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

-- Single host module, plain Lua

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

local cassandra = require "cassandra"

local client = assert(cassandra.new {

host = "127.0.0.1",

keyspace = "my_keyspace"

})

client:settimeout(1000)

assert(client:connect())

local res = assert(client:execute [[

CREATE TABLE users(

id uuid PRIMARY KEY,

name varchar,

age int

)

]])

print(res.type) -- "SCHEMA_CHANGE"

res = assert(client:execute("INSERT INTO users(id, name, age) VALUES(?, ?, ?)", {

cassandra.uuid("1144bada-852c-11e3-89fb-e0b9a54a6d11"),

"John O Reilly",

42

}))

print(res.type) -- "VOID"

local rows = assert(client:execute("SELECT * FROM users WHERE age = ?", {

age = 42 -- key/value args

}, {

named = true -- named arguments

}))

print(rows.type) -- "ROWS"

print(#rows) -- 1

print(rows[1].name) -- "John O Reilly"

client:close()

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

-- Cluster module, OpenResty

-- This approach allows the cluster to live as an upvalue in your module's main

-- chunk, assuming the `lua_code_cache` directive is enabled in your nginx

-- config. This approach will be the most efficient as it will avoid re-creating

-- the cluster variable on each request and will preserve the cached state of

-- your load-balancing policy and prepared statements directly in the Lua land.

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

--

-- my_module.lua

--

local cassandra = require "cassandra"

local Cluster = require "resty.cassandra.cluster"

-- cluster instance as an upvalue

local cluster

local _M = {}

function _M.init_cluster(...)

cluster = assert(Cluster.new(...))

-- we also retrieve the cluster's nodes informations early, to avoid

-- slowing down our first incoming request, which would have triggered

-- a refresh should this not be done already.

assert(cluster:refresh())

end

function _M.execute(...)

return cluster:execute(...)

end

return _M

--

-- nginx.conf

--

http {

lua_shared_dict cassandra 1m; # shm storing cluster information

lua_code_cache on; # ensure the upvalue is preserved beyond a single request

init_by_lua_block {

-- will trigger a refresh of the cluster before the first request, but requires

-- LuaSocket since cosockets are not available in the 'init_by_lua' context.

local my_module = require "my_module"

my_module.init_cluster {

shm = "cassandra", -- defined in http block

contact_points = {"127.0.0.1", "127.0.0.2"},

keyspace = "my_keyspace"

}

}

server {

location / {

content_by_lua_block {

local my_module = require "my_module"

local rows, err = my_module.execute("SELECT * FROM users WHERE id = ? AND name = ?", {

cassandra.uuid("1144bada-852c-11e3-89fb-e0b9a54a6d11"),

"John O Reilly"

})

if not rows then

ngx.log(ngx.ERR, "could not retrieve users: ", err)

ngx.exit(500)

end

for i, row in ipairs(rows) do

ngx.say(i, ": ", rows[i].name) -- "1: John O Reilly"

end

}

}

}

}