mirror of
https://gitea.com/mcereda/oam.git
synced 2026-02-09 21:54:24 +00:00
251 lines
9.0 KiB
Markdown
251 lines
9.0 KiB
Markdown
# PeerDB
|
|
|
|
Fast, simple, and cost effective Postgres replication.
|
|
|
|
1. [TL;DR](#tldr)
|
|
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>Gotchas</summary>
|
|
|
|
- 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 1em 1em;">
|
|
<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 1em 1em;">
|
|
|
|
```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 1em 1em;">
|
|
|
|
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 1em 1em;">
|
|
|
|
```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>
|
|
|
|
- When creating alerts through the APIs, the alert's ID in the request's data must be `-1`.<br/>
|
|
This **will** create duplicates.
|
|
|
|
- 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].
|
|
|
|
</details>
|
|
|
|
<details>
|
|
<summary>Setup</summary>
|
|
|
|
<details style="padding: 0 0 0 1em">
|
|
<summary>Check requirements</summary>
|
|
|
|
```sql
|
|
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
|
|
ALTER SYSTEM SET wal_level = logical;
|
|
ALTER SYSTEM SET max_wal_senders = 10;
|
|
ALTER SYSTEM SET max_replication_slots = 10;
|
|
```
|
|
|
|
</details>
|
|
|
|
```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 APIs.
|
|
curl -fsS --url 'http://localhost:3000/api/v1/peers/list' -X 'GET' \
|
|
-H "Authorization: Basic $(printf '%s' ':' 'your password here' | base64)"
|
|
```
|
|
|
|
```sql
|
|
-- List peers.
|
|
SELECT id, name, type FROM peers;
|
|
|
|
-- Create peers.
|
|
CREATE PEER IF NOT EXISTS some_pg_peer FROM POSTGRES WITH (
|
|
host='some.pg.fqdn',
|
|
port='5432',
|
|
database='postgres',
|
|
user='postgres',
|
|
password='password'
|
|
);
|
|
|
|
-- Delete peers.
|
|
DELETE FROM peers WHERE name == 'some_pg_peer';
|
|
```
|
|
|
|
</details>
|
|
|
|
<details>
|
|
<summary>Real world use cases</summary>
|
|
|
|
```sh
|
|
# List peers.
|
|
psql "host=localhost port=9900 password=$(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>
|
|
|
|
## Further readings
|
|
|
|
- [Website]
|
|
- [Codebase]
|
|
- [Documentation]
|
|
|
|
### Sources
|
|
|
|
- [Public IPs For PeerDB Cloud]
|
|
- [API Reference]
|
|
|
|
<!--
|
|
Reference
|
|
═╬═Time══
|
|
-->
|
|
|
|
<!-- In-article sections -->
|
|
<!-- Knowledge base -->
|
|
<!-- Files -->
|
|
<!-- Upstream -->
|
|
[api reference]: https://docs.peerdb.io/peerdb-api/reference
|
|
[codebase]: https://github.com/PeerDB-io/peerdb
|
|
[documentation]: https://docs.peerdb.io/
|
|
[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
|
|
[website]: https://www.peerdb.io/
|
|
|
|
<!-- Others -->
|