The services
The services section
Services are the main functionality of Epazote, is where the URL’s and the rules based on the response are defined, since options vary from service to service, an example could help better to understand the setup:
services:
my service 1:
url: http://myservice.domain.tld/_healthcheck_
timeout: 5
seconds: 60
log: http://monitor.domain.tld
expect:
status: 200
header:
content-type: application/json
body: find this string on my site
if_not:
cmd: sv restart /services/my_service_1
notify: [email protected]
msg: |
line 1 bla bla
line 2
if_status:
500:
cmd: reboot
404:
cmd: sv restart /services/cache
msg: restarting cache
notify: [email protected] [email protected]
if_header:
x-amqp-kapputt:
cmd: restart abc
notify: [email protected]
msg: |
The rabbit is angry
& hungry
x-db-kapputt:
cmd: svc restart /services/db
other service:
url: https://self-signed.ssl.tld/ping
header:
Origin: http://localhost
Accept-Encoding: gzip
insecure: true
ssl:
hours: 48
minutes: 3
redirect service:
url: http://test.domain.tld/
follow: yes
hour: 1
threshold:
unhealthy: 1
expect:
status: 302
if_not:
cmd: service restart abc
notify: yes
emoji: 1F600-1F621
salt-master:
test: pgrep -f salt
if_not:
cmd: service restart salt_master
notify: [email protected]
services - name of service (string)
An unique string that identifies your service, in the above example, there are 3 services named: - my service 1 - other service - redirect service
services - url (string)
URL of the service to supervise
services - follow (boolean true/false)
By default if a 302 Status code is received, Epazote will not follow it, if you would like to follow all redirects, this setting must be set to true.
services - insecure (boolean true/false)
This option explicitly allows Epazote to perform “insecure” SSL connections. It will disable the certificate verification.
services - ssl (seconds, minutes, hours)
Alert before the certificate expires:
ssl:
hours: 24
services - stop (int)
Defines the number or times the cmd will be executed, by default the cmd
is executed only once, with the intention to avoid indefinitely loops. If value
is set to -1 the cmd never stops. defaults to 0, stop 2 will execute
“0, 1, 2” (3 times) the cmd.
services - timeout in seconds (int)
Timeout specifies a time limit for the HTTP requests, A value of zero means no timeout, defaults to 5 seconds.
services - retry_limit (int)
Specifies the number of times to retry an request, defaults to 3.
services - retry_interval (int)
Specifies the time between attempts in milliseconds. The default value is 500 (0.5 seconds).
services - read_limit (int)
Read only N number of bytes instead of the full
body. This helps to make a more “complete” request and
avoid getting an HTTP status code 408 when testing aws ELB.
services - threshold (healthy/unhealthy)
Alert after the threshold has been reached, by default is set to 0 (disabled):
threshold:
healthy: 2
unhealth: 2
If set to 0 it will be disabled.
services - seconds, minutes, hours
How often to check the service, the options are: (Only one should be used)
- seconds N
- minutes N
- hours N
N should be an integer, defaults to 60 seconds.
services - log (URL)
An URL to post all events, default disabled.
services - expect
The expect block options are:
- status (int)
- header (key, value)
- body (regular expression)
- if_not (Action block)
services - expect - status
An Integer representing the expected HTTP Status Code
services - expect - header (start_with match)
A key-value map of expected headers, it can be only one or more.
The headers will be considered valid if they starts with the required value,
for example if you want to check for Content-type: application/json; charset=utf-8
you can simple do something like:
header:
Content-Type: application/json
This helps to simplify the matching and useful in cases where the headers
changes, for example: Content-Range: bytes 100-64656926/64656927 can be
matched with:
header:
Content-Range: bytes
services - expect - body
A regular expression used to match a string on the body of the site, use full in cases you want to ensure that the content delivered is always the same or keeps a pattern.
services - expect (How it works)
The expect logic tries to implement a
if-else logic status, header,
body are the if and the if_not block becomes the else.
if
status
header
body
else:
if_not
In must cases only one option is required, check on the above example for the service named “redirect service”.
In case that more than one option is used, this is the order in how they are evaluated, no meter how they where introduced on the configuration file:
1. body
2. status
3. header
The reason for this order is related to performance, at the end we want to
monitor/supervise the services in an efficient way avoiding to waste extra
resources, in must cases only the HTTP Headers are enough to take an action,
therefore we don’t need to read the full body page, because of this if no
body is defined, Epazote will only read the Headers saving with this
time and process time.
services - expect - if_not
if_not is a block with an action of what to do it we don’t get what we where
expecting (expect). See services - Actions
services - if_status & if_header
There maybe cases in where third-party dependencies are down and because of this
your application could not be working properly, for this cases the if_status
and if_header could be useful.
For example if the database is your application could start responding an status code 500 or either a custom header and based on does values take execute an action:
The format for if_status is a key-pair where key is an int representing an
HTTP status code, and the value an Action option
The format for if_header is a key-pair where key is a string of something
you could relate/match and has in other if_X conditions, value is an Action.
This are the only if's and the order of execution:
1. if_status
2. if_header
3. if_not
This means that if a service uses if_status and if_not, it will
evaluate first the if_status and execute an Action if required, in case
an if_status and if_header are set, same applies, first is evaluated
if_status, then if_header and last if_not.
services - Actions
An Action has five options: - cmd - notify - msg - emoji - http
They can be used all together, only one or either none.
services - Actions - cmd (string)
cmd Contains the command to be executed.
services - Actions - notify (string)
notify Should contain yes, the email email address or addresses (space separated)
of the recipients that will be notified when the action is executed.
If the string is yes the global recipients will be used.
services - Actions - msg (list)
msg:
- send this if exit 0 (all OK)
- send this if exit 1 (something is wrong)
Based on the exit status either msg[0] or msg[1] is used,
services - Actions - emoji (list)
emoji Unicode characters
to be used in the subject, example:
emoji:
- 1F600
- 1F621
If services are OK they will use the first 1F600 if not they will
use 1F621, if set to 0 no emoji will be used. The idea behind using
unicode/emoji
is to cough attention faster and not just ignore the email thinking is spam.
service - Actions - http (list(key, value))
A custom URL to GET/POST depending on the exit status, example:
http:
- url: "https://api.hipchat.com/v1/rooms/message?auth_token=your_token&room_id=7&from=Alerts&message=service+OK+_name_+_because_"
- url: "https://api.hipchat.com/"
header:
Content-Type: application/x-www-form-urlencoded
data: |
room_id=10&from=Alerts&message=_name_+exit+code+_exit_
method: POST
When a service fails or returns an exit 1 the second url
https://api.hipchat.com/ with method POST and the custom data
will be used, notice that all the ocurances on the data that are within an
_(key)_ will be replaced with the corresponding value, in this case:
room_id=10&from=Alerts&message=_name_+exit+code+_exit_
will be replaced with:
room_id=10&from=Alerts&message=SERVICE NAME+exit+code+0
When recovery the first url will be used, in this case will be a GET instead of a post, so:
https://api.hipchat.com/v1/rooms/message?auth_token=your_token&room_id=7&from=Alerts&message=service+OK+_name_+_because_
becomes:
https://api.hipchat.com/v1/rooms/message?auth_token=your_token&room_id=7&from=Alerts&message=service+OK+SERVICE+NAME+STATUS+200
notice that the name, exit, because are been replaced with the values of name, exit, because of the service.
services - Test
Epazote It is mainly used for HTTP services, for supervising other applications that don’t listen or accept HTTP connections, like a database, cache engine, etc. There are tools like daemontools, immortal as already mentioned, even so, Epazote can eventually be used to execute an action based on the exit of a command for example:
salt-master:
test: pgrep -f salt
if_not:
cmd: service restart salt_master
notify: [email protected]
In this case: test: pgrep -f salt will execute the cmd on the if_not
block in case the exit code is > 0, from the pgrep man page:
EXIT STATUS
The pgrep and pkill utilities return one of the following values upon exit:
0 One or more processes were matched.
1 No processes were matched.
2 Invalid options were specified on the command line.
3 An internal error occurred.
Extra setup
green dots give some comfort – Because of this when using the log
option an extra service could be configure as a receiver for all the post
that Epazote produce and based on the data obtained create a custom
dashboard, something similar to: https://status.cloud.google.com/ or
http://status.aws.amazon.com/