iHow to declare new probes - reed-alert - Lightweight agentless alerting system for server	Err	bitreich.org	70
hgit clone git://bitreich.org/reed-alert/ git://enlrupgkhuxnvlhsf6lc3fziv5h2hhfrinws65d7roiv6bfj7d652fid.onion/reed-alert/	URL:git://bitreich.org/reed-alert/ git://enlrupgkhuxnvlhsf6lc3fziv5h2hhfrinws65d7roiv6bfj7d652fid.onion/reed-alert/	bitreich.org	70
1Log	/scm/reed-alert/log.gph	bitreich.org	70
1Files	/scm/reed-alert/files.gph	bitreich.org	70
1Refs	/scm/reed-alert/refs.gph	bitreich.org	70
1Tags	/scm/reed-alert/tag	bitreich.org	70
1README	/scm/reed-alert/file/README.gph	bitreich.org	70
1LICENSE	/scm/reed-alert/file/LICENSE.gph	bitreich.org	70
i---	Err	bitreich.org	70
1commit a384acbcfd91a1067dc91a83d1f16fc23a6c881f	/scm/reed-alert/commit/a384acbcfd91a1067dc91a83d1f16fc23a6c881f.gph	bitreich.org	70
1parent f352b8458e9b406ce8795bf00c704c260c511cd6	/scm/reed-alert/commit/f352b8458e9b406ce8795bf00c704c260c511cd6.gph	bitreich.org	70
hAuthor: Solene Rapenne <solene@perso.pw>	URL:mailto:solene@perso.pw	bitreich.org	70
iDate:   Mon, 22 Jan 2018 08:06:19 +0100	Err	bitreich.org	70
i	Err	bitreich.org	70
iHow to declare new probes	Err	bitreich.org	70
i	Err	bitreich.org	70
iDiffstat:	Err	bitreich.org	70
i  M README                              |      76 +++++++++++++++++++++++++++++++	Err	bitreich.org	70
i	Err	bitreich.org	70
i1 file changed, 76 insertions(+), 0 deletions(-)	Err	bitreich.org	70
i---	Err	bitreich.org	70
1diff --git a/README b/README	/scm/reed-alert/file/README.gph	bitreich.org	70
i@@ -370,3 +370,79 @@ than 98%, the "buzzer" alert will make some bad noises in the room to	Err	bitreich.org	70
i warn me about this.	Err	bitreich.org	70
i 	Err	bitreich.org	70
i Note : escalation is an alias for the **or** function.	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+Extend with your own probes	Err	bitreich.org	70
i+===========================	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+It is likely that you want to write your own probes. While using the	Err	bitreich.org	70
i+command probe can be convenient, you may want to have a probe with	Err	bitreich.org	70
i+more parameters and better integration than the command probe.	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+There are two methods for adding probes :	Err	bitreich.org	70
i+- in the configuration file before using it	Err	bitreich.org	70
i+- in a separated lisp file that you load from the configuration file	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+If you want to reuse for multiples configuration files or servers, I	Err	bitreich.org	70
i+would recommend a separate file, otherwise, adding it at the top of	Err	bitreich.org	70
i+the configuration file can be convenient too.	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+Using a shell command	Err	bitreich.org	70
i+---------------------	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+A minimum of Common LISP comprehension is needed for this. But using	Err	bitreich.org	70
i+the easiest way to go by writing a probe using a command shell, the	Err	bitreich.org	70
i+declaration can be really simple.	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+We are going to write a probe that will use curl to fetch an page and	Err	bitreich.org	70
i+then grep on the output to look for a pattern. The return code of grep	Err	bitreich.org	70
i+will be the return status of the probe, if grep finds the pattern,	Err	bitreich.org	70
i+it's a success, if not it's a failure.	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+In the following code, the "create-probe" part is a macro that will	Err	bitreich.org	70
i+write most of the code for you. Then, we use "command-return-code"	Err	bitreich.org	70
i+function which will execute the shell command passed as a string (or	Err	bitreich.org	70
i+as a list) and return the correct values in case of success or	Err	bitreich.org	70
i+failure.	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+    (create-probe	Err	bitreich.org	70
i+     check-http-pattern	Err	bitreich.org	70
i+     (command-return-code (format nil "curl ~a | grep -i ~a"	Err	bitreich.org	70
i+                                  (getf params :url) (getf params :pattern))))	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+If you don't know LISP, "format" function works like "printf", using	Err	bitreich.org	70
i+"~a" instead of "%s". This is the only required thing to know if you	Err	bitreich.org	70
i+want to reuse the previous code.	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+Then we can call it like this :	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+    (=> notifier check-http-pattern :url "http://127.0.0.1"; :pattern "Powered by cl-yag")	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+Using plain LISP	Err	bitreich.org	70
i+----------------	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+We have seen previously how tocreate new probes from a shell command,	Err	bitreich.org	70
i+but one may want to do it in LISP, allowing to use full features of	Err	bitreich.org	70
i+the language and even some libraries to check values in a database for	Err	bitreich.org	70
i+example. I recommend to read the "probes.lisp" file, it's the best way	Err	bitreich.org	70
i+to learn how to write a new probe. But as an example, we will learn	Err	bitreich.org	70
i+from the easiest probe included : file-exists	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+    (create-probe	Err	bitreich.org	70
i+     file-exists	Err	bitreich.org	70
i+     (let ((result (probe-file (getf params :path))))	Err	bitreich.org	70
i+       (if result	Err	bitreich.org	70
i+           t	Err	bitreich.org	70
i+           (list nil "file not found"))))	Err	bitreich.org	70
i+	Err	bitreich.org	70
i+Like before, we use the "create-probe" macro and give a name to the	Err	bitreich.org	70
i+probe. Then, we have to write some code, in the current case, check if	Err	bitreich.org	70
i+the file exists. Finally, if it is a success, we have to return **t**,	Err	bitreich.org	70
i+if it fails we return a list containing **nil** and a value or a	Err	bitreich.org	70
i+string. The second element in the list will replaced %result% in the	Err	bitreich.org	70
i+notification command, so you can use something explicit, a	Err	bitreich.org	70
i+concatenation of a message with the return value etc..". Parameters	Err	bitreich.org	70
i+should be get with getf from **params** variable, allowing to use a	Err	bitreich.org	70
i+default value in case it's not defined in the configuration file.	Err	bitreich.org	70
.