App Config - Startup retry #47857

mrm9084 · 2026-01-29T20:04:51Z

Description

Adds retry to startup. When all replicas fail there will be an attempt to retry the failed store for a period of time. By default 100s, minimal 30s, maximum 600s.

Also, refactors the load method to be split into a number of helper method to make this readable.

All SDK Contribution checklist:

The pull request does not introduce [breaking changes]
CHANGELOG is updated for new features, bug fixes or other significant changes.
I have read the contribution guidelines.

General Guidelines and Best Practices

Title of the pull request is clear and informative.
There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

Pull request includes test coverage for the included changes.

Copilot

Pull request overview

This pull request adds a startup retry mechanism to Azure App Configuration for Java to handle transient failures during application startup. When all replicas fail to load configuration, the provider will automatically retry with exponential backoff until a configurable timeout expires.

Changes:

Added startup-timeout configuration property (default: 100s, min: 30s, max: 600s) to control retry duration during startup
Refactored AzureAppConfigDataLoader.load() into smaller helper methods (loadConfiguration, attemptLoadFromClients, setupMonitoringState, handleReplicaFailure) for improved readability
Implemented retry loop with intelligent backoff that waits until the next client becomes available before retrying

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
README.md	Added documentation for new startup-timeout configuration option
CHANGELOG.md	Documented the new startup retry feature
AppConfigurationProperties.java	Added startupTimeout field with default value and validation (30-600 seconds)
AzureAppConfigDataResource.java	Added startupTimeout parameter to constructor and getter method
AzureAppConfigDataLocationResolver.java	Passed startupTimeout from properties to resources
AzureAppConfigDataLoader.java	Refactored load method and implemented retry logic with backoff for startup failures
ConnectionManager.java	Added getMillisUntilNextClientAvailable() to calculate wait time until next replica is available
AppConfigurationReplicaClientFactory.java	Added wrapper method to expose getMillisUntilNextClientAvailable
ConfigStore.java	Minor code quality improvements (variable naming, isEmpty() usage)
ConnectionManagerTest.java	Added comprehensive tests for getMillisUntilNextClientAvailable method
AzureAppConfigDataResourceTest.java	Updated test constructor calls to include startupTimeout parameter
AzureAppConfigDataLoaderTest.java	Added tests for startup retry behavior and refresh non-retry behavior

...ring/cloud/appconfiguration/config/implementation/properties/AppConfigurationProperties.java

.../com/azure/spring/cloud/appconfiguration/config/implementation/AzureAppConfigDataLoader.java

Copilot · 2026-01-29T20:15:07Z

.../com/azure/spring/cloud/appconfiguration/config/implementation/AzureAppConfigDataLoader.java

+                if (waitTime > 0) {
+                    logger.debug("All replicas in backoff for store: " + resource.getEndpoint() 
+                        + ". Waiting " + waitTime + "ms before retry.");
+                    try {
+                        Thread.sleep(waitTime);
+                    } catch (InterruptedException e) {
+                        Thread.currentThread().interrupt();
+                        return lastException;
                    }
-                    storeState.setLoadState(resource.getEndpoint(), true); // Success - configuration loaded, exit loop
-                    lastException = null;
-                    // Break out of the loop since we have successfully loaded configuration
-                    break;
-                } catch (AppConfigurationStatusException e) {
-                    reloadFailed = true;
-                    replicaClientFactory.backoffClient(resource.getEndpoint(), currentClient.getEndpoint());
-                    lastException = e;
-                    // Log the specific replica failure with context
-                    AppConfigurationReplicaClient nextClient = replicaClientFactory
-                        .getNextActiveClient(resource.getEndpoint(), false);
-                    logReplicaFailure(currentClient, "status exception", nextClient != null, e);
-                    client = nextClient;
-                } catch (Exception e) {
-                    // Store the exception to potentially use if all replicas fail
-                    lastException = e; // Log the specific replica failure with context
-                    replicaClientFactory.backoffClient(resource.getEndpoint(), currentClient.getEndpoint());
-                    AppConfigurationReplicaClient nextClient = replicaClientFactory
-                        .getNextActiveClient(resource.getEndpoint(), false);
-                    logReplicaFailure(currentClient, "exception", nextClient != null, e);
-                    client = nextClient;
                }


If getMillisUntilNextClientAvailable returns 0 (indicating a client is available) but attemptLoadFromClients continues to fail, the retry loop could spin rapidly without any delay between attempts. Consider adding a minimum delay (e.g., 100ms) even when waitTime is 0 to prevent potential tight loops in edge cases where clients appear available but consistently fail.

Copilot · 2026-01-29T20:15:07Z

.../azure/spring/cloud/appconfiguration/config/implementation/AzureAppConfigDataLoaderTest.java


-        resource = new AzureAppConfigDataResource(true, configStore, profiles, false, Duration.ofMinutes(1));
+        // Startup resource (isRefresh = false)
+        resource = new AzureAppConfigDataResource(true, configStore, profiles, true, Duration.ofMinutes(1), Duration.ofSeconds(30));


The resource and refreshResource initialization appears to have the 'startup' parameter values swapped. According to the constructor documentation, the 4th parameter is 'startup' where true means startup operation and false means refresh operation. However, 'resource' is being initialized with startup=true but is used as a startup resource (isRefresh would be false), while 'refreshResource' is initialized with startup=false but should be used as a refresh resource (isRefresh would be true). This is backwards - the resource intended for startup should have startup=true, and the resource intended for refresh should have startup=false, but the naming and usage in the tests suggest they are inverted.

Suggested change

resource = new AzureAppConfigDataResource(true, configStore, profiles, true, Duration.ofMinutes(1), Duration.ofSeconds(30));

resource = new AzureAppConfigDataResource(false, configStore, profiles, true, Duration.ofMinutes(1), Duration.ofSeconds(30));

Copilot · 2026-01-29T20:15:07Z

...in/java/com/azure/spring/cloud/appconfiguration/config/implementation/ConnectionManager.java

+            }
+        }
+
+        return earliestAvailable.toEpochMilli() - now.toEpochMilli();


If no clients exist or all have Instant.MAX as backoffEnd, earliestAvailable will remain Instant.MAX, and the calculation 'earliestAvailable.toEpochMilli() - now.toEpochMilli()' will produce an extremely large positive value or potentially overflow. Consider adding a guard to return a sensible maximum value or Long.MAX_VALUE when earliestAvailable is still Instant.MAX.

Suggested change

return earliestAvailable.toEpochMilli() - now.toEpochMilli();

// If no clients exist or all have Instant.MAX as backoffEnd, avoid overflowing the duration.

if (Instant.MAX.equals(earliestAvailable)) {

return Long.MAX_VALUE;

}

long millisUntilAvailable = earliestAvailable.toEpochMilli() - now.toEpochMilli();

return millisUntilAvailable > 0 ? millisUntilAvailable : 0;

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

mrm9084 added 4 commits January 29, 2026 10:44

Refactor + Startup Retry

3a43016

Update AzureAppConfigDataLoader.java

1a87bd9

Adding Tests

6c2a36e

Updating readme, correct location

dc1db90

Copilot AI review requested due to automatic review settings January 29, 2026 20:04

mrm9084 requested review from a team, Netyyyy, avanigupta, moarychan, rossgrambo, rujche and saragluna as code owners January 29, 2026 20:04

github-actions bot added the azure-spring All azure-spring related issues label Jan 29, 2026

Copilot started reviewing on behalf of mrm9084 January 29, 2026 20:05 View session

Copilot AI reviewed Jan 29, 2026

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

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App Config - Startup retry #47857

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	resource = new AzureAppConfigDataResource(true, configStore, profiles, true, Duration.ofMinutes(1), Duration.ofSeconds(30));
	resource = new AzureAppConfigDataResource(false, configStore, profiles, true, Duration.ofMinutes(1), Duration.ofSeconds(30));

-        return earliestAvailable.toEpochMilli() - now.toEpochMilli();
+        // If no clients exist or all have Instant.MAX as backoffEnd, avoid overflowing the duration.
+        if (Instant.MAX.equals(earliestAvailable)) {
+            return Long.MAX_VALUE;
+        }
+        long millisUntilAvailable = earliestAvailable.toEpochMilli() - now.toEpochMilli();
+        return millisUntilAvailable > 0 ? millisUntilAvailable : 0;

App Config - Startup retry #47857

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mrm9084 commented Jan 29, 2026

Description

All SDK Contribution checklist:

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