graph: Turn jailing of queries off by default

Author: lutter

docs/environment-variables.md

@@ -120,8 +120,10 @@ those.
 - `GRAPH_LOAD_THRESHOLD`: If wait times for getting database connections go
   above this threshold, throttle queries until the wait times fall below
   the threshold. Value is in milliseconds, and defaults to 0 which
-  turns throttling off and any associated statistics collection off.
+  turns throttling and any associated statistics collection off.
 - `GRAPH_LOAD_JAIL_THRESHOLD`: When the system is overloaded, any query
   that causes more than this fraction of the effort will be rejected for as
   long as the process is running (i.e., even after the overload situation
-  is resolved) Defaults to 0.1
+  is resolved) If this variable is not set, no queries will ever be jailed,
+  but they will still be subject to normal load management when the system
+  is overloaded.

graph/src/data/graphql/effort.rs

@@ -28,6 +28,8 @@ lazy_static! {
         Duration::from_millis(threshold)
     };
 
+    static ref JAIL_QUERIES: bool = env::var("GRAPH_LOAD_JAIL_THRESHOLD").is_ok();
+
     static ref JAIL_THRESHOLD: f64 = {
         env::var("GRAPH_LOAD_JAIL_THRESHOLD")
             .ok()
@@ -36,7 +38,7 @@ lazy_static! {
                     panic!("GRAPH_LOAD_JAIL_THRESHOLD must be a number, but is `{}`", s)
                 })
             })
-            .unwrap_or(0.1)
+            .unwrap_or(1e9)
     };
 
     static ref WAIT_STAT_CHECK_INTERVAL: Duration = Duration::from_secs(1);
@@ -322,7 +324,7 @@ impl LoadManager {
         let query_effort = query_effort.unwrap_or_else(|| total_effort).as_millis() as f64;
         let total_effort = total_effort.as_millis() as f64;
 
-        if known_query && query_effort / total_effort > *JAIL_THRESHOLD {
+        if known_query && *JAIL_QUERIES && query_effort / total_effort > *JAIL_THRESHOLD {
             // Any single query that causes at least JAIL_THRESHOLD of the
             // effort in an overload situation gets killed
             warn!(self.logger, "Jailing query";