Reference · Tenants

tenant_from

tenant_from(str | fn) -> null

What it does

Says how a request's tenant is found, at the top of a program. With a domain, tenant_from("example.com"), the tenant is the part of the host before it: acme.example.com is acme. With a function, tenant_from((request) => ...), the tenant is what the function gives for the request (a header, a path segment, a lookup), a name or null. A name is lowercase letters, digits, - and _, at most 63, starting with a letter or a digit; anything else is no tenant. It gives null. See Many tenants.

Examples

tenant_from("example.com")          // acme.example.com is tenant "acme"db.open("data/{tenant}.db")         // a SQLite file per tenantdb.migrate()route GET / = <h1>Welcome, {tenant()}</h1>

tenant_from((request) => request.headers["x-tenant"])let registry = db.connect("registry.db")db.open((tenant) => registry.one("select url from tenants where name = ?", tenant)?.url)

print(tenant_from("example.com"))print(tenant())

nullnull

Edge cases

• The domain is read without case and without a leading dot: ".Example.COM" is example.com. It is a bare domain, not a URL: no / or : in it.
• Setting the rule gives no tenant to the code at the top of the program: tenant() there is still null. The rule is applied to each request.
• A request whose host does not fit (the bare domain, another domain, a subdomain that is not a valid name) has no tenant: tenant() is null and db.* calls give an error value. A made-up subdomain opens no database.
• A function is asked for every request; what it gives is checked as a name, so a value from a header cannot reach a file or database name unchecked.
• The last tenant_from call wins.

print(tenant_from(".Example.COM"), tenant())print(tenant_from((req) => req.headers["x-tenant"]), tenant())

null nullnull null

Errors

An empty domain, one with a / or a :, and an argument that is neither a string nor a function are runtime errors, not error values.

tenant_from("https://example.com/")

line 1: `tenant_from` needs a domain such as "example.com", got "https://example.com/"

tenant_from(42)

line 1: `tenant_from` expects a domain or a function of the request, got int

Chaining

It stands alone at the top of the program, before db.open. To sign a tenant up from a request that has none yet, use with_tenant:

tenant_from("example.com")db.open("data/{tenant}.db")route POST /signup { form: { name: str } } {    with_tenant(name, () => db.exec("insert into settings (plan) values ('free')"))   // makes acme.db    redirect(`https://${name}.example.com/`)}

See also

tenant, with_tenant, db.open, db.tenants

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