diff --git a/.eslintrc.json b/.eslintrc.json
new file mode 100644
index 0000000..77831d0
--- /dev/null
+++ b/.eslintrc.json
@@ -0,0 +1,27 @@
+{
+  "env": {
+    "node": true,
+    "mocha": true,
+    "es6": true
+  },
+  "extends": "eslint:recommended",
+  "installedESLint": true,
+  "root": true,
+  "rules": {
+    "comma-dangle": [2, "only-multiline"],
+    "dot-notation": 2,
+    "indent": [2, 4, {"SwitchCase": 1}],
+    "one-var": [2, "never"],
+    "no-trailing-spaces": [2, { "skipBlankLines": false }],
+    "keyword-spacing": [2, {
+      "before": true,
+      "after": true
+    }],
+    "no-delete-var": 2,
+    "no-empty": ["error", { "allowEmptyCatch": true }],
+    "no-label-var": 2,
+    "no-shadow": 2,
+    "no-unused-vars": [ 1, { "args": "none" }],
+    "no-console": 0
+  }
+}
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..fcdc330
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,20 @@
+language: node_js
+node_js:
+    - "4"
+    - "6"
+
+services:
+    - redis-server
+
+before_script:
+
+script:
+    - npm run lint
+    - npm test
+
+after_success:
+    - npm install istanbul codecov
+    - npm run cover
+    - ./node_modules/.bin/codecov
+
+sudo: false
diff --git a/README.md b/README.md
index 5fcb65c..16de39a 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,78 @@
-# haraka-plugin-limit
-Enforce many types of limits on a Haraka mail server.
+# limit
+
+Apply several types of limits to SMTP connections.
+
+Each limit type has a max value that can be defined in limit.ini. The default is empty / disabled until a value has been set.
+
+## See Also
+
+To set rate limits on connections and recipients, see the `rate_limit` plugin.
+
+## concurrency
+
+When `[concurrency]max` is defined, it limits the maximum number of simultaneous connections per IP address. Connection attempts in excess of the limit are delayed for `disconnect_delay` seconds (default: 3) before being disconnected.
+
+This works best in conjunction with a history / reputation database, so that
+one can assign very low concurrency (1) to bad or unknown senders and higher
+limits for reputable mail servers.
+
+### History
+
+History: when enabled, the `history` setting is the name of a plugin that stores IP history / reputation results. The result store must have a positive value for good connections and negative integers for poor / undesirable connections. Karma is one such plugin.
+
+
+## recipients
+
+When `[recipients]max` is defined, each connection is limited to that number of recipients. The limit is imposed against **all** recipient attempts. Attempts in excess of the limit are issued a temporary failure.
+
+
+## unrecognized_commands
+
+When `[unrecognized_commands]max` is set, a connection that exceeeds the limit is disconnected.
+
+Unrecognized commands are normally SMTP verbs invalidly issued by the client.
+Examples:
+
+* issuing AUTH when we didn't advertise AUTH extension
+* issuing STARTTLS when we didn't advertise STARTTLS
+* invalid SMTP verbs
+
+
+### Limitations
+
+The unrecognized_command hook is used by the `tls` and `auth` plugins, so
+running this plugin before those would result in valid operations getting
+counted against that connections limits. The solution is simple: list
+`limit` in config/plugins after those.
+
+
+## errors
+
+When `[errors]max` is set, a connection that exceeeds the limit is disconnected. Errors that count against this limit include:
+
+* issuing commands out of turn (MAIL before EHLO, RCPT before MAIL, etc)
+* attempting MAIL on port 465/587 without AUTH
+* MAIL or RCPT addresses that fail to parse
+
+# Error Handling
+
+## Too high counters
+
+If the NoSQL store is Redis and Haraka is restarted or crashes while active
+connections are open, the concurrency counters might be inflated. This is
+handled by the [concurrency]reset setting (default: 10m), which:
+
+* ssc: sets collection expiration time
+* redis: empties the concurrency hash
+* RAM: empties the in-memory hash of all keys
+
+## Too low counters
+
+Because the redis and RAM objects are emptied periodically, connections that
+are open while the collections are emptied will be too low. When
+that happens, log messages like these might be emitted:
+
+    resetting 0 to 1
+    resetting -1 to 1
+
+This is a harmless error condition that is repaired automatically.
diff --git a/config/limit.ini b/config/limit.ini
new file mode 100644
index 0000000..0caa58c
--- /dev/null
+++ b/config/limit.ini
@@ -0,0 +1,46 @@
+; limits imposed on connection(s)
+; see also: rate_limit
+
+[redis]
+; host=127.0.0.1
+; port=6387
+db=4
+;
+; expire: minutes concurrency information is cached in RAM, default: 10
+; expire=10
+
+; there are no defaults unless shown. Limits are disabled until a max value is set.
+; help: haraka -h limits
+
+[concurrency]
+; max=3
+; disconnect_delay=5
+; reset=10   // default: minutes
+
+; History: when enabled, the value must be a plugin which stores IP history
+;   results. The result store must have a positive value for good connections
+;   and negative integers for poor / undesirable connections. At present,
+;   karma is the only such plugin.
+; history=karma
+; history_bad=1
+; history_none=3
+; history_good=10
+
+
+[recipients]
+; max= 20
+; max_relaying= 100
+
+; The same history notes for [concurrency] apply here.
+; history=karma
+; history_bad=5
+; history_none=15
+; history_good=50
+
+
+[unrecognized_commands]
+; max= 10
+
+
+[errors]
+; max= 10
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..8224d84
--- /dev/null
+++ b/index.js
@@ -0,0 +1,241 @@
+'use strict';
+
+var constants = require('haraka-constants');
+
+exports.register = function () {
+    var plugin = this;
+    plugin.inherits('haraka-plugin-redis');
+
+    plugin.register_hook('init_master',  'init_redis_plugin');
+    plugin.register_hook('init_child',   'init_redis_plugin');
+
+    plugin.load_limit_ini();
+
+    if (plugin.cfg.concurrency) {
+        plugin.register_hook('connect_init', 'incr_concurrency');
+        plugin.register_hook('connect',      'check_concurrency');
+        plugin.register_hook('disconnect',   'decr_concurrency');
+    }
+
+    if (plugin.cfg.errors) {
+        ['helo','ehlo','mail','rcpt','data'].forEach(function (hook) {
+            plugin.register_hook(hook, 'max_errors');
+        });
+    }
+
+    if (plugin.cfg.recipients) {
+        plugin.register_hook('rcpt', 'max_recipients');
+    }
+
+    if (plugin.cfg.unrecognized_commands) {
+        plugin.register_hook('unrecognized_command', 'max_unrecognized_commands');
+    }
+};
+
+exports.load_limit_ini = function () {
+    var plugin = this;
+    plugin.cfg = plugin.config.get('limit.ini', function () {
+        plugin.load_limit_ini();
+    });
+
+    if (!plugin.cfg.concurrency) {   // no config file
+        plugin.cfg.concurrency = {};
+    }
+
+    plugin.merge_redis_ini();
+};
+
+exports.max_unrecognized_commands = function(next, connection, cmd) {
+    var plugin = this;
+    if (!plugin.cfg.unrecognized_commands) { return next(); }
+
+    connection.results.add(plugin, {fail: 'unrecognized: ' + cmd, emit: true});
+    connection.results.incr(plugin, {unrec_cmds: 1});
+
+    var max = parseFloat(plugin.cfg.unrecognized_commands.max);
+    if (!max || isNaN(max)) { return next(); }
+
+    var uc = connection.results.get(plugin.name);
+    if (parseFloat(uc.unrec_cmds) <= max) { return next(); }
+
+    connection.results.add(plugin, {fail: 'unrec_cmds.max'});
+    return next(constants.DENYDISCONNECT, 'Too many unrecognized commands');
+};
+
+exports.max_errors = function (next, connection) {
+    var plugin = this;
+    if (!plugin.cfg.errors) { return next(); } // disabled in config
+
+    var max = parseFloat(plugin.cfg.errors.max);
+    if (!max || isNaN(max)) { return next(); }
+
+    if (connection.errors <= max) { return next(); }
+
+    connection.results.add(plugin, {fail: 'errors.max'});
+    return next(constants.DENYSOFTDISCONNECT, 'Too many errors');
+};
+
+exports.max_recipients = function (next, connection, params) {
+    var plugin = this;
+    if (!plugin.cfg.recipients) { return next(); } // disabled in config
+
+    var max = plugin.get_recipient_limit(connection);
+    if (!max) { return next(); }
+
+    var c = connection.rcpt_count;
+    var count = c.accept + c.tempfail + c.reject + 1;
+    if (count <= max) { return next(); }
+
+    connection.results.add(plugin, {fail: 'recipients.max'});
+    return next(constants.DENYSOFT, 'Too many recipients');
+};
+
+exports.get_recipient_limit = function (connection) {
+    var plugin = this;
+
+    if (connection.relaying && plugin.cfg.recipients.max_relaying) {
+        return plugin.cfg.recipients.max_relaying;
+    }
+
+    var history_plugin = plugin.cfg.concurrency.history;
+    if (!history_plugin) {
+        return plugin.cfg.recipients.max;
+    }
+
+    var results = connection.results.get(history_plugin);
+    if (!results) {
+        connection.logerror(plugin, 'no ' + history_plugin + ' results,' +
+               ' disabling history due to misconfiguration');
+        delete plugin.cfg.recipients.history;
+        return plugin.cfg.recipients.max;
+    }
+
+    if (results.history === undefined) {
+        connection.logerror(plugin, 'no history from : ' + history_plugin);
+        return plugin.cfg.recipients.max;
+    }
+
+    var history = parseFloat(results.history);
+    connection.logdebug(plugin, 'history: ' + history);
+    if (isNaN(history)) { history = 0; }
+
+    if (history > 0) return plugin.cfg.recipients.history_good || 50;
+    if (history < 0) return plugin.cfg.recipients.history_bad  || 2;
+    return plugin.cfg.recipients.history_none || 15;
+};
+
+exports.incr_concurrency = function (next, connection) {
+    var plugin = this;
+    if (!plugin.cfg.concurrency) { return next(); }
+
+    var dbkey = plugin.get_key(connection);
+
+    plugin.db.incrby(dbkey, 1, function (err, concurrent) {
+
+        if (concurrent === undefined) {
+            connection.logerror(plugin, 'concurrency not returned by incrby!');
+            return next();
+        }
+        if (isNaN(concurrent)) {
+            connection.logerror(plugin, 'concurrency isNaN!');
+            return next();
+        }
+
+        connection.logdebug(plugin, 'concurrency incremented to ' + concurrent);
+
+        // repair negative concurrency counters
+        if (concurrent < 1) {
+            connection.loginfo(plugin, 'resetting ' + concurrent + ' to 1');
+            plugin.db.set(dbkey, 1);
+        }
+
+        connection.notes.limit=concurrent;
+        next();
+    });
+};
+
+exports.get_key = function (connection) {
+    return 'concurrency|' + connection.remote.ip;
+};
+
+exports.check_concurrency = function (next, connection) {
+    var plugin = this;
+
+    var max = plugin.get_concurrency_limit(connection);
+    if (!max || isNaN(max)) {
+        connection.logerror(plugin, "no limit?!");
+        return next();
+    }
+    connection.logdebug(plugin, 'concurrent max: ' + max);
+
+    var concurrent = parseInt(connection.notes.limit);
+
+    if (concurrent <= max) {
+        connection.results.add(plugin, { pass: concurrent + '/' + max});
+        return next();
+    }
+
+    connection.results.add(plugin, {
+        fail: 'concurrency: ' + concurrent + '/' + max,
+    });
+
+    var delay = 3;
+    if (plugin.cfg.concurrency.disconnect_delay) {
+        delay = parseFloat(plugin.cfg.concurrency.disconnect_delay);
+    }
+
+    // Disconnect slowly.
+    setTimeout(function () {
+        return next(constants.DENYSOFTDISCONNECT, 'Too many concurrent connections');
+    }, delay * 1000);
+};
+
+exports.get_concurrency_limit = function (connection) {
+    var plugin = this;
+
+    var history_plugin = plugin.cfg.concurrency.history;
+    if (!history_plugin) {
+        return plugin.cfg.concurrency.max;
+    }
+
+    var results = connection.results.get(history_plugin);
+    if (!results) {
+        connection.logerror(plugin, 'no ' + history_plugin + ' results,' +
+               ' disabling history due to misconfiguration');
+        delete plugin.cfg.concurrency.history;
+        return plugin.cfg.concurrency.max;
+    }
+
+    if (results.history === undefined) {
+        connection.loginfo(plugin, 'no IP history from : ' + history_plugin);
+        return plugin.cfg.concurrency.max;
+    }
+
+    var history = parseFloat(results.history);
+    connection.logdebug(plugin, 'history: ' + history);
+    if (isNaN(history)) { history = 0; }
+
+    if (history < 0) { return plugin.cfg.concurrency.history_bad  || 1; }
+    if (history > 0) { return plugin.cfg.concurrency.history_good || 5; }
+    return plugin.cfg.concurrency.history_none || 3;
+};
+
+exports.decr_concurrency = function (next, connection) {
+    var plugin = this;
+    if (!plugin.cfg.concurrency) { return next(); }
+
+    var dbkey = plugin.get_key(connection);
+    plugin.db.incrby(dbkey, -1, function (err, concurrent) {
+        connection.logdebug(plugin, 'decrement concurrency to ' + concurrent);
+
+        // if connections didn't increment properly (this happened a lot
+        // before we added the connect_init hook), the counter can go
+        // negative. check for and repair negative concurrency counters
+        if (concurrent < 0) {
+            connection.loginfo(plugin, 'resetting ' + concurrent + ' to 1');
+            plugin.db.set(dbkey, 1);
+        }
+
+        return next();
+    });
+};
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..f5078a2
--- /dev/null
+++ b/package.json
@@ -0,0 +1,39 @@
+{
+  "name": "haraka-plugin-limit",
+  "version": "1.0.0",
+  "description": "enforce various types of limits on remote MTAs",
+  "main": "limit.js",
+  "directories": {
+    "test": "test"
+  },
+  "dependencies": {
+    "haraka-constants": "^1.0.2",
+    "haraka-plugin-redis": "*",
+    "redis": "^2.6.5"
+  },
+  "devDependencies": {
+    "eslint": "^3.14.1",
+    "haraka-test-fixtures": "^1.0.13",
+    "nodeunit": "^0.10.2"
+  },
+  "scripts": {
+    "lint": "./node_modules/.bin/eslint *.js test/*.js",
+    "test": "./run_tests"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/haraka/haraka-plugin-limit.git"
+  },
+  "keywords": [
+    "haraka",
+    "smtp",
+    "mta",
+    "limit"
+  ],
+  "author": "Matt Simerson <matt@tnpi.net>",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/haraka/haraka-plugin-limit/issues"
+  },
+  "homepage": "https://github.com/haraka/haraka-plugin-limit#readme"
+}
diff --git a/run_tests b/run_tests
new file mode 100755
index 0000000..22222c3
--- /dev/null
+++ b/run_tests
@@ -0,0 +1,33 @@
+#!/usr/bin/env node
+
+"use strict";
+
+try {
+    var reporter = require('nodeunit').reporters.default;
+}
+catch(e) {
+    console.log("Error: " + e.message);
+    console.log("");
+    console.log("Cannot find nodeunit module.");
+    console.log("Please run the following:");
+    console.log("");
+    console.log("    npm install");
+    console.log("");
+    process.exit();
+}
+
+process.chdir(__dirname);
+
+if (process.argv[2]) {
+    console.log("Running tests: ", process.argv.slice(2));
+    reporter.run(process.argv.slice(2), undefined, function (err) {
+        process.exit(((err) ? 1 : 0));
+    });
+}
+else {
+    reporter.run([
+        'test',
+    ], undefined, function (err) {
+        process.exit(((err) ? 1 : 0));
+    });
+}
diff --git a/test/limit.js b/test/limit.js
new file mode 100644
index 0000000..395a914
--- /dev/null
+++ b/test/limit.js
@@ -0,0 +1,169 @@
+'use strict';
+
+var constants    = require('haraka-constants');
+var fixtures     = require('haraka-test-fixtures');
+
+var _set_up = function (done) {
+
+    this.plugin = new fixtures.plugin('index');
+
+    this.plugin.cfg = { main: {} };
+
+    this.connection = new fixtures.connection.createConnection();
+    this.connection.results = new fixtures.result_store(this.connection);
+    this.connection.transaction = new fixtures.transaction.createTransaction();
+
+    this.plugin.register();
+    done();
+};
+
+exports.inheritance = {
+    setUp : function (done) {
+        this.plugin = new fixtures.plugin('index');
+        done();
+    },
+    'inherits redis': function (test) {
+        test.expect(1);
+        this.plugin.inherits('haraka-plugin-redis');
+        test.equal(typeof this.plugin.load_redis_ini, 'function');
+        test.done();
+    },
+    'can call parent functions': function (test) {
+        test.expect(1);
+        this.plugin.inherits('haraka-plugin-redis');
+        this.plugin.load_redis_ini();
+        test.ok(this.plugin.redisCfg); // loaded config
+        test.done();
+    },
+    'register': function (test) {
+        test.expect(1);
+        this.plugin.register();
+        test.ok(this.plugin.cfg); // loaded config
+        test.done();
+    },
+};
+
+exports.max_errors = {
+    setUp : _set_up,
+    'none': function (test) {
+        // console.log(this);
+        test.expect(2);
+        var cb = function (rc, msg) {
+            // console.log(arguments);
+            test.equal(rc, null);
+            test.equal(msg, null);
+            test.done();
+        };
+        this.plugin.max_errors(cb, this.connection);
+    },
+    'too many': function (test) {
+        // console.log(this);
+        test.expect(2);
+        var cb = function (rc, msg) {
+            // console.log(arguments);
+            test.equal(rc, constants.DENYSOFTDISCONNECT);
+            test.equal(msg, 'Too many errors');
+            test.done();
+        };
+        this.connection.errors=10;
+        this.plugin.cfg.errors = { max: 9 };
+        this.plugin.max_errors(cb, this.connection);
+    },
+};
+
+exports.max_recipients = {
+    setUp : _set_up,
+    'none': function (test) {
+        test.expect(2);
+        var cb = function (rc, msg) {
+            // console.log(arguments);
+            test.equal(rc, null);
+            test.equal(msg, null);
+            test.done();
+        };
+        this.plugin.max_recipients(cb, this.connection);
+    },
+    'too many': function (test) {
+        test.expect(2);
+        var cb = function (rc, msg) {
+            // console.log(arguments);
+            test.equal(rc, constants.DENYSOFT);
+            test.equal(msg, 'Too many recipients');
+            test.done();
+        };
+        this.connection.rcpt_count = { accept: 3, tempfail: 5, reject: 4 };
+        this.plugin.cfg.recipients = { max: 10 };
+        this.plugin.max_recipients(cb, this.connection);
+    },
+};
+
+exports.max_unrecognized_commands = {
+    setUp : _set_up,
+    'none': function (test) {
+        // console.log(this);
+        test.expect(2);
+        var cb = function (rc, msg) {
+            // console.log(arguments);
+            test.equal(rc, null);
+            test.equal(msg, null);
+            test.done();
+        };
+        this.plugin.max_unrecognized_commands(cb, this.connection);
+    },
+    'too many': function (test) {
+        // console.log(this);
+        test.expect(2);
+        var cb = function (rc, msg) {
+            // console.log(arguments);
+            test.equal(rc, constants.DENYDISCONNECT);
+            test.equal(msg, 'Too many unrecognized commands');
+            test.done();
+        };
+        this.plugin.cfg.unrecognized_commands = { max: 5 };
+        this.connection.results.incr(this.plugin, {'unrec_cmds': 6});
+        this.plugin.max_unrecognized_commands(cb, this.connection);
+    },
+};
+
+// exports.check_concurrency = {
+//     setUp : _set_up,
+//     'none': function (test) {
+//         test.expect(2);
+//         var cb = function (rc, msg) {
+//             // console.log(arguments);
+//             test.equal(rc, null);
+//             test.equal(msg, null);
+//             test.done();
+//         };
+//         this.plugin.check_concurrency(cb, this.connection);
+//     },
+//     'at max': function (test) {
+//         test.expect(2);
+//         var cb = function (rc, msg) {
+//             // console.log(arguments);
+//             test.equal(rc, null);
+//             test.equal(msg, null);
+//             test.done();
+//         };
+//         var self = this;
+//         self.plugin.cfg.concurrency.history = undefined;
+//         self.plugin.cfg.concurrency = { max: 4 };
+//         self.connection.notes.limit=4;
+//         self.plugin.check_concurrency(cb, self.connection);
+//     },
+//     'too many': function (test) {
+//         test.expect(2);
+//         var cb = function (rc, msg) {
+//             // console.log(arguments);
+//             test.equal(rc, constants.DENYSOFTDISCONNECT);
+//             test.equal(msg, 'Too many concurrent connections');
+//             test.done();
+//         };
+//         var self = this;
+//         self.plugin.cfg.concurrency.history = undefined;
+//         self.plugin.cfg.concurrency = { max: 4 };
+//         self.plugin.cfg.concurrency.disconnect_delay=1;
+//         self.connection.notes.limit=5;
+//         self.plugin.check_concurrency(cb, self.connection);
+//     },
+// };