etcd_fdw

A foreign data wrapper around etcd for postgres

Setup

• Install pgrx on your machine cargo install --locked cargo-pgrx --version 0.14.3
• Setup pgrx cargo pgrx init
• Install protoc and protobuf (needed by etcd-client)
  • Instructions can be found here
• Have some kind of etcd you want to test and run

Build

• To build simply run cargo pgrx run with or without the --release flag

Try out something yourself

Currently we can only read from etcd. Here's an example of how to connect to your etcd instance and read some KVs

create extension etcd_fdw;

CREATE foreign data wrapper etcd_fdw handler etcd_fdw_handler validator etcd_fdw_validator;

CREATE SERVER my_etcd_server foreign data wrapper etcd_fdw options (connstr '127.0.0.1:2379');

CREATE foreign table test (key text, value text) server my_etcd_server options(rowid 'key');

SELECT * FROM test;

Which would yield something like:

 key | value
-----+-------
 bar | baz
 foo | bar
(2 rows)

the rowid option is required. As are the names key and value for the columns.

Usage

CREATE SERVER options

etcd_fdw accepts the following options via the CREATE SERVER command:

• connstr as string, requuired

  Connetion string for etcd server i.e. 127.0.0.1:2379

• ssl_key as string, optional, no default

  The path name of the client private key file.

• ssl_cert as string, optional, no default

  The path name of the client public key certificate file.

• ssl_ca as string, optional, no default

  The path name of the Certificate Authority (CA) certificate file. This option, if used, must specify the same certificate used by the server.

• ssl_servername as string, optional, no default

  The domain name to use for verifying the server’s TLS certificate during the handshake. This value must match the Common Name (CN) or one of the Subject Alternative Names (SANs) in the server’s certificate.

• username as string, optional, no default

  Username to use when connecting to etcd.

• password as string, optional, no default

  Password to authenticate to the etcd server with.

• connect_timeout as string, optional, default = 10

  Timeout in seconds for establishing the initial connection to the etcd server.

• request_timeout as string, optional, default = 30

  Timeout in seconds to each request after the connection has been established.

What doesn't work

etcd_fdw supports almost all kinds of CRUD operations. What doesn't work is modifying the key (which is the rowid value) directly using UPDATE statements. What does work is the following workflow:

etcd_fdw=# SELECT * FROM test;
  key  | value
-------+-------
 bar   | baz
 foo   | abc
(2 rows)
etcd_fdw=# INSERT INTO TEST (key,value) SELECT key || '_new', value FROM test;
INSERT 0 2
etcd_fdw=# DELETE FROM test WHERE NOT key LIKE '%_new';
DELETE 2
etcd_fdw=# SELECT * FROM test;
    key    | value
-----------+-------
 bar_new   | baz
 foo_new   | abc