[Fix] Stability

migrations/001_initial_schema.sql

@@ -1,3 +1,8 @@
+CREATE TABLE IF NOT EXISTS iotas (
+    id BIGINT NOT NULL PRIMARY KEY,
+    public_key BLOB NOT NULL
+);
+
 CREATE TABLE IF NOT EXISTS users (
     id BIGINT NOT NULL PRIMARY KEY,
     iota_id BIGINT NOT NULL,
@@ -10,14 +15,15 @@ CREATE TABLE IF NOT EXISTS users (
     sub_end BIGINT NOT NULL DEFAULT 0,
     public_key BLOB NOT NULL,
     token BLOB NOT NULL,
+
     UNIQUE KEY uk_users_username (username),
-    UNIQUE KEY uk_users_iota_id (iota_id)
+    KEY idx_users_iota_id (iota_id),
+
+    CONSTRAINT fk_users_iota
+        FOREIGN KEY (iota_id)
+        REFERENCES iotas (id)
 );
 
-CREATE TABLE IF NOT EXISTS iotas (
-    id BIGINT NOT NULL PRIMARY KEY,
-    public_key BLOB NOT NULL
-);
 
 CREATE TABLE IF NOT EXISTS omikrons (
     id BIGINT NOT NULL PRIMARY KEY,

migrations/002_registration_leases.sql

@@ -0,0 +1,13 @@
+-- Registration IDs are allocated before the user row is created.  Keep the
+-- allocation durable and bound to the Iota that requested it so a completed
+-- registration can safely be retried after any response is lost.
+CREATE TABLE registration_leases (
+    token CHAR(36) CHARACTER SET ascii COLLATE ascii_bin NOT NULL PRIMARY KEY,
+    user_id BIGINT NOT NULL UNIQUE,
+    iota_id BIGINT NOT NULL,
+    expires_at DATETIME NOT NULL,
+    completed_at DATETIME NULL,
+    CONSTRAINT fk_registration_leases_iota
+        FOREIGN KEY (iota_id) REFERENCES iotas (id),
+    INDEX idx_registration_leases_expiry (expires_at)
+);

migrations/003_registration_lease_request_id.sql

@@ -0,0 +1,8 @@
+-- A relay retry uses the original MTP request ID.  Make allocation idempotent
+-- for that authenticated Iota/request pair, so a lost response returns the
+-- same user ID and lease rather than allocating another one.
+ALTER TABLE registration_leases
+    -- Existing leases predate retry correlation; leave their request ID NULL
+    -- rather than assigning a shared sentinel that could violate uniqueness.
+    ADD COLUMN request_id INT UNSIGNED NULL,
+    ADD CONSTRAINT uk_registration_leases_iota_request UNIQUE (iota_id, request_id);