Add storage behind a trait

Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/aerogramme/pulls/32

3 files changed, 1002 insertions, 0 deletions

diff --git a/src/storage/garage.rs b/src/storage/garage.rs
new file mode 100644
index 0000000..90b84d6
--- /dev/null
+++ b/src/storage/garage.rs
@@ -0,0 +1,489 @@
+use crate::storage::*;
+use aws_sdk_s3::{self as s3, error::SdkError, operation::get_object::GetObjectError};
+use serde::Serialize;
+
+#[derive(Clone, Debug, Serialize)]
+pub struct GarageConf {
+    pub region: String,
+    pub s3_endpoint: String,
+    pub k2v_endpoint: String,
+    pub aws_access_key_id: String,
+    pub aws_secret_access_key: String,
+    pub bucket: String,
+}
+
+#[derive(Clone, Debug)]
+pub struct GarageBuilder {
+    conf: GarageConf,
+    unicity: Vec<u8>,
+}
+
+impl GarageBuilder {
+    pub fn new(conf: GarageConf) -> anyhow::Result<Arc<Self>> {
+        let mut unicity: Vec<u8> = vec![];
+        unicity.extend_from_slice(file!().as_bytes());
+        unicity.append(&mut rmp_serde::to_vec(&conf)?);
+        Ok(Arc::new(Self { conf, unicity }))
+    }
+}
+
+#[async_trait]
+impl IBuilder for GarageBuilder {
+    async fn build(&self) -> Result<Store, StorageError> {
+        let s3_creds = s3::config::Credentials::new(
+            self.conf.aws_access_key_id.clone(),
+            self.conf.aws_secret_access_key.clone(),
+            None,
+            None,
+            "aerogramme",
+        );
+
+        let sdk_config = aws_config::from_env()
+            .region(aws_config::Region::new(self.conf.region.clone()))
+            .credentials_provider(s3_creds)
+            .endpoint_url(self.conf.s3_endpoint.clone())
+            .load()
+            .await;
+
+        let s3_config = aws_sdk_s3::config::Builder::from(&sdk_config)
+            .force_path_style(true)
+            .build();
+
+        let s3_client = aws_sdk_s3::Client::from_conf(s3_config);
+
+        let k2v_config = k2v_client::K2vClientConfig {
+            endpoint: self.conf.k2v_endpoint.clone(),
+            region: self.conf.region.clone(),
+            aws_access_key_id: self.conf.aws_access_key_id.clone(),
+            aws_secret_access_key: self.conf.aws_secret_access_key.clone(),
+            bucket: self.conf.bucket.clone(),
+            user_agent: None,
+        };
+
+        let k2v_client = match k2v_client::K2vClient::new(k2v_config) {
+            Err(e) => {
+                tracing::error!("unable to build k2v client: {}", e);
+                return Err(StorageError::Internal);
+            }
+            Ok(v) => v,
+        };
+
+        Ok(Box::new(GarageStore {
+            bucket: self.conf.bucket.clone(),
+            s3: s3_client,
+            k2v: k2v_client,
+        }))
+    }
+    fn unique(&self) -> UnicityBuffer {
+        UnicityBuffer(self.unicity.clone())
+    }
+}
+
+pub struct GarageStore {
+    bucket: String,
+    s3: s3::Client,
+    k2v: k2v_client::K2vClient,
+}
+
+fn causal_to_row_val(row_ref: RowRef, causal_value: k2v_client::CausalValue) -> RowVal {
+    let new_row_ref = row_ref.with_causality(causal_value.causality.into());
+    let row_values = causal_value
+        .value
+        .into_iter()
+        .map(|k2v_value| match k2v_value {
+            k2v_client::K2vValue::Tombstone => Alternative::Tombstone,
+            k2v_client::K2vValue::Value(v) => Alternative::Value(v),
+        })
+        .collect::<Vec<_>>();
+
+    RowVal {
+        row_ref: new_row_ref,
+        value: row_values,
+    }
+}
+
+#[async_trait]
+impl IStore for GarageStore {
+    async fn row_fetch<'a>(&self, select: &Selector<'a>) -> Result<Vec<RowVal>, StorageError> {
+        let (pk_list, batch_op) = match select {
+            Selector::Range {
+                shard,
+                sort_begin,
+                sort_end,
+            } => (
+                vec![shard.to_string()],
+                vec![k2v_client::BatchReadOp {
+                    partition_key: shard,
+                    filter: k2v_client::Filter {
+                        start: Some(sort_begin),
+                        end: Some(sort_end),
+                        ..k2v_client::Filter::default()
+                    },
+                    ..k2v_client::BatchReadOp::default()
+                }],
+            ),
+            Selector::List(row_ref_list) => (
+                row_ref_list
+                    .iter()
+                    .map(|row_ref| row_ref.uid.shard.to_string())
+                    .collect::<Vec<_>>(),
+                row_ref_list
+                    .iter()
+                    .map(|row_ref| k2v_client::BatchReadOp {
+                        partition_key: &row_ref.uid.shard,
+                        filter: k2v_client::Filter {
+                            start: Some(&row_ref.uid.sort),
+                            ..k2v_client::Filter::default()
+                        },
+                        single_item: true,
+                        ..k2v_client::BatchReadOp::default()
+                    })
+                    .collect::<Vec<_>>(),
+            ),
+            Selector::Prefix { shard, sort_prefix } => (
+                vec![shard.to_string()],
+                vec![k2v_client::BatchReadOp {
+                    partition_key: shard,
+                    filter: k2v_client::Filter {
+                        prefix: Some(sort_prefix),
+                        ..k2v_client::Filter::default()
+                    },
+                    ..k2v_client::BatchReadOp::default()
+                }],
+            ),
+            Selector::Single(row_ref) => {
+                let causal_value = match self
+                    .k2v
+                    .read_item(&row_ref.uid.shard, &row_ref.uid.sort)
+                    .await
+                {
+                    Err(k2v_client::Error::NotFound) => {
+                        tracing::debug!(
+                            "K2V item not found  shard={}, sort={}, bucket={}",
+                            row_ref.uid.shard,
+                            row_ref.uid.sort,
+                            self.bucket,
+                        );
+                        return Err(StorageError::NotFound);
+                    }
+                    Err(e) => {
+                        tracing::error!(
+                            "K2V read item shard={}, sort={}, bucket={} failed: {}",
+                            row_ref.uid.shard,
+                            row_ref.uid.sort,
+                            self.bucket,
+                            e
+                        );
+                        return Err(StorageError::Internal);
+                    }
+                    Ok(v) => v,
+                };
+
+                let row_val = causal_to_row_val((*row_ref).clone(), causal_value);
+                return Ok(vec![row_val]);
+            }
+        };
+
+        let all_raw_res = match self.k2v.read_batch(&batch_op).await {
+            Err(e) => {
+                tracing::error!(
+                    "k2v read batch failed for {:?}, bucket {} with err: {}",
+                    select,
+                    self.bucket,
+                    e
+                );
+                return Err(StorageError::Internal);
+            }
+            Ok(v) => v,
+        };
+
+        let row_vals = all_raw_res
+            .into_iter()
+            .fold(vec![], |mut acc, v| {
+                acc.extend(v.items);
+                acc
+            })
+            .into_iter()
+            .zip(pk_list.into_iter())
+            .map(|((sk, cv), pk)| causal_to_row_val(RowRef::new(&pk, &sk), cv))
+            .collect::<Vec<_>>();
+
+        Ok(row_vals)
+    }
+    async fn row_rm<'a>(&self, select: &Selector<'a>) -> Result<(), StorageError> {
+        let del_op = match select {
+            Selector::Range {
+                shard,
+                sort_begin,
+                sort_end,
+            } => vec![k2v_client::BatchDeleteOp {
+                partition_key: shard,
+                prefix: None,
+                start: Some(sort_begin),
+                end: Some(sort_end),
+                single_item: false,
+            }],
+            Selector::List(row_ref_list) => {
+                // Insert null values with causality token = delete
+                let batch_op = row_ref_list
+                    .iter()
+                    .map(|v| k2v_client::BatchInsertOp {
+                        partition_key: &v.uid.shard,
+                        sort_key: &v.uid.sort,
+                        causality: v.causality.clone().map(|ct| ct.into()),
+                        value: k2v_client::K2vValue::Tombstone,
+                    })
+                    .collect::<Vec<_>>();
+
+                return match self.k2v.insert_batch(&batch_op).await {
+                    Err(e) => {
+                        tracing::error!("Unable to delete the list of values: {}", e);
+                        Err(StorageError::Internal)
+                    }
+                    Ok(_) => Ok(()),
+                };
+            }
+            Selector::Prefix { shard, sort_prefix } => vec![k2v_client::BatchDeleteOp {
+                partition_key: shard,
+                prefix: Some(sort_prefix),
+                start: None,
+                end: None,
+                single_item: false,
+            }],
+            Selector::Single(row_ref) => {
+                // Insert null values with causality token = delete
+                let batch_op = vec![k2v_client::BatchInsertOp {
+                    partition_key: &row_ref.uid.shard,
+                    sort_key: &row_ref.uid.sort,
+                    causality: row_ref.causality.clone().map(|ct| ct.into()),
+                    value: k2v_client::K2vValue::Tombstone,
+                }];
+
+                return match self.k2v.insert_batch(&batch_op).await {
+                    Err(e) => {
+                        tracing::error!("Unable to delete the list of values: {}", e);
+                        Err(StorageError::Internal)
+                    }
+                    Ok(_) => Ok(()),
+                };
+            }
+        };
+
+        // Finally here we only have prefix & range
+        match self.k2v.delete_batch(&del_op).await {
+            Err(e) => {
+                tracing::error!("delete batch error: {}", e);
+                Err(StorageError::Internal)
+            }
+            Ok(_) => Ok(()),
+        }
+    }
+
+    async fn row_insert(&self, values: Vec<RowVal>) -> Result<(), StorageError> {
+        let batch_ops = values
+            .iter()
+            .map(|v| k2v_client::BatchInsertOp {
+                partition_key: &v.row_ref.uid.shard,
+                sort_key: &v.row_ref.uid.sort,
+                causality: v.row_ref.causality.clone().map(|ct| ct.into()),
+                value: v
+                    .value
+                    .iter()
+                    .next()
+                    .map(|cv| match cv {
+                        Alternative::Value(buff) => k2v_client::K2vValue::Value(buff.clone()),
+                        Alternative::Tombstone => k2v_client::K2vValue::Tombstone,
+                    })
+                    .unwrap_or(k2v_client::K2vValue::Tombstone),
+            })
+            .collect::<Vec<_>>();
+
+        match self.k2v.insert_batch(&batch_ops).await {
+            Err(e) => {
+                tracing::error!("k2v can't insert some value: {}", e);
+                Err(StorageError::Internal)
+            }
+            Ok(v) => Ok(v),
+        }
+    }
+    async fn row_poll(&self, value: &RowRef) -> Result<RowVal, StorageError> {
+        loop {
+            if let Some(ct) = &value.causality {
+                match self
+                    .k2v
+                    .poll_item(&value.uid.shard, &value.uid.sort, ct.clone().into(), None)
+                    .await
+                {
+                    Err(e) => {
+                        tracing::error!("Unable to poll item: {}", e);
+                        return Err(StorageError::Internal);
+                    }
+                    Ok(None) => continue,
+                    Ok(Some(cv)) => return Ok(causal_to_row_val(value.clone(), cv)),
+                }
+            } else {
+                match self.k2v.read_item(&value.uid.shard, &value.uid.sort).await {
+                    Err(k2v_client::Error::NotFound) => {
+                        self.k2v
+                            .insert_item(&value.uid.shard, &value.uid.sort, vec![0u8], None)
+                            .await
+                            .map_err(|e| {
+                                tracing::error!("Unable to insert item in polling logic: {}", e);
+                                StorageError::Internal
+                            })?;
+                    }
+                    Err(e) => {
+                        tracing::error!("Unable to read item in polling logic: {}", e);
+                        return Err(StorageError::Internal);
+                    }
+                    Ok(cv) => return Ok(causal_to_row_val(value.clone(), cv)),
+                }
+            }
+        }
+    }
+
+    async fn blob_fetch(&self, blob_ref: &BlobRef) -> Result<BlobVal, StorageError> {
+        let maybe_out = self
+            .s3
+            .get_object()
+            .bucket(self.bucket.to_string())
+            .key(blob_ref.0.to_string())
+            .send()
+            .await;
+
+        let object_output = match maybe_out {
+            Ok(output) => output,
+            Err(SdkError::ServiceError(x)) => match x.err() {
+                GetObjectError::NoSuchKey(_) => return Err(StorageError::NotFound),
+                e => {
+                    tracing::warn!("Blob Fetch Error, Service Error: {}", e);
+                    return Err(StorageError::Internal);
+                }
+            },
+            Err(e) => {
+                tracing::warn!("Blob Fetch Error, {}", e);
+                return Err(StorageError::Internal);
+            }
+        };
+
+        let buffer = match object_output.body.collect().await {
+            Ok(aggreg) => aggreg.to_vec(),
+            Err(e) => {
+                tracing::warn!("Fetching body failed with {}", e);
+                return Err(StorageError::Internal);
+            }
+        };
+
+        let mut bv = BlobVal::new(blob_ref.clone(), buffer);
+        if let Some(meta) = object_output.metadata {
+            bv.meta = meta;
+        }
+        tracing::debug!("Fetched {}/{}", self.bucket, blob_ref.0);
+        Ok(bv)
+    }
+    async fn blob_insert(&self, blob_val: BlobVal) -> Result<(), StorageError> {
+        let streamable_value = s3::primitives::ByteStream::from(blob_val.value);
+
+        let maybe_send = self
+            .s3
+            .put_object()
+            .bucket(self.bucket.to_string())
+            .key(blob_val.blob_ref.0.to_string())
+            .set_metadata(Some(blob_val.meta))
+            .body(streamable_value)
+            .send()
+            .await;
+
+        match maybe_send {
+            Err(e) => {
+                tracing::error!("unable to send object: {}", e);
+                Err(StorageError::Internal)
+            }
+            Ok(_) => {
+                tracing::debug!("Inserted {}/{}", self.bucket, blob_val.blob_ref.0);
+                Ok(())
+            }
+        }
+    }
+    async fn blob_copy(&self, src: &BlobRef, dst: &BlobRef) -> Result<(), StorageError> {
+        let maybe_copy = self
+            .s3
+            .copy_object()
+            .bucket(self.bucket.to_string())
+            .key(dst.0.clone())
+            .copy_source(format!("/{}/{}", self.bucket.to_string(), src.0.clone()))
+            .send()
+            .await;
+
+        match maybe_copy {
+            Err(e) => {
+                tracing::error!(
+                    "unable to copy object {} to {} (bucket: {}), error: {}",
+                    src.0,
+                    dst.0,
+                    self.bucket,
+                    e
+                );
+                Err(StorageError::Internal)
+            }
+            Ok(_) => {
+                tracing::debug!("copied {} to {} (bucket: {})", src.0, dst.0, self.bucket);
+                Ok(())
+            }
+        }
+    }
+    async fn blob_list(&self, prefix: &str) -> Result<Vec<BlobRef>, StorageError> {
+        let maybe_list = self
+            .s3
+            .list_objects_v2()
+            .bucket(self.bucket.to_string())
+            .prefix(prefix)
+            .into_paginator()
+            .send()
+            .try_collect()
+            .await;
+
+        match maybe_list {
+            Err(e) => {
+                tracing::error!(
+                    "listing prefix {} on bucket {} failed: {}",
+                    prefix,
+                    self.bucket,
+                    e
+                );
+                Err(StorageError::Internal)
+            }
+            Ok(pagin_list_out) => Ok(pagin_list_out
+                .into_iter()
+                .map(|list_out| list_out.contents.unwrap_or(vec![]))
+                .flatten()
+                .map(|obj| BlobRef(obj.key.unwrap_or(String::new())))
+                .collect::<Vec<_>>()),
+        }
+    }
+    async fn blob_rm(&self, blob_ref: &BlobRef) -> Result<(), StorageError> {
+        let maybe_delete = self
+            .s3
+            .delete_object()
+            .bucket(self.bucket.to_string())
+            .key(blob_ref.0.clone())
+            .send()
+            .await;
+
+        match maybe_delete {
+            Err(e) => {
+                tracing::error!(
+                    "unable to delete {} (bucket: {}), error {}",
+                    blob_ref.0,
+                    self.bucket,
+                    e
+                );
+                Err(StorageError::Internal)
+            }
+            Ok(_) => {
+                tracing::debug!("deleted {} (bucket: {})", blob_ref.0, self.bucket);
+                Ok(())
+            }
+        }
+    }
+}
diff --git a/src/storage/in_memory.rs b/src/storage/in_memory.rs
new file mode 100644
index 0000000..3c3a94c
--- /dev/null
+++ b/src/storage/in_memory.rs
@@ -0,0 +1,334 @@
+use crate::storage::*;
+use std::collections::{BTreeMap, HashMap};
+use std::ops::Bound::{self, Excluded, Included, Unbounded};
+use std::sync::{Arc, RwLock};
+use tokio::sync::Notify;
+
+/// This implementation is very inneficient, and not completely correct
+/// Indeed, when the connector is dropped, the memory is freed.
+/// It means that when a user disconnects, its data are lost.
+/// It's intended only for basic debugging, do not use it for advanced tests...
+
+#[derive(Debug, Default)]
+pub struct MemDb(tokio::sync::Mutex<HashMap<String, Arc<MemBuilder>>>);
+impl MemDb {
+    pub fn new() -> Self {
+        Self(tokio::sync::Mutex::new(HashMap::new()))
+    }
+
+    pub async fn builder(&self, username: &str) -> Arc<MemBuilder> {
+        let mut global_storage = self.0.lock().await;
+        global_storage
+            .entry(username.to_string())
+            .or_insert(MemBuilder::new(username))
+            .clone()
+    }
+}
+
+#[derive(Debug, Clone)]
+enum InternalData {
+    Tombstone,
+    Value(Vec<u8>),
+}
+impl InternalData {
+    fn to_alternative(&self) -> Alternative {
+        match self {
+            Self::Tombstone => Alternative::Tombstone,
+            Self::Value(x) => Alternative::Value(x.clone()),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct InternalRowVal {
+    data: Vec<InternalData>,
+    version: u64,
+    change: Arc<Notify>,
+}
+impl std::default::Default for InternalRowVal {
+    fn default() -> Self {
+        Self {
+            data: vec![],
+            version: 1,
+            change: Arc::new(Notify::new()),
+        }
+    }
+}
+impl InternalRowVal {
+    fn concurrent_values(&self) -> Vec<Alternative> {
+        self.data.iter().map(InternalData::to_alternative).collect()
+    }
+
+    fn to_row_val(&self, row_ref: RowRef) -> RowVal {
+        RowVal {
+            row_ref: row_ref.with_causality(self.version.to_string()),
+            value: self.concurrent_values(),
+        }
+    }
+}
+
+#[derive(Debug, Default, Clone)]
+struct InternalBlobVal {
+    data: Vec<u8>,
+    metadata: HashMap<String, String>,
+}
+impl InternalBlobVal {
+    fn to_blob_val(&self, bref: &BlobRef) -> BlobVal {
+        BlobVal {
+            blob_ref: bref.clone(),
+            meta: self.metadata.clone(),
+            value: self.data.clone(),
+        }
+    }
+}
+
+type ArcRow = Arc<RwLock<HashMap<String, BTreeMap<String, InternalRowVal>>>>;
+type ArcBlob = Arc<RwLock<BTreeMap<String, InternalBlobVal>>>;
+
+#[derive(Clone, Debug)]
+pub struct MemBuilder {
+    unicity: Vec<u8>,
+    row: ArcRow,
+    blob: ArcBlob,
+}
+
+impl MemBuilder {
+    pub fn new(user: &str) -> Arc<Self> {
+        tracing::debug!("initialize membuilder for {}", user);
+        let mut unicity: Vec<u8> = vec![];
+        unicity.extend_from_slice(file!().as_bytes());
+        unicity.extend_from_slice(user.as_bytes());
+        Arc::new(Self {
+            unicity,
+            row: Arc::new(RwLock::new(HashMap::new())),
+            blob: Arc::new(RwLock::new(BTreeMap::new())),
+        })
+    }
+}
+
+#[async_trait]
+impl IBuilder for MemBuilder {
+    async fn build(&self) -> Result<Store, StorageError> {
+        Ok(Box::new(MemStore {
+            row: self.row.clone(),
+            blob: self.blob.clone(),
+        }))
+    }
+
+    fn unique(&self) -> UnicityBuffer {
+        UnicityBuffer(self.unicity.clone())
+    }
+}
+
+pub struct MemStore {
+    row: ArcRow,
+    blob: ArcBlob,
+}
+
+fn prefix_last_bound(prefix: &str) -> Bound<String> {
+    let mut sort_end = prefix.to_string();
+    match sort_end.pop() {
+        None => Unbounded,
+        Some(ch) => {
+            let nc = char::from_u32(ch as u32 + 1).unwrap();
+            sort_end.push(nc);
+            Excluded(sort_end)
+        }
+    }
+}
+
+impl MemStore {
+    fn row_rm_single(&self, entry: &RowRef) -> Result<(), StorageError> {
+        tracing::trace!(entry=%entry, command="row_rm_single");
+        let mut store = self.row.write().or(Err(StorageError::Internal))?;
+        let shard = &entry.uid.shard;
+        let sort = &entry.uid.sort;
+
+        let cauz = match entry.causality.as_ref().map(|v| v.parse::<u64>()) {
+            Some(Ok(v)) => v,
+            _ => 0,
+        };
+
+        let bt = store.entry(shard.to_string()).or_default();
+        let intval = bt.entry(sort.to_string()).or_default();
+
+        if cauz == intval.version {
+            intval.data.clear();
+        }
+        intval.data.push(InternalData::Tombstone);
+        intval.version += 1;
+        intval.change.notify_waiters();
+
+        Ok(())
+    }
+}
+
+#[async_trait]
+impl IStore for MemStore {
+    async fn row_fetch<'a>(&self, select: &Selector<'a>) -> Result<Vec<RowVal>, StorageError> {
+        tracing::trace!(select=%select, command="row_fetch");
+        let store = self.row.read().or(Err(StorageError::Internal))?;
+
+        match select {
+            Selector::Range {
+                shard,
+                sort_begin,
+                sort_end,
+            } => Ok(store
+                .get(*shard)
+                .unwrap_or(&BTreeMap::new())
+                .range((
+                    Included(sort_begin.to_string()),
+                    Excluded(sort_end.to_string()),
+                ))
+                .map(|(k, v)| v.to_row_val(RowRef::new(shard, k)))
+                .collect::<Vec<_>>()),
+            Selector::List(rlist) => {
+                let mut acc = vec![];
+                for row_ref in rlist {
+                    let maybe_intval = store
+                        .get(&row_ref.uid.shard)
+                        .map(|v| v.get(&row_ref.uid.sort))
+                        .flatten();
+                    if let Some(intval) = maybe_intval {
+                        acc.push(intval.to_row_val(row_ref.clone()));
+                    }
+                }
+                Ok(acc)
+            }
+            Selector::Prefix { shard, sort_prefix } => {
+                let last_bound = prefix_last_bound(sort_prefix);
+
+                Ok(store
+                    .get(*shard)
+                    .unwrap_or(&BTreeMap::new())
+                    .range((Included(sort_prefix.to_string()), last_bound))
+                    .map(|(k, v)| v.to_row_val(RowRef::new(shard, k)))
+                    .collect::<Vec<_>>())
+            }
+            Selector::Single(row_ref) => {
+                let intval = store
+                    .get(&row_ref.uid.shard)
+                    .ok_or(StorageError::NotFound)?
+                    .get(&row_ref.uid.sort)
+                    .ok_or(StorageError::NotFound)?;
+                Ok(vec![intval.to_row_val((*row_ref).clone())])
+            }
+        }
+    }
+
+    async fn row_rm<'a>(&self, select: &Selector<'a>) -> Result<(), StorageError> {
+        tracing::trace!(select=%select, command="row_rm");
+
+        let values = match select {
+            Selector::Range { .. } | Selector::Prefix { .. } => self
+                .row_fetch(select)
+                .await?
+                .into_iter()
+                .map(|rv| rv.row_ref)
+                .collect::<Vec<_>>(),
+            Selector::List(rlist) => rlist.clone(),
+            Selector::Single(row_ref) => vec![(*row_ref).clone()],
+        };
+
+        for v in values.into_iter() {
+            self.row_rm_single(&v)?;
+        }
+        Ok(())
+    }
+
+    async fn row_insert(&self, values: Vec<RowVal>) -> Result<(), StorageError> {
+        tracing::trace!(entries=%values.iter().map(|v| v.row_ref.to_string()).collect::<Vec<_>>().join(","), command="row_insert");
+        let mut store = self.row.write().or(Err(StorageError::Internal))?;
+        for v in values.into_iter() {
+            let shard = v.row_ref.uid.shard;
+            let sort = v.row_ref.uid.sort;
+
+            let val = match v.value.into_iter().next() {
+                Some(Alternative::Value(x)) => x,
+                _ => vec![],
+            };
+
+            let cauz = match v.row_ref.causality.map(|v| v.parse::<u64>()) {
+                Some(Ok(v)) => v,
+                _ => 0,
+            };
+
+            let bt = store.entry(shard).or_default();
+            let intval = bt.entry(sort).or_default();
+
+            if cauz == intval.version {
+                intval.data.clear();
+            }
+            intval.data.push(InternalData::Value(val));
+            intval.version += 1;
+            intval.change.notify_waiters();
+        }
+        Ok(())
+    }
+    async fn row_poll(&self, value: &RowRef) -> Result<RowVal, StorageError> {
+        tracing::trace!(entry=%value, command="row_poll");
+        let shard = &value.uid.shard;
+        let sort = &value.uid.sort;
+        let cauz = match value.causality.as_ref().map(|v| v.parse::<u64>()) {
+            Some(Ok(v)) => v,
+            _ => 0,
+        };
+
+        let notify_me = {
+            let mut store = self.row.write().or(Err(StorageError::Internal))?;
+            let bt = store.entry(shard.to_string()).or_default();
+            let intval = bt.entry(sort.to_string()).or_default();
+
+            if intval.version != cauz {
+                return Ok(intval.to_row_val(value.clone()));
+            }
+            intval.change.clone()
+        };
+
+        notify_me.notified().await;
+
+        let res = self.row_fetch(&Selector::Single(value)).await?;
+        res.into_iter().next().ok_or(StorageError::NotFound)
+    }
+
+    async fn blob_fetch(&self, blob_ref: &BlobRef) -> Result<BlobVal, StorageError> {
+        tracing::trace!(entry=%blob_ref, command="blob_fetch");
+        let store = self.blob.read().or(Err(StorageError::Internal))?;
+        store
+            .get(&blob_ref.0)
+            .ok_or(StorageError::NotFound)
+            .map(|v| v.to_blob_val(blob_ref))
+    }
+    async fn blob_insert(&self, blob_val: BlobVal) -> Result<(), StorageError> {
+        tracing::trace!(entry=%blob_val.blob_ref, command="blob_insert");
+        let mut store = self.blob.write().or(Err(StorageError::Internal))?;
+        let entry = store.entry(blob_val.blob_ref.0.clone()).or_default();
+        entry.data = blob_val.value.clone();
+        entry.metadata = blob_val.meta.clone();
+        Ok(())
+    }
+    async fn blob_copy(&self, src: &BlobRef, dst: &BlobRef) -> Result<(), StorageError> {
+        tracing::trace!(src=%src, dst=%dst, command="blob_copy");
+        let mut store = self.blob.write().or(Err(StorageError::Internal))?;
+        let blob_src = store.entry(src.0.clone()).or_default().clone();
+        store.insert(dst.0.clone(), blob_src);
+        Ok(())
+    }
+    async fn blob_list(&self, prefix: &str) -> Result<Vec<BlobRef>, StorageError> {
+        tracing::trace!(prefix = prefix, command = "blob_list");
+        let store = self.blob.read().or(Err(StorageError::Internal))?;
+        let last_bound = prefix_last_bound(prefix);
+        let blist = store
+            .range((Included(prefix.to_string()), last_bound))
+            .map(|(k, _)| BlobRef(k.to_string()))
+            .collect::<Vec<_>>();
+        Ok(blist)
+    }
+    async fn blob_rm(&self, blob_ref: &BlobRef) -> Result<(), StorageError> {
+        tracing::trace!(entry=%blob_ref, command="blob_rm");
+        let mut store = self.blob.write().or(Err(StorageError::Internal))?;
+        store.remove(&blob_ref.0);
+        Ok(())
+    }
+}
diff --git a/src/storage/mod.rs b/src/storage/mod.rs
new file mode 100644
index 0000000..1f86f71
--- /dev/null
+++ b/src/storage/mod.rs
@@ -0,0 +1,179 @@
+/*
+ *
+ * This abstraction goal is to leverage all the semantic of Garage K2V+S3,
+ * to be as tailored as possible to it ; it aims to be a zero-cost abstraction
+ * compared to when we where directly using the K2V+S3 client.
+ *
+ * My idea: we can encapsulate the causality token
+ * into the object system so it is not exposed.
+ */
+
+pub mod garage;
+pub mod in_memory;
+
+use async_trait::async_trait;
+use std::collections::HashMap;
+use std::hash::Hash;
+use std::sync::Arc;
+
+#[derive(Debug, Clone)]
+pub enum Alternative {
+    Tombstone,
+    Value(Vec<u8>),
+}
+type ConcurrentValues = Vec<Alternative>;
+
+#[derive(Debug, Clone)]
+pub enum StorageError {
+    NotFound,
+    Internal,
+}
+impl std::fmt::Display for StorageError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("Storage Error: ")?;
+        match self {
+            Self::NotFound => f.write_str("Item not found"),
+            Self::Internal => f.write_str("An internal error occured"),
+        }
+    }
+}
+impl std::error::Error for StorageError {}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct RowUid {
+    pub shard: String,
+    pub sort: String,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct RowRef {
+    pub uid: RowUid,
+    pub causality: Option<String>,
+}
+impl std::fmt::Display for RowRef {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "RowRef({}, {}, {:?})",
+            self.uid.shard, self.uid.sort, self.causality
+        )
+    }
+}
+
+impl RowRef {
+    pub fn new(shard: &str, sort: &str) -> Self {
+        Self {
+            uid: RowUid {
+                shard: shard.to_string(),
+                sort: sort.to_string(),
+            },
+            causality: None,
+        }
+    }
+    pub fn with_causality(mut self, causality: String) -> Self {
+        self.causality = Some(causality);
+        self
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct RowVal {
+    pub row_ref: RowRef,
+    pub value: ConcurrentValues,
+}
+
+impl RowVal {
+    pub fn new(row_ref: RowRef, value: Vec<u8>) -> Self {
+        Self {
+            row_ref,
+            value: vec![Alternative::Value(value)],
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct BlobRef(pub String);
+impl std::fmt::Display for BlobRef {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "BlobRef({})", self.0)
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct BlobVal {
+    pub blob_ref: BlobRef,
+    pub meta: HashMap<String, String>,
+    pub value: Vec<u8>,
+}
+impl BlobVal {
+    pub fn new(blob_ref: BlobRef, value: Vec<u8>) -> Self {
+        Self {
+            blob_ref,
+            value,
+            meta: HashMap::new(),
+        }
+    }
+
+    pub fn with_meta(mut self, k: String, v: String) -> Self {
+        self.meta.insert(k, v);
+        self
+    }
+}
+
+#[derive(Debug)]
+pub enum Selector<'a> {
+    Range {
+        shard: &'a str,
+        sort_begin: &'a str,
+        sort_end: &'a str,
+    },
+    List(Vec<RowRef>), // list of (shard_key, sort_key)
+    #[allow(dead_code)]
+    Prefix {
+        shard: &'a str,
+        sort_prefix: &'a str,
+    },
+    Single(&'a RowRef),
+}
+impl<'a> std::fmt::Display for Selector<'a> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Range {
+                shard,
+                sort_begin,
+                sort_end,
+            } => write!(f, "Range({}, [{}, {}[)", shard, sort_begin, sort_end),
+            Self::List(list) => write!(f, "List({:?})", list),
+            Self::Prefix { shard, sort_prefix } => write!(f, "Prefix({}, {})", shard, sort_prefix),
+            Self::Single(row_ref) => write!(f, "Single({})", row_ref),
+        }
+    }
+}
+
+#[async_trait]
+pub trait IStore {
+    async fn row_fetch<'a>(&self, select: &Selector<'a>) -> Result<Vec<RowVal>, StorageError>;
+    async fn row_rm<'a>(&self, select: &Selector<'a>) -> Result<(), StorageError>;
+    async fn row_insert(&self, values: Vec<RowVal>) -> Result<(), StorageError>;
+    async fn row_poll(&self, value: &RowRef) -> Result<RowVal, StorageError>;
+
+    async fn blob_fetch(&self, blob_ref: &BlobRef) -> Result<BlobVal, StorageError>;
+    async fn blob_insert(&self, blob_val: BlobVal) -> Result<(), StorageError>;
+    async fn blob_copy(&self, src: &BlobRef, dst: &BlobRef) -> Result<(), StorageError>;
+    async fn blob_list(&self, prefix: &str) -> Result<Vec<BlobRef>, StorageError>;
+    async fn blob_rm(&self, blob_ref: &BlobRef) -> Result<(), StorageError>;
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct UnicityBuffer(Vec<u8>);
+
+#[async_trait]
+pub trait IBuilder: std::fmt::Debug {
+    async fn build(&self) -> Result<Store, StorageError>;
+
+    /// Returns an opaque buffer that uniquely identifies this builder
+    fn unique(&self) -> UnicityBuffer;
+}
+
+pub type Builder = Arc<dyn IBuilder + Send + Sync>;
+pub type Store = Box<dyn IStore + Send + Sync>;