Allow cache configuration

- Currently, you can configure ttl and jitter

src/configuration.rs

@@ -77,6 +77,7 @@ mod test {
     use core::time::Duration;
     use std::convert::TryInto;
 
+    use crate::configuration::api::v1::Cache;
     use threescalers::http::mapping_rule::{Method, RestRule};
 
     use crate::threescale::{
@@ -121,6 +122,10 @@ mod test {
                 token: "atoken".into(),
                 ttl: Some(300),
             }),
+            cache: Some(Cache {
+                ttl: Some(10),
+                jitter: Some(15),
+            }),
             backend: Some(Backend {
                 name: Some("backend-name".into()),
                 upstream: Upstream {
@@ -283,6 +288,10 @@ mod test {
                 },
                 "token": "atoken"
               },
+              "cache": {
+                "ttl": 10,
+                "jitter": 15
+              },
               "backend": {
                 "name": "backend-name",
                 "upstream": {

src/configuration/api/v1.rs

@@ -3,12 +3,19 @@ use serde::{Deserialize, Serialize};
 use crate::configuration::MissingError;
 use crate::threescale::{Backend, Service, System};
 
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Cache {
+    pub ttl: Option<u64>,
+    pub jitter: Option<u64>,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(rename = "3scale")]
 pub struct Configuration {
     pub system: Option<System>,
     pub backend: Option<Backend>,
     pub services: Option<Vec<Service>>,
+    pub cache: Option<Cache>,
     // pass request to the next filter in the chain
     pub passthrough_metadata: Option<bool>,
 }

src/proxy/root_context.rs

@@ -336,14 +336,13 @@ impl RootAuthThreescale {
     }
 
     fn get_next_tick(&self) -> Option<(Duration, Duration)> {
-        self.get_system_config().map(|sys| {
-            let jitter = self.rng.next_u32() as u64 & 0x0F; // add 0-15 seconds on top
-
-            // ensure we only do this at most once per minute, and at least not within the timeout
-            let original_ttl = sys
-                .upstream()
-                .timeout
-                .clamp(Duration::from_secs(MIN_SYNC), sys.ttl());
+        self.get_configuration().map(|config| {
+            let cache = config.cache.as_ref();
+            let max_jitter = cache.and_then(|cache| cache.jitter).unwrap_or(15);
+            let original_ttl =
+                Duration::from_secs(cache.and_then(|cache| cache.ttl).unwrap_or(MIN_SYNC));
+
+            let jitter = self.rng.next_u32() as u64 & max_jitter;
             let ttl = original_ttl.saturating_add(Duration::from_secs(jitter));
             info!(
                 self,