enterprise/service-settings

Examples demonstrating how to configure the listen_ip for KrakenD. An empty string or no declaration means listening on all interfaces. Specific IPv4 and IPv6 addresses can also be used.

```json
"172.12.1.1"
```

```json
"::1"
```

--------------------------------

### Get milliseconds from timestamp or duration

Source: https://www.krakend.io/docs/enterprise/security-policies/built-in-functions

The `getMilliseconds` function extracts the milliseconds from a timestamp or a duration string. The index starts at 0 and ends at 999.

```go
timestamp(now).getMilliseconds() // returns 0 at midnight sharp
```

--------------------------------

### User Request Example for OpenAI Integration

Source: https://www.krakend.io/docs/enterprise/ai-gateway/openai

This example shows how a user can send a POST request to the configured KrakenD endpoint, including optional instructions and the main content for the LLM.

```bash
$curl -XPOST --json '{"instructions": "Act as a 1000 dollar consultant", "contents": "Tell me a consultant joke"}' http://localhost:8080/openapi
```