File Log plugin | Kong Docs

Append request and response data in JSON format to a log file. You can also specify streams (for example, /dev/stdout and /dev/stderr), which is especially useful when running Kong in Kubernetes.

This plugin uses blocking I/O, which could affect performance when writing to physical files on slow (spinning) disks.

Configuration Reference

This plugin is compatible with DB-less mode.

In DB-less mode, you configure Kong Gateway declaratively. Therefore, the Admin API is mostly read-only. The only tasks it can perform are all related to handling the declarative config, including:

Setting a target's health status in the load balancer
Validating configurations against schemas
Uploading the declarative configuration using the /config endpoint

Example plugin configuration

Enable on a service

Enable on a route

Enable on a consumer

Enable globally

The following examples provide some typical configurations for enabling the file-log plugin on a service.

Admin API

Kubernetes

Declarative (YAML)

Konnect Cloud

Kong Manager

Make the following request:

curl -X POST http://localhost:8001/services/SERVICE_NAME|SERVICE_ID/plugins \
    --data "name=file-log"  \
    --data "config.path=/tmp/file.log"

Replace SERVICE_NAME|SERVICE_ID with the id or name of the service that this plugin configuration will target.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: file-log-example
config: 
  path: /tmp/file.log
plugin: file-log

Next, apply the KongPlugin resource to a service by annotating the service as follows:

apiVersion: v1
kind: Service
metadata:
  name: SERVICE_NAME|SERVICE_ID
  labels:
    app: SERVICE_NAME|SERVICE_ID
  annotations:
    konghq.com/plugins: file-log-example
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
    name: SERVICE_NAME|SERVICE_ID
  selector:
    app: SERVICE_NAME|SERVICE_ID

Replace SERVICE_NAME|SERVICE_ID with the id or name of the service that this plugin configuration will target.

Note: The KongPlugin resource only needs to be defined once and can be applied to any service, consumer, or route in the namespace. If you want the plugin to be available cluster-wide, create the resource as a KongClusterPlugin instead of KongPlugin.

Add this section to your declarative configuration file:

plugins:
- name: file-log
  service: SERVICE_NAME|SERVICE_ID
  config: 
    path: /tmp/file.log

Replace SERVICE_NAME|SERVICE_ID with the id or name of the service that this plugin configuration will target.

You can configure this plugin through the Konnect UI.

From the Service Hub, select a service version, then set up the plugin:

In the Plugins section, click Add Plugin.
Find and select the File Log plugin.
Configure the plugin’s parameters.

You can test out the plugin with the following sample configuration:
- Config.Path: /tmp/file.log
Click Create.

You can configure this plugin through the Kong Manager UI.

In Kong Manager, select the workspace.
From the Services section, click View for the service row.
From the plugin section, click Add Plugin.
Find and select the File Log plugin.
If the option is available, select Scoped.
Add the service name and ID to the Service field if it is not already pre-filled.
Configure the plugin’s parameters.

You can test out the plugin with the following sample configuration:
- Config.Path: /tmp/file.log
Click Create.

The following examples provide some typical configurations for enabling the file-log plugin on a route.

Admin API

Kubernetes

Declarative (YAML)

Konnect Cloud

Kong Manager

Make the following request:

curl -X POST http://localhost:8001/routes/ROUTE_NAME|ROUTE_ID/plugins \
  --data "name=file-log"  \
    --data "config.path=/tmp/file.log"

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: file-log-example
config: 
  path: /tmp/file.log
plugin: file-log

Then, apply it to an ingress (route or routes) by annotating the ingress as follows:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ROUTE_NAME|ROUTE_ID
  annotations:
    kubernetes.io/ingress.class: kong
    konghq.com/plugins: file-log-example
spec:
  rules:
  - host: examplehostname.com
    http:
      paths:
      - path: /bar
        backend:
          service:
            name: echo
            port:
              number: 80

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

Note: The KongPlugin resource only needs to be defined once and can be applied to any service, consumer, or route in the namespace. If you want the plugin to be available cluster-wide, create the resource as a KongClusterPlugin instead of KongPlugin.

Add this section to your declarative configuration file:

plugins:
- name: file-log
  route: ROUTE_NAME
  config: 
    path: /tmp/file.log

Replace ROUTE_NAME|ROUTE_ID with the id or name of the route that this plugin configuration will target.

You can configure this plugin through the Konnect UI.

From the Service Hub, select a service version, then set up the plugin:

Select a route.
In the Plugins section, click Add Plugin.
Find and select the File Log plugin.
Configure the plugin’s parameters.

You can test out the plugin with the following sample configuration:
- Config.Path: /tmp/file.log
Click Create.

You can configure this plugin through the Kong Manager UI.

In Kong Manager, select the workspace.
Open Routes from the menu, then click View for the route row.
From the plugin section, click Add Plugin.
Find and select the File Log plugin.
If the option is available, select Scoped.
Add the route ID if it is not already prefilled.
Configure the plugin’s parameters.

You can test out the plugin with the following sample configuration:
- Config.Path: /tmp/file.log
Click Create.

The following examples provide some typical configurations for enabling the file-log plugin on a consumer.

Admin API

Kubernetes

Declarative (YAML)

Kong Manager

Make the following request:

curl -X POST http://localhost:8001/consumers/CONSUMER_NAME|CONSUMER_ID/plugins \
  --data "name=file-log"  \
    --data "config.path=/tmp/file.log"

Replace CONSUMER_NAME|CONSUMER_ID with the id or name of the consumer that this plugin configuration will target.

You can combine consumer.id, service.id, or route.id in the same request, to further narrow the scope of the plugin.

First, create a KongPlugin resource:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: file-log-example
config: 
  path: /tmp/file.log
plugin: file-log

Then, apply it to a consumer by annotating the KongConsumer resource as follows:

apiVersion: configuration.konghq.com/v1
kind: KongConsumer
metadata:
  name: CONSUMER_NAME|CONSUMER_ID
  annotations:
    konghq.com/plugins: file-log-example
    kubernetes.io/ingress.class: kong

Replace CONSUMER_NAME|CONSUMER_ID with the id or name of the consumer that this plugin configuration will target.

Note: The KongPlugin resource only needs to be defined once and can be applied to any service, consumer, or route in the namespace. If you want the plugin to be available cluster-wide, create the resource as a KongClusterPlugin instead of KongPlugin.

Add this section to your declarative configuration file:

plugins:
- name: file-log
  consumer: CONSUMER_NAME|CONSUMER_ID
  config: 
    path: /tmp/file.log

Replace CONSUMER_NAME|CONSUMER_ID with the id or name of the consumer that this plugin configuration will target.

You can configure this plugin through the Kong Manager UI.

In Kong Manager, select the workspace.
From the Consumers section, click View for the consumer row.
Select the Plugins tab, then click Add Plugin.
Find and select the File Log plugin.
If the option is available, select Scoped.
Add the consumer ID if it is not already prefilled.
Configure the plugin’s parameters.

You can test out the plugin with the following sample configuration:
- Config.Path: /tmp/file.log
Click Create.

A plugin which is not associated to any service, route, or consumer is considered global, and will be run on every request. Read the Plugin Reference and the Plugin Precedence sections for more information.

The following examples provide some typical configurations for enabling the file-log plugin globally.

Admin API

Kubernetes

Declarative (YAML)

Kong Manager

Make the following request:

curl -X POST http://localhost:8001/plugins/ \
  --data "name=file-log"  \
    --data "config.path=/tmp/file.log"

Create a KongClusterPlugin resource and label it as global:

apiVersion: configuration.konghq.com/v1
kind: KongClusterPlugin
metadata:
  name: <global-file-log>
  annotations:
    kubernetes.io/ingress.class: kong
  labels:
    global: \"true\"
config: 
  path: /tmp/file.log
plugin: file-log

Add a plugins entry in the declarative configuration file:

plugins:
- name: file-log
  config: 
    path: /tmp/file.log

You can configure this plugin through the Kong Manager UI.

In Kong Manager, select the workspace.
Open Plugins from the menu, then click New Plugin.
Find and select the File Log plugin.
If the option is available, set the plugin scope to Global.
Configure the plugin’s parameters.

You can test out the plugin with the following sample configuration:
- Config.Path: /tmp/file.log
Click Create.

Parameters

Here's a list of all the parameters which can be used in this plugin's configuration:

Form Parameter	Description
`name` required Type: string	The name of the plugin, in this case `file-log`.
`service.name` or `service.id` Type: string	The name or ID of the service the plugin targets. Set one of these parameters if adding the plugin to a service through the top-level `/plugins` endpoint. Not required if using `/services/SERVICE_NAME\|SERVICE_ID/plugins`.
`route.name` or `route.id` Type: string	The name or ID of the route the plugin targets. Set one of these parameters if adding the plugin to a route through the top-level `/plugins` endpoint. Not required if using `/routes/ROUTE_NAME\|ROUTE_ID/plugins`.
`consumer.name` or `consumer.id` Type: string	The name or ID of the consumer the plugin targets. Set one of these parameters if adding the plugin to a consumer through the top-level `/plugins` endpoint. Not required if using `/consumers/CONSUMER_NAME\|CONSUMER_ID/plugins`.
`enabled` Type: boolean Default value: `true`	Whether this plugin will be applied.
`config.path` required Type: string	The file path of the output log file. The plugin creates the log file if it doesn’t exist yet. Make sure Kong has write permissions to this file.
`config.reopen` required Type: boolean Default value: `false`	Determines whether the log file is closed and reopened on every request. If the file is not reopened, and has been removed/rotated, the plugin keeps writing to the stale file descriptor, and hence loses information.
`config.custom_fields_by_lua` optional Type: map	A list of key-value pairs, where the key is the name of a log field and the value is a chunk of Lua code, whose return value sets or replaces the log field value. Requires Kong 2.4.x or above.

Log format

Every request is logged separately in a JSON object, separated by a new line \n, with the following format:

{
  "latencies": {
    "request": 515,
    "kong": 58,
    "proxy": 457
  },
  "service": {
    "host": "httpbin.org",
    "created_at": 1614232642,
    "connect_timeout": 60000,
    "id": "167290ee-c682-4ebf-bdea-e49a3ac5e260",
    "protocol": "http",
    "read_timeout": 60000,
    "port": 80,
    "path": "/anything",
    "updated_at": 1614232642,
    "write_timeout": 60000,
    "retries": 5,
    "ws_id": "54baa5a9-23d6-41e0-9c9a-02434b010b25"
  },
  "request": {
    "querystring": {},
    "size": 138,
    "uri": "/log",
    "url": "http://localhost:8000/log",
    "headers": {
      "host": "localhost:8000",
      "accept-encoding": "gzip, deflate",
      "user-agent": "HTTPie/2.4.0",
      "accept": "*/*",
      "connection": "keep-alive"
    },
    "method": "GET"
  },
  "tries": [
    {
      "balancer_latency": 0,
      "port": 80,
      "balancer_start": 1614232668399,
      "ip": "18.211.130.98"
    }
  ],
  "client_ip": "192.168.144.1",
  "workspace": "54baa5a9-23d6-41e0-9c9a-02434b010b25",
  "upstream_uri": "/anything",
  "response": {
    "headers": {
      "content-type": "application/json",
      "date": "Thu, 25 Feb 2021 05:57:48 GMT",
      "connection": "close",
      "access-control-allow-credentials": "true",
      "content-length": "503",
      "server": "gunicorn/19.9.0",
      "via": "kong/2.2.1.0-enterprise-edition",
      "x-kong-proxy-latency": "57",
      "x-kong-upstream-latency": "457",
      "access-control-allow-origin": "*"
    },
    "status": 200,
    "size": 827
  },
  "route": {
    "id": "78f79740-c410-4fd9-a998-d0a60a99dc9b",
    "paths": [
      "/log"
    ],
    "protocols": [
      "http"
    ],
    "strip_path": true,
    "created_at": 1614232648,
    "ws_id": "54baa5a9-23d6-41e0-9c9a-02434b010b25",
    "request_buffering": true,
    "updated_at": 1614232648,
    "preserve_host": false,
    "regex_priority": 0,
    "response_buffering": true,
    "https_redirect_status_code": 426,
    "path_handling": "v0",
    "service": {
      "id": "167290ee-c682-4ebf-bdea-e49a3ac5e260"
    }
  },
  "started_at": 1614232668342
}

JSON object considerations

A few considerations on the JSON object:

request contains properties about the request sent by the client.
response contains properties about the response sent to the client.
tries contains the list of (re)tries (successes and failures) made by the load balancer for this request.
route contains Kong Gateway properties about the specific Route requested.
service contains Kong Gateway properties about the Service associated with the requested Route.
authenticated_entity contains Kong Gateway properties about the authenticated credential (if an authentication plugin has been enabled).
workspaces contains Kong Gateway properties of the Workspaces associated with the requested Route. Only in Kong Gateway version >= 0.34.x. For Kong Gateway version >= 2.1.x, there is a ws_id on services and routes that reference the workspace ID.
consumer contains the authenticated Consumer (if an authentication plugin has been enabled).
latencies contains some data about the latencies involved:
- proxy is the time it took for the final service to process the request.
- kong is the internal Kong latency that it took to run all the plugins.
- request is the time elapsed between the first bytes were read from the client and after the last bytes were sent to the client. Useful for detecting slow clients.
client_ip contains the original client IP address.
started_at contains the UTC timestamp of when the request has started to be processed.

Log plugins enabled on services and routes contain information about the service or route.

Kong process errors

This logging plugin logs HTTP request and response data, and also supports streams data (TCP, TLS, and UDP).

If you are looking for the Kong process error file (which is the nginx error file), you can find it at the following path:

{prefix}/logs/error.log

Custom Fields by Lua

The custom_fields_by_lua configuration allows for the dynamic modification of log fields using Lua code. Below is an example configuration that removes the existing route field in the logs:

curl -i -X POST --url http://kong:8001/plugins ... --data config.custom_fields_by_lua.route="return nil"

Similarly, new fields can be added:

curl -i -X POST --url http://kong:8001/plugins ... --data config.custom_fields_by_lua.header="return kong.request.get_header('h1')"

Limitations

Lua code runs in a restricted sandbox environment, whose behavior is governed by the untrusted_lua configuration properties configuration properties.

Sandboxing consists of several limitations in the way the Lua code can be executed, for heightened security.

The following functions are not available because they can be used to abuse the system:

string.rep: Can be used to allocate millions of bytes in one operation.
{set|get}metatable: Can be used to modify the metatables of global objects (strings, numbers).
collectgarbage: Can be abused to kill the performance of other workers.
_G: Is the root node which has access to all functions. It is masked by a temporary table.
load{file|string}: Is deemed unsafe because it can grant access to the global environment.
raw{get|set|equal}: Potentially unsafe because sandboxing relies on some metatable manipulation.
string.dump: Can display confidential server information (such as implementation of functions).
math.randomseed: Can affect the host system. Kong Gateway already seeds the random number generator properly.
All os.* (except os.clock, os.difftime, and os.time). os.execute can significantly alter the host system.
io.*: Provides access to the hard drive.
dofile|require: Provides access to the hard drive.

The exclusion of require means that plugins must only use PDK functions kong.*. The ngx.* abstraction is also available, but it is not guaranteed to be present in future versions of the plugin.

In addition to the above restrictions:

All the provided modules (like string or table) are read-only and can’t be modified.
Bytecode execution is disabled.

Further, as code runs in the context of the log phase, only PDK methods that can run in said phase can be used.

Changelog

Kong Gateway 2.4.x

Added custom_fields_by_lua configuration option.

About this Plugin
Plugin Version	3.0.x
Made by	Kong Inc.
Categories	Logging
DB-less compatible?	Yes
Konnect Cloud compatible?	Yes
Compatible protocols	`http` `https` `grpc` `grpcs` `tcp` `tls` `udp`