Systemd: Add DefaultTasksMax=infinity to service file

[icinga2] / doc / 15-troubleshooting.md

# Icinga 2 Troubleshooting <a id="troubleshooting"></a>

## Required Information <a id="troubleshooting-information-required"></a>

Please ensure to provide any detail which may help reproduce and understand your issue.
Whether you ask on the community channels or you create an issue at [GitHub](https://github.com/Icinga), make sure
that others can follow your explanations. If necessary, draw a picture and attach it for
better illustration. This is especially helpful if you are troubleshooting a distributed
setup.

We've come around many community questions and compiled this list. Add your own
findings and details please.

* Describe the expected behavior in your own words.
* Describe the actual behavior in one or two sentences.
* Ensure to provide general information such as:
        * How was Icinga 2 installed (and which repository in case) and which distribution are you using
        * `icinga2 --version`
        * `icinga2 feature list`
        * `icinga2 daemon -C`
        * [Icinga Web 2](https://www.icinga.com/products/icinga-web-2/) version (screenshot from System - About)
        * [Icinga Web 2 modules](https://www.icinga.com/products/icinga-web-2-modules/) e.g. the Icinga Director (optional)
* Configuration insights:
        * Provide complete configuration snippets explaining your problem in detail
        * Your [icinga2.conf](04-configuring-icinga-2.md#icinga2-conf) file
        * If you run multiple Icinga 2 instances, the [zones.conf](04-configuring-icinga-2.md#zones-conf) file (or `icinga2 object list --type Endpoint` and `icinga2 object list --type Zone`) from all affected nodes.
* Logs
        * Relevant output from your main and [debug log](15-troubleshooting.md#troubleshooting-enable-debug-output) in `/var/log/icinga2`. Please add step-by-step explanations with timestamps if required.
        * The newest Icinga 2 crash log if relevant, located in `/var/log/icinga2/crash`
* Additional details
        * If the check command failed, what's the output of your manual plugin tests?
        * In case of [debugging](20-development.md#development) Icinga 2, the full back traces and outputs

## Analyze your Environment <a id="troubleshooting-analyze-environment"></a>

There are many components involved on a server running Icinga 2. When you
analyze a problem, keep in mind that basic system administration knowledge
is also key to identify bottlenecks and issues.

> **Tip**
>
> [Monitor Icinga 2](08-advanced-topics.md#monitoring-icinga) and use the hints for further analysis.

* Analyze the system's performance and dentify bottlenecks and issues.
* Collect details about all applications (e.g. Icinga 2, MySQL, Apache, Graphite, Elastic, etc.).
* If data is exchanged via network (e.g. central MySQL cluster) ensure to monitor the bandwidth capabilities too.
* Add graphs and screenshots to your issue description

Install tools which help you to do so. Opinions differ, let us know if you have any additions here!

### Analyse your Linux/Unix Environment <a id="troubleshooting-analyze-environment-linux"></a>

[htop](https://hisham.hm/htop/) is a better replacement for `top` and helps to analyze processes
interactively.

```
yum install htop
apt-get install htop
```

If you are for example experiencing performance issues, open `htop` and take a screenshot.
Add it to your question and/or bug report.

Analyse disk I/O performance in Grafana, take a screenshot and obfuscate any sensitive details.
Attach it when posting a question to the community channels.

The [sysstat](https://github.com/sysstat/sysstat) package provides a number of tools to
analyze the performance on Linux. On FreeBSD you could use `systat` for example.

```
yum install sysstat
apt-get install sysstat
```

Example for `vmstat` (summary of memory, processes, etc.):

```
// summary
vmstat -s
// print timestamps, format in MB, stats every 1 second, 5 times
vmstat -t -S M 1 5
```

Example for `iostat`:

```
watch -n 1 iostat
```

Example for `sar`:
```
sar //cpu
sar -r //ram
sar -q //load avg
sar -b //I/O
```

`sysstat` also provides the `iostat` binary. On FreeBSD you could use `systat` for example.

If you are missing checks and metrics found in your analysis, add them to your monitoring!

### Analyze your Windows Environment <a id="troubleshooting-analyze-environment-windows"></a>

A good tip for Windows are the tools found inside the [Sysinternals Suite](https://technet.microsoft.com/en-us/sysinternals/bb842062.aspx).

You can also start `perfmon` and analyze specific performance counters.
Keep notes which could be important for your monitoring, and add service
checks later on.

## Enable Debug Output <a id="troubleshooting-enable-debug-output"></a>

### Enable Debug Output on Linux/Unix <a id="troubleshooting-enable-debug-output-linux"></a>

Enable the `debuglog` feature:

    # icinga2 feature enable debuglog
    # service icinga2 restart

The debug log file can be found in `/var/log/icinga2/debug.log`.

Alternatively you may run Icinga 2 in the foreground with debugging enabled. Specify the console
log severity as an additional parameter argument to `-x`.

    # /usr/sbin/icinga2 daemon -x notice

The [log severity](09-object-types.md#objecttype-filelogger) can be one of `critical`, `warning`, `information`, `notice`
and `debug`.

### Enable Debug Output on Windows <a id="troubleshooting-enable-debug-output-windows"></a>

Open a command prompt with administrative privileges and enable the debug log feature.

    C:> icinga2.exe enable feature debuglog

Ensure that the Icinga 2 service already writes the main log into `C:\ProgramData\icinga2\var\log\icinga2`.
Restart the Icinga 2 service and open the newly created `debug.log` file.

    C:> net stop icinga2
    C:> net start icinga2

## List Configuration Objects <a id="list-configuration-objects"></a>

The `icinga2 object list` CLI command can be used to list all configuration objects and their
attributes. The tool also shows where each of the attributes was modified.

> **Tip**
>
> Use the Icinga 2 API to access [config objects at runtime](12-icinga2-api.md#icinga2-api-config-objects) directly.

That way you can also identify which objects have been created from your [apply rules](17-language-reference.md#apply).

    # icinga2 object list

    Object 'localhost!ssh' of type 'Service':
      * __name = 'localhost!ssh'
      * check_command = 'ssh'
        % = modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 5:3-5:23
      * check_interval = 60
        % = modified in '/etc/icinga2/conf.d/templates.conf', lines 24:3-24:21
      * host_name = 'localhost'
        % = modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 4:3-4:25
      * max_check_attempts = 3
        % = modified in '/etc/icinga2/conf.d/templates.conf', lines 23:3-23:24
      * name = 'ssh'
      * retry_interval = 30
        % = modified in '/etc/icinga2/conf.d/templates.conf', lines 25:3-25:22
      * templates = [ 'ssh', 'generic-service' ]
        % += modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 1:0-7:1
        % += modified in '/etc/icinga2/conf.d/templates.conf', lines 22:1-26:1
      * type = 'Service'
      * vars
        % += modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 6:3-6:19
        * sla = '24x7'
          % = modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 6:3-6:19

    [...]

You can also filter by name and type:

    # icinga2 object list --name *ssh* --type Service
    Object 'localhost!ssh' of type 'Service':
      * __name = 'localhost!ssh'
      * check_command = 'ssh'
        % = modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 5:3-5:23
      * check_interval = 60
        % = modified in '/etc/icinga2/conf.d/templates.conf', lines 24:3-24:21
      * host_name = 'localhost'
        % = modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 4:3-4:25
      * max_check_attempts = 3
        % = modified in '/etc/icinga2/conf.d/templates.conf', lines 23:3-23:24
      * name = 'ssh'
      * retry_interval = 30
        % = modified in '/etc/icinga2/conf.d/templates.conf', lines 25:3-25:22
      * templates = [ 'ssh', 'generic-service' ]
        % += modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 1:0-7:1
        % += modified in '/etc/icinga2/conf.d/templates.conf', lines 22:1-26:1
      * type = 'Service'
      * vars
        % += modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 6:3-6:19
        * sla = '24x7'
          % = modified in '/etc/icinga2/conf.d/hosts/localhost/ssh.conf', lines 6:3-6:19

    Found 1 Service objects.

    [2014-10-15 14:27:19 +0200] information/cli: Parsed 175 objects.

Runtime modifications via the [REST API](12-icinga2-api.md#icinga2-api-config-objects)
are not immediately updated. Furthermore there is a known issue with
[group assign expressions](17-language-reference.md#group-assign) which are not reflected in the host object output.
You need to restart Icinga 2 in order to update the `icinga2.debug` cache file.


## Where are the check command definitions? <a id="check-command-definitions"></a>

Icinga 2 features a number of built-in [check command definitions](10-icinga-template-library.md#icinga-template-library) which are
included with

    include <itl>
    include <plugins>

in the [icinga2.conf](04-configuring-icinga-2.md#icinga2-conf) configuration file. These files are not considered configuration files and will be overridden
on upgrade, so please send modifications as proposed patches upstream. The default include path is set to
`LocalStateDir + "/share/icinga2/includes"`.

You should add your own command definitions to a new file in `conf.d/` called `commands.conf`
or similar.

## Checks <a id="troubleshooting-checks"></a>

### Executed Command for Checks <a id="checks-executed-command"></a>

* Use the Icinga 2 API to [query](12-icinga2-api.md#icinga2-api-config-objects-query) host/service objects
for their check result containing the executed shell command.
* Use the Icinga 2 [console cli command](11-cli-commands.md#cli-command-console)
to fetch the checkable object, its check result and the executed shell command.
* Alternatively enable the [debug log](15-troubleshooting.md#troubleshooting-enable-debug-output) and look for the executed command.

Example for a service object query using a [regex match](18-library-reference.md#global-functions-regex)
on the name:

    $ curl -k -s -u root:icinga -H 'Accept: application/json' -H 'X-HTTP-Method-Override: GET' -X POST 'https://localhost:5665/v1/objects/services' \
    -d '{ "filter": "regex(pattern, service.name)", "filter_vars": { "pattern": "^http" }, "attrs": [ "__name", "last_check_result" ] }' | python -m json.tool
    {
        "results": [
            {
                "attrs": {
                    "__name": "example.localdomain!http",
                    "last_check_result": {
                        "active": true,
                        "check_source": "example.localdomain",
                        "command": [
                            "/usr/local/sbin/check_http",
                            "-I",
                            "127.0.0.1",
                            "-u",
                            "/"
                        ],

      ...

                    }
                },
                "joins": {},
                "meta": {},
                "name": "example.localdomain!http",
                "type": "Service"
            }
        ]
    }

Example for using the `icinga2 console` CLI command evaluation functionality:

    $ ICINGA2_API_PASSWORD=icinga icinga2 console --connect 'https://root@localhost:5665/' \
    --eval 'get_service("example.localdomain", "http").last_check_result.command' | python -m json.tool
    [
        "/usr/local/sbin/check_http",
        "-I",
        "127.0.0.1",
        "-u",
        "/"
    ]

Example for searching the debug log:

    # icinga2 feature enable debuglog
    # systemctl restart icinga2
    # tail -f /var/log/icinga2/debug.log | grep "notice/Process"


### Checks are not executed <a id="checks-not-executed"></a>

* Check the [debug log](15-troubleshooting.md#troubleshooting-enable-debug-output) to see if the check command gets executed.
* Verify that failed depedencies do not prevent command execution.
* Make sure that the plugin is executable by the Icinga 2 user (run a manual test).
* Make sure the [checker](11-cli-commands.md#enable-features) feature is enabled.
* Use the Icinga 2 API [event streams](12-icinga2-api.md#icinga2-api-event-streams) to receive live check result streams.

Examples:

    # sudo -u icinga /usr/lib/nagios/plugins/check_ping -4 -H 127.0.0.1 -c 5000,100% -w 3000,80%

    # icinga2 feature enable checker
    The feature 'checker' is already enabled.

Fetch all check result events matching the `event.service` name `random`:

    $ curl -k -s -u root:icinga -X POST 'https://localhost:5665/v1/events?queue=debugchecks&types=CheckResult&filter=match%28%22random*%22,event.service%29'


### Check Fork Errors <a id="check-fork-errors"></a>

We've learned that newer kernel versions introduce a [fork limit for cgroups](https://lwn.net/Articles/663873/)
which is enabled in SLES 12 SP2+ for example. The default value
for `DefaultTasksMax` in Systemd is set to `512`.

Icinga 2 relies on forking child processes to execute commands
and might therefore hit this limit in larger setups.

The error message could look like this:

    2017-01-12T11:55:40.742685+01:00 icinga2-master1 kernel: [65567.582895] cgroup: fork rejected by pids controller in /system.slice/icinga2.service

In order to solve the problem, increase the value for `DefaultTasksMax`
or set it to `infinity`:


    [root@icinga2-master1.localdomain /]# cp /usr/lib/systemd/system/icinga2.service /etc/systemd/system/icinga2.service
    [root@icinga2-master1.localdomain /]# vim /etc/systemd/system/icinga2.service

    [Service]

    DefaultTasksMax=infinity

    [root@icinga2-master1.localdomain /]# systemctl daemon-reload
    [root@icinga2-master1.localdomain /]# systemctl restart icinga2

Please note that this setting is available since Systemd version 226.

> **Note**
>
> Future versions of Icinga 2 will add the setting as default.

### Late Check Results <a id="late-check-results"></a>

[Icinga Web 2](https://www.icinga.com/products/icinga-web-2/) provides
a dashboard overview for `overdue checks`.

The REST API provides the [status] URL endpoint with some generic metrics
on Icinga and its features.

    # curl -k -s -u root:icinga 'https://localhost:5665/v1/status' | python -m json.tool | less

You can also calculate late check results via the REST API:

* Fetch the `last_check` timestamp from each object
* Compare the timestamp with the current time and add `check_interval` multiple times (change it to see which results are really late, like five times check_interval)

You can use the [icinga2 console](11-cli-commands.md#cli-command-console) to connect to the instance, fetch all data
and calculate the differences. More infos can be found in [this blogpost](https://www.icinga.com/2016/08/11/analyse-icinga-2-problems-using-the-console-api/).

    # ICINGA2_API_USERNAME=root ICINGA2_API_PASSWORD=icinga icinga2 console --connect 'https://localhost:5665/'

    <1> => var res = []; for (s in get_objects(Service).filter(s => s.last_check < get_time() - 2 * s.check_interval)) { res.add([s.__name, DateTime(s.last_check).to_string()]) }; res

    [ [ "10807-host!10807-service", "2016-06-10 15:54:55 +0200" ], [ "mbmif.int.netways.de!disk /", "2016-01-26 16:32:29 +0100" ] ]

Or if you are just interested in numbers, call [len](18-library-reference.md#array-len) on the result array `res`:

    <2> => var res = []; for (s in get_objects(Service).filter(s => s.last_check < get_time() - 2 * s.check_interval)) { res.add([s.__name, DateTime(s.last_check).to_string()]) }; res.len()

    2.000000

If you need to analyze that problem multiple times, just add the current formatted timestamp
and repeat the commands.

    <23> => DateTime(get_time()).to_string()

    "2017-04-04 16:09:39 +0200"

    <24> => var res = []; for (s in get_objects(Service).filter(s => s.last_check < get_time() - 2 * s.check_interval)) { res.add([s.__name, DateTime(s.last_check).to_string()]) }; res.len()

    8287.000000

More details about the Icinga 2 DSL and its possibilities can be
found in the [language](17-language-reference.md#language-reference) and [library](18-library-reference.md#library-reference) reference chapters.

### Late Check Results in Distributed Environments <a id="late-check-results-distributed"></a>

When it comes to a distributed HA setup, each node is responsible for a load-balanced amount of checks.
Host and Service objects provide the attribute `paused`. If this is set to `false`, the current node
actively attempts to schedule and execute checks. Otherwise the node does not feel responsible.

    <3> => var res = {}; for (s in get_objects(Service).filter(s => s.last_check < get_time() - 2 * s.check_interval)) { res[s.paused] += 1 }; res
    {
      @false = 2.000000
      @true = 1.000000
    }

You may ask why this analysis is important? Fair enough - if the numbers are not inverted in a HA zone
with two members, this may give a hint that the cluster nodes are in a split-brain scenario, or you've
found a bug in the cluster.


If you are running a cluster setup where the master/satellite executes checks on the client via
[top down command endpoint](06-distributed-monitoring.md#distributed-monitoring-top-down-command-endpoint) mode,
you might want to know which zones are affected.

This analysis assumes that clients which are not connected, have the string `connected` in their
service check result output and their state is `UNKNOWN`.

    <4> => var res = {}; for (s in get_objects(Service)) { if (s.state==3) { if (match("*connected*", s.last_check_result.output)) { res[s.zone] += [s.host_name] } } };  for (k => v in res) { res[k] = len(v.unique()) }; res

    {
      Asia = 31.000000
      Europe = 214.000000
      USA = 207.000000
    }

The result set shows the configured zones and their affected hosts in a unique list. The output also just prints the numbers
but you can adjust this by omitting the `len()` call inside the for loop.

## Notifications are not sent <a id="notifications-not-sent"></a>

* Check the [debug log](15-troubleshooting.md#troubleshooting-enable-debug-output) to see if a notification is triggered.
* If yes, verify that all conditions are satisfied.
* Are any errors on the notification command execution logged?

Please ensure to add these details with your own description
to any question or issue posted to the community channels.

Verify the following configuration:

* Is the host/service `enable_notifications` attribute set, and if so, to which value?
* Do the [notification](09-object-types.md#objecttype-notification) attributes `states`, `types`, `period` match the notification conditions?
* Do the [user](09-object-types.md#objecttype-user) attributes `states`, `types`, `period` match the notification conditions?
* Are there any notification `begin` and `end` times configured?
* Make sure the [notification](11-cli-commands.md#enable-features) feature is enabled.
* Does the referenced NotificationCommand work when executed as Icinga user on the shell?

If notifications are to be sent via mail, make sure that the mail program specified inside the
[NotificationCommand object](09-object-types.md#objecttype-notificationcommand) exists.
The name and location depends on the distribution so the preconfigured setting might have to be
changed on your system.


Examples:

    # icinga2 feature enable notification
    The feature 'notification' is already enabled.

You can use the Icinga 2 API [event streams](12-icinga2-api.md#icinga2-api-event-streams) to receive live notification streams:

    $ curl -k -s -u root:icinga -X POST 'https://localhost:5665/v1/events?queue=debugnotifications&types=Notification'


## Feature is not working <a id="feature-not-working"></a>

* Make sure that the feature configuration is enabled by symlinking from `features-available/`
to `features-enabled` and that the latter is included in [icinga2.conf](04-configuring-icinga-2.md#icinga2-conf).
* Are the feature attributes set correctly according to the documentation?
* Any errors on the logs?

Look up the [object type](09-object-types.md#object-types) for the required feature and verify it is enabled:

    # icinga2 object list --type <feature object type>

Example for the `graphite` feature:

    # icinga2 object list --type GraphiteWriter

## Configuration is ignored <a id="configuration-ignored"></a>

* Make sure that the line(s) are not [commented out](17-language-reference.md#comments) (starting with `//` or `#`, or
encapsulated by `/* ... */`).
* Is the configuration file included in [icinga2.conf](04-configuring-icinga-2.md#icinga2-conf)?

Run the [configuration validation](11-cli-commands.md#config-validation) and add `notice` as log severity.
Search for the file which should be included i.e. using the `grep` CLI command.

    # icinga2 daemon -C -x notice | grep command

## Configuration attributes are inherited from <a id="configuration-attribute-inheritance"></a>

Icinga 2 allows you to import templates using the [import](17-language-reference.md#template-imports) keyword. If these templates
contain additional attributes, your objects will automatically inherit them. You can override
or modify these attributes in the current object.

The [object list](15-troubleshooting.md#list-configuration-objects) CLI command allows you to verify the attribute origin.

## Configuration Value with Single Dollar Sign <a id="configuration-value-dollar-sign"></a>

In case your configuration validation fails with a missing closing dollar sign error message, you
did not properly escape the single dollar sign preventing its usage as [runtime macro](03-monitoring-basics.md#runtime-macros).

    critical/config: Error: Validation failed for Object 'ping4' (Type: 'Service') at /etc/icinga2/zones.d/global-templates/windows.conf:24: Closing $ not found in macro format string 'top-syntax=${list}'.

Correct the custom attribute value to

    "top-syntax=$${list}"

## Cluster and Clients Troubleshooting <a id="troubleshooting-cluster"></a>

This applies to any Icinga 2 node in a [distributed monitoring setup](06-distributed-monitoring.md#distributed-monitoring-scenarios).

You should configure the [cluster health checks](06-distributed-monitoring.md#distributed-monitoring-health-checks) if you haven't
done so already.

> **Note**
>
> Some problems just exist due to wrong file permissions or applied packet filters. Make
> sure to check these in the first place.

### Cluster Troubleshooting Connection Errors <a id="troubleshooting-cluster-connection-errors"></a>

General connection errors could be one of the following problems:

* Incorrect network configuration
* Packet loss
* Firewall rules preventing traffic

Use tools like `netstat`, `tcpdump`, `nmap`, etc. to make sure that the cluster communication
works (default port is `5665`).

    # tcpdump -n port 5665 -i any

    # netstat -tulpen | grep icinga

    # nmap yourclusternode.localdomain

### Cluster Troubleshooting SSL Errors <a id="troubleshooting-cluster-ssl-errors"></a>

If the cluster communication fails with SSL error messages, make sure to check
the following

* File permissions on the SSL certificate files
* Does the used CA match for all cluster endpoints?
  * Verify the `Issuer` being your trusted CA
  * Verify the `Subject` containing your endpoint's common name (CN)
  * Check the validity of the certificate itself

Steps on the client `icinga2-node2.localdomain`:

    # ls -la /etc/icinga2/pki

    # cd /etc/icinga2/pki/
    # openssl x509 -in icinga2-node2.localdomain.crt -text
    Certificate:
        Data:
            Version: 1 (0x0)
            Serial Number: 2 (0x2)
        Signature Algorithm: sha1WithRSAEncryption
            Issuer: C=DE, ST=Bavaria, L=Nuremberg, O=NETWAYS GmbH, OU=Monitoring, CN=Icinga CA
            Validity
                Not Before: Jan  7 13:17:38 2014 GMT
                Not After : Jan  5 13:17:38 2024 GMT
            Subject: C=DE, ST=Bavaria, L=Nuremberg, O=NETWAYS GmbH, OU=Monitoring, CN=icinga2-node2.localdomain
            Subject Public Key Info:
                Public Key Algorithm: rsaEncryption
                    Public-Key: (4096 bit)
                    Modulus:
                    ...

Try to manually connect from `icinga2-node2.localdomain` to the master node `icinga2-node1.localdomain`:

    # openssl s_client -CAfile /etc/icinga2/pki/ca.crt -cert /etc/icinga2/pki/icinga2-node2.localdomain.crt -key /etc/icinga2/pki/icinga2-node2.localdomain.key -connect icinga2-node1.localdomain:5665

    CONNECTED(00000003)
    ---
    ...

If the connection attempt fails or your CA does not match, [verify the master and client certificates](15-troubleshooting.md#troubleshooting-cluster-ssl-certificate-verification).

#### Cluster Troubleshooting Unauthenticated Clients <a id="troubleshooting-cluster-unauthenticated-clients"></a>

Unauthenticated nodes are able to connect. This is required for client setups.

Master:

    [2015-07-13 18:29:25 +0200] information/ApiListener: New client connection for identity 'icinga-client' (unauthenticated)

Client as command execution bridge:

    [2015-07-13 18:29:26 +1000] notice/ApiEvents: Discarding 'execute command' message from 'icinga-master': Invalid endpoint origin (client not allowed).

If these messages do not go away, make sure to [verify the master and client certificates](15-troubleshooting.md#troubleshooting-cluster-ssl-certificate-verification).

#### Cluster Troubleshooting SSL Certificate Verification <a id="troubleshooting-cluster-ssl-certificate-verification"></a>

Make sure to verify the client's certificate and its received `ca.crt` in `/etc/icinga2/pki` and ensure that
both instances are signed by the **same CA**.

    # openssl verify -verbose -CAfile /etc/icinga2/pki/ca.crt /etc/icinga2/pki/icinga2-node1.localdomain.crt
    icinga2-node1.localdomain.crt: OK

    # openssl verify -verbose -CAfile /etc/icinga2/pki/ca.crt /etc/icinga2/pki/icinga2-node2.localdomain.crt
    icinga2-node2.localdomain.crt: OK

Fetch the `ca.crt` file from the client node and compare it to your master's `ca.crt` file:

    # scp icinga2-node2:/etc/icinga2/pki/ca.crt test-client-ca.crt
    # diff -ur /etc/icinga2/pki/ca.crt test-client-ca.crt

On SLES11 you'll need to use the `openssl1` command instead of `openssl`.

### Cluster Troubleshooting Message Errors <a id="troubleshooting-cluster-message-errors"></a>

At some point, when the network connection is broken or gone, the Icinga 2 instances
will be disconnected. If the connection can't be re-established between endpoints in the same HA zone,
they remain in a Split-Brain-mode and history may differ.

Although the Icinga 2 cluster protocol stores historical events in a [replay log](15-troubleshooting.md#troubleshooting-cluster-replay-log)
for later synchronisation, you should make sure to check why the network connection failed.

### Cluster Troubleshooting Command Endpoint Errors <a id="troubleshooting-cluster-command-endpoint-errors"></a>

Command endpoints can be used [for clients](06-distributed-monitoring.md#distributed-monitoring-top-down-command-endpoint)
as well as inside an [High-Availability cluster](06-distributed-monitoring.md#distributed-monitoring-scenarios).

There is no cli command for manually executing the check, but you can verify
the following (e.g. by invoking a forced check from the web interface):

* `/var/log/icinga2/icinga2.log` contains connection and execution errors.
 * The ApiListener is not enabled to [accept commands](06-distributed-monitoring.md#distributed-monitoring-top-down-command-endpoint).
 * `CheckCommand` definition not found on the remote client.
 * Referenced check plugin not found on the remote client.
 * Runtime warnings and errors, e.g. unresolved runtime macros or configuration problems.
* Specific error messages are also populated into `UNKNOWN` check results including a detailed error message in their output.
* Verify the `check_source` object attribute. This is populated by the node executing the check.
* More verbose logs are found inside the [debug log](15-troubleshooting.md#troubleshooting-enable-debug-output).

* Use the Icinga 2 API [event streams](12-icinga2-api.md#icinga2-api-event-streams) to receive live check result streams.

Fetch all check result events matching the `event.service` name `remote-client`:

    $ curl -k -s -u root:icinga -X POST 'https://localhost:5665/v1/events?queue=debugcommandendpoint&types=CheckResult&filter=match%28%22remote-client*%22,event.service%29'



### Cluster Troubleshooting Config Sync <a id="troubleshooting-cluster-config-sync"></a>

If the cluster zones do not sync their configuration, make sure to check the following:

* Within a config master zone, only one configuration master is allowed to have its config in `/etc/icinga2/zones.d`.
** The master syncs the configuration to `/var/lib/icinga2/api/zones/` during startup and only syncs valid configuration to the other nodes.
** The other nodes receive the configuration into `/var/lib/icinga2/api/zones/`.
* The `icinga2.log` log file in `/var/log/icinga2` will indicate whether this ApiListener
[accepts config](06-distributed-monitoring.md#distributed-monitoring-top-down-config-sync), or not.

Verify the object's [version](09-object-types.md#object-types) attribute on all nodes to
check whether the config update and reload was succesful or not.

### Cluster Troubleshooting Overdue Check Results <a id="troubleshooting-cluster-check-results"></a>

If your master does not receive check results (or any other events) from the child zones
(satellite, clients, etc.), make sure to check whether the client sending in events
is allowed to do so.

The [distributed monitoring conventions](06-distributed-monitoring.md#distributed-monitoring-conventions)
apply. So, if there's a mismatch between your client node's endpoint name and its provided
certificate's CN, the master will deny all events.

> **Tip**
>
> [Icinga Web 2](02-getting-started.md#setting-up-icingaweb2) provides a dashboard view
> for overdue check results.

Enable the [debug log](15-troubleshooting.md#troubleshooting-enable-debug-output) on the master
for more verbose insights.

If the client cannot authenticate, it's a more general [problem](15-troubleshooting.md#troubleshooting-cluster-unauthenticated-clients).

The client's endpoint is not configured on nor trusted by the master node:

    Discarding 'check result' message from 'icinga2b': Invalid endpoint origin (client not allowed).

The check result message sent by the client does not belong to the zone the checkable object is
in on the master:

    Discarding 'check result' message from 'icinga2b': Unauthorized access.


### Cluster Troubleshooting Replay Log <a id="troubleshooting-cluster-replay-log"></a>

If your `/var/lib/icinga2/api/log` directory grows, it generally means that your cluster
cannot replay the log on connection loss and re-establishment. A master node for example
will store all events for not connected endpoints in the same and child zones.

Check the following:

* All clients are connected? (e.g. [cluster health check](06-distributed-monitoring.md#distributed-monitoring-health-checks)).
* Check your [connection](15-troubleshooting.md#troubleshooting-cluster-connection-errors) in general.
* Does the log replay work, e.g. are all events processed and the directory gets cleared up over time?
* Decrease the `log_duration` attribute value for that specific [endpoint](09-object-types.md#objecttype-endpoint).