Updated Host Volumes guide
Added read_only to highlight them Style updates
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Charlie Voiselle
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@ -28,13 +28,13 @@ them, Docker volumes have to either be deployed to all clients or operators have
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to use an additional, manually-maintained constraint to inform the scheduler
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where they are present.
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## Reference Material
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## Reference material
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- [Nomad `host_volume` specification][host_volume spec]
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- [Nomad `volume` specification][volume spec]
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- [Nomad `volume_mount` specification][volume_mount spec]
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## Estimated Time to Complete
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## Estimated time to complete
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20 minutes
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@ -66,22 +66,22 @@ Ensure it is installed on a node with access to port 3306 on your Nomad clients:
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Ubuntu:
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```bash
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$ sudo apt install mysql-client
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sudo apt install mysql-client
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```
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CentOS:
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```bash
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$ sudo yum install mysql
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sudo yum install mysql
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```
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macOS via Homebrew:
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```bash
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$ brew install mysql-client
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brew install mysql-client
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```
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### Step 1: Create a Directory to Use as a Mount Target
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### Step 1: Create a directory to use as a mount target
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On a Nomad client node in your cluster, create a directory that will be used for
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persisting the MySQL data. For this example, let's create the directory
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@ -98,8 +98,7 @@ run as the `root` user.
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sudo chown «Nomad user» /opt/mysql/data
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```
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### Step 2: Configure the `mysql` Host Volume on the Client
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### Step 2: Configure the `mysql` host volume on the client
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Edit the Nomad configuration on this Nomad client to create the Host Volume.
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@ -131,7 +130,7 @@ Drivers = docker,exec,java,mock_driver,raw_exec,rkt
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...
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```
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### Step 3: Create the `mysql.nomad` Job File
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### Step 3: Create the `mysql.nomad` job file
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We are now ready to deploy a MySQL database that can use Nomad Host Volumes for
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storage. Create a file called `mysql.nomad` and provide it the following
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@ -146,8 +145,12 @@ job "mysql-server" {
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count = 1
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volume "mysql" {
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type = "host"
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source = "mysql"
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type = "host"
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read_only = false
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config {
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source = "mysql"
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}
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}
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restart {
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@ -163,6 +166,7 @@ job "mysql-server" {
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volume_mount {
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volume = "mysql"
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destination = "/var/lib/mysql"
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read_only = false
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}
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env = {
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@ -203,16 +207,27 @@ job "mysql-server" {
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}
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```
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* The service name is `mysql-server` which we will use later to connect to the
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#### Notes about the above job specification
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- The service name is `mysql-server` which we will use later to connect to the
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database.
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### Step 4: Deploy the MySQL Database
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- The `read_only` argument is supplied on all of the volume-related stanzas in
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to help highlight all of the places you would need to change to make a
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read-only volume mount. Please see the [`host_volume`][host_volume spec],
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[`volume`][volume spec], and [`volume_mount`][volume_mount spec] specifications
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for more details.
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- For lower-memory instances, you might need to reduce the requested memory in
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the resources stanza to harmonize with available resources in your cluster.
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### Step 4: Deploy the MySQL database
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Register the job file you created in the previous step with the following
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command:
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```
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$ nomad run mysql.nomad
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$ nomad run mysql.nomad
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==> Monitoring evaluation "aa478d82"
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Evaluation triggered by job "mysql-server"
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Allocation "6c3b3703" created: node "be8aad4e", group "mysql-server"
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@ -231,7 +246,7 @@ Task Group Queued Starting Running Failed Complete Lost
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mysql-server 0 0 1 0 0 0
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```
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### Step 5: Connect to MySQL
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### Step 5: Connect to MySQL
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Using the mysql client (installed in [Prerequisite 1]), connect to the database
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and access the information:
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@ -239,6 +254,7 @@ and access the information:
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```
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mysql -h mysql-server.service.consul -u web -p -D itemcollection
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```
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The password for this demo database is `password`.
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~> **Please Note:** This guide is for demo purposes and does not follow best
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@ -249,7 +265,7 @@ Consul is installed alongside Nomad in this cluster so we were able to
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connect using the `mysql-server` service name we registered with our task in
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our job file.
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### Step 6: Add Data to MySQL
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### Step 6: Add data to MySQL
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Once you are connected to the database, verify the table `items` exists:
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@ -290,6 +306,7 @@ Run the `INSERT INTO` command as many times as you like with different values.
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mysql> INSERT INTO items (name) VALUES ('hat');
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mysql> INSERT INTO items (name) VALUES ('keyboard');
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```
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Once you you are done, type `exit` and return back to the Nomad client command
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line:
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@ -298,7 +315,7 @@ mysql> exit
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Bye
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```
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### Step 7: Stop and Purge the Database Job
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### Step 7: Stop and purge the database job
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Run the following command to stop and purge the MySQL job from the cluster:
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@ -322,11 +339,10 @@ network filesystem, like NFS, or cluster-aware filesystem, like glusterFS. This
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can enable more complex, automatic failure-recovery scenarios in the event of a
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node failure.
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### Step 8: Re-deploy the Database
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### Step 8: Re-deploy the database
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Using the `mysql.nomad` job file from [Step
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3](#step-3-create-the-mysql-nomad-job-file), re-deploy the database to the Nomad
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cluster.
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Using the `mysql.nomad` job file from [Step 3], re-deploy the database to the
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Nomad cluster.
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```
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==> Monitoring evaluation "61b4f648"
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@ -336,7 +352,7 @@ cluster.
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==> Evaluation "61b4f648" finished with status "complete"
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```
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### Step 9: Verify Data
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### Step 9: Verify data
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Once you re-connect to MySQL, you should be able to see that the information you
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added prior to destroying the database is still present:
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@ -356,18 +372,20 @@ mysql> select * from items;
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6 rows in set (0.00 sec)
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```
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### Step 10: Tidying Up
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### Step 10: Tidying up
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Once you have completed this guide, you should perform the following cleanup steps:
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* Stop and purge the `mysql-server` job.
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* Remove the `host_volume "mysql"` stanza from your Nomad client configuration
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and restart the Nomad service on that client
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* Remove the /opt/mysql/data folder and as much of the directory tree that you
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no longer require.
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- Stop and purge the `mysql-server` job.
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- Remove the `host_volume "mysql"` stanza from your Nomad client configuration
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and restart the Nomad service on that client
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- Remove the /opt/mysql/data folder and as much of the directory tree that you
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no longer require.
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[Prerequisite 1]: #prerequisite-1-install-the-mysql-client
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[Step 3]: #step-3-create-the-mysql-nomad-job-file
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[host_volume spec]: /docs/configuration/client.html#host_volume-stanza
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[volume spec]: /docs/job-specification/volume.html
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[volume_mount spec]: /docs/job-specification/volume_mount.html
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