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What's new

  • version 0.3.4 Release
    • upgrade cheshire to 5.3.1
    • using edn/read-string rather than clojure read-string to avoid security risk.
  • version 0.3.2 Release
    • upgrade dependency library version.
  • version 0.3.1 Release
    • define custom options of command.
    • log error log when execute a command.
    • add a command option :log to log function request and result and client ip.
    • log warn when a execution time of a function is too log.
    • using easyconf to config cost parameter :warning-cost-ms (default 100ms)
  • version 0.3.0 Release. (add http-only and secure into default cookie attrs to improve security.
  • version 0.2.9 Release. (require clojure 1.4.0) fixed that can not get the real ip address of client when using nginx proxy.

A simple clojure rpc using clojure and json protocol

all the arguments of the function and the result must satisfy the rule:

(= form (f-decode (f-encode form)))

if use clj protocol f-encode/f-decode => pr-str/read-string

if use json protocol (using cheshire json) f-encode/f-decode => generate-string/parse-string

request and response.

  • clj-rpc supports single invoke rpc and multi invoke prc.
  • the request and response using json-rpc alike message
  • request and reply messages both are put in http body. using utf-8 encoding.

single invoke

  • request :

    {:method method-name :params [param1 param2 ...] :id request-id}

  • response: (when error is nil then the rpc invoke is successful, otherwise fail)

    {:result execute-result :id request-id :error {:code 401 :message "some message" :data other-data-related-error}}

multi invoke

  • requests : [request1 request2 ...]
  • response : [response1 response2 ...]


the http url format like

http://host:port/[clj | json]/invoke?token=client-token

token: this is optional, the meaning of token will be explained below.

export command

When we export a command, that mean we add a function that client can remote invoke it.


(export-commands ns fn-names & [options])


(export-commands 'clojure.core ["+" "-"] 
   [ [:require-context true] [:params-check {0 [:number]}] ])

this example mean we export a function + - of the clojure.core

And the client must supply a token that can get context, and the (get-in context [:number]) must equal the first parameter of invoke.

The context token and params check will explain below.

context and params check

  • clj-rpc server will use a token to identify the client.
  • every token specify a unique client.
  • Token can be passed to server by query token parameter or cookie.

When we start a clj-rpc server we can specific get-context function, that is a function that can get context of the client by the token. like (get-context token). You can see the example in the section Usage.

When we export a command, we can add options context check and params check according to the context that we can get by the client token.


Provided we have exported commands like above in the section export commands

we have a get-context function like below,

(defn my-get-context [token]
  (get {"token1" {:number 1} "token2" {:number 2}}))

If we remote invoke function like (+ 1 3) with token3,

then we will get a error, because token3 can not get a context.

and if we invoke function like (+ 2 3) with token1

then we will get an error too. because (not= 2 (get-in {:number 1} [:number]))

and if we invoke function like (+ 1 3) with token1,

then we will get a correct answer 4.

inject invoke parameter

Sometime, some parameters that method need (like client-ip) that the web client can not get. we can dynamic inject this kind of parameters (from ring request) into method.

the export-commands support options like [ [:params-inject [ [:remote-addr] [:header "host] ] ]]

and clj-rpc will (get-in request [:remote-addr]) and (get-in request [:header "host"]) as the first and second parameter of the method that client invokes.


(defn fn-do-something [client-ip username]
      ... )

(export-commands 'mynamespace ["fn-do-something"]
                 [ [:params-inject [ [:remote-addr] ] ]])

Then the client will invoke function like (fn-do-something username) and the clj-rpc will dynamic invoke like (fn-do-something "" username)

Notice: Now, clj-rpc only supports to inject params into the front of the parameters that client supplied .

log the request and result of function invokes

Since 0.3.1 you can define to enable clj-rpc log function using option :log, like [ [:log log-level] ] , log-level can be :trace :debug :info :warn :error :fatal.


(defn log-func [v]
   (apply str (reverse v)))

(export-commands 'mynamespace ["log-func"]
                 [ [:log :info] ])

When you invoke (log-func "hello"), the clj-rpc will log like below:

2012-11-15 14:53:25,957 WARN  clj-rpc.context: client-ip : {:method-request {:method "log-func", :params ["hello"]}, :response {:result "olleh", :id nil}}

define custom options of commands

Since 0.3.1 , you can define new custom option by implement two multi method defined in the clj-rpc.context namespace.

Example: we add a new option named :custom

(ns mynamespace
   (:require [clj-rpc.context :as context]))

;;this method is mandatory and give you opportunity to change the
;;method-request according to the request and option, you must return
;;a new method-request
;;if you don't do anything, just return the old method-request
(defmethod context/render-method-request  :custom
           [option-key option-value request method-request]
           ;; do some thing to change method-request

;;this method is option, default return the old response
;;you can change the response according to the option or do some side effects. 
(defmethod context/render-response :custom
           [option-key option-value request response]
           ;;do some thing to change response or do something side
           ;;effect according to the response.

;;now you can export commands with new option like below
;;the option-value can be any data type
;;in this example is {:key1 :a :key2 :b}
(export-commands 'mynamespace ['fn-1 'fn-2] 
                 [ [:custom {:key1 :a :key2 b}]])

user data

Sometime , we need to access data (like session) related the connection.

Because this is a rpc invoke procedure, so when programmer writes functions we assume them do not and we do not want them to know anything about session in order to separate the logic code and web framework.

So clj-rpc.user-data supplies three functions to let programmer can access connection related data.

  • (save-user-data! data) return data
  • (get-user-data!)
  • (delete-user-data) return nil

Notice: this three functions should be used in the function that will be exported.

(ns rpc.demo
  (:require [clj-rpc.user-data :as store]))

;;example function to using save-user-data!
(defn fn-save-data 
  (store/save-user-data! {:save-time (System/currentTimeMillis)}))

;;example function to using get-user-data!
(defn fn-get-data

;;example function to using delete-user-data!
(defn fn-delete-data


add to project.clj

[clj-rpc "0.3.4"]

sample code:

(ns rpc.demo
 (:require [clj-rpc.server :as server]
           [clj-rpc.client :as client]))
 ;=============server code ===============

 ;;this is a function we want to export, 
 ;;but we want the specific user can invoke this function.
 (defn user-info 

 ;;this is a get-context function.
 (defn get-context [token]
    (get {"token1" {:username "user1"}} token))

 ;;export user-info function
 (server/export-commands 'rpc.demo ["user-info"]
     [ [:require-context true] [:params-check {0 [:username]}] ])    
 ;;export all functions in the namespace clojure.core
 (server/export-commands 'clojure.core nil)
 ;;export other namespace
 ;;start http server, the "clj-rpc-cookie" just a example value.
 (server/start {:fn-get-context get-context 
                :token-cookie-key "clj-rpc-cookie-key" }) 

 ;==============client code ===============
 ;; Obtain handle to endpoint
 (def endp (client/rpc-endpoint :server "localhost"))

 ;; get all export commands
 (client/help endp)
 ;; invoke some command
 ;; remote invoke the function (str "hello," "world") and return the result
 (client/invoke-rpc endp "str" ["hello, " "world"])

 ;;invoke the user-info function correctly.
 (client/invoke-rpc-with-token endp "token1" "user-info" ["user1"])  


integrate test.

clj-rpc.helper supplies the support for support integrate test.

example can refer to clj-rpc.test.helper.clj in test folder.

clean timeout user data.

clj-rpc.user-data unit supplies two method can clean the timeout userdata.

  • (clean-timeout! now timeout) ===> clean user data once
  • (periodical-clean-data! interval timeout) ===> clean user data every interval time.

custom define error code and message

If you want to return to client client custom error code and error message, you just need to invoke function raise-error in clj-rpc.error namespace.

add require

(:require [clj-rpc.error :as error]

raise an error with code and error data in your logic code:

;;only code
(defn my-custom-api [] 
    (if condition
      (error/raise-error 300 "error")

;;with error data
(defn my-custom-api [] 
    (if condition
      (error/raise-error 300 "error" {:data "error data"})


Copyright (C) 2011

Distributed under the Eclipse Public License, the same as Clojure.

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