Stream Azure Spring Cloud app logs in real-time

• 01/14/2019
• 3 minutes to read
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This article applies to: ✔️ Java ✔️ C#

Azure Spring Cloud 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

• Install Azure CLI extension for Spring Cloud, minimum version 0.2.0 .
• An instance of Azure Spring Cloud with a running application, for example Spring Cloud app.

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-cloud app logs -n auth-service

This will return logs:

...
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-cloud app show -n auth-service --query properties.activeDeployment.properties.instances -o table

With results:

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-cloud app logs -n auth-service -i 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 Cloud service, select App Instances.

Continuously stream new logs

By default, az spring-cloud 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-cloud app logs -n auth-service -f

To check all the logging options supported:

az spring-cloud app logs -h 

Format JSON structured logs

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-cloud app logs -n 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-cloud app logs -n 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-cloud app logs -n 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}

Next steps

• Quickstart: Monitoring Azure Spring Cloud apps with logs, metrics, and tracing
• Analyze logs and metrics with diagnostics settings