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crates/iota-analytics-indexer/README.md

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+IOTA Analytical Indexer
+=======================
+
+The IOTA Analytical Indexer is a service that exports data from the main IOTA network to a remote big object store (S3/GCS/Azure) for further analytical processing.
+
+**Key Features**
+----------------
+
+* Exports data from the IOTA network to a remote big object store
+* Provides BigQuery and Snowflake schemas for the exported data
+* Does not perform any analysis on its own
+
+**Architecture**
+----------------
+
+When running the indexer, one needs to specify object type that would be extracted from checkpoints and uploaded to the cloud.
+
+The following object types are supported:
+- Checkpoint
+- Object
+- Transaction
+- TransactionObjects
+- Event
+- MoveCall
+- MovePackage
+- DynamicField
+- WrappedObject
+
+Only one object type can be passed in given run, to process multiple object types it is needed to run multiple analytical indexer instances.
+
+In general, the data flow is as follows:
+
+* Checkpoints are read via JSON RPC using reused code from `iota_data_ingestion_core`.
+* Checkpoints are processed by an appropriate handler (e.g. `EventHandler`), which extracts relevant objects from each transaction of the checkpoint.
+* Objects are passed to the Writer, which writes the objects to a local temporary store in CSV or Parquet format.
+* The `AnalyticsProcessor` syncs the objects from the local store to the remote store (S3/GCS/Azure, or also local, for testing purposes).
+* Every 5 minutes the last processed checkpoint ID is fetched from BigQuery/Snowflake and reported as a metric.
+
+**Note:** It is assumed that data from the big object store will be readable from BigQuery/Snowflake automatically, the indexer is not putting the data in BigQuery/Snowflake tables explicitly.
+
+Here is a graph summarizing the data flow:
+
+```mermaid
+---
+config:
+  look: handDrawn
+  theme: neutral
+---
+flowchart TD
+    FNODE["Fullnode/Indexer"] <-->|JSON RPC| CPREADER["`IndexerExecutor/CheckpointReader from the **iota_data_ingestion_core** package`"];
+    subgraph "`**iota-analytical-indexer**`"
+        CPREADER -->|"`Executor calls **AnalyticsProcessor** for each checkpoint, which in turn passes the checkpoint to appropriate Handler`"| HANDLER["CheckpointHandler/EventHandler etc., depending on indexer configuration"]
+        HANDLER -->|"`**AnalyticsProcessor** reads object data extracted from the checkpoint by the Handler and passes it to the Writer`"| WRITER["CSVWriter/ParquetWriter"]
+        WRITER -->|Writes objects to temporary local storage| DISK[Temporary Local Storage]
+        DISK --> REMOTESYNC["`Task inside of **AnalyticsProcessor** that removes files from Local Storage and uploads them to Remote Storage(S3/GCS/Azure)`"]
+        WRITER -->|"`Once every few checkpoints, **AnalyticsProcessor** calls cut() to prepare file to be sent, FileMetadata is sent to the Remote Sync Task which triggers the sync`"| REMOTESYNC
+        REMOTESYNC -->|Some process outside of analytical indexer makes the newly uploaded data available via BigQuery/Snowflake tables| BQSF["BigQuery/Snowflake"]
+        BQSF -->|"Every 5 minutes max processed checkpoint number is read from the tables"| METRICS[Analytics Indexer Prometheus Metrics]
+    end
+
+linkStyle 6 color:red;
+```
+
+**Metrics**
+-----------
+
+ - total_received - count of checkpoints processed in given run
+ - last_uploaded_checkpoint - id of last checkpoint uploaded to the big object store
+ - max_checkpoint_on_store - id of last checkpoint available via BigQuery/Snowflake tables