Kong Gateway

2.7.x

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kong.ctx

Current request context data

kong.ctx.shared

A table that has the lifetime of the current request and is shared between all plugins. It can be used to share data between several plugins in a given request.

Since only relevant in the context of a request, this table cannot be accessed from the top-level chunk of Lua modules. Instead, it can only be accessed in request phases, which are represented by the rewrite, access, header_filter, response, body_filter, log, and preread phases of the plugin interfaces. Accessing this table in those functions (and their callees) is fine.

Values inserted in this table by a plugin will be visible by all other plugins. One must use caution when interacting with its values, as a naming conflict could result in the overwrite of data.

Phases

rewrite, access, header_filter, response, body_filter, log, preread

Usage

-- Two plugins A and B, and if plugin A has a higher priority than B's
-- (it executes before B):

-- plugin A handler.lua
function plugin_a_handler:access(conf)
  kong.ctx.shared.foo = "hello world"

  kong.ctx.shared.tab = {
    bar = "baz"
  }
end

-- plugin B handler.lua
function plugin_b_handler:access(conf)
  kong.log(kong.ctx.shared.foo) -- "hello world"
  kong.log(kong.ctx.shared.tab.bar) -- "baz"
end

kong.ctx.plugin

A table that has the lifetime of the current request - Unlike kong.ctx.shared, this table is not shared between plugins. Instead, it is only visible for the current plugin instance. That is, if several instances of the rate-limiting plugin are configured (e.g. on different Services), each instance has its own table, for every request.

Because of its namespaced nature, this table is safer for a plugin to use than kong.ctx.shared since it avoids potential naming conflicts, which could lead to several plugins unknowingly overwriting each other’s data.

Since only relevant in the context of a request, this table cannot be accessed from the top-level chunk of Lua modules. Instead, it can only be accessed in request phases, which are represented by the rewrite, access, header_filter, body_filter, log, and preread phases of the plugin interfaces. Accessing this table in those functions (and their callees) is fine.

Values inserted in this table by a plugin will be visible in successful phases of this plugin’s instance only. For example, if a plugin wants to save some value for post-processing during the log phase:

Phases

rewrite, access, header_filter, response, body_filter, log, preread

Usage

-- plugin handler.lua

function plugin_handler:access(conf)
  kong.ctx.plugin.val_1 = "hello"
  kong.ctx.plugin.val_2 = "world"
end

function plugin_handler:log(conf)
  local value = kong.ctx.plugin.val_1 .. " " .. kong.ctx.plugin.val_2

  kong.log(value) -- "hello world"
end