Using Cassandra as a metrics store¶

To start using a CQL store you just have to specify CQL hosts in axon-server.yml:

cql_hosts :
    - 192.168.0.1:9042
    - 192.168.0.2:9042
    ...

By default, the AxonOps server automatically creates the necessary keyspace and tables. You can override this behavior by specifying the following field in axon-server.yml:

cql_autocreate_tables : false
cql_keyspace : "axonops"
cql_keyspace_replication : "{ 'class' : 'SimpleStrategy', 'replication_factor' : 1 }"

We recommend setting up at least a 3 nodes cluster with NetworkTopologyStrategy and a replication_factor of 3.

Connecting to encrypted Cassandra metrics store¶

We recommend setting up a Secured Socket Layer connection to Cassandra with the following fields in axon-server.yml:

cql_ssl: true
cql_skip_verify: false
cql_ca_file: '/path/to/ca_cert'
cql_cert_file: '/path/to/cert_file'
cql_key_file: '/path/to/key_file'

Metrics cache recommendations¶

When using Cassandra as a metrics store the AxonOps server can cache metrics data in memory to further improve performance. This is configured using the cql_metrics_cache_max_items and cql_metrics_cache_max_size_mb options in axon-server.yml. The default values are shown here:

cql_metrics_cache_max_items: 5000000
cql_metrics_cache_max_size_mb: 400

The recommended settings for these options are as follows:

Cassandra Nodes	cql_metrics_cache_max_items	cql_metrics_cache_max_size_mb
<10	5000000	1000
<50	5000000	4000
100	10000000	10000
200	10000000	20000

These sizes can be tuned to balance memory use in AxonOps against the read workload on Cassandra. When tuning these parameters it is recommended to set cql_metrics_cache_max_items to a high value and limit the cache size with cql_metrics_cache_max_size_mb.

Other CQL fields¶

You can also specify the following fields:

cql_proto_version int                   
cql_batch_size  int                   
cql_page_size int                   
cql_local_dc string                
cql_username string                
cql_password string                
cql_max_concurrent_reads int                   
cql_retrypolicy_numretries int                   
cql_retrypolicy_min string "1s"
cql_retrypolicy_max string "10s"
cql_reconnectionpolicy_maxretries int                   
cql_reconnectionpolicy_initialinterval string "1s"
cql_reconnectionpolicy_maxinterval string  "10s"
cql_metrics_cache_max_size_mb int64 in MB               
cql_metrics_cache_max_items  int64 in MB                        
cql_read_consistency string (controls the consistency of read operations, defaults to LOCAL_ONE)              
cql_write_consistency string (controls the consistency of write operations, defaults to LOCAL_ONE)               
cql_lvl1_compaction_window_size int (used for the table named 'metrics5' when you let axonserver managing the tables automatically)                  
cql_lvl2_compaction_window_size int (used for the table named 'metrics60' when you let axonserver managing the tables automatically)                  
cql_lvl3_compaction_window_size int (used for the table named 'metrics720' when you let axonserver managing the tables automatically)                  
cql_lvl4_compaction_window_size int (used for the table named 'metrics7200' when you let axonserver managing the tables automatically)                  
cql_lvl5_compaction_window_size int (used for the table named 'metrics86400' when you let axonserver managing the tables automatically)

The CQL for the default tables are the following:

CREATE TABLE IF NOT EXISTS axonops.metrics5 (
    orgid text,
    metricid int,
    time int,
    value float,
    PRIMARY KEY ((orgid, metricid), time)
) WITH CLUSTERING ORDER BY (time DESC)
   AND caching = {'keys': 'ALL', 'rows_per_partition': '256'}
   AND compaction = {'class': 'TimeWindowCompactionStrategy', 'compaction_window_size': '1', 'compaction_window_unit': 'DAYS', 'max_threshold': '32', 'min_threshold': '4'}
   AND default_time_to_live = 604800
   AND comment = '7 days retention for 5 seconds resolution metrics';

CREATE TABLE IF NOT EXISTS axonops.metrics60 (
    orgid text,
    metricid int,
    time int,
    value float,
    PRIMARY KEY ((orgid, metricid), time)
) WITH CLUSTERING ORDER BY (time DESC)
   AND caching = {'keys': 'ALL', 'rows_per_partition': '256'}
   AND compaction = {'class': 'TimeWindowCompactionStrategy', 'compaction_window_size': '1', 'compaction_window_unit': 'DAYS', 'max_threshold': '32', 'min_threshold': '4'}
   AND default_time_to_live = 2592000
   AND comment = '30 days retention for 60 seconds resolution metrics';

CREATE TABLE IF NOT EXISTS axonops.metrics720 (
    orgid text,
    metricid int,
    time int,
    value float,
    PRIMARY KEY ((orgid, metricid), time)
) WITH CLUSTERING ORDER BY (time DESC)
   AND caching = {'keys': 'ALL', 'rows_per_partition': '256'}
   AND compaction = {'class': 'TimeWindowCompactionStrategy', 'compaction_window_size': '4', 'compaction_window_unit': 'DAYS', 'max_threshold': '32', 'min_threshold': '4'}
   AND default_time_to_live = 5184000
   AND comment = '60 days retention for 720 seconds resolution metrics';

CREATE TABLE IF NOT EXISTS axonops.metrics7200 (
    orgid text,
    metricid int,
    time int,
    value float,
    PRIMARY KEY ((orgid, metricid), time)
) WITH CLUSTERING ORDER BY (time DESC)
   AND caching = {'keys': 'ALL', 'rows_per_partition': '256'}
   AND compaction = {'class': 'TimeWindowCompactionStrategy', 'compaction_window_size': '30', 'compaction_window_unit': 'DAYS', 'max_threshold': '32', 'min_threshold': '4'}
   AND default_time_to_live = 15552000
   AND comment = '180 days retention for 7200 seconds resolution metrics';

CREATE TABLE IF NOT EXISTS axonops.metrics86400 (
    orgid text,
    metricid int,
    time int,
    value float,
    PRIMARY KEY ((orgid, metricid), time)
) WITH CLUSTERING ORDER BY (time DESC)
   AND caching = {'keys': 'ALL', 'rows_per_partition': '365'}
   AND compaction = {'class': 'TimeWindowCompactionStrategy', 'compaction_window_size': '60', 'compaction_window_unit': 'DAYS', 'max_threshold': '32', 'min_threshold': '4'}
   AND default_time_to_live = 31536000
   AND comment = '365 days retention for 86400 seconds resolution metrics';