9.0 KiB
RBAC Performance Analysis
This describes the analysis of the legacy-data-import which took way too long, which turned out to be a problem in the RBAC-access-rights-check.
Our Performance-Problem
During the legacy data import for hosting assets we noticed massive performance problems. The import of about 2200 hosting-assets (IP-numbers, managed-webspaces, managed- and cloud-servers) as well as the creation of booking-items and booking-projects as well as necessary office-data entities (persons, contacts, partners, debitors, relations) took 10-25 minutes.
We could not find a pattern, why the import mostly took about 25 minutes, but sometimes took just 10 minutes. The impression that it had to do with too many other parallel processes, e.g. browser with BBB or IntelliJ IDEA was proved wrong, but stopping all unnecessary processes and performing the import again.
Preparation
Configuring PostgreSQL
The pg_stat_statements PostgreSQL-Extension can be used to measure how long queries take and how often they are called.
The module auto_explain can be used to automatically run EXPLAIN on long-running queries.
To use this extension and module, we extended the PostgreSQL-Docker-image:
FROM postgres:15.5-bookworm
RUN apt-get update && \
apt-get install -y postgresql-contrib && \
apt-get clean
COPY etc/postgresql-log-slow-queries.conf /etc/postgresql/postgresql.conf
And create an image from it:
docker build -t postgres-with-contrib:15.5-bookworm .
Then we created a config file for PostgreSQL in etc/postgresql-log-slow-queries.conf:
shared_preload_libraries = 'pg_stat_statements,auto_explain'
log_min_duration_statement = 1000
log_statement = 'all'
log_duration = on
pg_stat_statements.track = all
auto_explain.log_min_duration = '1s' # Logs queries taking longer than 1 second
auto_explain.log_analyze = on # Include actual run times
auto_explain.log_buffers = on # Include buffer usage statistics
auto_explain.log_format = 'json' # Format the log output in JSON
listen_addresses = '*'
And a Docker-Compose config in 'docker-compose.yml':
version: '3.8'
services:
postgres:
image: postgres-with-contrib:15.5-bookworm
container_name: custom-postgres
environment:
POSTGRES_PASSWORD: password
volumes:
- /home/mi/Projekte/Hostsharing/hsadmin-ng/etc/postgresql-log-slow-queries.conf:/etc/postgresql/postgresql.conf
ports:
- "5432:5432"
command:
- bash
- -c
- >
apt-get update &&
apt-get install -y postgresql-contrib &&
docker-entrypoint.sh postgres -c config_file=/etc/postgresql/postgresql.conf
Activate the pg_stat_statements Extension
The pg_stat_statements extension was activated in our Liquibase-scripts:
create extension if not exists "pg_stat_statements";
Running the Tweaked PostgreSQL
Now we can run PostgreSQL with activated slow-query-logging:
docker-compose up -d
Running the Import
Using an environment like this:
export HSADMINNG_POSTGRES_JDBC_URL=jdbc:postgresql://localhost:5432/postgres
export HSADMINNG_POSTGRES_ADMIN_USERNAME=postgres
export HSADMINNG_POSTGRES_ADMIN_PASSWORD=password
export HSADMINNG_POSTGRES_RESTRICTED_USERNAME=restricted
export HSADMINNG_SUPERUSER=superuser-alex@hostsharing.net
We can now run the hosting-assets-import:
time gw-importHostingAssets
Fetch the Query Statistics
And afterward we can query the statistics in PostgreSQL:
SELECT pg_stat_statements_reset();
Analysis Result
RBAC-Access-Rights Detection query
This CTE query was run over 4000 times during a single import and takes in total the whole execution time of the import process:
WITH RECURSIVE grants AS (
SELECT descendantUuid, ascendantUuid, $5 AS level
FROM RbacGrants
WHERE assumed
AND ascendantUuid = any(subjectIds)
UNION ALL
SELECT g.descendantUuid, g.ascendantUuid, grants.level + $6 AS level
FROM RbacGrants g
INNER JOIN grants ON grants.descendantUuid = g.ascendantUuid
WHERE g.assumed
),
granted AS (
SELECT DISTINCT descendantUuid
FROM grants
)
SELECT DISTINCT perm.objectUuid
FROM granted
JOIN RbacPermission perm ON granted.descendantUuid = perm.uuid
JOIN RbacObject obj ON obj.uuid = perm.objectUuid
WHERE (requiredOp = $7 OR perm.op = requiredOp)
AND obj.objectTable = forObjectTable
LIMIT maxObjects+$8
That query is used to determine access rights of the currently active RBAC-subject(s).
We used EXPLAIN with a concrete version (parameters substituted with real values) of that query and got this result:
QUERY PLAN
Limit (cost=6549.08..6549.35 rows=54 width=16)
CTE grants
-> Recursive Union (cost=4.32..5845.97 rows=1103 width=36)
-> Bitmap Heap Scan on rbacgrants (cost=4.32..15.84 rows=3 width=36)
Recheck Cond: (ascendantuuid = ANY ('{ad1133dc-fbb7-43c9-8c20-0da3f89a2388}'::uuid[]))
Filter: assumed
-> Bitmap Index Scan on rbacgrants_ascendantuuid_idx (cost=0.00..4.32 rows=3 width=0)
Index Cond: (ascendantuuid = ANY ('{ad1133dc-fbb7-43c9-8c20-0da3f89a2388}'::uuid[]))
-> Nested Loop (cost=0.29..580.81 rows=110 width=36)
-> WorkTable Scan on grants grants_1 (cost=0.00..0.60 rows=30 width=20)
-> Index Scan using rbacgrants_ascendantuuid_idx on rbacgrants g (cost=0.29..19.29 rows=4 width=32)
Index Cond: (ascendantuuid = grants_1.descendantuuid)
Filter: assumed
-> Unique (cost=703.11..703.38 rows=54 width=16)
-> Sort (cost=703.11..703.25 rows=54 width=16)
Sort Key: perm.objectuuid
-> Nested Loop (cost=31.60..701.56 rows=54 width=16)
-> Hash Join (cost=31.32..638.78 rows=200 width=16)
Hash Cond: (perm.uuid = grants.descendantuuid)
-> Seq Scan on rbacpermission perm (cost=0.00..532.92 rows=28392 width=32)
-> Hash (cost=28.82..28.82 rows=200 width=16)
-> HashAggregate (cost=24.82..26.82 rows=200 width=16)
Group Key: grants.descendantuuid
-> CTE Scan on grants (cost=0.00..22.06 rows=1103 width=16)
-> Index Only Scan using rbacobject_objecttable_uuid_key on rbacobject obj (cost=0.28..0.31 rows=1 width=16)
Index Cond: ((objecttable = 'hs_hosting_asset'::text) AND (uuid = perm.objectuuid))
Office-Relations-Query
SELECT hore1_0.uuid,a1_0.uuid,a1_0.familyname,a1_0.givenname,a1_0.persontype,a1_0.salutation,a1_0.title,a1_0.tradename,a1_0.version,c1_0.uuid,c1_0.caption,c1_0.emailaddresses,c1_0.phonenumbers,c1_0.postaladdress,c1_0.version,h1_0.uuid,h1_0.familyname,h1_0.givenname,h1_0.persontype,h1_0.salutation,h1_0.title,h1_0.tradename,h1_0.version,hore1_0.mark,hore1_0.type,hore1_0.version
FROM hs_office_relation_rv hore1_0
LEFT JOIN hs_office_person_rv a1_0 ON a1_0.uuid=hore1_0.anchoruuid
LEFT JOIN hs_office_contact_rv c1_0 ON c1_0.uuid=hore1_0.contactuuid
LEFT JOIN hs_office_person_rv h1_0 ON h1_0.uuid=hore1_0.holderuuid
WHERE hore1_0.uuid=$1
That query into the hs_office_relation_rv-table is presumably the query to determine the partner of a debitor, which requires two of such queries each (Debitor -> Debitor-Relation -> Debitor-Anchor == Partner-Holder -> Partner-Relation -> Partner).
Total-Query-Time > Total-Import-Runtime
That both queries total up to more than the runtime of the import-process is most likely due to internal parallel query processing.
Attempts to Mitigate the Problem
VACUUM ANALYZE
In the middle of the import, we updated the PostgreSQL statistics to recalibrate the query optimizer:
VACUUM ANALYZE;
This did not improve the performance.
Improving Indexes
The sequentiap
create index on RbacPermission (objectUuid, op); create index on RbacPermission (opTableName, op);
We were suspicious about the sequential scan over all rbacpermission rows which was done by PostgreSQL to execute a HashJoin strategy. Turning off that strategy by
ALTER FUNCTION queryAccessibleObjectUuidsOfSubjectIds SET enable_hashjoin = off;
did not improve the performance though. The HashJoin was actually still applied, but no full table scan anymore:
[...]
QUERY PLAN
-> Hash Join (cost=36.02..40.78 rows=1 width=16)
Hash Cond: (grants.descendantuuid = perm.uuid)
-> HashAggregate (cost=13.32..15.32 rows=200 width=16)
Group Key: grants.descendantuuid
-> CTE Scan on grants (cost=0.00..11.84 rows=592 width=16)
[...]
The HashJoin strategy could be great if the hash-map could be kept for multiple invocations. But during an import process, of course, there are always new rows in the underlying table and the hash-map would be outdated immediately.