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Nico Schottelius, 12/29/2021 01:35 PM

The ungleich monitoring infrastructure

Monitoring Guide

We are using prometheus, grafana, blackbox_exporter and monit for monitoring.

Architecture v2 overview

  • There is 1 internal IPv6 only monitoring system per place
    • emonitor1.place5.ungleich.ch (real hardware)
    • emonitor1.place6.ungleich.ch (real hardware)
    • Main role: alert if services are down
  • There is 1 external dual stack monitoring system
    • monitoring.place4.ungleich.ch
    • Main role: alert if one or more places are unreachable from outside
    • Also monitors all nodes to be have all data available
  • There is 1 customer enabled monitoring system
    • monitoring-v3.ungleich.ch
    • Uses LDAP
    • Runs on a VM
  • There are many monitored systems
  • Systems can be marked as intentionally down (but still kept monitored)
  • Monitoring systems are built with the least amount of external dependencies

Monitoring and Alerting workflow

  • Once per day the SRE team checks the relevant dashboards
    • Are systems down that should not be?
    • Is there a trend visible of systems failing?
  • If the monitoring system sent a notification about a failed system
    • The SRE team fixes it the same day if possible
  • If the monitoring system sent a critical error message
    • Instant fixes are to be applied by the SRE team

Adding a new production system

  • Install the correct exporter (often: node_exporter)
  • Limit access via nftables

Configuring prometheus

Use promtool check config to verify the configuration.

[21:02:48] server1.place11:~# promtool check config /etc/prometheus/prometheus.yml 
Checking /etc/prometheus/prometheus.yml
  SUCCESS: 4 rule files found

Checking /etc/prometheus/blackbox.rules
  SUCCESS: 3 rules found

Checking /etc/prometheus/ceph-alerts.rules
  SUCCESS: 8 rules found

Checking /etc/prometheus/node-alerts.rules
  SUCCESS: 8 rules found

Checking /etc/prometheus/uplink-monitoring.rules
  SUCCESS: 1 rules found

Configuring emonitors

cdist config -bj7 -p3 -vv emonitor1.place{5,6,7}.ungleich.ch

Querying prometheus

Use promtool query instant to query values:

[21:00:26] server1.place11:~# promtool query instant http://localhost:9090 'probe_success{dc="place5"} == 1'
probe_success{dc="place5", instance="193.192.225.73", job="routers-place5", protocol="ipv4", sensiblehostname="router1"} => 1 @[1593889492.577]
probe_success{dc="place5", instance="195.141.230.103", job="routers-place5", protocol="ipv4", sensiblehostname="router2"} => 1 @[1593889492.577]
probe_success{dc="place5", instance="2001:1700:3500::12", job="routers-place5", protocol="ipv6", sensiblehostname="router2"} => 1 @[1593889492.577]
probe_success{dc="place5", instance="2001:1700:3500::2", job="routers-place5", protocol="ipv6", sensiblehostname="router1"} => 1 @[1593889492.577]

Typical queries:

Creating a sum of all metrics that contains a common label. For instance summing over all jobs:

sum by (job) (probe_success)

[17:07:58] server1.place11:/etc/prometheus# promtool  query instant http://localhost:9090 'sum by (job) (probe_success)
'
{job="routers-place5"} => 4 @[1593961699.969]
{job="uplink-place5"} => 4 @[1593961699.969]
{job="routers-place6'"} => 4 @[1593961699.969]
{job="uplink-place6"} => 4 @[1593961699.969]
{job="core-services"} => 3 @[1593961699.969]
[17:08:19] server1.place11:/etc/prometheus#

Combining different metrics for filtering. For instance to filter all metrics of type "probe_success" which also have a metric probe_ip_protocol with value = 4

  • probe_ip_protocol{dc="place5", instance="147.78.195.249", job="routers-place5", protocol="ipv4"} => 4 @[1593961766.619]

The operator on is used to filter

sum(probe_success * on(instance) probe_ip_protocol == 4)

Creating an alert:

  • if the sum of all jobs of a certain regex and match on ip protocol is 0
    • this particular job indicates total loss of connectivity
  • We want to get a vector like this:
    • job="routers-place5", protocol = 4
    • job="uplink-place5", protocol = 4
    • job="routers-place5", protocol = 6
    • job="uplink-place5", protocol = 6

Query for IPv4 of all routers:

[17:09:26] server1.place11:/etc/prometheus# promtool  query instant http://localhost:9090 'sum(probe_success{job=~"routers-.*"} * on(instance) group_left(job) probe_ip_protocol == 4) by (job)'
{job="routers-place5"} => 8 @[1593963562.281]
{job="routers-place6'"} => 8 @[1593963562.281]

Query for all IPv4 of all routers:

[17:39:22] server1.place11:/etc/prometheus# promtool  query instant http://localhost:9090 'sum(probe_success{job=~"routers-.*"} * on(instance) group_left(job) probe_ip_protocol == 6) by (job)'
{job="routers-place5"} => 12 @[1593963626.483]
{job="routers-place6'"} => 12 @[1593963626.483]
[17:40:26] server1.place11:/etc/prometheus#

Query for all IPv6 uplinks:

[17:40:26] server1.place11:/etc/prometheus# promtool  query instant http://localhost:9090 'sum(probe_success{job=~"uplink-.*"} * on(instance) group_left(job) probe_ip_protocol == 6) by (job)'
{job="uplink-place5"} => 12 @[1593963675.835]
{job="uplink-place6"} => 12 @[1593963675.835]
[17:41:15] server1.place11:/etc/prometheus#

Query for all IPv4 uplinks:

[17:41:15] server1.place11:/etc/prometheus# promtool  query instant http://localhost:9090 'sum(probe_success{job=~"uplink-.*"} * on(instance) group_left(job) probe_ip_protocol == 4) by (job)'
{job="uplink-place5"} => 8 @[1593963698.108]
{job="uplink-place6"} => 8 @[1593963698.108]

The values 8 and 12 means:

  • 8 = 4 (ip version 4) * probe_success (2 routers are up)
  • 8 = 6 (ip version 6) * probe_success (2 routers are up)

To normalise, we would need to divide by 4 (or 6):

[17:41:38] server1.place11:/etc/prometheus# promtool  query instant http://localhost:9090 'sum(probe_success{job=~"uplink-.*"} * on(instance) group_left(job) probe_ip_protocol == 4) by (job) / 4'
{job="uplink-place5"} => 2 @[1593963778.885]
{job="uplink-place6"} => 2 @[1593963778.885]
[17:42:58] server1.place11:/etc/prometheus# promtool  query instant http://localhost:9090 'sum(probe_success{job=~"uplink-.*"} * on(instance) group_left(job) probe_ip_protocol == 6) by (job) / 6'
{job="uplink-place5"} => 2 @[1593963788.276]
{job="uplink-place6"} => 2 @[1593963788.276]

However if we are only interested in whether 0 are up, it does not matter as 0*4 = 0 and 0*6 = 0.

Using Grafana

  • Username for changing items: "admin"
  • Username for viewing dashboards: "ungleich"
  • Passwords in the password store

Managing alerts

Showing current alerts:

# Alpine needs URL (why?)
amtool alert query --alertmanager.url=http://localhost:9093

# Debian
amtool alert query

[14:54:35] monitoring.place6:~# amtool alert query
Alertname            Starts At                 Summary                                                               
InstanceDown         2020-07-01 10:24:03 CEST  Instance red1.place5.ungleich.ch down                                 
InstanceDown         2020-07-01 10:24:03 CEST  Instance red3.place5.ungleich.ch down                                 
InstanceDown         2020-07-05 12:51:03 CEST  Instance apu-router2.place5.ungleich.ch down                          
UngleichServiceDown  2020-07-05 13:51:19 CEST  Ungleich internal service https://staging.swiss-crowdfunder.com down  
InstanceDown         2020-07-05 13:55:33 CEST  Instance https://swiss-crowdfunder.com down                           
CephHealthSate       2020-07-05 13:59:49 CEST  Ceph Cluster is not healthy.                                          
LinthalHigh          2020-07-05 14:01:41 CEST  Temperature on risinghf-19 is 32.10012512207032                       
[14:54:41] monitoring.place6:~#

Silencing alerts:

[14:59:45] monitoring.place6:~# amtool silence add -c "Ceph is actually fine" alertname=CephHealthSate
4a5c65ff-4af3-4dc9-a6e0-5754b00cd2fa
[15:00:06] monitoring.place6:~# amtool silence query
ID                                    Matchers                  Ends At                  Created By  Comment                
4a5c65ff-4af3-4dc9-a6e0-5754b00cd2fa  alertname=CephHealthSate  2020-07-05 14:00:06 UTC  root        Ceph is actually fine  
[15:00:13] monitoring.place6:~#

Better using author and co. TOBEFIXED

Severity levels

The following notions are used:

  • critical = panic = calling to the whole team
  • warning = something needs to be fixed = email to sre, non paging
  • info = not good, might be an indication for fixing something, goes to a matrix room

Labeling

Labeling in Prometheus is a science on its own and has a lot of pitfalls. Let's start with some:

  • The relabel_configs are applied BEFORE scraping
  • The metric_relabel_configs are applied AFTER scraping (contains different labels!)
  • regular expression are not the "default" RE, but RE2
  • metric_label_config does not apply to automatic labels like up !
    • You need to use relabel_configs

Setting "roles"

We use the label "role" to define a primary purpose per host. Example from 2020-07-07:

    relabel_configs:
      - source_labels: [__address__]
        regex:         '.*(server|monitor|canary-vm|vpn|server|apu-router|router).*.ungleich.ch.*'
        target_label:  'role'
        replacement:   '$1'
      - source_labels: [__address__]
        regex:         'ciara.*.ungleich.ch.*'
        target_label:  'role'
        replacement:   'server'
      - source_labels: [__address__]
        regex:         '.*:9283'
        target_label:  'role'
        replacement:   'ceph'
      - source_labels: [__address__]
        regex:         '((ciara2|ciara4).*)'
        target_label:  'role'
        replacement:   'down'
      - source_labels: [__address__]
        regex:         '.*(place.*).ungleich.ch.*'
        target_label:  'dc'
        replacement:   '$1'

What happens here:

  • address contains the hostname+port, f.i. server1.placeX.ungleich.ch:9100
  • We apply some roles by default (the server, monitor etc.)
  • Special rule for ciara, which does not match the serverX pattern
  • ciara2 and ciara4 in above example are intentionally down
  • At the end we setup the "dc" label in case the host is in a place of ungleich

Marking hosts down

If a host or service is intentionally down, change its role to down.

SMS and Voice notifications

We use https://ecall.ch.

Uses email sender based authorization.

Alertmanager clusters

  • The outside monitors form one alertmanager cluster
  • The inside monitors form one alertmanager cluster

Monit

We use monit for monitoring and restarting daemons. See `__ungleich_monit` type in dot-cdist. This is very similar to supervise and co.

Service/Customer monitoring

  • A few blackbox things can be found on the datacenter monitoring infrastructure.
  • There's a new prometheus+grafana setup at https://service-monitoring.ungleich.ch/, deployed by @Timothée Floure for Matrix-as-a-Service monitoring. At time of writing, it also monitors the VPN server and staticwebhosting. No alertmanager yet. Partially manual.

Monitoring Rules

The following is a description of logical rules that (are, need to be, should be) in place.

External Monitoring/Alerting

To be able to catch multiple uplink errors, there should be 2 external prometheus systems operating in a cluster for alerting (alertmanagers).
The retention period of these monitoring servers can be low, as their main purpose is link down detection. No internal services need to be monitored.

External Uplink monitoring (IPv6, IPv4)

  • There should be 2 external systems that monitor via ping the two routers per place
    • Whether IPv4 and IPv6 are done by the same systems does not matter
    • However there need to be
      • 2 for IPv4 (place4, place7)
      • 2 for IPv6 (place4, ?)
  • If all uplinks of one place are down for at least 5m, we send out an emergency alert

External DNS monitoring (IPv6, IPv4)

  • There should be 2 external systems that monitor whether our authoritative DNS servers are working
  • We query whether ipv4.ungleich.ch resolves to an IPv4 address
  • We query whether ipv6.ungleich.ch resolves to an IPv6 address
  • If all external servers fail for 5m, we send out an emergency alert

Internal ceph monitors

  • Monitor whether there is a quorom
    • If there is no quorum for at least 15m, we send out an emergency alert

Monitoring monitoring

  • The internal monitors monitor whether the external monitors are reachable

Typical tasks

Adding customer monitoring

Customers can have their own alerts. By default, if customer resources are monitored, we ...

  • If we do not have access to the VM: ask the user to setup prometheus node exporter and whitelist port 9100 to be accessible from 2a0a:e5c0:2:2:0:c8ff:fe68:bf3b
  • Otherwise do above step ourselves
  • ensure the customer has an LDAP account
  • create a folder on grafana of https://monitoring-v3.ungleich.ch/ with the same name as the LDAP user (for instance "nicocustomer")
  • Modify the permissions of the folder
    • Remove the standard Viewer Role
    • Add User -> the LDAP user -> View

Setup a dashboard. If it allows selecting nodes:

  • Limit the variable by defining the regex in the dashboard settings

If the user requested alerts

  • Configure them in cdist, type __dcl_monitoring_server2020/files/prometheus-v3/

Finally:

cdist config -v monitoring-v3.ungleich.ch

Old Monitoring

Before 2020-07 our monitoring incorporated more services/had a different approach:

We used the following technology / products for the monitoring:

  • consul (service discovery)
  • prometheus (exporting, gathering, alerting)
  • Grafana (presenting)

Prometheus and grafana are located on the monitoring control machines

  • monitoring.place5.ungleich.ch
  • monitoring.place6.ungleich.ch

The monitoring machines above are now being replaced by emonitor1.place5.ungleich.ch and emonitor1.place6.ungleich.ch. The difference is that the new machines are independent from ceph and have a dedicated uplink.

Consul

We used a consul cluster for each datacenter (e.g. place5 and place6).
The servers are still located on the physical machines (red{1..3} resp. black{1..3}) and the agents are running on all other monitored machines (such as servers and VMs)

consul is configured to publish the service its host is providing (e.g. the exporters)

There is a inter-datacenter communication (wan gossip) [https://www.consul.io/docs/guides/datacenters.html]

Consul has some drawbacks (nodes leaving the cluster -> node by default not monitored anymore) and the advantage of fully dynamic monitoring is not a big advantage for physical machines of which we already have an inventory.

Authentication

The grafana authentication worked over ldap. (See The ungleich LDAP guide)
All users in the devops group will be mapped to the Admin role, all other users will be Viewers

This was retired and monitoring servers have static usernames to be independent of the LDAP infrastructure.

Updated by Nico Schottelius almost 3 years ago · 34 revisions