{"id":2683,"date":"2012-06-23T12:45:45","date_gmt":"2012-06-23T11:45:45","guid":{"rendered":"http:\/\/www.devco.net\/?p=2683"},"modified":"2012-12-30T00:16:29","modified_gmt":"2012-12-29T23:16:29","slug":"mcollective-2-0-complex-discovery-statements","status":"publish","type":"post","link":"https:\/\/www.devco.net\/archives\/2012\/06\/23\/mcollective-2-0-complex-discovery-statements.php","title":{"rendered":"MCollective 2.0 &#8211; Complex Discovery Statements"},"content":{"rendered":"<p>This ia a post in a series of posts I am doing about <a href=\"http:\/\/www.devco.net\/archives\/2012\/06\/16\/a-look-at-mcollective-2-0-0-and-beyond.php\">MCollective 2.0 and later<\/a>. <\/p>\n<p>In the past discovery was reasonably functional, certainly at the time I first demoed it around 2009 it was very unique.  Now other discovery frameworks exist that does all sorts of interesting things and so we did 3 huge improvements to discovery in MCollective that again puts it apart from the rest, these are:<\/p>\n<ul>\n<li>Complex discovery language with full boolean support etc<\/li>\n<li>Plugins that lets you query any node data as discovery sources<\/li>\n<li>Plugins that lets you use any data available to the client as discovery sources<\/li>\n<\/ul>\n<p>I&#8217;ll focus on the first one today.  A quick example will be best.<\/p>\n<p><code><\/p>\n<pre lang=\"console\">\r\n$ mco service restart httpd -S \"((customer=acme and environment=staging) or environment=development) and \/apache\/\"\r\n<\/pre>\n<p><\/code><\/p>\n<p>Here we are a hypothetical hosting company and we want to restart all the apache services for development.  One of the customers though use their staging environment as development so it&#8217;s a bit more complex.  This discovery query will find the <em>acme<\/em> customers staging environment and development for everyone else and then select the apache machines out of those.<\/p>\n<p>You can also do excludes and some other bits, these 2 statements are identical:<\/p>\n<p><code><\/p>\n<pre lang=\"console\">\r\n$ mco find -S \"environment=development and !customer=acme\"\r\n$ mco find -S \"environment=development and not customer=acme\"\r\n<\/pre>\n<p><\/code><\/p>\n<p>This basic form of the language can be described with the EBNF below:<\/p>\n<p><code><\/p>\n<pre lang=\"console\">\r\ncompound = [\"(\"] expression [\")\"] {[\"(\"] expression [\")\"]}\r\nexpression = [!|not]statement [\"and\"|\"or\"] [!|not] statement\r\nchar = A-Z | a-z | < | > | => | =< | _ | - |* | \/ { A-Z | a-z | < | > | => | =< | _ | - | * | \/ | }\r\nint = 0|1|2|3|4|5|6|7|8|9{|0|1|2|3|4|5|6|7|8|9|0}\r\n<\/pre>\n<p><\/code><\/p>\n<p>It's been extended since but more on that below and in a future post.<\/p>\n<p>It's very easy to use this filter in your code, here's a Ruby script that sets the same compound filter and restarts apache:<\/p>\n<p><code><\/p>\n<pre lang=\"ruby\">\r\n#!\/usr\/bin\/ruby\r\n\r\nrequire \"mcollective\"\r\n\r\ninclude MCollective::RPC\r\n\r\nc = rpcclient(\"service\")\r\nc.compound_filter '((customer=acme and environment=staging) or environment=development) and \/apache\/'\r\n\r\nprintrpc c.restart(:service => \"httpd\")\r\n<\/pre>\n<p><\/code><\/p>\n<p>These filters are combined with other filters so you're welcome to mix in Identity filters etc using the other filter types and they will be evaluated additively.<\/p>\n<p>These filters also supports querying node data, a simple example of such a query can be seen here:<\/p>\n<p><code><\/p>\n<pre lang=\"console\">\r\n$ mco service restart httpd -S \"fstat('\/etc\/httpd\/conf\/httpd.conf').md5 = \/51b08b8\/\"\r\n<\/pre>\n<p><\/code><\/p>\n<p>This will match all machines with a certain MD5 hash for the apache config file and restart them.  More on these plugins the next post where I'll show you how to write your own and use them.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>This ia a post in a series of posts I am doing about MCollective 2.0 and later. In the past discovery was reasonably functional, certainly at the time I first demoed it around 2009 it was very unique. Now other discovery frameworks exist that does all sorts of interesting things and so we did 3 [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","footnotes":""},"categories":[7],"tags":[121,85,78,106,13],"_links":{"self":[{"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/posts\/2683"}],"collection":[{"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/comments?post=2683"}],"version-history":[{"count":13,"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/posts\/2683\/revisions"}],"predecessor-version":[{"id":2882,"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/posts\/2683\/revisions\/2882"}],"wp:attachment":[{"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/media?parent=2683"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/categories?post=2683"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.devco.net\/wp-json\/wp\/v2\/tags?post=2683"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}