diff --git a/Cargo.toml b/Cargo.toml
index dc4f5ed9b..fdc3933ec 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,5 +11,5 @@ members = ["copper",
     "copper_log_runtime",
     "copper_datalogger",
     "copper_clock",
-    "copper_traits"]
+    "copper_traits", "copper_log_reader"]
 resolver = "2"
diff --git a/copper_datalogger/src/lib.rs b/copper_datalogger/src/lib.rs
index 66568a030..607f961e4 100644
--- a/copper_datalogger/src/lib.rs
+++ b/copper_datalogger/src/lib.rs
@@ -19,7 +19,7 @@ use bincode::{decode_from_reader, decode_from_slice};
 use bincode_derive::Decode as dDecode;
 use bincode_derive::Encode as dEncode;
 
-use copper::{CuError, CuResult, Stream};
+use copper::{CuError, CuResult, DataLogType, Stream};
 
 const MAIN_MAGIC: [u8; 4] = [0xB4, 0xA5, 0x50, 0xFF];
 
@@ -31,21 +31,15 @@ struct MainHeader {
     first_section_offset: u16, // This is to align with a page at write time.
 }
 
-#[derive(dEncode, dDecode, Copy, Clone)]
-pub enum EntryType {
-    StructuredLogLine,
-    CopperList,
-}
-
 #[derive(dEncode, dDecode)]
 struct SectionHeader {
     magic: [u8; 2],
-    entry_type: EntryType,
+    entry_type: DataLogType,
     section_size: u32, // offset of section_magic + section_size -> should be the index of the next section_magic
 }
 
 struct MmapStream {
-    entry_type: EntryType,
+    entry_type: DataLogType,
     parent_logger: Arc<Mutex<DataLogger>>,
     current_slice: &'static mut [u8],
     current_position: usize,
@@ -54,7 +48,7 @@ struct MmapStream {
 
 impl MmapStream {
     fn new(
-        entry_type: EntryType,
+        entry_type: DataLogType,
         parent_logger: Arc<Mutex<DataLogger>>,
         current_slice: &'static mut [u8],
         minimum_allocation_amount: usize,
@@ -114,7 +108,7 @@ impl Drop for MmapStream {
 
 pub fn stream(
     logger: Arc<Mutex<DataLogger>>,
-    entry_type: EntryType,
+    entry_type: DataLogType,
     minimum_allocation_amount: usize,
 ) -> impl Stream {
     let clone = logger.clone();
@@ -208,7 +202,7 @@ impl DataLogger {
     }
 
     /// The returned slice is section_size or greater.
-    fn add_section(&mut self, entry_type: EntryType, section_size: usize) -> &mut [u8] {
+    fn add_section(&mut self, entry_type: DataLogType, section_size: usize) -> &mut [u8] {
         // align current_position to the next page
         self.current_global_position =
             (self.current_global_position + self.page_size - 1) & !(self.page_size - 1);
@@ -264,24 +258,41 @@ impl Drop for DataLogger {
 // Section iterator returning the [u8] of the current section
 pub struct SectionIterator {
     reader: BufReader<File>,
+    datalogtype: Option<DataLogType>,
 }
 
 impl Iterator for SectionIterator {
     type Item = Vec<u8>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        let section_header: SectionHeader = decode_from_reader(&mut self.reader, standard())
-            .expect("Failed to decode section header");
-        let mut section = vec![0; section_header.section_size as usize];
-        self.reader
-            .read_exact(section.as_mut_slice())
-            .expect("Failed to read section");
-        Some(section)
+        let answer: Option<Vec<u8>> = loop {
+            if let Ok(section_header) =
+                decode_from_reader::<SectionHeader, _, _>(&mut self.reader, standard())
+            {
+                let mut section = vec![0; section_header.section_size as usize];
+                let read = self.reader.read_exact(section.as_mut_slice());
+                if read.is_err() {
+                    break None;
+                }
+                if let Some(datalogtype) = self.datalogtype {
+                    if section_header.entry_type == datalogtype {
+                        break Some(section);
+                    }
+                }
+            } else {
+                break None;
+            }
+        };
+        answer
     }
 }
 
 // make an iterator to read back a serialzed datalogger from a file
-pub fn read_datalogger(file_path: &Path) -> io::Result<impl Iterator<Item = Vec<u8>>> {
+// optionally filter by type
+pub fn read_datalogger(
+    file_path: &Path,
+    datalogtype: Option<DataLogType>,
+) -> io::Result<impl Iterator<Item = Vec<u8>>> {
     let mut file = OpenOptions::new().read(true).open(file_path)?;
     let mut header = [0; 4096];
     let s = file.read(&mut header).unwrap();
@@ -306,6 +317,7 @@ pub fn read_datalogger(file_path: &Path) -> io::Result<impl Iterator<Item = Vec<
 
     Ok(SectionIterator {
         reader: BufReader::new(file),
+        datalogtype,
     })
 }
 
@@ -332,8 +344,8 @@ mod tests {
         let used = {
             let mut logger =
                 DataLogger::new(&file_path, Some(100000)).expect("Failed to create logger");
-            logger.add_section(EntryType::StructuredLogLine, 1024);
-            logger.add_section(EntryType::CopperList, 2048);
+            logger.add_section(DataLogType::StructuredLogLine, 1024);
+            logger.add_section(DataLogType::CopperList, 2048);
             let used = logger.used();
             assert!(used < 3 * 4096); // ie. 3 headers, 1 page max per
                                       // logger drops
@@ -353,7 +365,7 @@ mod tests {
         let tmp_dir = TempDir::new().expect("could not create a tmp dir");
         let (logger, _) = make_a_logger(&tmp_dir);
         {
-            let stream = stream(logger.clone(), EntryType::StructuredLogLine, 1024);
+            let stream = stream(logger.clone(), DataLogType::StructuredLogLine, 1024);
             assert_eq!(logger.lock().unwrap().sections_in_flight.len(), 1);
         }
         let lg = logger.lock().unwrap();
@@ -365,9 +377,9 @@ mod tests {
     fn test_two_sections_self_cleaning_in_order() {
         let tmp_dir = TempDir::new().expect("could not create a tmp dir");
         let (logger, _) = make_a_logger(&tmp_dir);
-        let s1 = stream(logger.clone(), EntryType::StructuredLogLine, 1024);
+        let s1 = stream(logger.clone(), DataLogType::StructuredLogLine, 1024);
         assert_eq!(logger.lock().unwrap().sections_in_flight.len(), 1);
-        let s2 = stream(logger.clone(), EntryType::StructuredLogLine, 1024);
+        let s2 = stream(logger.clone(), DataLogType::StructuredLogLine, 1024);
         assert_eq!(logger.lock().unwrap().sections_in_flight.len(), 2);
         drop(s2);
         assert_eq!(logger.lock().unwrap().sections_in_flight.len(), 1);
@@ -381,9 +393,9 @@ mod tests {
     fn test_two_sections_self_cleaning_out_of_order() {
         let tmp_dir = TempDir::new().expect("could not create a tmp dir");
         let (logger, _) = make_a_logger(&tmp_dir);
-        let s1 = stream(logger.clone(), EntryType::StructuredLogLine, 1024);
+        let s1 = stream(logger.clone(), DataLogType::StructuredLogLine, 1024);
         assert_eq!(logger.lock().unwrap().sections_in_flight.len(), 1);
-        let s2 = stream(logger.clone(), EntryType::StructuredLogLine, 1024);
+        let s2 = stream(logger.clone(), DataLogType::StructuredLogLine, 1024);
         assert_eq!(logger.lock().unwrap().sections_in_flight.len(), 2);
         drop(s1);
         assert_eq!(logger.lock().unwrap().sections_in_flight.len(), 1);
@@ -400,12 +412,12 @@ mod tests {
         let p = f.as_path();
         println!("Path : {:?}", p);
         {
-            let mut stream = stream(logger.clone(), EntryType::StructuredLogLine, 1024);
+            let mut stream = stream(logger.clone(), DataLogType::StructuredLogLine, 1024);
             stream.log(&1u32);
             stream.log(&2u32);
             stream.log(&3u32);
         }
-        let mut sections = read_datalogger(p).unwrap();
+        let mut sections = read_datalogger(p, Some(DataLogType::StructuredLogLine)).unwrap();
         let section = sections.next().unwrap();
         let mut reader = BufReader::new(&section[..]);
         let v1: u32 = decode_from_reader(&mut reader, standard()).unwrap();
diff --git a/copper_log/Cargo.toml b/copper_log/Cargo.toml
index 0d6bf563e..32d761321 100644
--- a/copper_log/Cargo.toml
+++ b/copper_log/Cargo.toml
@@ -8,13 +8,12 @@ name = "copper_log"
 path = "src/lib.rs"
 proc-macro = true
 
-[[bin]]
-name = "copper_log_extract"
-path = "src/log_extract.rs"
-
 [dependencies]
 proc-macro2 = { version = "1.0.83" }
 quote = "1.0.36"
 syn = { version = "2.0.65", features = ["full"] }
 rkv = { version = "0.19.0", features = ["lmdb"] }
 lazy_static = { version = "1.4.0" }
+bincode_derive = "2.0.0-rc.3"
+bincode = "2.0.0-rc.3"
+copper-value = { path = "../copper_value" }
diff --git a/copper_log/src/lib.rs b/copper_log/src/lib.rs
index 49b616a30..df21c74d5 100644
--- a/copper_log/src/lib.rs
+++ b/copper_log/src/lib.rs
@@ -5,6 +5,7 @@ extern crate proc_macro;
 use crate::index::{check_and_insert, intern_string};
 use proc_macro::TokenStream;
 use quote::quote;
+use std::fmt::Display;
 use syn::parse::Parser;
 use syn::Token;
 use syn::{Expr, ExprAssign, ExprLit, Lit};
diff --git a/copper_log/src/log_extract.rs b/copper_log/src/log_extract.rs
deleted file mode 100644
index ee53a2250..000000000
--- a/copper_log/src/log_extract.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-fn main (){
-    println!("Hello");
-}
diff --git a/copper_log_reader/Cargo.toml b/copper_log_reader/Cargo.toml
new file mode 100644
index 000000000..918c5e39f
--- /dev/null
+++ b/copper_log_reader/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "copper-log-reader"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+copper-log-runtime = { path = "../copper_log_runtime" }
+rkv = { version = "0.19.0", features = ["lmdb"] }
+byteorder = "1.5.0"
+bincode = "2.0.0-rc.3"
diff --git a/copper_log_reader/src/lib.rs b/copper_log_reader/src/lib.rs
new file mode 100644
index 000000000..a6c54199a
--- /dev/null
+++ b/copper_log_reader/src/lib.rs
@@ -0,0 +1,70 @@
+use bincode::config::standard;
+use bincode::decode_from_std_read;
+use byteorder::{ByteOrder, LittleEndian};
+use copper_log_runtime::CuLogEntry;
+use rkv::backend::Lmdb;
+use rkv::{Rkv, StoreOptions, Writer};
+use std::io::Read;
+use std::path::Path;
+
+pub fn extract_copper_log_index(mut src: impl Read, index: &Path) {
+    let mut all_strings = Vec::<String>::new();
+    let env = Rkv::new::<Lmdb>(&index).unwrap();
+    let index_to_string = env
+        .open_single("index_to_string", StoreOptions::default())
+        .expect("Failed to open index_to_string store");
+    let db_eader = env.read().unwrap();
+    let ri = index_to_string.iter_start(&db_eader);
+    let mut i = ri.expect("Failed to start iterator");
+    while let Some(Ok(v)) = i.next() {
+        let (k, v) = v;
+        let index = LittleEndian::read_u32(&k) as usize;
+
+        if let rkv::Value::Str(s) = v {
+            if all_strings.len() <= index as usize {
+                all_strings.resize(index as usize + 1, String::new());
+            }
+
+            all_strings[index] = s.to_string();
+            println!("{} -> {}", index, s);
+        }
+    }
+    let entry = decode_from_std_read::<CuLogEntry, _, _>(&mut src, standard());
+    let entry = entry.expect("Failed to decode CuLogEntry");
+    println!(
+        "Entry: {} -> {} with params {:?}",
+        entry.msg_index, all_strings[entry.msg_index as usize], entry.params
+    );
+    //FIXME: Entry: 1 -> Just a string {} with params [I16(61)]
+    compile_error!("ici");
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+    use std::io::Cursor;
+    /*
+        Just a string {} CuLogEntry { msg_index: 1, paramname_indexes: [0], params: [String("zarma")] }
+        anonymous param constants {} {} CuLogEntry { msg_index: 2, paramname_indexes: [0, 0], params: [U16(42), U8(43)] }
+        named param constants {} {} CuLogEntry { msg_index: 3, paramname_indexes: [4, 5], params: [I32(3), I32(2)] }
+        mixed named param constants, {} {} {} CuLogEntry { msg_index: 6, paramname_indexes: [0, 4, 5], params: [I32(54), I32(3), I32(2)] }
+        complex tuple CuLogEntry { msg_index: 7, paramname_indexes: [0], params: [Seq([I32(1), String("toto"), F64(3.34), Bool(true), Char('a')])] }
+        Struct CuLogEntry { msg_index: 8, paramname_indexes: [0], params: [Map({String("a"): I32(3), String("b"): I32(4)})] }
+        Allocations: +{}B -{}B CuLogEntry { msg_index: 1, paramname_indexes: [2, 3], params: [U64(1003932), U64(1002876)] }
+         AFTER CLOSE {}  CuLogEntry { msg_index: 10, paramname_indexes: [0], params: [String("AFTER CLOSE")] }
+    */
+
+    // const stored_log: &[u8] = include_bytes!("../test/teststructlog.copper");
+
+    #[test]
+    fn test_extract_copper_log() {
+        let hex_string = "01 01 00 01 05 7A 61 72 6D 61 02 02 00 00 02 2A 2B 03 02 04 05 02 06 04 06 03 00 04 05 03 6C 06 04 07 01 00 01 05 02 04 74 6F 74 6F B8 1E 85 EB 51 B8 0A 40 01 61 08 01 00 01 02 01 61 06 01 62 08 01 02 02 03 02 FC 9C 51 0F 00 FC 7C 4D 0F 00 0A 01 00 01 0B 41 46 54 45 52 20 43 4C 4F 53 45 43 4C 4F 53 45 00 00 00 00";
+        let bytes: Vec<u8> = hex_string
+            .split_whitespace()
+            .map(|s| u8::from_str_radix(s, 16).expect("Parse error"))
+            .collect();
+        let mut reader = Cursor::new(bytes.as_slice());
+        extract_copper_log_index(reader, Path::new("test/copper_log_index"));
+    }
+}
diff --git a/copper_log_reader/test/copper_log_index/data.mdb b/copper_log_reader/test/copper_log_index/data.mdb
new file mode 100644
index 000000000..5023d0291
Binary files /dev/null and b/copper_log_reader/test/copper_log_index/data.mdb differ
diff --git a/copper_log_reader/test/copper_log_index/lock.mdb b/copper_log_reader/test/copper_log_index/lock.mdb
new file mode 100644
index 000000000..9e12e2a89
Binary files /dev/null and b/copper_log_reader/test/copper_log_index/lock.mdb differ
diff --git a/copper_log_reader/test/teststructlog.copper b/copper_log_reader/test/teststructlog.copper
new file mode 100644
index 000000000..b4a9b865e
Binary files /dev/null and b/copper_log_reader/test/teststructlog.copper differ
diff --git a/copper_log_runtime/src/lib.rs b/copper_log_runtime/src/lib.rs
index ca9a11875..1018d90da 100644
--- a/copper_log_runtime/src/lib.rs
+++ b/copper_log_runtime/src/lib.rs
@@ -1,7 +1,7 @@
 use bincode::enc::write::Writer;
 use bincode_derive::{Decode, Encode};
 use copper_traits::{CuResult, Stream};
-pub use copper_value as value; // Part of the API, do not remove.
+pub use copper_value as value;
 use copper_value::Value;
 use kanal::{bounded, Sender};
 use once_cell::sync::OnceCell;
@@ -16,6 +16,9 @@ static QUEUE: OnceCell<Sender<CuLogEntry>> = OnceCell::new();
 #[allow(dead_code)]
 pub const ANONYMOUS: u32 = 0;
 
+/// The lifetime of this struct is the lifetime of the logger.
+pub struct LoggerRuntime {}
+
 #[derive(Debug, Encode, Decode)]
 pub struct CuLogEntry {
     pub msg_index: u32,
@@ -47,10 +50,6 @@ impl CuLogEntry {
         self.params.push(param);
     }
 }
-
-/// The lifetime of this struct is the lifetime of the logger.
-pub struct LoggerRuntime {}
-
 impl LoggerRuntime {
     pub fn init(destination: impl Stream + 'static) -> Self {
         QUEUE
@@ -79,7 +78,9 @@ fn initialize_queue(mut destination: impl Stream + 'static) -> Sender<CuLogEntry
 
     let handle = thread::spawn(move || loop {
         if let Ok(data) = receiver.recv() {
-            destination.log(&data);
+            if let Err(err) = destination.log(&data) {
+                eprintln!("Failed to log data: {}", err);
+            }
         } else {
             break;
         }
diff --git a/copper_log_test/src/main.rs b/copper_log_test/src/main.rs
index 66ce667ca..fc007a7b1 100644
--- a/copper_log_test/src/main.rs
+++ b/copper_log_test/src/main.rs
@@ -1,4 +1,5 @@
-use copper_datalogger::{stream, DataLogger, EntryType};
+use copper::DataLogType;
+use copper_datalogger::{stream, DataLogger};
 use copper_log::debug;
 use copper_log_runtime::LoggerRuntime;
 use copper_value::to_value;
@@ -11,7 +12,7 @@ fn main() {
     let data_logger = Arc::new(Mutex::new(
         DataLogger::new(path.as_path(), Some(100000)).expect("Failed to create logger"),
     ));
-    let mut stream = stream(data_logger.clone(), EntryType::StructuredLogLine, 1024);
+    let mut stream = stream(data_logger.clone(), DataLogType::StructuredLogLine, 1024);
     let rt = LoggerRuntime::init(stream);
     #[derive(Serialize)]
     struct Test {
@@ -22,13 +23,12 @@ fn main() {
     {
         let hop = copper::monitoring::ScopedAllocCounter::new();
         let gigantic_vec = vec![0u8; 1_000_000];
-        debug!("Just a string");
-        debug!("anonymous param constants {} {}", 3u16, 2u8);
+        debug!("Just a string {}", "zarma");
+        debug!("anonymous param constants {} {}", 42u16, 43u8);
         debug!("named param constants {} {}", a = 3, b = 2);
         debug!("mixed named param constants, {} {} {}", a = 3, 54, b = 2);
         debug!("complex tuple", mytuple);
         debug!("Struct", Test { a: 3, b: 4 });
-        debug!("u8", gigantic_vec[999999]);
     }
     debug!(" AFTER CLOSE {} ", "AFTER CLOSE");
     rt.close();
diff --git a/copper_traits/src/lib.rs b/copper_traits/src/lib.rs
index 9eb76e772..a1980a301 100644
--- a/copper_traits/src/lib.rs
+++ b/copper_traits/src/lib.rs
@@ -1,4 +1,4 @@
-use bincode::Encode;
+use bincode::{Decode as dDecode, Encode, Encode as dEncode};
 use std::error::Error;
 use std::fmt::{Display, Formatter};
 
@@ -54,3 +54,9 @@ pub type CuResult<T> = Result<T, CuError>;
 pub trait Stream: Sync + Send {
     fn log(&mut self, obj: &impl Encode) -> CuResult<()>;
 }
+
+#[derive(dEncode, dDecode, Copy, Clone, Debug, PartialEq)]
+pub enum DataLogType {
+    StructuredLogLine,
+    CopperList,
+}