state: limit refused writes per user

A write every node would refuse is rolled back by forking the document
at the heads before it, under the write lock, at a cost that grows with
the document's history. A user could ask for such writes in a loop.

Count each user's refused writes over the last minute. Past
--refused-writes-per-minute (default 10), its writes are answered 429
without being tried, until the oldest refusal leaves the minute.

1 files changed, 5 insertions, 0 deletions

diff --git a/docs/example.toml b/docs/example.toml
index 70d65b2..c152b8b 100644
--- a/docs/example.toml
+++ b/docs/example.toml
@@ -105,6 +105,11 @@ htpasswd = "/etc/continuum/htpasswd"
 # together at most.
 # key-logins-per-user = 100
 
+# Writes a user may have refused within a minute because every node would refuse them
+# (docs/access.md); past it, its writes are answered 429 untried for a while. Each
+# refusal costs a copy of the document.
+# refused-writes-per-minute = 10
+
 # The hash of the swarm's genesis change (hex, as its genesis node logs it and GET
 # /admin/epochs shows it): joining with an empty document, the only root this node
 # takes. Without, the one its peers name, none while they name different ones