Dimas Maryanto

Dimas Maryanto

I am an Instructure at Udemy and Chief Technology Officer at PT. Tabeldata Informatika

Docker for DevOps engineer 6 minute read

Hai semuanya, di materi kali ini kita akan membahas tentang Expose Instruction pada Dockerfile, diantaranya yang akan kita bahas yaitu

  1. Expose default port by sevice
  2. Custom port
  3. Multiple port in same image

Expose default port

The EXPOSE instruction informs Docker that the container listens on the specified network ports at runtime. You can specify whether the port listens on TCP or UDP, and the default is TCP if the protocol is not specified.

EXPOSE <port> [<port>/<protocol>...]

The EXPOSE instruction does not actually publish the port. It functions as a type of documentation between the person who builds the image and the person who runs the container, about which ports are intended to be published. To actually publish the port when running the container, use the -p flag on docker run to publish and map one or more ports, or the -P flag to publish all exposed ports and map them to high-order ports.

By default, EXPOSE assumes TCP. You can also specify UDP:

EXPOSE 80/udp

To expose on both TCP and UDP, include two lines:

EXPOSE 80/tcp
EXPOSE 80/udp

Contoh penggunaanya, misalnya kita akan meng-expose port 80 dengan protocol TCP pada web-server yang telah kita buat di materi sebelumnya seperti berikut:

Jika dijalankan maka hasilnya seperti berikut:

➜ 07-dockerfile  docker build -t dimmaryanto93/centos:1.0 .
[+] Building 49.5s (8/8) FINISHED
 => [internal] load build definition from Dockerfile                                                               0.0s
 => => transferring dockerfile: 32B                                                                                0.0s
 => [internal] load .dockerignore                                                                                  0.0s
 => => transferring context: 35B                                                                                   0.0s
 => [internal] load metadata for docker.io/library/centos:7                                                        0.0s
 => CACHED [1/3] FROM docker.io/library/centos:7                                                                   0.0s
 => [internal] load build context                                                                                  0.0s
 => => transferring context: 3.14kB                                                                                0.0s
 => [2/3] RUN yum install epel-release -y && yum install nginx -y && yum clean all                                49.1s
 => [3/3] COPY index.html /usr/share/nginx/html/index.html                                                         0.0s
 => exporting to image                                                                                             0.3s
 => => exporting layers                                                                                            0.3s
 => => writing image sha256:55fdc633367c3a0f79bea9f0c0f3f94dec1fb30c7ae89191ae8ec9d36b8f674e                       0.0s
 => => naming to docker.io/dimmaryanto93/centos:1.0

➜ 07-dockerfile  docker image inspect dimmaryanto93/centos:1.0 -f '{{json .Config.ExposedPorts }}'
{"80/tcp":{}}

➜ 07-dockerfile  docker run --name webapp -p 80:80 -d dimmaryanto93/centos:1.0
c62bc7a6e61e8abb0b56a3f4ac86b312c9d6ba8b13f5fb147ccafd21c0105207

➜ 07-dockerfile  curl localhost
StatusCode        : 200
StatusDescription : OK
Content           : <!DOCTYPE html>
                    <html lang="en">

                    <head>
                        <meta charset="UTF-8">
                        <meta http-equiv="X-UA-Compatible" content="IE=edge">
                        <title>Belajar HTML</title>

                        <!--Import Google Icon Font--...
RawContent        : HTTP/1.1 200 OK
                    Connection: keep-alive
                    Accept-Ranges: bytes
                    Content-Length: 3105
                    Content-Type: text/html
                    Date: Sun, 20 Jun 2021 04:28:24 GMT
                    ETag: "60bb3f04-c21"
                    Last-Modified: Sat, 05 Jun 2021...
Forms             : {}
Headers           : {[Connection, keep-alive], [Accept-Ranges, bytes], [Content-Length, 3105], [Content-Type,
                    text/html]...}
Images            : {}
InputFields       : {}
Links             : {@{innerHTML=Webapp Cources; innerText=Webapp Cources; outerHTML=<a class="brand-logo"
                    href="#">Webapp Cources</a>; outerText=Webapp Cources; tagName=A; class=brand-logo; href=#},
                    @{innerHTML=HTML; innerText=HTML; outerHTML=<a href="sass.html">HTML</a>; outerText=HTML;
                    tagName=A; href=sass.html}, @{innerHTML=CSS; innerText=CSS; outerHTML=<a
                    href="badges.html">CSS</a>; outerText=CSS; tagName=A; href=badges.html}, @{innerHTML=JavaScript;
                    innerText=JavaScript; outerHTML=<a href="collapsible.html">JavaScript</a>; outerText=JavaScript;
                    tagName=A; href=collapsible.html}...}
ParsedHtml        : System.__ComObject
RawContentLength  : 3105

Jika coba akses dari browser dengan alamat localhost, maka hasilnya seperti berikut:

hasilnya

Expose custom port

Atau selain itu kita juga bisa custom port, misalnya masih pada Dockerfile sebelumnya kita coba edit Listen 80 pada /etc/nginx/nginx.conf

Seperti berikut:

Jika kita jalankan maka hasilnya seperti berikut:

➜ 07-dockerfile  docker build -t dimmaryanto93/centos:1.0 .
[+] Building 0.4s (9/9) FINISHED
 => [internal] load build definition from Dockerfile                                                               0.0s
 => => transferring dockerfile: 537B                                                                               0.0s
 => [internal] load .dockerignore                                                                                  0.0s
 => => transferring context: 35B                                                                                   0.0s
 => [internal] load metadata for docker.io/library/centos:7                                                        0.0s
 => [1/4] FROM docker.io/library/centos:7                                                                          0.0s
 => [internal] load build context                                                                                  0.0s
 => => transferring context: 32B                                                                                   0.0s
 => CACHED [2/4] RUN yum install epel-release -y && yum install nginx -y && yum clean all                          0.0s
 => CACHED [3/4] COPY index.html /usr/share/nginx/html/index.html                                                  0.0s
 => [4/4] RUN sed -i "s|80|8080|g" /etc/nginx/nginx.conf                                                           0.2s
 => exporting to image                                                                                             0.1s
 => => exporting layers                                                                                            0.0s
 => => writing image sha256:5d6df3b2384a47e4f9d47d7306d2d7ab9e8534498239e2b51d49ffa2c1ed4675                       0.0s
 => => naming to docker.io/dimmaryanto93/centos:1.0

 ➜ 07-dockerfile  docker image inspect dimmaryanto93/centos:1.0 -f '{{json .Config.ExposedPorts }}'
{"8080/tcp":{}}

➜ 07-dockerfile  docker run --name webapp-changed-port -p 8080:8080 -d dimmaryanto93/centos:1.0
ce103ccf4446890e3de2e2f8b201d8fc7aff3139c12b893b2ca05551146c5c27

➜ 07-dockerfile ✗  curl http://localhost:8080
StatusCode        : 200
StatusDescription : OK
Content           : <!DOCTYPE html>
                    <html lang="en">

                    <head>
                        <meta charset="UTF-8">
                        <meta http-equiv="X-UA-Compatible" content="IE=edge">
                        <title>Belajar HTML</title>

                        <!--Import Google Icon Font--...
RawContent        : HTTP/1.1 200 OK
                    Connection: keep-alive
                    Accept-Ranges: bytes
                    Content-Length: 3105
                    Content-Type: text/html
                    Date: Sun, 20 Jun 2021 04:42:25 GMT
                    ETag: "60bb3f04-c21"
                    Last-Modified: Sat, 05 Jun 2021...
Forms             : {}
Headers           : {[Connection, keep-alive], [Accept-Ranges, bytes], [Content-Length, 3105], [Content-Type,
                    text/html]...}
Images            : {}
InputFields       : {}
Links             : {@{innerHTML=Webapp Cources; innerText=Webapp Cources; outerHTML=<a class="brand-logo"
                    href="#">Webapp Cources</a>; outerText=Webapp Cources; tagName=A; class=brand-logo; href=#},
                    @{innerHTML=HTML; innerText=HTML; outerHTML=<a href="sass.html">HTML</a>; outerText=HTML;
                    tagName=A; href=sass.html}, @{innerHTML=CSS; innerText=CSS; outerHTML=<a
                    href="badges.html">CSS</a>; outerText=CSS; tagName=A; href=badges.html}, @{innerHTML=JavaScript;
                    innerText=JavaScript; outerHTML=<a href="collapsible.html">JavaScript</a>; outerText=JavaScript;
                    tagName=A; href=collapsible.html}...}
ParsedHtml        : System.__ComObject
RawContentLength  : 3105

Jika coba akses dari browser dengan alamat localhost:8080, maka hasilnya seperti berikut:

hasilnya

Expose multiple ports

Atau kita juga bisa menggunakan multiple port, contohnya jika kita aktifkan module ssl pada nginx seperti berikut:

Buatlah file dengan nama nginx-ssl.conf seperti berikut:

Kemudian edit file Dockerfile seperti berikut

Jika dijalankan maka hasilnya seperti berikut:

➜ 07-dockerfile  docker build -t dimmaryanto93/centos:1.0 .
[+] Building 33.9s (10/10) FINISHED
 => [internal] load build definition from Dockerfile                                                               0.0s
 => => transferring dockerfile: 32B                                                                                0.0s
 => [internal] load .dockerignore                                                                                  0.0s
 => => transferring context: 35B                                                                                   0.0s
 => [internal] load metadata for docker.io/library/centos:7                                                        0.0s
 => CACHED [1/5] FROM docker.io/library/centos:7                                                                   0.0s
 => [internal] load build context                                                                                  0.0s
 => => transferring context: 738B                                                                                  0.0s
 => [2/5] RUN yum install epel-release -y && yum install nginx -y && yum clean all                                33.2s
 => [3/5] COPY index.html /usr/share/nginx/html/index.html                                                         0.0s
 => [4/5] COPY nginx-ssl.conf /etc/nginx/conf.d/nginx-ssl.conf;                                                    0.0s
 => [5/5] RUN sed -i "s|80|8080|g" /etc/nginx/nginx.conf                                                           0.2s
 => exporting to image                                                                                             0.3s
 => => exporting layers                                                                                            0.3s
 => => writing image sha256:7b6c1dd89bd8b7f97b37cb48e73ae14074ffe8655c2c5bc3c7bfd7772b224b19                       0.0s
 => => naming to docker.io/dimmaryanto93/centos:1.0

➜ 07-dockerfile  docker image inspect dimmaryanto93/centos:1.0 -f '{{json .Config.ExposedPorts }}'
{"443/tcp":{},"8080/tcp":{}}

NOTES: jika ingin menjalankan image tersebut, kita perlu siapkan ssl certificatenya dulu kemudian kita copy ke /etc/pki/nginx/server.crt dan /etc/pki/nginx/private/server.key menggunakan openssl

Cleanup

Seperti biasa, setelah kita mencobanya. kita bersih-bersih ya. berikut perintahnya:

For Bash script:

For Powershell script:

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