Setting up Solr to improve search performance

While performing IMAP search on just the headers is usually fast, running search in message text in standard setup of MailSuite Pro could use improvement. That's done by setting up and configuring an additional search module, we use Apache Solr for this purpose.

The configuration is performed as follows (with superuser/root privileges):

1. Install Dovecot packages:

apt install dovecot-core dovecot-imapd dovecot-lmtpd dovecot-managesieved dovecot-mysql dovecot-pop3d dovecot-sieve dovecot-solr

2. Install Java:

apt install default-jre

3. Install Solr:

wget https://downloads.apache.org/lucene/solr/8.11.1/solr-8.11.1.tgz
tar xzf solr-8.11.1.tgz solr-8.11.1/bin/install_solr_service.sh --strip-components=2
bash ./install_solr_service.sh solr-8.11.1.tgz
systemctl start solr

4. Init Solr schema namespace:

su - solr -c "/opt/solr/bin/solr create -c dovecot -n dovecot"

Solr configuration is found under /var/solr/data/dovecot/conf/ directory:

ls -la /var/solr/data/dovecot/conf/
total 52
drwxr-xr-x 3 solr solr  4096 Oct  7 12:33 .
drwxr-xr-x 4 solr solr  4096 Sep 28 14:55 ..
drwxr-xr-x 2 solr solr  4096 Sep 28 14:21 lang
-rw-r--r-- 1 solr solr  6127 Oct  7 12:33 managed-schema
-rw-r--r-- 1 solr solr   882 Oct  6 12:43 protwords.txt
-rw-r--r-- 1 solr solr  6944 Oct  7 12:33 schema.xml.bak
-rw-r--r-- 1 solr solr 11287 Sep 28 15:00 solrconfig.xml
-rw-r--r-- 1 solr solr   781 Jun 10 20:23 stopwords.txt
-rw-r--r-- 1 solr solr  1124 Jun 10 20:23 synonyms.txt

5. Reconfigure Dovecot

In /etc/dovecot/conf.d/10-mail.conf file, make sure fts and fts_solr are included in list of mail_plugins:

mail_plugins =  $mail_plugins fts fts_solr virtual

Also, add the following section into /etc/dovecot/conf.d/90-plugin.conf file:

plugin {
    fts = solr
    fts_solr = url=http://127.0.0.1:8983/solr/dovecot/
    fts_autoindex = yes
}

6. Restart services to apply changes:

service dovecot restart
service solr  restart