diff --git a/CHANGES.md b/CHANGES.md
index c36181d..540eaa4 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,12 @@
 # Latest changes + history
 
+## version 0.7.5
+- Fix leak on observers when registering same metric twice.
+- Add `metric_id()` on `InputMetric`
+
+## version 0.7.4
+- Reexport `ObserveWhen` to make it public 
+
 ## version 0.7.3
 - Fixed / shushed a bunch of `clippy` warnings 
 - Made `clippy` part of `make` checks
diff --git a/Cargo.toml b/Cargo.toml
index d1c5623..f76a513 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "dipstick"
-version = "0.7.4"
+version = "0.7.5"
 authors = ["Francis Lalonde <fralalonde@gmail.com>"]
 
 description = """A fast, all-purpose metrics library decoupling instrumentation from reporting backends.
diff --git a/README.md b/README.md
index 1b4a1a2..8a6634e 100755
--- a/README.md
+++ b/README.md
@@ -80,6 +80,11 @@ in the `[dependencies]` section:
 dipstick = "0.7.4"
 ```
 
+## External features
+
+Configuring dipstick from a text file is possible using 
+the [spirit-dipstick](https://crates.io/crates/spirit-dipstick) crate.  
+
 ## Building
 When building the crate prior to PR or release, just run plain old `make`. 
 This will in turn run `cargo` a few times to run tests, benchmarks, lints, etc.
diff --git a/src/bucket/atomic.rs b/src/bucket/atomic.rs
index 3779707..d5377c6 100755
--- a/src/bucket/atomic.rs
+++ b/src/bucket/atomic.rs
@@ -257,10 +257,10 @@ impl InputScope for AtomicBucket {
     fn new_metric(&self, name: MetricName, kind: InputKind) -> InputMetric {
         let scores = write_lock!(self.inner)
             .metrics
-            .entry(self.prefix_append(name))
+            .entry(self.prefix_append(name.clone()))
             .or_insert_with(|| Arc::new(AtomicScores::new(kind)))
             .clone();
-        InputMetric::new(move |value, _labels| scores.update(value))
+        InputMetric::new(name.join("/"), move |value, _labels| scores.update(value))
     }
 }
 
diff --git a/src/core/attributes.rs b/src/core/attributes.rs
index f9467ea..a261c22 100755
--- a/src/core/attributes.rs
+++ b/src/core/attributes.rs
@@ -57,8 +57,9 @@ impl Default for Buffering {
     }
 }
 
-type Shared<T> = Arc<RwLock<T>>;
-type Listener = Arc<Fn(Instant) -> () + Send + Sync + 'static>;
+pub type MetricId = String;
+pub type Shared<T> = Arc<RwLock<T>>;
+pub type Listener = Arc<Fn(Instant) -> () + Send + Sync + 'static>;
 
 /// Attributes common to metric components.
 /// Not all attributes used by all components.
@@ -67,7 +68,7 @@ pub struct Attributes {
     naming: NameParts,
     sampling: Sampling,
     buffering: Buffering,
-    flush_listeners: Shared<Vec<Listener>>,
+    flush_listeners: Shared<HashMap<MetricId, Listener>>,
     tasks: Shared<Vec<CancelHandle>>,
 }
 
@@ -108,7 +109,7 @@ where
 {
     fn notify_flush_listeners(&self) {
         let now = Instant::now();
-        for listener in read_lock!(self.get_attributes().flush_listeners).iter() {
+        for listener in read_lock!(self.get_attributes().flush_listeners).values() {
             (listener)(now)
         }
     }
@@ -130,8 +131,10 @@ where
     pub fn on_flush(self) {
         let gauge = self.metric;
         let op = self.operation;
-        write_lock!(self.target.get_attributes().flush_listeners)
-            .push(Arc::new(move |now| gauge.write(op(now), Labels::default())));
+        let mut listeners = write_lock!(self.target.get_attributes().flush_listeners);
+        if !listeners.contains_key(gauge.metric_id()) {
+            listeners.insert(gauge.metric_id().clone(), Arc::new(move |now| gauge.write(op(now), Labels::default())));
+        }
     }
 
     /// Observe the metric's value periodically.
diff --git a/src/core/input.rs b/src/core/input.rs
index 734c1a9..05e09d8 100755
--- a/src/core/input.rs
+++ b/src/core/input.rs
@@ -2,6 +2,7 @@ use core::clock::TimeHandle;
 use core::label::Labels;
 use core::name::MetricName;
 use core::{Flush, MetricValue};
+use core::attributes::MetricId;
 
 use std::fmt;
 use std::sync::Arc;
@@ -75,6 +76,7 @@ pub trait InputScope: Flush {
 /// A metric is actually a function that knows to write a metric value to a metric output.
 #[derive(Clone)]
 pub struct InputMetric {
+    identifier: MetricId,
     inner: Arc<Fn(MetricValue, Labels) + Send + Sync>,
 }
 
@@ -86,8 +88,9 @@ impl fmt::Debug for InputMetric {
 
 impl InputMetric {
     /// Utility constructor
-    pub fn new<F: Fn(MetricValue, Labels) + Send + Sync + 'static>(metric: F) -> InputMetric {
+    pub fn new<F: Fn(MetricValue, Labels) + Send + Sync + 'static>(identifier: MetricId, metric: F) -> InputMetric {
         InputMetric {
+            identifier,
             inner: Arc::new(metric),
         }
     }
@@ -97,6 +100,11 @@ impl InputMetric {
     pub fn write(&self, value: MetricValue, labels: Labels) {
         (self.inner)(value, labels)
     }
+
+    /// Returns the unique identifier of this metric.
+    pub fn metric_id(&self) -> &MetricId {
+        &self.identifier
+    }
 }
 
 /// Used to differentiate between metric kinds in the backend.
diff --git a/src/core/locking.rs b/src/core/locking.rs
index b5b1b9d..634bd80 100755
--- a/src/core/locking.rs
+++ b/src/core/locking.rs
@@ -37,9 +37,9 @@ impl InputScope for LockingOutput {
             .inner
             .lock()
             .expect("LockingOutput")
-            .new_metric(name, kind);
+            .new_metric(name.clone(), kind);
         let mutex = self.inner.clone();
-        InputMetric::new(move |value, labels| {
+        InputMetric::new(name.join("/"), move |value, labels| {
             // lock when collecting values
             let _guard = mutex.lock().expect("LockingOutput");
             raw_metric.write(value, labels)
diff --git a/src/core/proxy.rs b/src/core/proxy.rs
index 96523a0..9142ec4 100755
--- a/src/core/proxy.rs
+++ b/src/core/proxy.rs
@@ -145,7 +145,7 @@ impl InnerProxy {
                 break;
             }
 
-            if let Some(mut metric) = metric.upgrade() {
+            if let Some(metric) = metric.upgrade() {
                 // check if metric targeted by _lower_ namespace
                 if metric.target.borrow().1 > namespace.len() {
                     continue;
@@ -254,7 +254,7 @@ impl InputScope for Proxy {
                     proxy
                 }
             });
-        InputMetric::new(move |value, labels| proxy.target.borrow().0.write(value, labels))
+        InputMetric::new(name.join("/"), move |value, labels| proxy.target.borrow().0.write(value, labels))
     }
 }
 
diff --git a/src/multi/multi_in.rs b/src/multi/multi_in.rs
index 7a10c49..728c141 100755
--- a/src/multi/multi_in.rs
+++ b/src/multi/multi_in.rs
@@ -90,7 +90,7 @@ impl InputScope for MultiInputScope {
             .iter()
             .map(move |scope| scope.new_metric(name.clone(), kind))
             .collect();
-        InputMetric::new(move |value, labels| {
+        InputMetric::new(name.join("/"), move |value, labels| {
             for metric in &metrics {
                 metric.write(value, labels.clone())
             }
diff --git a/src/output/log.rs b/src/output/log.rs
index be30e9d..5b205a2 100755
--- a/src/output/log.rs
+++ b/src/output/log.rs
@@ -117,7 +117,7 @@ impl InputScope for LogScope {
 
         if self.is_buffered() {
             // buffered
-            InputMetric::new(move |value, labels| {
+            InputMetric::new(name.join("/"), move |value, labels| {
                 let mut buffer = Vec::with_capacity(32);
                 match template.print(&mut buffer, value, |key| labels.lookup(key)) {
                     Ok(()) => {
@@ -131,7 +131,7 @@ impl InputScope for LogScope {
             // unbuffered
             let level = self.log.level;
             let target = self.log.target.clone();
-            InputMetric::new(move |value, labels| {
+            InputMetric::new(name.join("/"), move |value, labels| {
                 let mut buffer = Vec::with_capacity(32);
                 match template.print(&mut buffer, value, |key| labels.lookup(key)) {
                     Ok(()) => {
diff --git a/src/output/map.rs b/src/output/map.rs
index e43b8b9..cf8be99 100755
--- a/src/output/map.rs
+++ b/src/output/map.rs
@@ -58,9 +58,9 @@ impl InputScope for StatsMapScope {
     fn new_metric(&self, name: MetricName, _kind: InputKind) -> InputMetric {
         let name = self.prefix_append(name);
         let write_to = self.inner.clone();
-        let name: String = name.join(".");
-        InputMetric::new(move |value, _labels| {
-            let _previous = write_to.write().expect("Lock").insert(name.clone(), value);
+        let key: String = name.join(".");
+        InputMetric::new(name.join("/"), move |value, _labels| {
+            let _previous = write_to.write().expect("Lock").insert(key.clone(), value);
         })
     }
 }
diff --git a/src/queue/queue_in.rs b/src/queue/queue_in.rs
index 79a6718..8b332fb 100755
--- a/src/queue/queue_in.rs
+++ b/src/queue/queue_in.rs
@@ -185,9 +185,9 @@ impl WithAttributes for InputQueueScope {
 impl InputScope for InputQueueScope {
     fn new_metric(&self, name: MetricName, kind: InputKind) -> InputMetric {
         let name = self.prefix_append(name);
-        let target_metric = self.target.new_metric(name, kind);
+        let target_metric = self.target.new_metric(name.clone(), kind);
         let sender = self.sender.clone();
-        InputMetric::new(move |value, mut labels| {
+        InputMetric::new(name.join("/"), move |value, mut labels| {
             labels.save_context();
             if let Err(e) = sender.send(InputQueueCmd::Write(target_metric.clone(), value, labels))
             {
diff --git a/src/queue/queue_out.rs b/src/queue/queue_out.rs
index 1628ec1..8a276db 100755
--- a/src/queue/queue_out.rs
+++ b/src/queue/queue_out.rs
@@ -174,9 +174,9 @@ impl WithAttributes for OutputQueueScope {
 impl InputScope for OutputQueueScope {
     fn new_metric(&self, name: MetricName, kind: InputKind) -> InputMetric {
         let name = self.prefix_append(name);
-        let target_metric = Arc::new(self.target.new_metric(name, kind));
+        let target_metric = Arc::new(self.target.new_metric(name.clone(), kind));
         let sender = self.sender.clone();
-        InputMetric::new(move |value, mut labels| {
+        InputMetric::new(name.join("/"), move |value, mut labels| {
             labels.save_context();
             if let Err(e) = sender.send(OutputQueueCmd::Write(target_metric.clone(), value, labels))
             {