Re: Hot to model data in DB (PostgreSQL) for SNMP-like multiple configurations

[Alban Hertroys <haramrae@xxxxxxxxx>]

Is there a reason not to use a relational model instead of json(b) here? I think that is in fact considered best practice.

On Fri, 8 Mar 2019 at 15:40, Alexandru Lazarev <alexandru.lazarev@xxxxxxxxx> wrote:

I am working on product managing and monitoring Network (NMS-like products).

Product manages configuration of network devices, for now each device has stored its configuration in simple table - this was the original design.

CREATE TABLE public.configuration
(
  id integer NOT NULL,
  config json NOT NULL,
  CONSTRAINT configuration_pkey PRIMARY KEY (id),
)

A config looks like:

{
    "_id": 20818132,
    "type": "Modem",
    "data": [{
            "oid": "1.3.6.1.4.1.9999.3.10.2.2.25.4.1.40",
            "instance": "24",
            "value": "null"
        },
        {
            "oid": "1.3.6.1.4.1.9999.3.5.10.1.86",
            "instance": "0",
            "value": "562"
        },
        {
            "oid": "1.3.6.1.4.1.9999.3.5.10.3.92.4.1",
            "instance": "0",
            "value": "0"
        },
        {
            "oid": "1.3.6.1.4.1.9999.3.10.2.2.25.4.1.43",
            "instance": "24",
            "value": "vlan24"
        },
        {
            "oid": "1.3.6.1.4.1.9999.3.10.2.2.25.4.1.43",
            "instance": "25",
            "value": "vlan25"
        }
    ]
}

And there are many plv8 (_javascript_ procedural language extension for PostgreSQL) stored procedures working on bulks of such config, reading some OIDs, changing them conditionally, removing some of them and adding others, especially in use cases like: There are some upper-level META-configuration of different level, which during change have to update all their updated parameters to all affected leaves configs. An simple test-example (but without touching 'data' node)

CREATE OR REPLACE FUNCTION public.process_jsonb_plv8()
  RETURNS void AS
$BODY$
var CFG_TABLE_NAME = "configurations";
var selPlan = plv8.prepare( "select c.config from " + CFG_TABLE_NAME + " c where c.id = $1", ['int'] );
var updPlan = plv8.prepare( 'update ' + CFG_TABLE_NAME + ' set config = $1 where id = $2', ['jsonb','int'] );

try {

    var ids = plv8.execute('select id from devices');

    for (var i = 0; i < ids.length; i++) {
        var db_cfg = selPlan.execute(ids[i].id); //Get current json config from DB
        var cfg = db_cfg[0].config;
        cfg["key0"] = 'plv8_json'; //-add some dummy key
        updPlan.execute(cfg, ids[i].id); //put uopdated JSON config in DB
        plv8.elog(NOTICE, "UPDATED = " + ids[i].id);


    }
} finally {
    selPlan.free();
    updPlan.free();
}

return;$BODY$
  LANGUAGE plv8 VOLATILE
  COST 100;

For real use-cases plv8 SPs are more complicated, doing FOR-LOOP through ALL OIDs object of 'data' array, checking if it is looking for and update value an/or remove it and/or add newer if necessary.

Since number of devices in DB increased from several hundreds to 40K or even 70K, and number of OID+Instance combinations also increased from several hundred to ~1K and sometimes up to 10K within a config, we start facing slowness in bulk (especially global -> update to ALL Devices) updates/searches.

In order to get rid off FOR LOOP step for each configuration I've converted data-node from array to object (key-value model), something like :

{
    "_id": 20818132,
    "type": "Modem",
    "data": {
        "1.3.6.1.4.1.9999.3.10.2.2.25.4.1.40": {
            "24": "null"
        },
        "1.3.6.1.4.1.9999.3.5.10.1.86": {
            "0": "562"
        },
        "1.3.6.1.4.1.9999.3.5.10.3.92.4.1": {
            "0": "0"
        },
        "1.3.6.1.4.1.9999.3.10.2.2.25.4.1.43": {
            "24": "vlan24",
            "25": "vlan25"
        }
    }
}

Now in order to get a concrete OID (e.g. "1.3.6.1.4.1.9999.3.10.2.2.25.4.1.43") and/or its instance I do 1-2 O(1) operations instead O(n). And it become a bit faster. After I've changed column type from json to jsonb - I've got a lot of memory issues with plv8 stored procedures, so now ideas is:

What are the best practices to store such data and use cases in DB? taking in considerations following: - Bulk and global updates are often enough (user-done operation) - several times per week and it takes long time - several minutes, annoying user experience. - Consulting some OIDs only from concrete config is medium frequency use case - Consulting ALL devices have some specific OID (SNMP Parameter) settled to a specific value - medium frequency cases. - Consult (read) a configuration for a specific device as a whole document - often use case (it is send to device as json or as converted CSV, it is send in modified json format to other utilities, etc)

One of suggestion from other oppinions is to move ALL configurations to simple plain relational table

CREATE TABLE public.configuration_plain
(
  device_id integer,
  oid text,
  instance text,
  value text
)

Looking like

id	oid	instance	value
20818132	1.3.6.1.4.1.9999.2.13	0	VSAT
20818132	1.3.6.1.4.1.9999.3.10.2.2.10.15	0	0
20818132	1.3.6.1.4.1.9999.3.10.2.2.10.17	0	0
20818132	1.3.6.1.4.1.9999.3.10.2.2.10.18	0	1
20818132	1.3.6.1.4.1.9999.3.10.2.2.10.19	0	2
20818132	1.3.6.1.4.1.9999.3.10.2.2.10.8.1.1	24	24
20818132	1.3.6.1.4.1.9999.3.10.2.2.10.8.1.1	25	25
20818132	1.3.6.1.4.1.9999.3.10.2.2.10.8.1.2	24	vlan24
20818132	1.3.6.1.4.1.9999.3.10.2.2.10.8.1.2	25	VLAN_25

And now I end with a table of ~33 M rows for 40K devices * (700-900 OID+Instance combinations). Some simple selects and updates (especially if I add simple indexes on id, oid columns) works faster than JSON (less than 1 sec updating one OID for ALL devices), but on some stored procedures where I need to do some checks and business logic before manipulating concrete parameters in configuration - performance decrease again from 10 to 25 seconds in below example with each nee added operation:

CREATE OR REPLACE FUNCTION public.test_update_bulk_configuration_plain_plpg(
    sql_condition text, -- something like 'select id from devices'
    new_elements text, --collection of OIDs to be Added or Update, could be JSON Array or comma separated list, containing 1 or more (100) OIDs
    oids_to_delete text --collection of OIDs to Delete
    )
  RETURNS void AS
$BODY$
DECLARE
    r integer;
    cnt integer;
    ids int[];
    lid int;
BEGIN
    RAISE NOTICE 'start';
    EXECUTE 'SELECT ARRAY(' || sql_condition || ')' into ids;
    FOREACH lid IN ARRAY ids
    LOOP
        -- DELETE 
        -- Some business logic
        -- FOR .. IF .. BEGIN
            delete from configuration_plain c where c.oid = '1.3.6.1.4.1.9999.3.5.10.3.201.1.1' and instance = '10' and c.device_id = lid;
            delete from configuration_plain c where c.oid = 'Other OID' and instance = 'Index' and c.device_id = lid;
            -- other eventual deletes
        --END

        -- UPDATE
        -- Some business logic
        -- FOR .. IF .. BEGIN
            update configuration_plain c set value = '2' where c.oid = '1.3.6.1.4.1.9999.3.5.10.3.87' and c.device_id = lid;
            update configuration_plain c set value = '2' where c.oid = '1.3.6.1.4.1.9999.3.5.10.3.201.1.1' and instance = '1' and c.device_id = lid;        
            -- other eventual updates
        -- END

        --INSERT
        insert into configuration_plain (id, oid, instance, value) values (lid,'1.3.6.1.4.1.9999.3.5.10.3.201.1.1', '11', '11');
        -- OTHER eventually....
        insert into configuration_plain (id, oid, instance, value) values (lid,'OTHER_OID', 'Idx', 'Value of OID');
    END LOOP;
    RAISE NOTICE 'end';
    RETURN;
END
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;

So any best practices and advice on such data and use cases modeling in DB?

Regards,

AlexL

--

If you can't see the forest for the trees,
Cut the trees and you'll see there is no forest.