Gin Memcached Middleware

If you are using gin to build a webservice, and you want to use memcached to store your data, you will search some articles about how to create a middleware to do that. After read some articles, I only found this middleware. But I got no luck. I cannot get a value from a key on one endpoint after I set it on another endpoint. So I didn’t use gin session and create my own middleware with gomemcache.

package main

import (
    "github.com/gin-gonic/gin"
    "github.com/bradfitz/gomemcache/memcache"
)

func MCMiddleware(mc *memcache.Client) gin.HandlerFunc {
    return func(c *gin.Context) {
        c.Set("mem", mc)
        c.Next()
    }
}

func main() {
    r := gin.Default()

    mc := memcache.New("127.0.0.1:11211")

    r.Use(MCMiddleware(mc))

    r.GET("/set", func(c *gin.Context) {
        mem, _ := c.MustGet("mem").(*memcache.Client)
        mem.Set(&memcache.Item{Key: "somekey", Value: []byte("somevalue")})
        c.String(200, "ok\n")
    })

    r.GET("/get", func(c *gin.Context) {
        mem, _ := c.MustGet("mem").(*memcache.Client)
        data, _ := mem.Get("somekey")
        c.String(200, string([]byte(data.Value))+"\n")
    })

    r.Run(":8000")
}

Then you can set and get a value from a key on all endpoints.

linx@crawler ~ $ curl localhost:8000/set
ok
linx@crawler ~ $ curl localhost:8000/get
somevalue
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Gogstash – Logstash Alternative

I am now doing some projects that need a monitoring application to monitor the webservice. After having some chit and chat, we decide to use ELK (Elasticsearch, Logstash, and Kibana). If you want to know what ELK is, just search on Google and there will be so many articles related to it.

If you have already read some articles about ELK, you will know that ELK is the application to monitor and analyze all types of log.

  • Elasticsearch: indexing the data.
  • Logstash: log processing / parsing.
  • Kibana: visualize the data.

But after trying to configure and run ELK, I found out that Logstash is heavy to be run on the server with small specification. Because of this reason, I am trying to find some Logstash alternatives, and finally I found Gogstash, Logstash like, written in Golang.

While reading the documentation, I found out that there are some differences between Gogstash and Logstash when using the filter (I am using grok filter in Logstash). I tried to apply same pattern in Gogstash but it didn’t work. After all these things, I decide to use another filter. I am using gonx filter.

Although grok pattern and gonx pattern is different, it is not so difficult to create the configuration for gonx filter. And after some modification, Gogstash run smoothly. For your information, I am using flask for building the webservice, and this is an example line of the application log.

192.168.100.57 - - [05/Dec/2017 16:27:27] "GET / HTTP/1.1" 200 -

There are two types of Gogstash configuration, json and yml format. Here is my yml configuration.

input:
  - type: file
    path: '/home/linggar/webapp/nohup.out'

filter:
  - type: gonx
    format: '$clientip - - [$date $time] "$full_request" $status -'
    source: message
  - type: gonx
    format: '$verb $request HTTP/$httpversion'
    source: full_request

output:
  - type: elastic
    url: 'http://127.0.0.1:9200'
    index: gogstash_log
    document_type: testtype

And that’s it. Although Gogstash is not as powerful as Logstash, it is very light and one of so many Logstash alternatives which you could try.

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Wifi Id Misconfiguration

Everyone, especially Indonesian people, should know what wifi id is. Yes, wifi id is an internet hotspot that provided by Indonesian Telkom. Some wifi id internet hotspot need no account, so everyone could do browsing with no cost, but most of it, the wifi id internet hotspot need account to access it. It means, you have to pay additional fee to get the account if you subscribe Telkom internet connection. Or, you could buy wifi id voucher directly on wifi id landing page.

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Ebean Partial Column Selection

Okay, because of some reasons, I have to learn Java and choose a Java web framework for my next project. After seeing around, I choose playframework, and I am using MySQL for the database.

After reading some documentation, I use Evolution and Ebean for the ORM. And then I found a problem when using Ebean. It still returning all columns although I selected some columns with this method based on this documentation.

List<MyModel> getUser = MyModel.find.select("columnA, columnB").findList()

After searching some solutions on google, I found this solution. So you have to do it like this.

JsonContext jc = Ebean.json();
List<MyModel> getUser = MyModel.find.select("columnA, columnB").findList();
String allUser = jc.toJson(getUser);

But when you use this method, the type of result will be a string type, so do not forget using Json.parse() if you want to use it as an object.

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