Add simple stats API

src/lib.rs

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 pub mod hostcalls;
+pub mod stats;
 pub mod traits;
 pub mod types;
 

src/stats.rs

@@ -0,0 +1,107 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use crate::hostcalls;
+use crate::traits;
+use crate::types;
+
+pub struct Counter {
+    id: u32,
+    name: String,
+}
+
+impl Counter {
+    pub fn counter(name: String) -> Counter {
+        let returned_id = hostcalls::define_metric(types::MetricType::Counter, &name).unwrap();
+        Counter {
+            id: returned_id,
+            name,
+        }
+    }
+}
+
+impl traits::Metric for Counter {
+    fn id(&self) -> u32 {
+        self.id
+    }
+
+    fn name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    fn record(&self, _: u64) {
+        // A Counter can only be incremented.
+        return;
+    }
+}
+
+pub struct Gauge {
+    id: u32,
+    name: String,
+}
+
+impl Gauge {
+    pub fn gauge(name: String) -> Gauge {
+        let returned_id = hostcalls::define_metric(types::MetricType::Gauge, &name).unwrap();
+        Gauge {
+            id: returned_id,
+            name,
+        }
+    }
+}
+
+impl traits::Metric for Gauge {
+    fn id(&self) -> u32 {
+        self.id
+    }
+
+    fn name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    fn increment(&self, _: i64) {
+        // A gauge can only be recorded.
+        return;
+    }
+}
+
+pub struct Histogram {
+    id: u32,
+    name: String,
+}
+
+impl Histogram {
+    pub fn histogram(name: String) -> Histogram {
+        let returned_id = hostcalls::define_metric(types::MetricType::Histogram, &name).unwrap();
+        Histogram {
+            id: returned_id,
+            name,
+        }
+    }
+}
+
+impl traits::Metric for Histogram {
+    fn id(&self) -> u32 {
+        self.id
+    }
+
+    fn name(&self) -> &str {
+        self.name.as_str()
+    }
+
+    fn increment(&self, _: i64) {
+        // A Histogram can only be recorded.
+        return;
+    }
+}

src/traits.rs

@@ -534,3 +534,32 @@ pub trait HttpContext: Context {
 
     fn on_log(&mut self) {}
 }
+
+pub trait Metric {
+    fn name(&self) -> &str;
+    fn id(&self) -> u32;
+
+    fn value(&self) -> u64 {
+        match hostcalls::get_metric(self.id()) {
+            Ok(value) => value,
+            Err(Status::NotFound) => panic!("metric not found: {}", self.name()),
+            Err(err) => panic!("unexpected status: {:?}", err),
+        }
+    }
+
+    fn record(&self, value: u64) {
+        match hostcalls::record_metric(self.id(), value) {
+            Ok(_) => return,
+            Err(Status::NotFound) => panic!("metric not found: {}", self.name()),
+            Err(err) => panic!("unexpected status: {:?}", err),
+        }
+    }
+
+    fn increment(&self, offset: i64) {
+        match hostcalls::increment_metric(self.id(), offset) {
+            Ok(_) => return,
+            Err(Status::NotFound) => panic!("metric not found: {}", self.name()),
+            Err(err) => panic!("unexpected status: {:?}", err),
+        }
+    }
+}