rewriting.md

Rewriting

Series names can be rewritten as they pass through the system by Rewriter rules, which are processed in series. This can be done via regex (expensive), or with a string check (cheap)

With string check

Basic rules use simple old/new text replacement, and support a Max parameter to specify the maximum number of matched items to be replaced.

With regexular expression

This is activated by wrapping the "old" parameter with forward slashes and setting "max" to -1. The "new" value can include submatch identifiers in the format ${1}.

Note that for performance reasons, these regular expressions don't support lookaround (lookahead, lookforward) For more information see:

• this ticket
• syntax documentation
• golang's regular expression package documentation

Examples

Using the new config style

This is the recommended approach. The new config style also supports an extra field: not: skips the rewriting if the metric matches the pattern. The pattern can either be a substring, or a regex enclosed in forward slashes.

# basic rewriter rule to replace first occurrence of "foo" with "bar"
[[rewriter]]
old = 'foo'
new = 'bar'
not = ''
max = -1

# regexp rewriter rule to add a prefix of "prefix." to all series
[[rewriter]]
old = '/^/'
new = 'prefix.'
not = ''
max = -1

# regexp rewriter rule to replace "server.X" with "servers.X.collectd"
[[rewriter]]
old = '/server\.([^.]+)/'
new = 'servers.${1}.collectd'
not = ''
max = -1

# same, except don't do it if the metric already contains the word collectd
[[rewriter]]
old = '/server\.([^.]+)/'
new = 'servers.${1}.collectd'
not = 'collectd'
max = -1

Using init commands

(deprecated)

# basic rewriter rule to replace first occurrence of "foo" with "bar"
addRewriter foo bar 1

# regexp rewriter rule to add a prefix of "prefix." to all series
addRewriter /^/ prefix. -1

# regexp rewriter rule to replace "server.X" with "servers.X.collectd"
addRewriter /server\.([^.]+)/ servers.${1}.collectd -1