Ceilometer/ComplexFilterExpressionsInAPIQueries
Contents
Architecture
The purpose of the improvement is to support rich query functionality in Ceilometer API. The current query support is limited, it's grammar cannot be extended easily.
REST Resources
The new solution includes new REST resources for provide complex queries for both the meter and alarm related data:
REST Resource | Functionality | Returned Object Type |
---|---|---|
'/query/meters' | retrieve samples for meter(s) | Sample |
'/query/alarms' | retrieve alarms | Alarm |
'/query/alarms/history' | retrieve alarm history | AlarmChange |
As new resources were defined, the simple query support remained as it is now, which means that the API is backward compatible and also a new query grammar could be defined without limitations.
POST request
The new solution uses POST request, as the functionality of the query part of the GET request is very limited.
Expression Language
filter := [] | expression expression := simple_expression | complex_expression simple_expression := [simple_operator, field_name, value] simple_operator := = | != | < | <= | > | >= complex_expression := [complex_operator, expression, expression] complex_operator := and | or
Where
- field_name is the name of a field of the Sample, Alarm or AlarmChange object
- currently directly mapped to db column name
- value can be int, float, string, or iso date string for timestamp field
Orderby
List of field_name and sort instruction pairs:
orderby: ["field_name1", "ASC", "field_name2", "DESC", field_name3, "ASC", ...]
Limit
Number of rows returned, defined value should be int.
Supported DB drivers
- SQLAlchmey
- MongoDB
API example
Filter expression
Check for cpu_util samples reported between 18:00-18:15 or between 18:30 - 18:45 where the utilization is between 23 and 26 percent.
cpu_util > 23% AND cpu_util < 26% AND ((timestamp < 2013-12-01T18:15:00 AND timestamp > 2013-12-01T18:00:00) OR (timestamp < 2013-12-02T18:45:00 AND timestamp > 2013-12-02T18:30:00))
Pretty printed json:
["and", ["and", ["and", ["=", "counter_name", "cpu_util"], [">", "counter_volume", 0.23]], ["and", ["=", "counter_name", "cpu_util"], ["<", "counter_volume", 0.26]]], ["or", ["and", [">", "timestamp", "2013-12-01T18:00:00"], ["<", "timestamp", "2013-12-01T18:15:00"]], ["and", [">", "timestamp", "2013-12-01T18:30:00"], ["<", "timestamp", "2013-12-01T18:45:00"]]]]
Filter expression in the POST request body:
{ "filter" : "[\"and\",[\"and\",[\"and\",[\"=\", \"counter_name\", \"cpu_util\"],[\">\", \"counter_volume\", 0.23]],[\"and\",[\"=\", \"counter_name\", \"cpu_util\"],[\"<\", \"counter_volume\", 0.26]]],[\"or\",[\"and\",[\">\", \"timestamp\", \"2013-12-01T18:00:00\"],[\"<\", \"timestamp\", \"2013-12-01T18:15:00\"]],[\"and\",[\">\", \"timestamp\", \"2013-12-01T18:30:00\"],[\"<\", \"timestamp\", \"2013-12-01T18:45:00\"]]]]" }
Samples query
{ "filter" : "[\"and\",[\"and\",[\"and\",[\"=\", \"counter_name\", \"cpu_util\"],[\">\", \"counter_volume\", 0.23]],[\"and\",[\"=\", \"counter_name\", \"cpu_util\"],[\"<\", \"counter_volume\", 0.26]]],[\"or\",[\"and\",[\">\", \"timestamp\", \"2013-12-01T18:00:00\"],[\"<\", \"timestamp\", \"2013-12-01T18:15:00\"]],[\"and\",[\">\", \"timestamp\", \"2013-12-01T18:30:00\"],[\"<\", \"timestamp\", \"2013-12-01T18:45:00\"]]]]", "orderby" : ["cpu_util", "ASC", "timestamp", "DESC"], "limit" : 4 }