updated documentaion.

docs/getting_started/advanced_stores.md

@@ -0,0 +1,67 @@
+# Configurations and Usage of Advanced `store`'s
+
+## S3Store
+
+### Configuration
+
+The S3Store interfaces with S3 object storage via [boto3](https://pypi.org/project/boto3/).
+For this to work properly, you have to set your basic configuration in `~/.aws/config`
+```buildoutcfg
+[default]
+source_profile = default
+```
+
+Then, you have to set up your credentials in `~/.aws/credentials`
+```buildoutcfg
+[default]
+aws_access_key_id = YOUR_KEY
+aws_secret_access_key = YOUR_SECRET
+```
+
+For more information on the configuration please see the following [documentation](https://docs.aws.amazon.com/credref/latest/refdocs/settings-global.html).
+Note that while these configurations are in the `~/.aws` folder, they are shared by other similar services like the self-hosted [minio](https://min.io/) service.
+
+### Basic Usage
+
+MongoDB is not designed to handle large object storage.
+As such, we created an abstract object that combines the large object storage capabilities of Amazon S3 and the easy, python-friendly query language of MongoDB.
+These `S3Store`s all include an `index` store that only stores specific queryable data and the object key for retrieving the data from an S3 bucket using the `key` attribute (called `'fs_id'` by default).
+
+An entry of in the `index` may look something like this:
+```
+{
+    fs_id : "5fc6b87e99071dfdf04ca871"
+    task_id : "mp-12345"
+}
+```
+Please note that since we are giving users the ability to reconstruct the index store using the object metadata, the object size in the `index` is limited by the metadata and not MongoDB.
+Different S3 services might have different rules, but the limit is typically smaller: 8 KB for [aws](https://docs.aws.amazon.com/AmazonS3/latest/userguide/UsingMetadata.html)
+
+The `S3Store` should be constructed as follows:
+
+```python
+from maggma.stores import MongograntStore, S3Store
+index = MongograntStore("ro:mongodb03/js_cathodes",
+                        "atomate_aeccar0_fs_index",
+                        key="fs_id")
+s3store = S3Store(index=index,
+        bucket="<<BUCKET_NAME>>",
+        s3_profile="<<S3_PROFILE_NAME>>",
+        compress= True,
+        endpoint_url= "<<S3_URL>>",
+        sub_dir= "atomate_aeccar0_fs",
+        s3_workers=4
+       )
+```
+
+The `subdir` field creates subdirectories in the bucket to help the user organize their data.
+
+### Parallelism
+
+Once you start working with large quantities of data, the speed at which you process this data will often be limited by database I/O.
+For the most time-consuming upload part of the process, we have implemented thread-level parallelism in the `update` member function.
+The `update` function received an entire chunk of processed data as defined by `chunk_size`,
+however since `Store.update` is typically called in the `update_targets` part of a builder, where builder execution is not longer multi-threaded.
+As such, we multithread the execution inside of `update` using `s3_workers` threads to perform the database write operation.
+As a general rule of thumb, if you notice that your update step is taking too long, you should change the `s3_worker` field which is
+optimized differently based on server-side resources.

docs/getting_started/stores.md

@@ -15,15 +15,15 @@ Current working and tested Stores include:
 - VaulStore: uses Vault to get credentials for a MongoDB database
 - AliasingStore: aliases keys from the underlying store to new names
 - SandboxStore: provides permission control to documents via a `_sbxn` sandbox key
-- S3Store: provides an interface to an S3 Bucket either on AWS or self-hosted solutions
+- S3Store: provides an interface to an S3 Bucket either on AWS or self-hosted solutions ([additional documentation](advanced_stores.md))
 - JointStore: joins several MongoDB collections together, merging documents with the same `key`, so they look like one collection
 - ConcatStore: concatenates several MongoDB collections in series so they look like one collection
 
 ## The `Store` interface
 
 ### Initializing a Store
 
-All `Store`s have a few basic arguments that are critical to understand. Every `Store` has two attributes that the user should customize based on the data contained in that store: `key` and `last_updated_field`. The `key` defines how the `Store` tells documents part. Typically this is `_id` in MongoDB, but you could use your own field (be sure all values under the key field can be used to uniquely identify documents). `last_updated_field` tells `Store` how to order the documents by a date, which is typically in the `datetime` format, but can also be an ISO 8601-format (ex: `2009-05-28T16:15:00`) `Store`s can also take a `Validator` object to make sure the data going into obeys some schema.
+All `Store`s have a few basic arguments that are critical for basic usage. Every `Store` has two attributes that the user should customize based on the data contained in that store: `key` and `last_updated_field`. The `key` defines how the `Store` tells documents apart. Typically this is `_id` in MongoDB, but you could use your own field (be sure all values under the key field can be used to uniquely identify documents). `last_updated_field` tells `Store` how to order the documents by a date, which is typically in the `datetime` format, but can also be an ISO 8601-format (ex: `2009-05-28T16:15:00`) `Store`s can also take a `Validator` object to make sure the data going into obeys some schema.
 
 ### Using a Store
 
@@ -40,7 +40,7 @@ Stores provide a number of basic methods that make easy to use:
 - query: Standard mongo style `find` method that lets you search the store.
 - query_one: Same as above but limits returned results to just the first document that matches your query.
 - update: Update the documents into the collection. This will override documents if the key field matches.
-- ensure_index: This creates an index the underlying data-source for fast querying.
+- ensure_index: This creates an index for the underlying data-source for fast querying.
 - distinct: Gets distinct values of a field.
 - groupby: Similar to query but performs a grouping operation and returns sets of documents.
 - remove_docs: Removes documents from the underlying data source.

src/maggma/stores/aws.py

@@ -40,7 +40,7 @@ def __init__(
         endpoint_url: str = None,
         sub_dir: str = None,
         s3_workers: int = 1,
-        key: str = "task_id",
+        key: str = "fs_id",
         searchable_fields: Optional[List[str]] = None,
         **kwargs,
     ):