rsyslog logging

This document explains the structure of Redis Enterprise Software (RS) log entries that go into rsyslog and how to use these log entries to identify events. Also, we recommend that you secure your logs with a remote logging server and log rotation.

Logging concepts

RS adds to the log different log entries, from various cluster components, for various events and actions that take place in the cluster.

There might be many different log entries for a specific event that can be perceived externally as a single event.

For example, in order for the cluster to decide that a cluster node is down there might be various log entries added by different cluster components from various nodes with different descriptions, until the cluster gets to a final decision that the node is actually down. In other cases, similar entries might be added to the log and the cluster eventually gets to a decision that the node is actually not down.

In addition, some actions that might seem to the user as an atomic action, like removing a node from the cluster, are actually made up of several different events that take place in a sequence, and might also fail in the process.

As a result, Redis Labs enabled that by default all logs entries that are shown in the log page in the management UI are also written to syslog. Then rsyslog can be configured to monitor the syslog. All alerts are logged to syslog if the alerts are configured to be enabled, in addition to other log entries.

The log entries can be categorized into events and alerts. Events just get logged, while alerts have a state attached to them. In the Mapping UI events and alerts to log entries section below, there is a Category column that calls out for each event whether it is an event or alert. RS log entries include information about the specific event that occurred as detailed below in the Log entry structure section. In addition, rsyslog can be configured to add other information, like the event severity for example.

Since rsyslog entries do not include the severity information by default, you can use the following instructions in order to log that information (in Ubuntu): Add the following line to /etc/rsyslog.conf $template TraditionalFormatWithPRI,"%pri-text%:%timegenerated%:%HOSTNAME%:%syslogtag%:%msg:::drop-last-lf%\n”

And modify $ActionFileDefaultTemplate to use your new template $ActionFileDefaultTemplateTraditionalFormatWithPRI Make sure to save the changes and restart rsyslog in order for the changes to take effect. You can see the alerts and events under /var/log in messages log file.

Command components:

• %pri­text% ­adds the severity
• %timegenerated% ­adds the timestamp
• %HOSTNAME% ­adds the machine name
• %syslogtag% ­the RS message as detailed below in the Log entry structure section below.
• %msg:::drop­last­lf%n ­ removes duplicated log entries

Log entry structure

The log entries have the following basic structure: event_log[]:{<list of key value pairs in any order>}

• event_log­ plain static text is always shown at the beginning of the entry.
• processid­ the id of the process the logging in running under.
• listofkeyvaluepairsinanyorder­ a list of key value pairs describing the specific event. The key­values pairs can appear in any order. Some key­value pairs are always shown, and some appear depending on the specific event.
  • Key­value pairs that always appear:
    • “type” A unique code­name identifying the event logged. For the list of codenames relevant for this purpose please review the event code­name column in the Mapping UI events and alerts to log entries section below.
    • “object” has the format of “[:]”. Defines the object type, and id if relevant, of the object this event is related to. For example cluster, node with id, bdb with id, etc’.
    • “time” unix time, can be ignored in this context.
  • Key­value pairs that might appear depending on the specific entry:
    • “state” boolean with value true or false. This is relevant only for entries from category alert. True means that the alert is on. False means that the alert is off.
    • “global_threshold” a value of a threshold for alerts related to the “cluster"or “node"objects.
    • “threshold” a value of a threshold for alerts related to the “bdb” object.

Log entry samples

Below are examples of log entries that include the rsyslog configuration mentioned above that add the severity, timestamp and machine name.

Ephemeral storage passed threshold

Alert on” log entry sample: daemon.warning:Jun1414:49:20node1event_log[3464]:{“storage_util”: 90.061643120001,“global_threshold”:“70″,“object”:“node:1″,“state”: true,“time”:1434282560,“type”:“ephemeral_storage”}

The log entry above is an example of when the alert for node with id 1 “Ephemeral storage has reached 70% of its capacity” has been raised as result of storage utilization reaching the value of ~90%.

Log entry components:

• daemon.warning ­ severity of entry is warning
• Jun1414:49:20­ the timestamp of the event
• node1­ machine name
• event_log­ static text that always appears
• [3464]­ process id
• “storage_util”:90.061643120001­ current ephemeral storage utilization, in this case ~90%
• “global_threshold”:“70″­ the user configured threshold above which the alert is raised, in this case it is 70%
• “object”:“node:1″­ the object for which this alert has been raised for, in this case it is node with id 1
• “state”:true­ current state of the alert, in this case it is on
• “time”:1434282560­ can be ignored
• “type”:“ephemeral_storage"­ is the code name identifier of this specific event, see full mapping in the Mapping UI events and alerts to log entries section below

Alert off” log entry sample:

daemon.info:Jun1414:51:35node1event_log[3464]:{“storage_util”: 60.051723520008,“global_threshold”:“70″,“object”:“node:1″,“state”: false,“time”:1434283480,“type”:“ephemeral_storage”}

The log entry above is an example of when the alert for node with id 1 “Ephemeral storage has reached 70% of its capacity” has been turned off as result of storage utilization reaching the value of ~60%.

Log entry components:

• daemon.info ­ severity of entry is info
• Jun1414:51:35­ the timestamp of the event
• node1­ machine name
• event_log­ static text that always appears
• [3464]­ process id
• “storage_util”:60.051723520008­ current ephemeral storage utilization, in this case ~60%
• “global_threshold”:“70″­ the user configured threshold above which the alert is raised, in this case it is 70%
• “object”:“node:1″­ the object for which this alert has been raised for, in this case it is node with id 1
• “state”:false­ current state of the alert, in this case it is on
• “time”:1434283480­ can be ignored
• “type”:“ephemeral_storage"­ is the code name identifier of this specific event, see full mapping in the Mapping UI events and alerts to log entries section below Odd number of nodes with a minimum of three nodes alert

Alert on” log entry sample:

daemon.warning:Jun1415:25:00node1event_log[8310]:{“object”: “cluster”,“state”:true,“time”:1434284700,“node_count”:1,“type”: “even_node_count”}

The log entry above is an example of when the alert for “True high availability requires an odd number of nodes with a minimum of three nodes” has been turned on as result of the cluster having only one node.

Log entry components:

• daemon.warning­ severity of entry is warning
• Jun1415:25:00­ the timestamp of the event
• node1­ machine name
• event_log­ static text that always appears
• [8310]­ process id
• “object”:“cluster"­ the object for which this alert has been raised for, in this case it is the cluster
• “state”:true­ current state of the alert, in this case it is on
• “time”:1434284700­ can be ignored
• “node_count”:1­ the number of nodes in the cluster, in this case 1
• “type”:“even_node_count"­ is the code name identifier of this specific event, see full mapping in the Mapping UI events and alerts to log entries section below

Alert off” log entry sample:

daemon.warning:Jun1415:30:40node1event_log[8310]:{“object”: “cluster”,“state”:false,“time”:1434285200,“node_count”:3,“type”: “even_node_count”}

The log entry above is an example of when the alert for “True high availability requires an odd number of nodes with a minimum of three nodes” has been turned off as result of the cluster having 3 nodes.

Log entry components:

• daemon.info­ severity of entry is warning
• Jun1415:30:40­ the timestamp of the event
• node1­ machine name
• event_log­ static text that always appears
• [8310]­ process id
• “object”:“cluster"­ the object for which this alert has been raised for, in this case it is the cluster
• “state”:false­ current state of the alert, in this case it is off
• “time”:1434285200­ can be ignored
• “node_count”:3­ the number of nodes in the cluster, in this case 3
• “type”:“even_node_count"­ is the code name identifier of this specific event, see full mapping in the Mapping UI events and alerts to log entries section below Node has insufficient disk space for AOF rewrite

Alert on” log entry sample:

daemon.err:Jun1513:51:23node1event_log[34252]:{“used”:23457188, “missing”:604602126,“object”:“node:1″,“free”:9867264,“needed”: 637926578,“state”:true,“time”:1434365483,“disk”:705667072,“type”: “insufficient_disk_aofrw”}

The log entry above is an example of when the alert for “Node has insufficient disk space for AOF rewrite” has been turned on as result of not having enough persistent storage disk space for AOF rewrite purposes. It is missing 604602126 bytes.

Log entry components:

• daemon.err­ severity of entry is err
• Jun1513:51:23­ the timestamp of the event
• node1­ machine name
• event_log­ static text that always appears
• [34252]­ process id
• “used”:23457188­ the amount of disk space in bytes currently used for AOF files
• “missing”:604602126­ the amount of disk space in bytes that is currently missing for AOF rewrite purposes
• “object”:“node:1″­ the object for which this alert has been raised for, in this case it is node with id 1
• “free”:9867264­ the amount of disk space in bytes that is currently free
• “needed”:637926578­ the amount of total disk space in bytes that is needed for AOF rewrite purposes
• state”:true­ current state of the alert, in this case it is on
• “time”:1434365483­ can be ignored
• “disk”:705667072­ the total size in bytes of the persistent storage
• “type”:“insufficient_disk_aofrw"­ is the code name identifier of this specific event, see full mapping in the Mapping UI events and alerts to log entries section below

“Alert off” log entry sample: daemon.info:Jun1513:51:11node1event_log[34252]:{“used”:0,“missing”: ‐21614592,“object”:“node:1″,“free”:21614592,“needed”:0,“state”: false,“time”:1434365471,“disk”:705667072,“type”: “insufficient_disk_aofrw”}

Log entry components:

• daemon.info­ severity of entry is info
• Jun1513:51:11­ the timestamp of the event
• node1­ machine name
• event_log­ static text that always appears
• [34252]­ process id
• “used”:0­ the amount of disk space in bytes currently used for AOF files
• “missing”:‐21614592­ the amount of disk space in bytes that is currently missing for AOF rewrite purposes, in this case it is not missing because the number is negative
• “object”:“node:1″­ the object for which this alert has been raised for, in this case it is node with id 1
• “free”:21614592­ the amount of disk space in bytes that is currently free
• “needed”:0­ the amount of total disk space in bytes that is needed for AOF rewrite purposes, in this case no space is needed
• “state”:false­ current state of the alert, in this case it is off
• “time”:1434365471­ can be ignored
• “disk”:705667072­ the total size in bytes of the persistent storage
• “type”:“insufficient_disk_aofrw"­ is the code name identifier of this specific event, see full mapping in the Mapping UI events and alerts to log entries section below

Mapping UI events and alerts to log entries

Cluster and node related events

Event as shown in the UI	Event code­name	Object type	Category	Severity	Notes
Node failed	failed	node	alert	critical
Node joined	node_joined	cluster	event	info
Node removed	node_remove_completed node_remove_failed node_remove_abort_completed node_remove_abort_failed	cluster	event	info error info error	The remove node is a process that can fail and can also be aborted. If aborted, the abort can succeed or fail.
Node memory has reached % of its capacity	memory	node	alert	true: warning false: info	Has global_threshold parameter in the key/value section of the log entry.
Persistent storage has reached % of its capacity	persistent_storage	node	alert	true: warning false: info	Has global_threshold parameter in the key/value section of the log entry.
Ephemeral storage has reached	ephemeral_storage	node	alert	true: warning false: info	Has global_threshold parameter in the % of its capacity key/value section of the log entry.
CPU utilization has reached %	cpu_utilization	node	alert	true: warning false: info	Has global_threshold parameter in the key/value section of the log entry.
Network throughput has reached MB/s	net_throughput	node	alert	true: warning false: info	Has global_threshold parameter in the key/value section of the log entry.
Node has insufficient disk space for AOF rewrite	insufficient_disk_aofrw	node	alert	true: error false: info
Redis performance is degraded as result of disk I/O limits	aof_slow_disk_io	node	alert	true: error false: info
Cluster capacity is less than total memory allocated to its databases	ram_overcommit	cluster	alert	true: error false: info
Nodes rebalanced	rebalance_failed rebalance_completed rebalance_abort_failed rebalance_abort_completed	cluster	event	error info error info	The nodes rebalance is a process that can fail and can also be aborted. If aborted, the abort can succeed or fail.
Database replication requires at least two nodes in cluster	too_few_nodes_for_replication	cluster	alert	true: warning false: info
True high availability requires an odd number of nodes with a minimum of three nodes	even_node_count	cluster	alert	true: warning false: info
Not all nodes in the cluster are running the same Redis Labs Enterprise Cluster version	inconsistent_rl_sw	cluster	alert	true: warning false: info
Not all databases are running the same open source version	inconsistent_redis_sw	cluster	alert	true: warning false: info

Database related events

Event as shown in the UI	Event code-­name	Object type	Category	Severity	Notes
Dataset size has reached % of the memory limit	size	bdb	alert	true: warning false: info	Has threshold parameter in the key/value section of the log entry.
Throughput is higher than RPS (requests per second)	high_throughput	bdb	alert	true: warning false: info	Has threshold parameter in the key/value section of the log entry.
Throughput is lower than RPS (requests per second)	low_throughput	bdb	alert	true: warning false: info	Has threshold parameter in the key/value section of the log entry.
Latency is higher than msec	high_latency	bdb	alert	true: warning false: info	Has threshold parameter in the key/value section of the log entry.
Periodic backup has been delayed for longer than minutes	backup_delayed	bdb	alert	true: warning false: info	Has threshold parameter in the data: section of the log entry.
Replica Of ­database unable to sync with source	syncer_connection_error syncer_general_error	bdb	alert	error error
Replica Of sync lag is higher than seconds	high_syncer_lag	bdb	alert	true: warning false: info	Has threshold parameter in the key/value section of the log entry.