all: Change how WritableStore tracks the block pointer and cursor

chain/ethereum/src/chain.rs

@@ -217,7 +217,7 @@ impl Blockchain for Chain {
             .new(o!("component" => "FirehoseBlockStream"));
 
         let firehose_mapper = Arc::new(FirehoseMapper {});
-        let firehose_cursor = writable.block_cursor()?;
+        let firehose_cursor = writable.block_cursor();
 
         Ok(Box::new(FirehoseBlockStream::new(
             firehose_endpoint,

chain/near/src/chain.rs

@@ -127,7 +127,7 @@ impl Blockchain for Chain {
             .new(o!("component" => "FirehoseBlockStream"));
 
         let firehose_mapper = Arc::new(FirehoseMapper {});
-        let firehose_cursor = store.block_cursor()?;
+        let firehose_cursor = store.block_cursor();
 
         Ok(Box::new(FirehoseBlockStream::new(
             firehose_endpoint,

core/src/subgraph/instance_manager.rs

@@ -380,11 +380,7 @@ where
 
         // Initialize deployment_head with current deployment head. Any sort of trouble in
         // getting the deployment head ptr leads to initializing with 0
-        let deployment_head = store
-            .block_ptr()
-            .ok()
-            .and_then(|ptr| ptr.map(|ptr| ptr.number))
-            .unwrap_or(0) as f64;
+        let deployment_head = store.block_ptr().map(|ptr| ptr.number).unwrap_or(0) as f64;
         block_stream_metrics.deployment_head.set(deployment_head);
 
         let host_builder = graph_runtime_wasm::RuntimeHostBuilder::new(
@@ -484,7 +480,7 @@ where
                 ctx.inputs.unified_api_version.clone(),
             ),
             false => {
-                let start_block = ctx.inputs.store.block_ptr()?;
+                let start_block = ctx.inputs.store.block_ptr();
 
                 chain.new_polling_block_stream(
                     ctx.inputs.deployment.clone(),
@@ -626,7 +622,7 @@ where
             if should_try_unfail_deterministic {
                 should_try_unfail_deterministic = false;
 
-                if let Some(current_ptr) = ctx.inputs.store.block_ptr()? {
+                if let Some(current_ptr) = ctx.inputs.store.block_ptr() {
                     if let Some(parent_ptr) =
                         ctx.inputs.triggers_adapter.parent_ptr(&current_ptr).await?
                     {

graph/src/components/store.rs

@@ -1024,11 +1024,11 @@ pub trait SubgraphStore: Send + Sync + 'static {
 #[async_trait]
 pub trait WritableStore: Send + Sync + 'static {
     /// Get a pointer to the most recently processed block in the subgraph.
-    fn block_ptr(&self) -> Result<Option<BlockPtr>, StoreError>;
+    fn block_ptr(&self) -> Option<BlockPtr>;
 
     /// Returns the Firehose `cursor` this deployment is currently at in the block stream of events. This
     /// is used when re-connecting a Firehose stream to start back exactly where we left off.
-    fn block_cursor(&self) -> Result<Option<String>, StoreError>;
+    fn block_cursor(&self) -> Option<String>;
 
     /// Start an existing subgraph deployment.
     fn start_subgraph_deployment(&self, logger: &Logger) -> Result<(), StoreError>;

graph/tests/entity_cache.rs

@@ -46,11 +46,11 @@ impl MockStore {
 // The store trait must be implemented manually because mockall does not support async_trait, nor borrowing from arguments.
 #[async_trait]
 impl WritableStore for MockStore {
-    fn block_ptr(&self) -> Result<Option<BlockPtr>, StoreError> {
+    fn block_ptr(&self) -> Option<BlockPtr> {
         unimplemented!()
     }
 
-    fn block_cursor(&self) -> Result<Option<String>, StoreError> {
+    fn block_cursor(&self) -> Option<String> {
         unimplemented!()
     }
 

store/postgres/src/writable.rs

@@ -1,3 +1,4 @@
+use std::sync::Mutex;
 use std::time::Duration;
 use std::{collections::BTreeMap, sync::Arc};
 
@@ -325,6 +326,8 @@ fn same_subgraph(mods: &Vec<EntityModification>, id: &DeploymentHash) -> bool {
 #[allow(dead_code)]
 pub struct WritableAgent {
     store: Arc<WritableStore>,
+    block_ptr: Mutex<Option<BlockPtr>>,
+    block_cursor: Mutex<Option<String>>,
 }
 
 impl WritableAgent {
@@ -333,21 +336,26 @@ impl WritableAgent {
         logger: Logger,
         site: Arc<Site>,
     ) -> Result<Self, StoreError> {
+        let store = Arc::new(WritableStore::new(subgraph_store, logger, site)?);
+        let block_ptr = Mutex::new(store.block_ptr()?);
+        let block_cursor = Mutex::new(store.block_cursor()?);
         Ok(Self {
-            store: Arc::new(WritableStore::new(subgraph_store, logger, site)?),
+            store,
+            block_ptr,
+            block_cursor,
         })
     }
 }
 
 #[allow(unused_variables)]
 #[async_trait::async_trait]
 impl WritableStoreTrait for WritableAgent {
-    fn block_ptr(&self) -> Result<Option<BlockPtr>, StoreError> {
-        self.store.block_ptr()
+    fn block_ptr(&self) -> Option<BlockPtr> {
+        self.block_ptr.lock().unwrap().clone()
     }
 
-    fn block_cursor(&self) -> Result<Option<String>, StoreError> {
-        self.store.block_cursor()
+    fn block_cursor(&self) -> Option<String> {
+        self.block_cursor.lock().unwrap().clone()
     }
 
     fn start_subgraph_deployment(&self, logger: &Logger) -> Result<(), StoreError> {
@@ -356,6 +364,9 @@ impl WritableStoreTrait for WritableAgent {
     }
 
     fn revert_block_operations(&self, block_ptr_to: BlockPtr) -> Result<(), StoreError> {
+        *self.block_ptr.lock().unwrap() = Some(block_ptr_to.clone());
+        // FIXME: What about the firehose cursor? Why doesn't that get updated?
+
         // TODO: If we haven't written the block yet, revert in memory. If
         // we have, revert in the database
         self.store.revert_block_operations(block_ptr_to)
@@ -396,13 +407,18 @@ impl WritableStoreTrait for WritableAgent {
         deterministic_errors: Vec<SubgraphError>,
     ) -> Result<(), StoreError> {
         self.store.transact_block_operations(
-            block_ptr_to,
-            firehose_cursor,
+            block_ptr_to.clone(),
+            firehose_cursor.clone(),
             mods,
             stopwatch,
             data_sources,
             deterministic_errors,
-        )
+        )?;
+
+        *self.block_ptr.lock().unwrap() = Some(block_ptr_to);
+        *self.block_cursor.lock().unwrap() = firehose_cursor;
+
+        Ok(())
     }
 
     fn get_many(