File Log

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 requests with the following protocols:

• http
• https
• grpc
• grpcs
• tcp
• tls
• udp

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

Enable the plugin on a service

curl -X POST http://{HOST}:8001/services/{SERVICE}/plugins \
    --data "name=file-log"  \
    --data "config.path=/tmp/file.log" \
    --data "config.reopen=false"

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

apiVersion: v1
kind: Service
metadata:
  name: {SERVICE}
  labels:
    app: {SERVICE}
  annotations:
    konghq.com/plugins: <file-log-example>
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
    name: {SERVICE}
  selector:
    app: {SERVICE}

plugins:
- name: file-log
  service: {SERVICE}
  config: 
    path: /tmp/file.log
    reopen: false

Enable the plugin on a route

$ curl -X POST http://{HOST}:8001/routes/{ROUTE}/plugins \
    --data "name=file-log"  \
    --data "config.path=/tmp/file.log" \
    --data "config.reopen=false"

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

apiVersion: networking/v1beta1
kind: Ingress
metadata:
  name: {ROUTE}
  annotations:
    kubernetes.io/ingress.class: kong
    konghq.com/plugins: <file-log-example>
spec:
  rules:
  - host: examplehostname.com
    http:
      paths:
      - path: /bar
        backend:
          serviceName: echo
          servicePort: 80

plugins:
- name: file-log
  route: <route>
  config: 
    path: /tmp/file.log
    reopen: false

Enabling the plugin on a consumer

$ curl -X POST http://{HOST}:8001/consumers/{CONSUMER}/plugins \
    --data "name=file-log"  \
    --data "config.path=/tmp/file.log" \
    --data "config.reopen=false"

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

apiVersion: configuration.konghq.com/v1
kind: KongConsumer
metadata:
  name: {CONSUMER}
  annotations:
    konghq.com/plugins: <file-log-example>
    kubernetes.io/ingress.class: kong

plugins:
- name: file-log
  consumer: {CONSUMER}
  config: 
    path: /tmp/file.log
    reopen: false

Enable the plugin globally

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.

$ curl -X POST http://{HOST}:8001/plugins/ \
    --data "name=file-log"  \
    --data "config.path=/tmp/file.log" \
    --data "config.reopen=false"

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
  reopen: false
plugin: file-log

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

Parameters

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

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.