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Apache Module Troubleshooting Guide

Overview

Apache Issues

  • Exclude/configure a specific path for inspection.

One should be able to exclude a specific path for inspection by using a Location block. For instance, if the URL is https://devrc.rarediseasesnetwork.org/redcap_v10.6.17 and using http2.4, it would bypass authentication for all paths starting with redcap.

<LocationMatch "^(/redcap_.*)">
    AuthType None
    Satisfy Any
    Require all granted
</LocationMatch>

  • TCP TIME_WAITs spiking due to connections being closed when blocking.

Moving from the Apache post_read_request hook to the fixups hook (via SigSciEnableFixups On) seems to have resolved an issue where Apache is closing the TCP connection when blocking. The closes may cause larger TCP_WAIT counts when there is a larger number of blocks (e.g., rate limiting). SigSciEnableFixups On moves the inspection to slighly later in the module pipeline

  • Certain URLs, usually during authentication, may have issues with POST body requests that are causing errors.

To help narrow down whether POST body processing is the culprit, enable the following directive, SigSciAgentPostLen 0

The effects of this directive however will mean that the module is no longer reviewing the body contents of each request. This should only be used to help diagnosis problems in conjunction with additional logging.

Debugging

  • Additional logging can be enabled through the LogLevel directive. In Apache 2.2, Per-module logging is not possible, so stating apache.conf LogLevel debug # or LogLevel warn applies to the entire configuration, whereas in Apache 2.4+, applying a directive such as apache.conf LogLevel warn signalsciences:debug sets the main LogLevel to warn but enables debug for mod_signalsciences

References