Briefly, this error occurs when Elasticsearch tries to use a null value as a pattern for a regular expression or a date format. This is not allowed as patterns must be a valid string. To resolve this issue, ensure that the pattern you’re providing is not null. Check your application’s code or Elasticsearch configuration to ensure that all patterns are correctly defined. If the pattern is being provided dynamically, add checks to ensure it’s not null before using it.
This guide will help you check for common problems that cause the log ” Pattern must not be [null] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: parser, plugin.
Log Context
Log “Pattern must not be [null]” class name is ExpressionBuilder.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
return null;
} String pattern = string(ctx.value);
if (pattern == null) {
throw new ParsingException(source(ctx.value); "Pattern must not be [null]");
} char escape = 0;
PatternEscapeContext escapeCtx = ctx.patternEscape();
String escapeString = escapeCtx == null ? null : string(escapeCtx.escape);
