Read pool instances in an AlloyDB for PostgreSQL cluster let you scale read capacity
and offload read-only query workloads from your primary instance. You can
create a read pool instance by using the Google Cloud console or the
Google Cloud CLI.
A read pool instance can use a different machine series and machine type than
your primary instance's machine series and machine type. All nodes within a
single read pool instance use the same machine series and machine type. To
serve read traffic across multiple machine series or different machine types at
the same time, deploy separate read pool instances for each configuration. For
more information about supported machine series, see [Choose an
AlloyDB machine
type](https://docs.cloud.google.com/alloydb/docs/choose-machine-type#machine-series-configuration).
Optionally, you can enable
[transparent query forwarding](https://docs.cloud.google.com/alloydb/docs/transparent-query-forwarding.md.txt) to
optimize resource utilization by automatically routing read-only traffic.
## Before you begin
- The Google Cloud project you are using must have been [enabled to access AlloyDB](https://docs.cloud.google.com/alloydb/docs/quickstart/create-and-connect.md.txt#before-you-begin).
- You must have one of these IAM roles in the Google Cloud project you are using:
- `roles/alloydb.admin` (the AlloyDB Admin predefined IAM role)
- `roles/owner` (the Owner basic IAM role)
- `roles/editor` (the Editor basic IAM role)
If you don't have any of these roles, contact your Organization Administrator to request
access.
## Create a read pool instance
### Console
1. In the Google Cloud console, go to the **Clusters** page.
[Go to Clusters](https://console.cloud.google.com/alloydb/clusters)
2. Click a cluster in the **Resource Name** column.
3. Go to the **Instances in your cluster**
section, and click **Add read pool**.
4. Configure your read pool instance:
1. In the **Read pool instance ID** field, enter an ID for the read
pool instance.
2. In the **Node count** field, enter a node count.
The number of nodes in a read pool instance determines the
instance's overall computing capacity.
> [!NOTE]
> **Note:** You can have a maximum of 20 nodes across all the read pool instances in a cluster.
3. Select one of the following machine series for the read pool
instance, which can differ from your primary instance's machine
series:
- C4A (Google Axion-based machine series)
- N2 (x86-based machine series). This machine series is the default.
- C4 (x86-based machine series)
- Z3 (Intel Xeon-based machine series)
4. Select a machine type. All nodes in the read pool instance use the
machine series and machine type that you select. Supported vCPU
counts depend on the machine series:
- C4A supports 1, 2, 4, 8, 16, 32, 48, 64, and 72 vCPUs.
- N2 supports 2, 4, 8, 16, 32, 64, 96, and 128 vCPUs.
- C4 supports 4, 8, 16, 24, 32, 48, 96, 144, 192, and 288 vCPUs.
- Z3 supports 8, 14, 16, 22, 32, 44, and 88 vCPUs.
For more information about using the C4A Axion-based machine series,
including the 1-vCPU machine type, see
[Considerations when using the C4A Axion-based machine
series](https://docs.cloud.google.com/alloydb/docs/cluster-create#considerations-c4a).
5. Optional: To connect your applications and clients over the
public internet, click **Enable Public IP** in **Public IP
Connectivity** . Enabling public IP might require additional
configuration to secure your connection. For more information, see
[Connect using public IP](https://docs.cloud.google.com/alloydb/docs/connect-public-ip.md.txt).
By default, private IP is always enabled. For more information, see
[Enable private services
access](https://docs.cloud.google.com/alloydb/docs/configure-connectivity).
6. Optional: To enable managed connection pooling, select
**Enable managed connection pool** under **Managed connection
pool** . For more information, see
[Configure managed connection
pooling](https://docs.cloud.google.com/alloydb/docs/configure-managed-connection-pooling).
7. Choose your network security settings. To keep your data secure, use
mTLS encryption with AlloyDB connectors or SSL
encryption.
When you change your security settings, your instance remains
available for use, but AlloyDB drops existing
noncompliant connections.
8. Optional: Set custom flags to your instance. For each flag, follow
these steps:
1. Click **Advanced Configuration Options**.
2. Click **Add a database flag**.
3. Select a flag from the **New database flag** list.
4. Provide a value for the flag.
5. Click **Done**.
5. Click **Add read pool**.
### gcloud
To use the gcloud CLI, you can
[install and initialize](https://docs.cloud.google.com/sdk/docs/install-sdk.md.txt) the Google Cloud CLI, or you
can use [Cloud Shell](https://docs.cloud.google.com/shell/docs/using-cloud-shell.md.txt).
Use the [`gcloud alloydb instances create`](https://docs.cloud.google.com/sdk/gcloud/reference/alloydb/instances/create.md.txt)
command to create a read pool instance.
```bash
gcloud alloydb instances create INSTANCE_ID \
--instance-type=READ_POOL \
--read-pool-node-count=NODE_COUNT \
--region=REGION_ID \
--cluster=CLUSTER_ID \
--cpu-count=CPU_COUNT \
--machine-type=MACHINE_TYPE \
--project=PROJECT_ID
```
Replace the following:
- `INSTANCE_ID`: The ID of the instance you are creating.
It must begin with a lowercase letter and can contain lowercase
letters, numbers, and hyphens.
- `NODE_COUNT`: The number of nodes in the instance.
Specify a number `1` through `20`, inclusive. Note that you cannot
have more than 20 nodes across all read pool instances in a cluster.
- `REGION_ID`: The region of your existing cluster, in
which you want to create the read pool instance.
- `CLUSTER_ID`: The ID of your existing cluster, in
which you want to create the read pool instance.
- `CPU_COUNT`: the number of vCPUs that you want
for the instance.
- You must specify either `cpu_count` or `machine_type`.
- If only `cpu_count` is provided, an N2 instance is created with the following specifications:
- 2: 2 vCPUs, 16 GB RAM
- 4: 4 vCPUs, 32 GB RAM
- 8: 8 vCPUs, 64 GB RAM
- 16: 16 vCPUs, 128 GB RAM
- 32: 32 vCPUs, 256 GB RAM
- 64: 64 vCPUs, 512 GB RAM
- 96: 96 vCPUs, 768 GB RAM
- 128: 128 vCPUs, 864 GB RAM
- If both `machine_type` and `cpu_count` are provided, the `cpu_count` value must align with the number of vCPUs specified in the `machine_type`. For example, if `machine_type` is `n2-highmem-4`, then you must set `cpu_count` to `4`.
- `MACHINE_TYPE`: a supported machine type for the
read pool instance, such as `n2-highmem-4`, `c4-highmem-4-lssd`,
`c4a-highmem-4-lssd`, or `z3-highmem-14-standardlssd`. The read pool
instance can use a different machine series and machine type than the
primary instance's machine series and machine type, and all nodes in the
read pool instance use this machine type. For more information about
supported machine types, see
[Choose an AlloyDB machine
type](https://docs.cloud.google.com/alloydb/docs/choose-machine-type).
- `PROJECT_ID`: The ID of the project where your existing
cluster is located.
To create a read pool instance for a
Private Service Connect-enabled cluster, add the
`--allowed-psc-projects` flag to set a comma separated list of project IDs or
[project numbers](https://docs.cloud.google.com/resource-manager/docs/view-update-projects.md.txt#identifying_projects)
that you want to allow access to the instance---for example,
`my-project-1`, `12345`,`my-project-n`.
```bash
gcloud alloydb instances create INSTANCE_ID \
--instance-type=READ_POOL \
--region=REGION_ID \
--cluster=CLUSTER_ID \
--cpu-count=CPU_COUNT \
--machine-type=MACHINE_TYPE \
--project=PROJECT_ID \
--allowed-psc-projects=ALLOWED_PROJECT_LIST
```
Replace the following:
- `ALLOWED_PROJECT_LIST` (Optional): The comma-separated list of project IDs or project numbers that you want to allow access to the instance---for example,`my-project-1`, `12345`,`my-project-n`. You must set a list of allowed projects or numbers, if your cluster uses Private Service Connect as the method of connecting to the instance.
To enable managed connection pooling in your read pool instance, add the
`--enable-connection-pooling` flag to the
[`gcloud alloydb instances create`](https://docs.cloud.google.com/sdk/gcloud/reference/alloydb/instances/create.md.txt)
command:
```bash
gcloud alloydb instances create INSTANCE_ID \
--instance-type=READ_POOL \
--region=REGION_ID \
--cluster=CLUSTER_ID \
--cpu-count=CPU_COUNT \
--machine-type=MACHINE_TYPE \
--project=PROJECT_ID \
--enable-connection-pooling
```
To create a read pool instance for a public IP-enabled cluster, add the
`--assign-inbound-public-ip=ASSIGN_IPV4` parameter.
```bash
gcloud alloydb instances create INSTANCE_ID \
--instance-type=READ_POOL \
--region=REGION_ID \
--cluster=CLUSTER_ID \
--cpu-count=CPU_COUNT \
--machine-type=MACHINE_TYPE \
--project=PROJECT_ID \
--assign-inbound-public-ip=ASSIGN_IPV4
```
Optionally, you can pass the comma separated list of CIDR blocks, such as
`64.233.160.0/16` to the `--authorized-external-networks` parameter to set
authorized external networks on your instance.
> [!NOTE]
> **Note:** For Private Service Connect-enabled instances, additional settings are required. For more information, see [Connect to an instance using Private Service Connect](https://docs.cloud.google.com/alloydb/docs/configure-private-service-connect.md.txt).
## What's next
- Learn [options for connecting your read pool instance](https://docs.cloud.google.com/alloydb/docs/connection-overview.md.txt).
- [View instance details](https://docs.cloud.google.com/alloydb/docs/instance-view.md.txt).
- [Scale an instance](https://docs.cloud.google.com/alloydb/docs/instance-read-pool-scale.md.txt).
- [Restart an instance or read pool nodes](https://docs.cloud.google.com/alloydb/docs/instance-start-stop-restart.md.txt#restart).
- [Troubleshoot read pool queries](https://docs.cloud.google.com/alloydb/docs/troubleshoot/read-pools.md.txt).
- [Learn about sizing recommendations](https://docs.cloud.google.com/alloydb/docs/use-sizing-recommendations.md.txt).