Serverless Functions (serverless) - Apisix

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Description

The serverless functions consist of two plugins, serverless-pre-function and serverless-post-function. These plugins enable the execution of user-defined logic at the beginning and end of the execution phases the functions hook to.

Attributes

Name	Type	Required	Default	Valid values	Description
phase	string	False	"access"	["rewrite", "access", "header_filter", "body_filter", "log", "before_proxy"]	Phase before or after which the serverless function is executed.
functions	array[string]	True			List of functions that are executed sequentially.

Tips for Writing Functions

Only Lua functions are allowed in the serverless plugins and not other Lua code.

For example, anonymous functions are legal:

lua

return function()
    ngx.log(ngx.ERR, 'one')
end

Closures are also legal:

lua

local count = 1
return function()
    count = count + 1
    ngx.say(count)
end

But code other than functions are illegal:

lua

local count = 1
ngx.say(count)

Examples

:::note

You can fetch the admin_key from config.yaml and save to an environment variable with the following command:

bash

admin_key=$(yq '.deployment.admin.admin_key[0].key' conf/config.yaml | sed 's/"//g')

:::

The examples below demonstrate how you can configure the serverless-pre-function and serverless-post-function plugins for different scenarios.

Log Information before and after a Phase

The example below demonstrates how you can configure the serverless plugins to execute custom logics to log information to error logs before and after the rewrite phase.

Create a Route as such:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id": "serverless-pre-route",
    "uri": "/anything",
    "plugins": {
      "serverless-pre-function": {
        "phase": "rewrite",
        "functions" : [
          "return function() ngx.log(ngx.ERR, \"serverless pre function\"); end"
        ]
      },
      "serverless-post-function": {
        "phase": "rewrite",
        "functions" : [
          "return function(conf, ctx) ngx.log(ngx.ERR, \"match uri \", ctx.curr_req_matched and ctx.curr_req_matched._path); end"
        ]
      }
    },
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

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yaml

services:
  - name: httpbin
    routes:
      - name: serverless-pre-route
        uris:
          - /anything
        plugins:
          serverless-pre-function:
            phase: rewrite
            functions:
              - |
                return function()
                  ngx.log(ngx.ERR, "serverless pre function")
                end
          serverless-post-function:
            phase: rewrite
            functions:
              - |
                return function(conf, ctx)
                  ngx.log(ngx.ERR, "match uri ", ctx.curr_req_matched and ctx.curr_req_matched._path)
                end
    upstream:
      type: roundrobin
      nodes:
        - host: httpbin.org
          port: 80
          weight: 1

Synchronize the configuration to the gateway:

shell

adc sync -f adc.yaml

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yaml

apiVersion: v1
kind: Service
metadata:
  namespace: aic
  name: httpbin-external-domain
spec:
  type: ExternalName
  externalName: httpbin.org
---
apiVersion: apisix.apache.org/v1alpha1
kind: PluginConfig
metadata:
  namespace: aic
  name: serverless-functions-plugin-config
spec:
  plugins:
    - name: serverless-pre-function
      config:
        phase: rewrite
        functions:
          - |
            return function()
              ngx.log(ngx.ERR, "serverless pre function")
            end
    - name: serverless-post-function
      config:
        phase: rewrite
        functions:
          - |
            return function(conf, ctx)
              ngx.log(ngx.ERR, "match uri ", ctx.curr_req_matched and ctx.curr_req_matched._path)
            end
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  namespace: aic
  name: serverless-pre-route
spec:
  parentRefs:
    - name: apisix
  rules:
    - matches:
        - path:
            type: Exact
            value: /anything
      filters:
        - type: ExtensionRef
          extensionRef:
            group: apisix.apache.org
            kind: PluginConfig
            name: serverless-functions-plugin-config
      backendRefs:
        - name: httpbin-external-domain
          port: 80

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yaml

apiVersion: apisix.apache.org/v2
kind: ApisixUpstream
metadata:
  namespace: aic
  name: httpbin-external-domain
spec:
  ingressClassName: apisix
  externalNodes:
  - type: Domain
    name: httpbin.org
---
apiVersion: apisix.apache.org/v2
kind: ApisixRoute
metadata:
  namespace: aic
  name: serverless-pre-route
spec:
  ingressClassName: apisix
  http:
    - name: serverless-pre-route
      match:
        paths:
          - /anything
      upstreams:
        - name: httpbin-external-domain
      plugins:
        - name: serverless-pre-function
          config:
            phase: rewrite
            functions:
              - |
                return function()
                  ngx.log(ngx.ERR, "serverless pre function")
                end
        - name: serverless-post-function
          config:
            phase: rewrite
            functions:
              - |
                return function(conf, ctx)
                  ngx.log(ngx.ERR, "match uri ", ctx.curr_req_matched and ctx.curr_req_matched._path)
                end

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Apply the configuration:

shell

kubectl apply -f serverless-functions-ic.yaml

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Send the request to the Route:

shell

curl -i "http://127.0.0.1:9080/anything"

You should receive an HTTP/1.1 200 OK response and see the following entries in the error log:

text

2024/05/09 15:07:09 [error] 51#51: *3963 [lua] [string "return function() ngx.log(ngx.ERR, "serverles..."]:1: func(): serverless pre function, client: 172.21.0.1, server: _, request: "GET /anything HTTP/1.1", host: "127.0.0.1:9080"
2024/05/09 15:16:58 [error] 50#50: *9343 [lua] [string "return function(conf, ctx) ngx.log(ngx.ERR, "..."]:1: func(): match uri /anything, client: 172.21.0.1, server: _, request: "GET /anything HTTP/1.1", host: "127.0.0.1:9080"

The first entry is added by the pre-function and the second entry is added by the post-function.

Register Custom Variables

The example below demonstrates how you can register custom built-in variables using the serverless plugins and use the newly created variable in logs.

:::info

This example cannot be completed with the Ingress Controller because it does not support configuring Route labels.

:::

Start an example rsyslog server:

shell

docker run -d -p 514:514 --name example-rsyslog-server rsyslog/syslog_appliance_alpine

Create a Service with a serverless function to register a custom variable a6_route_labels, enable a logging plugin to later log the custom variable, and configure an upstream:

shell

curl "http://127.0.0.1:9180/apisix/admin/services" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id":"srv_custom_var",
    "plugins": {
      "serverless-pre-function": {
        "phase": "rewrite",
        "functions": [
          "return function() local core = require \"apisix.core\" core.ctx.register_var(\"a6_route_labels\", function(ctx) local route = ctx.matched_route and ctx.matched_route.value if route and route.labels then return route.labels end return nil end); end"
        ]
      },
      "syslog": {
        "host" : "172.0.0.1",
        "port" : 514,
        "flush_limit" : 1
      }
    },
    "upstream": {
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

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yaml

services:
  - name: srv-custom-var
    plugins:
      serverless-pre-function:
        phase: rewrite
        functions:
          - |
            return function()
              local core = require("apisix.core")
              core.ctx.register_var("a6_route_labels", function(ctx)
                local route = ctx.matched_route and ctx.matched_route.value
                if route and route.labels then
                  return route.labels
                end
                return nil
              end)
            end
      syslog:
        host: 172.0.0.1
        port: 514
        flush_limit: 1
    upstream:
      nodes:
        - host: httpbin.org
          port: 80
          weight: 1

Synchronize the configuration to the gateway:

shell

adc sync -f adc.yaml

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Next, update the log format for all syslog instances with the new variable by configuring the Plugin metadata:

shell

curl "http://127.0.0.1:9180/apisix/admin/plugin_metadata/syslog" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "log_format": {
      "host": "$host",
      "client_ip": "$remote_addr",
      "labels": "$a6_route_labels"
    }
  }'

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yaml

plugin_metadata:
  syslog:
    log_format:
      host: "$host"
      client_ip: "$remote_addr"
      labels: "$a6_route_labels"

Synchronize the configuration to the gateway:

shell

adc sync -f adc.yaml

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Finally, create a Route:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id":"route_custom_var",
    "uri":"/get",
    "service_id": "srv_custom_var",
    "labels": {
      "key": "test_a6_route_labels"
    }
}'

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yaml

# Other Configs
services:
  - name: srv-custom-var
    routes:
      - name: route-custom-var
        uris:
          - /get
        labels:
          key: test_a6_route_labels

Synchronize the configuration to the gateway:

shell

adc sync -f adc.yaml

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To verify the variable registration, send a request to the Route:

shell

curl "http://127.0.0.1:9080/get"

You should see a log entry in your syslog server similar to the following:

json

{
  "host":"127.0.0.1",
  "route_id":"route_custom_var",
  "client_ip":"172.19.0.1",
  "labels":{
    "key":"test_a6_route_labels"
  },
  "service_id":"srv_custom_var"
}

This verifies the custom variable was registered and it logs the labels information in a Route successfully.

Modify a Specific Field in Response Body

The example below demonstrates how you can use the serverless plugins to remove a specific field from a JSON response body.

Before proceeding with the removal, first configure a Route as follows to see the unmodified response:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes" -X PUT \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "id":"serverless-remove-body-info",
    "uri": "/get",
    "upstream": {
      "type": "roundrobin",
      "nodes": {
        "httpbin.org:80": 1
      }
    }
  }'

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yaml

services:
  - name: httpbin
    routes:
      - name: serverless-remove-body-info
        uris:
          - /get
    upstream:
      type: roundrobin
      nodes:
        - host: httpbin.org
          port: 80
          weight: 1

Synchronize the configuration to the gateway:

shell

adc sync -f adc.yaml

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yaml

apiVersion: v1
kind: Service
metadata:
  namespace: aic
  name: httpbin-external-domain
spec:
  type: ExternalName
  externalName: httpbin.org
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  namespace: aic
  name: serverless-remove-body-info
spec:
  parentRefs:
    - name: apisix
  rules:
    - matches:
        - path:
            type: Exact
            value: /get
      backendRefs:
        - name: httpbin-external-domain
          port: 80

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yaml

apiVersion: apisix.apache.org/v2
kind: ApisixUpstream
metadata:
  namespace: aic
  name: httpbin-external-domain
spec:
  ingressClassName: apisix
  externalNodes:
  - type: Domain
    name: httpbin.org
---
apiVersion: apisix.apache.org/v2
kind: ApisixRoute
metadata:
  namespace: aic
  name: serverless-remove-body-info
spec:
  ingressClassName: apisix
  http:
    - name: serverless-remove-body-info
      match:
        paths:
          - /get
      upstreams:
        - name: httpbin-external-domain

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Apply the configuration:

shell

kubectl apply -f serverless-remove-body-ic.yaml

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Send a request to the Route:

shell

curl "http://127.0.0.1:9080/get"

You should see a response similar to the following with your host and proxy's IP information:

json

{
  "args": {},
  "headers": {
    "Accept": "*/*",
    "Host": "127.0.0.1",
    "User-Agent": "curl/8.4.0",
    "X-Amzn-Trace-Id": "Root=1-663db30f-51448a1b635f2f4338a4fcfc",
    "X-Forwarded-Host": "127.0.0.1"
  },
  "origin": "172.19.0.1, 43.252.208.84",
  "url": "http://127.0.0.1/get"
}

To remove the origin field from the response, update the Route with serverless plugins:

shell

curl "http://127.0.0.1:9180/apisix/admin/routes/serverless-remove-body-info" -X PATCH \
  -H "X-API-KEY: ${admin_key}" \
  -d '{
    "plugins": {
      "serverless-pre-function": {
        "phase": "header_filter",
        "functions" : [
          "return function(conf, ctx) local core = require(\"apisix.core\") core.response.clear_header_as_body_modified() end"
        ]
      },
      "serverless-post-function": {
        "phase": "body_filter",
        "functions" : [
          "return function(conf, ctx) local cjson = require(\"cjson\") local core = require(\"apisix.core\") local body = core.response.hold_body_chunk(ctx) if not body then return end body = cjson.decode(body) body.origin = nil body = cjson.encode(body) ngx.arg[1] = body end"
        ]
      }
    }
  }'

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yaml

services:
  - name: httpbin
    routes:
      - name: serverless-remove-body-info
        uris:
          - /get
        plugins:
          serverless-pre-function:
            phase: header_filter
            functions:
              - |
                return function(conf, ctx)
                  local core = require("apisix.core")
                  core.response.clear_header_as_body_modified()
                end
          serverless-post-function:
            phase: body_filter
            functions:
              - |
                return function(conf, ctx)
                  local cjson = require("cjson")
                  local core = require("apisix.core")
                  local body = core.response.hold_body_chunk(ctx)
                  if not body then
                    return
                  end
                  body = cjson.decode(body)
                  body.origin = nil
                  body = cjson.encode(body)
                  ngx.arg[1] = body
                end
    upstream:
      type: roundrobin
      nodes:
        - host: httpbin.org
          port: 80
          weight: 1

Synchronize the configuration to the gateway:

shell

adc sync -f adc.yaml

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yaml

# Other Configs
# ---
apiVersion: apisix.apache.org/v1alpha1
kind: PluginConfig
metadata:
  namespace: aic
  name: serverless-remove-body-plugin-config
spec:
  plugins:
    - name: serverless-pre-function
      config:
        phase: header_filter
        functions:
          - |
            return function(conf, ctx)
              local core = require("apisix.core")
              core.response.clear_header_as_body_modified()
            end
    - name: serverless-post-function
      config:
        phase: body_filter
        functions:
          - |
            return function(conf, ctx)
              local cjson = require("cjson")
              local core = require("apisix.core")
              local body = core.response.hold_body_chunk(ctx)
              if not body then
                return
              end
              body = cjson.decode(body)
              body.origin = nil
              body = cjson.encode(body)
              ngx.arg[1] = body
            end
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  namespace: aic
  name: serverless-remove-body-info
spec:
  parentRefs:
    - name: apisix
  rules:
    - matches:
        - path:
            type: Exact
            value: /get
      filters:
        - type: ExtensionRef
          extensionRef:
            group: apisix.apache.org
            kind: PluginConfig
            name: serverless-remove-body-plugin-config
      backendRefs:
        - name: httpbin-external-domain
          port: 80

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yaml

# Other Configs
# ---
apiVersion: apisix.apache.org/v2
kind: ApisixRoute
metadata:
  namespace: aic
  name: serverless-remove-body-info
spec:
  ingressClassName: apisix
  http:
    - name: serverless-remove-body-info
      match:
        paths:
          - /get
      upstreams:
        - name: httpbin-external-domain
      plugins:
        - name: serverless-pre-function
          config:
            phase: header_filter
            functions:
              - |
                return function(conf, ctx)
                  local core = require("apisix.core")
                  core.response.clear_header_as_body_modified()
                end
        - name: serverless-post-function
          config:
            phase: body_filter
            functions:
              - |
                return function(conf, ctx)
                  local cjson = require("cjson")
                  local core = require("apisix.core")
                  local body = core.response.hold_body_chunk(ctx)
                  if not body then
                    return
                  end
                  body = cjson.decode(body)
                  body.origin = nil
                  body = cjson.encode(body)
                  ngx.arg[1] = body
                end

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Apply the configuration:

shell

kubectl apply -f serverless-remove-body-ic.yaml

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The pre-function calls clear_header_as_body_modified to clear body-related response headers such as Content-Length. The post-function collects the response body with hold_body_chunk, decodes the JSON payload, removes the origin field, and writes the updated body back to the response.

Send another request to the Route:

shell

curl "http://127.0.0.1:9080/get"

You should see a response without the origin information:

json

{
  "url":"http://127.0.0.1/get",
  "args":{},
  "headers":{
    "X-Forwarded-Host":"127.0.0.1",
    "Host":"127.0.0.1",
    "Accept":"*/*",
    "User-Agent":"curl/8.4.0",
    "X-Amzn-Trace-Id":"Root=1-663db276-1c15276864294d963c6e1755"
  }
}

For simpler response modifications, such as modifying HTTP status codes, request headers, or the entire response body, please use the response-rewrite plugin.