Distributed James Server — blobstore.properties

BlobStore

This file is optional. If omitted, the cassandra blob store will be used.

BlobStore is the dedicated component to store blobs, non-indexable content. James uses the BlobStore for storing blobs which are usually mail contents, attachments, deleted mails…

You can choose the underlying implementation of BlobStore to fit with your James setup.

It could be the implementation on top of Cassandra or file storage service S3 compatible like Openstack Swift and AWS S3.

Consult blob.properties in GIT to get some examples and hints.

Implementation choice

implementation :

cassandra: use cassandra based BlobStore
objectstorage: use Swift/AWS S3 based BlobStore

deduplication.enable: Mandatory. Supported value: true and false.

If you choose to enable deduplication, the mails with the same content will be stored only once.

Once this feature is enabled, there is no turning back as turning it off will lead to the deletion of all the mails sharing the same content once one is deleted.

This feature also requires a garbage collector mechanism to effectively drop blobs, which is not implemented yet.

Consequently, all the requested deletions will not be performed, meaning that blobstore will only grow.

If you are upgrading from James 3.5 or older, the deduplication was enabled.

Cassandra BlobStore Cache

A Cassandra cache can be enabled to reduce latency when reading small blobs frequently. A dedicated keyspace with a replication factor of one is then used. Cache eviction policy is TTL based. Only blobs below a given threshold will be stored. To be noted that blobs are stored within a single Cassandra row, hence a low threshold should be used.

Table 1. blobstore.properties cache related content
Property name	explanation
cache.enable	DEFAULT: false, optional, must be a boolean. Whether the cache should be enabled.
cache.cassandra.ttl	DEFAULT: 7 days, optional, must be a duration. Cache eviction policy is TTL based.
cache.cassandra.timeout	DEFAULT: 100ms, optional, must be a duration, cannot exceed 1 hour. Timeout after which this cache should be bypassed.
cache.sizeThresholdInBytes	DEFAULT: 8192, optional, must be a positive integer. Unit: bytes. Supported units: bytes, Kib, MiB, GiB, TiB Maximum size of stored objects expressed in bytes.

Object storage configuration

AWS S3 Configuration

Table 2. blobstore.properties S3 related properties
Property name	explanation
objectstorage.s3.endPoint	S3 service endpoint
objectstorage.s3.region	S3 region
objectstorage.s3.accessKeyId	S3 access key id
objectstorage.s3.secretKey	S3 access key secret

Buckets Configuration

Table 3. Bucket configuration
Property name	explanation
objectstorage.bucketPrefix	Bucket is an concept in James and similar to Containers in Swift or Buckets in AWS S3. BucketPrefix is the prefix of bucket names in James BlobStore
objectstorage.namespace	BlobStore default bucket name. Most of blobs storing in BlobStore are inside the default bucket. Unless a special case like storing blobs of deleted messages.

Blob Export

Blob Exporting is the mechanism to help James to export a blob from an user to another user. It is commonly used to export deleted messages (consult <a href="/server/config-vault">configuring deleted messages vault</a>). The deleted messages are transformed into a blob and James will export that blob to the target user.

This configuration helps you choose the blob exporting mechanism fit with your James setup and it is only applicable with Guice products.

Consult blob.properties in GIT to get some examples and hints.

Configuration for exporting blob content:

Table 4. blobstore.properties content
blob.export.implementation
localFile: Local File Exporting Mechanism (explained below). Default: localFile
linshare: LinShare Exporting Mechanism (explained below)

Local File Blob Export Configuration

For each request, this mechanism retrieves the content of a blob and save it to a distinct local file, then send an email containing the absolute path of that file to the target mail address.

Note: that absolute file path is the file location on James server. Therefore, if there are two or more James servers connected, it should not be considered an option.

blob.export.localFile.directory: The directory URL to store exported blob data in files, and the URL following James File System scheme. Default: file://var/blobExporting

LinShare Blob Export Configuration

Instead of exporting blobs in local file system, using LinShare helps you upload your blobs and people you have been shared to can access those blobs by accessing to LinShare server and download them.

This way helps you to share via whole network as long as they can access to LinShare server.

To get an example or details explained, visit blob.properties

blob.export.linshare.url: The URL to connect to LinShare

blob.export.linshare.token: The authentication token to connect to LinShare