mirror of
https://gitea.com/mcereda/oam.git
synced 2026-02-09 05:44:23 +00:00
514 lines
19 KiB
Markdown
514 lines
19 KiB
Markdown
# PeerDB
|
|
|
|
Fast, simple, and cost effective Postgres replication.
|
|
|
|
1. [TL;DR](#tldr)
|
|
1. [Setup](#setup)
|
|
1. [Authentication](#authentication)
|
|
1. [High availability](#high-availability)
|
|
1. [Components](#components)
|
|
1. [Peers](#peers)
|
|
1. [Mirrors](#mirrors)
|
|
1. [Alerts](#alerts)
|
|
1. [Gotchas](#gotchas)
|
|
1. [Further readings](#further-readings)
|
|
1. [Sources](#sources)
|
|
|
|
## TL;DR
|
|
|
|
<details>
|
|
<summary>Glossary</summary>
|
|
|
|
| Term | Summary |
|
|
| ------ | ------------------------------------------------------------------------- |
|
|
| Peer | Connection to a database that PeerDB can query |
|
|
| Mirror | Stream of changes, feed in real-time, from a source peer to a target peer |
|
|
| Alert | Notifications about issues in flows |
|
|
|
|
</details>
|
|
|
|
<details>
|
|
<summary>Setup</summary>
|
|
|
|
```sh
|
|
git clone 'https://github.com/PeerDB-io/peerdb.git' \
|
|
&& docker compose -f 'peerdb/docker-compose.yml' up -d
|
|
```
|
|
|
|
</details>
|
|
|
|
<details>
|
|
<summary>Usage</summary>
|
|
|
|
```sh
|
|
# Connect in SQL mode.
|
|
psql 'host=localhost port=9900 password=peerdb'
|
|
psql 'postgresql://peerdb.example.org:9900/?password=peerdb'
|
|
|
|
# Use the REST APIs.
|
|
curl -fsS --url 'http://localhost:3000/api/v1/peers/list' --request 'GET' \
|
|
--header "Authorization: Basic $(printf '%s' ':' 'your password here' | base64)"
|
|
curl -fsS --url 'http://localhost:3000/api/v1/peers/create' --request 'POST' \
|
|
--header "Authorization: Basic $(printf '%s' ':' 'your password here' | base64)" \
|
|
--header 'Content-Type: application/json' \
|
|
--data '{ … }'
|
|
```
|
|
|
|
</details>
|
|
|
|
<details>
|
|
<summary>Real world use cases</summary>
|
|
|
|
```sh
|
|
# List peers.
|
|
psql "host=localhost port=9900 password=$(gopass show -o 'peerdb/instance')" -c "SELECT id, name, type FROM peers;"
|
|
curl -fsS --url 'http://localhost:3000/api/v1/peers/list' \
|
|
-H "Authorization: Basic $(gopass show -o 'peerdb/instance' | xargs printf '%s' ':' | base64)"
|
|
```
|
|
|
|
</details>
|
|
|
|
## Setup
|
|
|
|
Deploy to K8S clusters using the [helm chart].<br/>
|
|
Make sure to override the `version` parameter.
|
|
|
|
The helm chart's repository was open sourced after ClickHouse's acquisition.<br/>
|
|
It was what PeerDB was using for on-premise customers beforehand.
|
|
|
|
### Authentication
|
|
|
|
By default, PeerDB UI is open.
|
|
|
|
Add authentication by setting the `PEERDB_PASSWORD` environment variable.
|
|
|
|
### High availability
|
|
|
|
If Catalog and Temporal are HA, then the whole service is pretty much HA.
|
|
|
|
## Components
|
|
|
|
### Peers
|
|
|
|
Peers are connection settings to databases that PeerDB can operate upon.
|
|
|
|
_Source_ PostgreSQL peers **require** logical replication to be enabled.
|
|
|
|
<details style="padding: 0 0 1rem 1rem">
|
|
|
|
```sql
|
|
-- Check settings
|
|
sourceDb=> SELECT name,setting FROM pg_settings WHERE name IN ('wal_level','rds.logical_replication');
|
|
name | setting
|
|
-------------------------+---------
|
|
rds.logical_replication | on
|
|
wal_level | logical
|
|
(2 rows)
|
|
```
|
|
|
|
```sql
|
|
-- Configure sources
|
|
ALTER SYSTEM SET wal_level = logical;
|
|
ALTER SYSTEM SET max_wal_senders = 10;
|
|
ALTER SYSTEM SET max_replication_slots = 10;
|
|
```
|
|
|
|
</details>
|
|
|
|
Operations:
|
|
|
|
<details style="padding: 0 0 0 1rem">
|
|
<summary>List</summary>
|
|
|
|
```sql
|
|
SELECT id, name, type FROM peers;
|
|
```
|
|
|
|
```plaintext
|
|
GET /api/v1/peers/list
|
|
```
|
|
|
|
</details>
|
|
|
|
<details style="padding: 0 0 0 1rem">
|
|
<summary>Create or update</summary>
|
|
|
|
```sql
|
|
CREATE PEER IF NOT EXISTS some_postgresql_peer
|
|
FROM POSTGRES
|
|
WITH (
|
|
host='pg.example.org',
|
|
port='5432',
|
|
database='postgres',
|
|
user='postgres',
|
|
password='password'
|
|
);
|
|
```
|
|
|
|
| Peer type | `peer.type` attribute | Configuration attribute |
|
|
| ---------- | --------------------- | ----------------------- |
|
|
| ClickHouse | `8` | `clickhouse_config` |
|
|
| Kafka | `9` | `kafka_config` |
|
|
| PostgreSQL | `3` or `'POSTGRES'` | `postgres_config` |
|
|
|
|
> The optional `"allow_update": true` attribute in the API seems to do **absolutely nothing** as of the time of writing.
|
|
|
|
```plaintext
|
|
POST /api/v1/peers/create
|
|
{
|
|
"allow_update": true,
|
|
"peer": {
|
|
"name": "some_postgresql_peer",
|
|
"type": "POSTGRES",
|
|
"postgres_config": {
|
|
"host": "pg.example.org",
|
|
"port": "5432",
|
|
"database": "postgres",
|
|
"user": "postgres",
|
|
"password": "password"
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
</details>
|
|
|
|
<details style="padding: 0 0 0 1rem">
|
|
<summary>Delete</summary>
|
|
|
|
```sql
|
|
DELETE FROM peers WHERE name == 'some_postgresql_peer';
|
|
```
|
|
|
|
</details>
|
|
|
|
### Mirrors
|
|
|
|
Mirrors can be in the following states:
|
|
|
|
| State | Returned string | Description |
|
|
| ---------- | ------------------- | ----------------------------------------------------------------------------------------------------- |
|
|
| Setup | `STATUS_SETUP` | The mirror is creating the target tables and metadata tables |
|
|
| Snapshot | `STATUS_SNAPSHOT` | The mirror is currently performing the initial snapshot of the tables defined in the mapping |
|
|
| Running | `STATUS_RUNNING` | The mirror has completed the initial snapshot, and is in its CDC phase |
|
|
| Pausing | `STATUS_PAUSING` | The mirror is in its CDC phase, and is in the process of pausing |
|
|
| Paused | `STATUS_PAUSED` | The mirror is in its CDC phase, and is paused |
|
|
| Terminated | `STATUS_TERMINATED` | The mirror has been deleted/terminated |
|
|
| Unknown | `STATUS_UNKNOWN` | The mirror is not found in PeerDB's catalog, or its status cannot be obtained due to some other issue |
|
|
|
|
Mirrors using _PostgreSQL_ peers as sources create [replication slots] in the source DB to get changes from.
|
|
|
|
Operations:
|
|
|
|
<details style="padding: 0 0 0 1rem">
|
|
<summary>List</summary>
|
|
|
|
```plaintext
|
|
GET /api/v1/mirrors/list
|
|
```
|
|
|
|
</details>
|
|
|
|
<details style="padding: 0 0 0 1rem">
|
|
<summary>Create</summary>
|
|
|
|
| Field | Type | Required | Default | Notes |
|
|
| --------------------------------------------- | --------------- | -------- | -------------------- | ------------------------------------------------ |
|
|
| `flow_job_name` | string | yes | | name of the mirror |
|
|
| `source_name` | string | yes | | name of the source peer |
|
|
| `destination_name` | string | yes | | name of the destination peer |
|
|
| `table_mappings` | array | yes | | |
|
|
| `table_mappings.source_table_identifier` | string | yes | | source schema and table |
|
|
| `table_mappings.destination_table_identifier` | string | yes | | destination schema and table |
|
|
| `table_mappings.exclude` | list of strings | no | [] | columns excluded from the sync |
|
|
| `table_mappings.columns` | list of objects | no | [] | ordering setting; for ClickHouse only |
|
|
| `table_mappings.columns.name` | string | yes | | name of the column |
|
|
| `table_mappings.columns.ordering` | number | yes | | rank of the column |
|
|
| `idle_timeout_seconds` | number | no | 60 | |
|
|
| `publication_name` | string | no | | will be created if not provided |
|
|
| `max_batch_size` | number | no | 1000000 | |
|
|
| `do_initial_snapshot` | boolean | yes | | |
|
|
| `snapshot_num_rows_per_partition` | number | no | 1000000 | only used for the initial snapshot |
|
|
| `snapshot_max_parallel_workers` | number | no | 4 | only used for the initial snapshot |
|
|
| `snapshot_num_tables_in_parallel` | number | no | 1 | only used for the initial snapshot |
|
|
| `resync` | boolean | no | false | the mirror **must be dropped** before re-syncing |
|
|
| `initial_snapshot_only` | boolean | no | false | |
|
|
| `soft_delete_col_name` | string | no | `_PEERDB_IS_DELETED` | |
|
|
| `synced_at_col_name` | string | no | `_PEERDB_SYNCED_AT` | |
|
|
|
|
```sql
|
|
CREATE MIRROR IF NOT EXISTS some_cdc_mirror
|
|
FROM main_pg TO snowflake_prod -- FROM source_peer TO target_peer
|
|
WITH TABLE MAPPING
|
|
(
|
|
public.regions:main_pg.regions, -- source_schema.table:target_schema.table
|
|
{
|
|
from: public.countries, -- source_schema.table
|
|
to: main_pg.countries, -- target_schema.table
|
|
exclude: [ local_name, size, … ] -- column_1, …, column_N
|
|
},
|
|
…
|
|
)
|
|
WITH ( do_initial_copy = true );
|
|
```
|
|
|
|
```plaintext
|
|
POST /api/v1/flows/cdc/create
|
|
{
|
|
"connection_configs": {
|
|
"flow_job_name": "some_cdc_mirror",
|
|
"source_name": "main_pg",
|
|
"destination_name": "snowflake_prod",
|
|
"do_initial_snapshot": true,
|
|
"table_mappings": [
|
|
{
|
|
"source_table_identifier": "public.regions",
|
|
"destination_table_identifier": "main_pg.regions"
|
|
},
|
|
{
|
|
"source_table_identifier": "public.countries",
|
|
"destination_table_identifier": "main_pg.countries",
|
|
"exclude": [
|
|
"local_name",
|
|
"size",
|
|
…
|
|
]
|
|
},
|
|
…
|
|
]
|
|
}
|
|
}'
|
|
```
|
|
|
|
</details>
|
|
|
|
<details style="padding: 0 0 0 1rem">
|
|
<summary>Get status</summary>
|
|
|
|
```plaintext
|
|
POST /api/v1/mirrors/status
|
|
{
|
|
"flowJobName": "some_cdc_mirror"
|
|
}
|
|
```
|
|
|
|
</details>
|
|
|
|
<details style="padding: 0 0 0 1rem">
|
|
<summary>Show configuration</summary>
|
|
|
|
```plaintext
|
|
POST /api/v1/mirrors/status
|
|
{
|
|
"flowJobName": "some_cdc_mirror",
|
|
"includeFlowInfo": true
|
|
}
|
|
```
|
|
|
|
</details>
|
|
|
|
### Alerts
|
|
|
|
Operations:
|
|
|
|
<details>
|
|
<summary>Create</summary>
|
|
|
|
```plaintext
|
|
POST /api/v1/alerts/config
|
|
{
|
|
"config": {
|
|
"id": -1,
|
|
"service_type": "slack",
|
|
"service_config": "{\"slot_lag_mb_alert_threshold\":15000,\"open_connections_alert_threshold\":20,\"auth_token\":\"xoxb-012345678901-0123456789012-1234ABcdEFGhijKLMnopQRST\",\"channel_ids\":[\"C01K23X4567\"]}",
|
|
"alert_for_mirrors": [
|
|
"some_cdc_mirror",
|
|
"some_other_mirror"
|
|
]
|
|
}
|
|
}
|
|
```
|
|
|
|
</details>
|
|
|
|
<details>
|
|
<summary>Show configuration</summary>
|
|
|
|
```plaintext
|
|
GET /api/v1/alerts/config
|
|
```
|
|
|
|
</details>
|
|
|
|
## Gotchas
|
|
|
|
- The [documentation] is **sorely lacking**.
|
|
|
|
- The product appears to have **not** been designed with configuration automation via IaC (nor APIs in general) in mind.
|
|
|
|
- The API proven **un**reliable, **non**-idempotent, or plain did **not** work as described in the [API Reference] as of
|
|
2025-03-19.<br/>
|
|
E.g., the `allow_update: true` data parameter in a request to the `peers/create` endpoint should make the APIs update
|
|
a peer's settings when one with the given name already exists, but the peer just does **not** get updated.
|
|
|
|
- API responses hide error messages behind a `200 OK` HTTP status code as of 2025-03-19.
|
|
|
|
<details style="padding: 0 0 1rem 1rem;">
|
|
<summary>Response example</summary>
|
|
|
|
Output of a `ansible.builtin.uri` Ansible task executed against the PeerDB server:
|
|
|
|
```json
|
|
{
|
|
"json": {
|
|
"message": "POSTGRES peer some_pg_peer was invalidated: failed to create connection: failed to connect to `user=me database=testDb`:\n\t172.31.40.46:6005 (dblab.example.org): tls error: server refused TLS connection\n\t172.31.40.46:6005 (dblab.example.org): failed SASL auth: FATAL: password authentication failed for user \"me\" (SQLSTATE 28P01)",
|
|
"status": "FAILED"
|
|
},
|
|
"msg": "OK (426 bytes)",
|
|
"status": 200,
|
|
"url": "http://localhost:3000/api/v1/peers/create",
|
|
}
|
|
```
|
|
|
|
</details>
|
|
|
|
- PeerDB seems **unable** to connect to peers which `host` parameter is `localhost` or `127.0.0.1`, but **can** connect
|
|
to the IP address of the system running the service (e.g., `192.168.1.10`).<br/>
|
|
This is most likely a Docker-related issue.
|
|
|
|
<details style="padding: 0 0 1rem 1rem;">
|
|
|
|
```sh
|
|
$ docker run --rm --name 'postgres' -d -p '10000:5432' -e POSTGRES_PASSWORD='password' 'postgres:15.5'
|
|
1cb9d450f1c1112601022dec4315a4dac7f564ee67760788850e4f61a8b5d8fb
|
|
|
|
$ psql 'host=localhost port=10000 user=postgres password=password' -c '\conninfo'
|
|
You are connected to database "postgres" as user "postgres" on host "localhost" (address "127.0.0.1") at port "10000".
|
|
|
|
$ psql 'host=192.168.1.10 port=10000 user=postgres password=password' -c '\conninfo'
|
|
You are connected to database "postgres" as user "postgres" on host "192.168.1.10" at port "10000".
|
|
|
|
$ psql 'host=localhost port=9900 user=me password=peerdb'
|
|
psql (15.8, server 14)
|
|
Type "help" for help.
|
|
me=> CREATE PEER IF NOT EXISTS some_pg_peer FROM POSTGRES WITH (host='localhost', port='10000', user='postgres', password='password', database='postgres');
|
|
ERROR: User provided error: ErrorInfo: ERROR, internal_error, failed to create peer: POSTGRES peer some_pg_peer was invalidated: failed to create connection: failed to connect to `user=postgres database=postgres`:
|
|
127.0.0.1:10000 (localhost): dial error: dial tcp 127.0.0.1:10000: connect: connection refused
|
|
[::1]:10000 (localhost): dial error: dial tcp [::1]:10000: connect: cannot assign requested address
|
|
127.0.0.1:10000 (localhost): dial error: dial tcp 127.0.0.1:10000: connect: connection refused
|
|
[::1]:10000 (localhost): dial error: dial tcp [::1]:10000: connect: cannot assign requested address
|
|
me=> CREATE PEER IF NOT EXISTS some_pg_peer FROM POSTGRES WITH (host='192.168.1.10', port='10000', user='postgres', password='password', database='postgres');
|
|
OK
|
|
```
|
|
|
|
</details>
|
|
|
|
- PostgreSQL peers do **not** accept connection options as of 2025-03-19.<br/>
|
|
This makes it impossible to specify any or override defaults.
|
|
|
|
<details style="padding: 0 0 1rem 1rem;">
|
|
|
|
The connection string is composed in code.<br/>
|
|
The [data structure specifying its parameters][peers.proto#PostgresConfig] does **not** accept options, **nor**
|
|
explicit connection strings.
|
|
|
|
```go
|
|
// https://github.com/PeerDB-io/peerdb/blob/6a591128908cbd76df8f7e4094ec838fac08dcda/protos/peers.proto#L73
|
|
message PostgresConfig {
|
|
string host = 1;
|
|
uint32 port = 2;
|
|
string user = 3;
|
|
string password = 4 [(peerdb_redacted) = true];
|
|
string database = 5;
|
|
// defaults to _peerdb_internal
|
|
optional string metadata_schema = 7;
|
|
optional SSHConfig ssh_config = 8;
|
|
}
|
|
```
|
|
|
|
</details>
|
|
|
|
- PostgreSQL peers have issues connecting to DBLab clones as of 2025-03-19.<br/>
|
|
Peers seemingly **require** SSL to connect to them for some reason, or fail the password authentication when given the
|
|
correct credentials.
|
|
|
|
<details style="padding: 0 0 1rem 1rem;">
|
|
|
|
```sh
|
|
$ nc -vz dblab.example.org 6005
|
|
Ncat: Version 7.93 ( https://nmap.org/ncat )
|
|
Ncat: Connected to 172.31.40.46:6005.
|
|
Ncat: 0 bytes sent, 0 bytes received in 0.04 seconds.
|
|
|
|
$ psql 'postgresql://dblab.example.org:6005/testDb?user=me&password=1q2w3e4r' -c '\conninfo'
|
|
You are connected to database "testDb" as user "me" on host "dblab.example.org" (address "172.31.40.46") at port "6005".
|
|
|
|
$ psql 'host=localhost port=9900 password=peerdb'
|
|
psql (15.8, server 14)
|
|
Type "help" for help.
|
|
|
|
me=> CREATE PEER IF NOT EXISTS some_pg_peer FROM POSTGRES WITH (host='dblab.example.org', port='6005', user='me', password='1q2w3e4r', database='testDb');
|
|
ERROR: User provided error: ErrorInfo: ERROR, internal_error, failed to create peer: POSTGRES peer some_pg_peer was invalidated: failed to create connection: failed to connect to `user=me database=testDb`:
|
|
172.31.40.46:6005 (dblab.example.org): tls error: server refused TLS connection
|
|
172.31.40.46:6005 (dblab.example.org): failed SASL auth: FATAL: password authentication failed for user "me" (SQLSTATE 28P01)
|
|
```
|
|
|
|
</details>
|
|
|
|
- SQL mode is provided by a translation service, which intercepts the `CREATE PEER` (or other resource) command and
|
|
uses it to create the correct resources in the PostgreSQL backend.<br/>
|
|
The translator does **not** expose **all** the resources (e.g., I could find no alert configuration), **nor** allows
|
|
for easy updates (e.g. the peers and mirrors data is encoded).<br/>
|
|
The data for peers and mirrors is encoded in ways that are **not** disclosed in the [documentation].
|
|
|
|
- Newly created mirrors will start replication right away.<br/>
|
|
Unless explicitly specified in their definition, this usually means taking an initial snapshot of the mapped tables
|
|
from the source peer.
|
|
|
|
- When in the `snapshot` state, mirrors **cannot** be paused.<br/>
|
|
If stopped (like stopping, restarting, or killing the container), it **will break** and will need to be restarted.
|
|
|
|
- **Paused** mirrors using PostgreSQL peers as source will **not** consume the logical replication's transaction log,
|
|
which **will** blow up in size (depending on the number of changes made to the source DB).
|
|
|
|
- When creating alerts through the APIs, the alert's ID in the request's data must be `-1`.<br/>
|
|
This **will** create duplicates.
|
|
|
|
## Further readings
|
|
|
|
- [Website]
|
|
- [Codebase]
|
|
- [Documentation]
|
|
- [Blog]
|
|
- [PeerDB UI - Deeper Dive: Part 1]
|
|
|
|
### Sources
|
|
|
|
- [Public IPs For PeerDB Cloud]
|
|
- [API Reference]
|
|
- [SQL reference]
|
|
- [Replication Slots]
|
|
|
|
<!--
|
|
Reference
|
|
═╬═Time══
|
|
-->
|
|
|
|
<!-- In-article sections -->
|
|
<!-- Knowledge base -->
|
|
<!-- Files -->
|
|
<!-- Upstream -->
|
|
[api reference]: https://docs.peerdb.io/peerdb-api/reference
|
|
[blog]: https://blog.peerdb.io/
|
|
[codebase]: https://github.com/PeerDB-io/peerdb
|
|
[documentation]: https://docs.peerdb.io/
|
|
[helm chart]: https://github.com/PeerDB-io/peerdb-enterprise
|
|
[peerdb ui - deeper dive: part 1]: https://blog.peerdb.io/peerdb-ui-deeper-dive-part-1
|
|
[peers.proto#PostgresConfig]: https://github.com/PeerDB-io/peerdb/blob/6a591128908cbd76df8f7e4094ec838fac08dcda/protos/peers.proto#L73
|
|
[public ips for peerdb cloud]: https://docs.peerdb.io/peerdb-cloud/ip-table
|
|
[sql reference]: https://docs.peerdb.io/sql/reference
|
|
[website]: https://www.peerdb.io/
|
|
|
|
<!-- Others -->
|
|
[replication slots]: https://www.postgresql.org/docs/current/logicaldecoding-explanation.html#LOGICALDECODING-REPLICATION-SLOTS
|