Redis Slowlog Test

The Redis Slow Log is a system to log queries that exceeded a specified execution time. The execution time does not include I/O operations like talking with the client, sending the reply and so forth, but just the time needed to actually execute the command (this is the only stage of command execution where the thread is blocked and can not serve other requests in the meantime).

As slow commands are one of the key causes for latencies in the Redis server, it is important that administrators swoop down on such commands and figure out what is ailing them. This is where the Slowlog test helps! This test captures and reports the count and complete details of slow commands, along with the duration per command, thus enabling administrators to quickly identify the command that is the slowest. Additionally, the test helps administrators review the maximum length configuration of the slow log, and the threshold set for capturing slow commands, so that the administrators can determine if these settings need to be tweaked.

Target of the test :A Redis server

Agent deploying the test : An internal agent (recommended)

Outputs of the test : One set of results for the target Redis server

Configurable parameters for the test
Parameters Description

Test period

How often should the test be executed

Host.

The host for which the test is to be configured.

Port

The port at which the specified HOST listens.

Redis Password and Confirm Password

In some high security environments, a password may have been set for the Redis server, so as to protect it from unauthorized accesses/abuse. If such a password has been set for the monitored Redis server, then specify that password against REDIS PASSWORD. Then, confirm the password by retyping it against CONFIRM PASSWORD.

If the Redis server is not password protected, then do not disturb the default setting of this parameter.

To determine whether/not the target Redis server is password-protected, do the following:

  • Login to the system hosting the Redis server.

  • Open the redis.conf file in the <REDIS_INSTALL_DIR>.

  • Look for the requirepass parameter in the file.

  • If this parameter exists, and is not preceded by a # (hash) symbol, it means that password protection is enabled for the Redis server. In this case, the string that follows the requirepass parameter is the password of the Redis server. For instance, say that the requirepass specification reads as follows:

    requirepass red1spr0

    According to this specification, the Redis server is protected using the password red1spr0. In this case therefore, you need to specify red1spr0 against REDIS PASSWORD.

  • On the other hand, if the requirepass parameter is prefixed by the # (hash) symbol as shown below, it means password protection is disabled.

    # requirepass red1spr0

    In this case, leave the REDIS PASSWORD parameter with its default setting.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise suite embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Slow command executions

Indicates the count of slow commands.

Number

The value 0 is desired for this measure. A high value could mean one/both the following:

  • The Redis server is taking too much time to execute many commands;

  • The threshold set for slow commands is incorrect

In the case of the former, use the detailed diagnosis of this measure to identify the slow commands, when each command was executed, and how long every command took to run. This will lead you to the slowest command.

In the case of the latter, take a look at the value of the Maximum slowlog command threshold measure. You may want to decrease this threshold setting by changing the slowlog-log-slower-than configuration parameter.

Average command duration

Indicates the average time it took for commands to execute.

Microseconds

If this value is abnormally high, you may want to check the detailed diagnosis of the Slow command executions measure to identify the slowest command.

Slowlog maximum length

Indicates the maximum number of commands that can be logged.

Number

The slowlog-max-len configuration setting governs the length of the slow log. The minimum value is 0. When a new command is logged and the slow log is already at its maximum length, the oldest one is removed from the queue of logged commands in order to make space.

If you want more slow commands to be logged in the slowlog, increase the value of the slowlog-max-len configuration setting.

Maximum slow log command threshold

Indicates the execution time, in microseconds, to exceed in order for the command to get logged in the slowlog.

Microseconds

The slowlog-log-slower-than configuration setting governs the value of this measure. Note that a negative number disables the slow log, while a value of zero forces the logging of every command.

If the value of the Slow command executions measure is abnormally high, you may want to review the slowlog-log-slower-than configuration setting to see if it needs to be fine-tuned to capture only those commands that are genuinely slow.