Stream Azure Spring Apps app logs in real-time

Article
05/24/2022
3 minutes to read

Note

Azure Spring Apps is the new name for the Azure Spring Cloud service. Although the service has a new name, you'll see the old name in some places for a while as we work to update assets such as screenshots, videos, and diagrams.

This article applies to: ✔️ Java ✔️ C#

This article applies to: ✔️ Basic/Standard tier ✔️ Enterprise tier

Azure Spring Apps enables log streaming in Azure CLI to get real-time application console logs for troubleshooting. You can also Analyze logs and metrics with diagnostics settings.

Prerequisites

Azure CLI with the Azure Spring Apps extension, minimum version 1.0.0. You can install the extension by using the following command: az extension add --name spring
An instance of Azure Spring Apps with a running application. For more information, see Quickstart: Deploy your first application to Azure Spring Apps.

Use CLI to tail logs

To avoid repeatedly specifying your resource group and service instance name, set your default resource group name and cluster name.

az config set defaults.group=<service group name>
az config set defaults.spring-cloud=<service instance name>

In following examples, the resource group and service name will be omitted in the commands.

Tail log for app with single instance

If an app named auth-service has only one instance, you can view the log of the app instance with the following command:

az spring app logs --name <application name>

This will return logs similar to the following examples, where auth-service is the application name.

...
2020-01-15 01:54:40.481  INFO [auth-service,,,] 1 --- [main] o.apache.catalina.core.StandardService  : Starting service [Tomcat]
2020-01-15 01:54:40.482  INFO [auth-service,,,] 1 --- [main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.22]
2020-01-15 01:54:40.760  INFO [auth-service,,,] 1 --- [main] o.a.c.c.C.[Tomcat].[localhost].[/uaa]  : Initializing Spring embedded WebApplicationContext
2020-01-15 01:54:40.760  INFO [auth-service,,,] 1 --- [main] o.s.web.context.ContextLoader  : Root WebApplicationContext: initialization completed in 7203 ms

...

Tail log for app with multiple instances

If multiple instances exist for the app named auth-service, you can view the instance log by using the -i/--instance option.

First, you can get the app instance names with following command.

az spring app show --name auth-service --query properties.activeDeployment.properties.instances --output table

This command produces results similar to the following output:

Name                                         Status    DiscoveryStatus
-------------------------------------------  --------  -----------------
auth-service-default-12-75cc4577fc-pw7hb  Running   UP
auth-service-default-12-75cc4577fc-8nt4m  Running   UP
auth-service-default-12-75cc4577fc-n25mh  Running   UP

Then, you can stream logs of an app instance with the option -i/--instance option:

az spring app logs --name auth-service --instance auth-service-default-12-75cc4577fc-pw7hb

You can also get details of app instances from the Azure portal. After selecting Apps in the left navigation pane of your Azure Spring Apps service, select App Instances.

Continuously stream new logs

By default, az spring app logs prints only existing logs streamed to the app console and then exits. If you want to stream new logs, add -f/--follow:

az spring app logs --name auth-service --follow

When you use --follow to tail instant logs, the Azure Spring Apps log streaming service will send heartbeat logs to the client every minute unless your application is writing logs constantly. These heartbeat log messages look like 2020-01-15 04:27:13.473: No log from server.

To check all the logging options supported:

az spring app logs --help

Format JSON structured logs

Note

Requires spring extension version 2.4.0 or later.

When the Structured application log is enabled for the app, the logs are printed in JSON format. This makes it difficult to read. The --format-json argument can be used to format the JSON logs into human readable format.

# Raw JSON log
$ az spring app logs --name auth-service
{"timestamp":"2021-05-26T03:35:27.533Z","logger":"com.netflix.discovery.DiscoveryClient","level":"INFO","thread":"main","mdc":{},"message":"Disable delta property : false"}
{"timestamp":"2021-05-26T03:35:27.533Z","logger":"com.netflix.discovery.DiscoveryClient","level":"INFO","thread":"main","mdc":{},"message":"Single vip registry refresh property : null"}

# Formatted JSON log
$ az spring app logs --name auth-service --format-json
2021-05-26T03:35:27.533Z  INFO [           main] com.netflix.discovery.DiscoveryClient   : Disable delta property : false
2021-05-26T03:35:27.533Z  INFO [           main] com.netflix.discovery.DiscoveryClient   : Single vip registry refresh property : null

The --format-json argument also takes optional customized format, using the keyword argument format string syntax.

# Custom format
$ az spring app logs --name auth-service --format-json="{message}{n}"
Disable delta property : false
Single vip registry refresh property : null

The default format being used is:

{timestamp} {level:>5} [{thread:>15.15}] {logger{39}:<40.40}: {message}{n}{stackTrace}