{"id":246,"date":"2022-02-12T23:00:00","date_gmt":"2022-02-13T04:00:00","guid":{"rendered":"http:\/\/sycured.127.0.0.1.sslip.io\/?p=246"},"modified":"2024-01-14T11:49:10","modified_gmt":"2024-01-14T16:49:10","slug":"container-multiple-processes","status":"publish","type":"post","link":"http:\/\/10.42.0.68:8080\/blog\/container-multiple-processes","title":{"rendered":"Container with multiple processes"},"content":{"rendered":"\n<p>Last week, I needed to create a docker image doing a simple thing:<\/p>\n\n\n\n<ul>\n<li>downloading 1 XML file<\/li>\n\n\n\n<li>converting it to JSON<\/li>\n\n\n\n<li>serve both files<\/li>\n<\/ul>\n\n\n\n<p>But I&#8217;ve a hard part: every 15 minutes, I need to look if a new version of the XML file is available and in case, running the entire process.<\/p>\n\n\n\n<p>Let&#8217;s go to see how I did it<\/p>\n\n\n\n<!--more-->\n\n\n\n<h2 class=\"wp-block-heading\">Requirements<\/h2>\n\n\n\n<ul>\n<li><a href=\"https:\/\/alpinelinux.org\/\">alpine linux<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.gnu.org\/software\/gawk\/\">gawk<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/unit.nginx.org\/\">nginx unit<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.python.org\/\">python<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.gnu.org\/software\/wget\/\">wget<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xml2json\">xml2json<\/a><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Docker image creation<\/h2>\n\n\n\n<p>I use <a href=\"https:\/\/github.com\/docker-library\/python\/blob\/e0dacc4c580f4ad0aa68136789add4e37bdaab91\/3.10\/alpine3.15\/Dockerfile\">Python container based on alpine linux<\/a> as the base, adding an <a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L2\">environment variable to avoid PIP cache<\/a>.<\/p>\n\n\n\n<p>To have multiple processes inside the contianer, I use <a href=\"https:\/\/github.com\/just-containers\/s6-overlay\">s6-overlay<\/a> and I think to <a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L13\">rewrite the global path<\/a> because by default it&#8217;s not including the path where Python binaries (pip, python) are installed.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Process with dependencies and type of run<\/h2>\n\n\n\n<p>S6-overlay permits to define dependencies between processes and it&#8217;s exactly what I need because:<\/p>\n\n\n\n<ul>\n<li>docker-entrypoint needs to run before running the real nginx daemon but without persistence, it&#8217;s a one-shot at boot<\/li>\n\n\n\n<li>cron daemon needs to run in the background and has 0 dependency<\/li>\n\n\n\n<li>nginx unit needs to run in the background when docker-entrypoint has ended the configuration<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">cron<\/h3>\n\n\n\n<p>To setup cron, we have few steps inside the Dockerfile:<\/p>\n\n\n\n<ul>\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L7\">copy the shell script<\/a> to execute cron as the daemon<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L21\">set this script<\/a> has &#8220;longrun&#8221;<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L28\">add it<\/a> to be run at boot<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">nginx unit<\/h3>\n\n\n\n<p>Steps:<\/p>\n\n\n\n<ul>\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L8\">copy the shell script<\/a> to execute nginx unit as a daemon<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L18\">set unit log file<\/a> to output on \/dev\/stdout<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L19\">set nginx access log<\/a> to output on \/dev\/stdout<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L22\">set this script<\/a> has &#8220;longrun&#8221;<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L23\">add docker-entrypoint<\/a> has a dependency<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L27\">add it<\/a> to be run at boot<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">docker-entrypoint<\/h3>\n\n\n\n<p>Steps:<\/p>\n\n\n\n<ul>\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/45e0b382736ed928a2c8eba043d355a07e27d895\/Dockerfile#L24\">create the directory<\/a> where we&#8217;ll have config files<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L25\">set this script<\/a> has &#8220;oneshot&#8221;<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L26\">set the command<\/a> to execute the docker-entrypoint (I don&#8217;t copy the file like for other services)<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Entrypoint<\/h3>\n\n\n\n<p>Finally, we&#8217;ll use s6 has <a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\/blob\/main\/Dockerfile#L39\">the entrypoint<\/a> for this container<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Link<\/h2>\n\n\n\n<p>The repository: <a href=\"https:\/\/github.com\/sycured\/xmltv_tnt_json_unit\">xmltv_tnt_json_unit<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Last week, I needed to create a docker image doing a simple thing: But I&#8217;ve a hard part: every 15 minutes, I need to look if a new version of the XML file is available and in case, running the entire process. Let&#8217;s go to see how I did it<\/p>\n","protected":false},"author":1,"featured_media":78,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"saved_in_kubio":false,"footnotes":""},"categories":[14],"tags":[24,29],"_links":{"self":[{"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/posts\/246"}],"collection":[{"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/comments?post=246"}],"version-history":[{"count":1,"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/posts\/246\/revisions"}],"predecessor-version":[{"id":247,"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/posts\/246\/revisions\/247"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/media\/78"}],"wp:attachment":[{"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/media?parent=246"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/categories?post=246"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/10.42.0.68:8080\/wp-json\/wp\/v2\/tags?post=246"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}