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Monitor

Monitoring the Chef Infra Server involves two types of checks: application and system. In addition monitoring the HTTP requests that workstations and nodes are making to the Chef Infra Server and per-disk data storage volumes is recommended.

Monitoring Priorities

The following sections describe the priorities for monitoring of the Chef Infra Server. In particular, running out of disk space is the primary cause of failure.

Disks

Over time, and with enough data, disks will fill up or exceed the per-disk quotas that may have been set for them and they will not be able to write data. A disk that is not able to write data will not be able to support certain components of the Chef Infra Server, such as PostgreSQL, service log files, and deleted file handles. Monitoring disk usage is the best way to ensure that disks don’t fill up or exceed their quota.

Use the following commands to monitor global disk usage on a Chef Infra Server with a typical installation:

du -sh /var/opt/opscode

and:

du -sh /var/log/opscode

To keep the Chef Infra Server healthy, both /var/opt/opscode and /var/log/opscode should never exceed 80% use. In situations where disk space grows at a rapid pace, it may be preferable to shut down the Chef Infra Server and contact Chef support.

The following components should be monitored for signs that disks may be rapidly filling up:

  • PostgreSQL PostgreSQL is the data store for the Chef Infra Server.
  • Log files If /var/log/opscode is taking up a lot of disk space, ensure that the Chef Infra Server log rotation cron job is running without errors. These errors can be found in /var/log/messages, /var/log/syslog and/or the root user’s local mail.
  • Deleted file handles Running processes with file handles associated with one (or more) deleted files will prevent the disk space being used by the deleted files from being reclaimed. Use the sudo lsof | grep '(deleted)' command to find all deleted file handles.

Application Checks

Application-level checks should be done periodically to ensure that there is enough disk space, enough memory, and that the front-end and back-end services are communicating.

Erlang

Many components of the Chef Infra Server are written using Erlang and run on the BEAM virtual machine. One feature of Erlang and BEAM is the ability to interact with the running service using a command shell. For example:

cd /opt/opscode/embedded
  export PATH=$PATH:/opt/opscode/bin:/opt/opscode/embedded/bin
  bin/erl -setcookie service_name -name me@127.0.0.1 -remsh service_name@127.0.0.1

where service_name is bifrost or erchef. This command will then open a shell that is connected to the Erchef processes:

Erlang R15B02 (erts-5.9.2) [source] [64-bit] ...

Warning

Connecting to the Erlang processes should only be done when directed by Chef support services.

To connect to the oc_bifrost service, use the following command:

erl -setcookie oc_bifrost -name me@127.0.0.1 -remsh oc_bifrost@127.0.0.1

To connect to the opscode-erchef service, use the following command:

erl -setcookie erchef -name me@127.0.0.1 -remsh erchef@127.0.0.1

To disconnect from the shell, use the following key sequence CTRL-g, q, and then ENTER.

The output from the shell after the CTRL-g looks similar to:

(erchef@127.0.0.1)1>
User switch command

then enter q, and then hit ENTER to exit the shell.

Some commands should not be entered when interacting with a running service while using the command shell, including:

  • q() kills the Erlang node
  • init:stop()
  • exit or exit() does nothing

eper tools

As root on the Chef Infra Server, point to the bundled eper package of debugging tools. Replace the 2nd and 5th path entries and the X.XX.X value in the following path with the items that occur on the system.

export ERL_LIB=:/opt/{chef-server,opscode}/embedded/service/{erchef,opscode-erchef}/lib/eper-X.XX.X/ebin/

Open an Erlang command shell to begin diagnosing service issues on the Chef Infra Server:

Eshell V5.10.4  (abort with ^G)
(erchef@127.0.0.1)1>

The dtop tool presents a view on the Erlang virtual machine that is similar to the linuxdagnostic command. The period at the end of the dtop command is required for the command to take effect.

(erchef@127.0.0.1)1> dtop:start().

To stop the dtop command, run:

(erchef@127.0.0.1)1> dtop:stop().

To disconnect from the shell, use the following key sequence CTRL-g, q, and then ENTER.

The output from the shell after the CTRL-g looks similar to:

(erchef@127.0.0.1)1>
User switch command

then enter q, and then hit ENTER to exit the shell.

Nginx

Use Nginx to monitor for services that may be returning 504 errors. Use the following command on a front-end machine:

grep 'HTTP/1.1" 504' /var/log/opscode/nginx/access.log

and then extract the URLs and sort them by uniq count:

grep 'HTTP/1.1" 504' nginx-access.log | cut -d' ' -f8 | sort | uniq -c | sort

In a large installation, restricting these results to a subset of results may be necessary:

tail -10000 nginx-access.log | grep 'HTTP/1.1" 504' | cut -d' ' -f8 | sort | uniq -c | sort

PostgreSQL

psql is the management tool for PostgreSQL. It can be used to obtain information about data stored in PostgreSQL. For more information about psql, see http://www.postgresql.org/docs/manuals/, and then the doc set appropriate for the version of PostgreSQL being used.

To connect to the PostgreSQL database, run the following command:

cd /opt/opscode/embedded/service/postgresql/
  export PATH=$PATH:/opt/opscode/bin:/opt/opscode/embedded/bin
  bin/psql -U opscode_chef

Warning

Connecting to the PostgreSQL database should only be done when directed by Chef support services.

Redis

The redis_lb service located on the back end machine handles requests that are made from the Nginx service that is located on all front end machines in a Chef Infra Server cluster.

In the event of a disk full condition for the Redis data store, the dump.rdb (the primary data store .rdb used by Redis) can become corrupt and saved as a zero byte file.

When this occurs, after the redis_lb service started, it’s logs will show a statement similar to the following:

2015-03-23_16:11:31.44256 [11529] 23 Mar 16:10:09.624 # Server started, Redis version 2.8.2
2015-03-23_16:11:31.44256 [11529] 23 Mar 16:10:09.624 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
2015-03-23_16:11:31.44257 [11529] 23 Mar 16:11:31.438 # Short read or OOM loading DB. Unrecoverable error, aborting now.

The dump.rdb file will be empty:

ls -al /var/opt/opscode/redis_lb/data/
total 20
drwxr-x--- 2 opscode opscode 4096 Mar 23 15:58 .
drwxr-x--- 4 opscode opscode 4096 Dec 22 18:59 ..
-rw-r--r-- 1 opscode opscode    0 Mar 23 15:58 dump.rdb

This situation is caused by a bug in Redis where saves are allowed to succeed even when the disk has been full for some time, and not just on edge cases where the disk becomes full as Redis is writing. To fix this issue, do the following:

  1. Stop the redis_lb service:

    chef-server-ctl stop redis_lb

  2. Remove the corrupt files:

    cd /var/opt/opscode/redis_lb/data
rm -fr *rdb

  3. Start the redis_lb service:

    chef-server-ctl start redis_lb

less /var/log/opscode/redis_lb/current
2015-03-23_17:05:18.82516 [28676] 23 Mar 17:05:18.825 * The server is now ready to accept connections on port 16379

  4. Reconfigure the Chef Infra Server to re-populate Redis:

    chef-server-ctl reconfigure

  5. Verify that Redis is re-populated, as indicated by the key dl_default:

    /opt/opscode/embedded/bin/redis-cli -p 16379 keys \*
1) "dl_default"

System Checks

System-level checks should be done for the ports and services status.

chef-backend-ctl status

The chef-backend-ctl status subcommand is used to check the status of services running in the Chef Backend server topology. This command will verify the status of the following services on the node it is run on:

  • leaderl
  • postgresql
  • etcd
  • epmd
  • elasticsearch

It will also check on the status of other nodes in the cluster, from the current node’s perspective. For example:

chef-backend-ctl status
Service Local Status Time in State Distributed Node Status
leaderl running (pid 1191) 53d 15h 11m 12s leader: 1; waiting: 0; follower: 2;    total: 3
epmd running (pid 1195) 53d 15h 11m 12s status: local-only
etcd running (pid 1189) 53d 15h 11m 12s health: green; healthy nodes: 3/3
postgresql running (pid 40686) 0d 12h 36m 23s leader: 1; offline: 0; syncing: 0;    synced: 2
elasticsearch running (pid 47423) 0d 12h 18m 6s state: green; nodes online: 3/3

System Local Status Distributed Node Status
disks /var/log/chef-backend: OK; /var/opt/chef-backend: OK health: green; healthy    nodes: 3/3

More information about each service can be found in the individual service logs in /var/opt/chef-backend/.

opscode-authz

The authz API provides a high-level view of the health of the opscode-authz service with a simple endpoint: _ping. This endpoint can be accessed using cURL and GNU Wget. For example:

curl http://localhost:9463/_ping

This command typically prints a lot of information. Use Python to use pretty-print output:

curl http://localhost:9463/_ping | python -mjson.tool

opscode-erchef

The status API provides a high-level view of the health of the system with a simple endpoint: _status. This endpoint can be accessed using cURL and GNU Wget. For example:

curl http://localhost:8000/_status

which will return something similar to:

{
  "status":"pong",
  "upstreams":{"upstream_service":"pong","upstream_service":"fail",...},
}

For each of the upstream services, pong or fail is returned. The possible upstream names are:

  • chef_sql (for the postgresql service)
  • oc_chef_authz (for the opscode-authz service)

If any of the status values return fail, this typically means the Chef Infra Server is unavailable for that service.

Nodes, Workstations

If a client makes an HTTP request to the server that returns a non-specific error message, this is typically an issue with the opscode-chef or opscode-erchef services. View the full error message for these services in their respective log files. The error is most often a stacktrace from the application error. In some cases, the error message will clearly indicate a problem with another service, which can then be investigated further. For non-obvious errors, please contact Chef support services.

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