Whether a resync should be tried or not

includes/classes/ElasticsearchErrorInterpreter.php

@@ -105,6 +105,16 @@ public function maybe_suggest_solution_for_es( $error ) {
 		}
 
 		if ( Utils\is_epio() ) {
+			if ( preg_match( '/you have reached the limit of indices your plan supports/', $error, $matches ) ) {
+				return [
+					'error'    => $error,
+					'solution' => sprintf(
+						/* translators: ElasticPress.io Article URL */
+						__( 'Please refer to <a href="%s">this article</a> outlining how to address this issue.', 'elasticpress' ),
+						'https://elasticpress.zendesk.com/hc/en-us/articles/26165267320461'
+					),
+				];
+			}
 			return [
 				'error'    => $error,
 				'solution' => sprintf(

includes/classes/IndexHelper.php

@@ -1412,8 +1412,10 @@ protected function on_error_update_and_clean( $error, $context = 'sync' ) {
 					esc_html__( 'Mapping failed: %s', 'elasticpress' ),
 					Utils\get_elasticsearch_error_reason( $error['message'] )
 				);
-				$message .= "\n";
-				$message .= esc_html__( 'Mapping has failed, which will cause ElasticPress search results to be incorrect. Please click `Delete all Data and Start a Fresh Sync` to retry mapping.', 'elasticpress' );
+				if ( $this->should_suggest_retry( $message ) ) {
+					$message .= "\n";
+					$message .= esc_html__( 'Mapping has failed, which will cause ElasticPress search results to be incorrect. Please click `Delete all Data and Start a Fresh Sync` to retry mapping.', 'elasticpress' );
+				}
 				break;
 			default:
 				/* translators: Error message */
@@ -1523,6 +1525,16 @@ protected function maybe_apply_feature_settings() {
 		Features::factory()->apply_draft_feature_settings();
 	}
 
+	/**
+	 * Whether to suggest retrying the sync or not.
+	 *
+	 * @param string $message The message returned by the hosting server
+	 * @return boolean
+	 */
+	protected function should_suggest_retry( $message ) {
+		return ! preg_match( '/you have reached the limit of indices your plan supports/', $message );
+	}
+
 	/**
 	 * Return singleton instance of class.
 	 *

tests/php/TestElasticsearchErrorInterpreter.php

@@ -132,4 +132,23 @@ public function test_maybe_suggest_solution_for_es_limit_fields() {
 		$this->assertSame( 'Limit of total fields [???] in index [???] has been exceeded', $suggested['error'] );
 		$this->assertSame( $solution, $suggested['solution'] );
 	}
+
+	/**
+	 * Test the `maybe_suggest_solution_for_es` method when the indices limit was reached on EP.io
+	 *
+	 * @since 5.1.0
+	 * @group elasticsearch-error-interpreter
+	 */
+	public function test_maybe_suggest_solution_for_es_limit_of_indices() {
+		$this->force_epio();
+
+		$error_interpreter = new ElasticsearchErrorInterpreter();
+
+		$error     = 'It seems you have reached the limit of indices your plan supports and we were not able to create a new index. Currently, you can have up to 3 indices.';
+		$solution  = 'Please refer to <a href="https://elasticpress.zendesk.com/hc/en-us/articles/26165267320461">this article</a> outlining how to address this issue.';
+		$suggested = $error_interpreter->maybe_suggest_solution_for_es( $error );
+
+		$this->assertSame( $error, $suggested['error'] );
+		$this->assertSame( $solution, $suggested['solution'] );
+	}
 }

tests/php/includes/classes/BaseTestCase.php

@@ -218,4 +218,13 @@ public function assertDecayDisabled( $query ) {
 			)
 		);
 	}
+
+	/**
+	 * Forces tests to use EP.io
+	 *
+	 * @since 5.1.0
+	 */
+	protected function force_epio() {
+		update_site_option( 'ep_host', 'https://prefix.elasticpress.io/' );
+	}
 }