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Description

This error occurs when a MySQL replication slave server has multiple active or configured replication channels. It indicates that a replication command (e.g., START SLAVE, STOP SLAVE, SHOW SLAVE STATUS) was executed without specifying which channel to operate on, as required in a multi-channel setup.

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Error Message

Multiple channels exist on the slave. Please provide channel name as an argument.

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Known Causes

3 known causes

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Omitting FOR CHANNEL Clause

Executing replication management commands (e.g., `START SLAVE`, `STOP SLAVE`) without explicitly specifying the `FOR CHANNEL 'channel_name'` clause when multiple channels are configured.

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Misunderstanding Multi-Channel Setup

The user might be unaware that the slave server is configured with more than one replication channel, leading to generic replication commands failing.

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Outdated Automation Scripts

Automated scripts or tools designed for single-channel replication environments are executed on a multi-channel slave without being updated to include channel specification.

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Solutions

3 solutions available

1. Specify the Channel Name in Replication Commands easy

Explicitly tell MySQL which replication channel to use.

1

When you encounter this error, it means your MySQL server is configured to use multiple replication channels, but you haven't specified which one to operate on. You need to include the `FOR CHANNEL 'channel_name'` clause in your replication commands.

2

For example, if you are trying to start replication and your channel is named 'my_channel', use the following command:

START SLAVE FOR CHANNEL 'my_channel';

3

Similarly, to stop replication for a specific channel:

STOP SLAVE FOR CHANNEL 'my_channel';

4

To check the status of a specific channel:

SHOW SLAVE STATUS FOR CHANNEL 'my_channel';

5

Identify your channel name by querying the `performance_schema.replication_channels` table if you are unsure.

SELECT * FROM performance_schema.replication_channels;

2. Consolidate Replication to a Single Channel medium

Remove unnecessary replication channels to simplify management.

1

If you are not intentionally using multiple replication channels, it's often best to consolidate them into a single, default channel. This simplifies administration and avoids ambiguity.

2

First, identify all existing replication channels. Run the following query on your slave server:

SELECT * FROM performance_schema.replication_channels;

3

For each channel you wish to remove (except the one you want to keep), stop replication for that channel and then remove its configuration. Be extremely cautious with this step, as it can disrupt replication.

STOP SLAVE FOR CHANNEL 'old_channel_name';
REMOVE SLAVE 'old_channel_name';

4

After removing unnecessary channels, you can manage replication using the default channel (or the single remaining channel) without specifying a channel name.

START SLAVE;
SHOW SLAVE STATUS;

5

Alternatively, if you are using older MySQL versions that don't fully support named channels via `performance_schema`, you might need to review and adjust `my.cnf` or `my.ini` configuration files for `master-host`, `master-user`, etc., to ensure only one set of replication parameters is active.

3. Configure Replication with a Specific Channel During Setup medium

Define a named channel from the start when setting up replication.

1

When setting up new replication channels, especially in environments where multiple channels are expected or desired, assign a clear and descriptive name to each channel from the outset.

2

Use the `CHANGE MASTER TO` statement with the `FOR CHANNEL` clause. For example, to configure a channel named 'app_replica':

CHANGE MASTER TO MASTER_HOST='master.example.com', MASTER_USER='repl_user', MASTER_PASSWORD='repl_password', MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=123 FOR CHANNEL 'app_replica';

3

After configuring the channel, start replication for it:

START SLAVE FOR CHANNEL 'app_replica';

4

This proactive naming convention prevents the 'Missing Replication Channel' error by ensuring clarity from the initial configuration.

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Related Errors

5 related errors

MySQL Error 3079: Missing Replication Channel