Linagora’s James newsletter: March 2017

Linagora have a team of developers devoted to the James server. We are already contributing for a few years to the project. This document will try to give you information about what we recently did in the James project, and give hints about the road-map we follow. We will also try to write it regularly.

Deploying James internally

We now use James as the mail server behind OpenPaaS. Thus we deployed it and use it on an daily base.

Our deployment is based on the following components :
— We enabled IMAP, SMTP and JMAP protocols
— We use Cassandra for storing e-mails
— We rely on ElasticSearch for searching e-mails
— We authenticate our users with LDAP
— So far everything is deployed on a single server
— We use Guice for bringing all pieces together.
— We plan to bring soon Sieve and ManageSieve part of this deployment as many people request filtering.

Let me share a few numbers with you :

— We handle about 100 users
— We have so far a number of 1.500.000 e-mails, that we imported using IMAP-sync scripts
— We receive around 15.000 incoming e-mails a day
— We execute 42.500 IMAP commands a day
— We answer 20.000 JMAP requests a day

This deployment helps us detecting bugs, and performance issues. We follow the current state of master branch, that we update at midnight with the built image uploaded to dockerhub.

The following results were obtained on a server with an Intel Xeon CPU E5–2650 2.00GHz 4 cores 4 threads) and 16 GB of RAM.

Tracking performance

Everybody wants to read their e-mails fast. Thus the team made performance tracking a priority. And we setup perf monitoring.

We started implementing Gatling load testing for the James server :

— First with a Gatling JMAP implementation.
— Then we added a naive SMTP implementation
— And finally contributed an IMAP DSL for Gatling

Running these load tests we :

— Succeeded to support 1.000 Thunderbird like users
— However, it turned out we had problems with 10.000 users.

The following results were obtained on a server with an Intel Xeon CPU (E3–1231 3.40GHz 4 cores 8 threads) with 32 GB of RAM. We run Gatling on the same host, thus it has performance impact on the results. So far Gatling is run manually when we take time for it. This might eventually become part of our CI. Also the testing server configuration we are using might change in the future.

Additionally, we added metrics a bit everywhere in James using the brand new metrics API. We collect and export everything in ElasticSearch using Dropwizard metrics. Then we graph it all using Grafana. This allows us to collect all statistics and percentiles. We decided to share our boards and installation guide with the community as part of the James project.

We track so far :

— Protocols detailed time execution (and count)
— Percentile of mailet and matcher executions
— Enqueue and Dequeue time

All these solutions allow us to identify the components that need improvement. For instance receiving too much incoming e-mails overload James with very heavy garbage collection. We then plan to move our mail queue to RabbitMQ, to parse e-mails only once on top of the mail pipeline, to reorganize a bit our configuration. A Camel upgrade (impossible in java-6) might also help.

MessageId refactoring

We succeeded to finish and merge the MessageId refactoring. This huge task allow us to address messages by their ID, outside of mailbox context.

This is required for JMAP protocol implementation.

This is now supported by the Cassandra and Memory implementation. We design a system of capabilities to allow enabling only the supported parts of protocols, in an implementation agnostic way.

Our incoming plans

We are pretty happy with the current state of the James server. We will then push for the 3.0 release of the James server.

For this :

— We need to do some load testing on top of JPA implementation
— We will continue doing bug fixes
— We need some additional performance enhancement, especially with IMAP SELECT command on large mailboxes
— We plan to start working again on the new website, which have been paused a few months

Useful links

Gatling James JMAP
Gatling IMAP
Gatling SMTP
Dopwizard metrics
ElasticSearch metrics
Grafana reporting in James
Our James image on DockerHub



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