1# Function Apps Troubleshooting
2 
3## Find Linked App Insights / Log Analytics
4 
5### Preferred: Use Azure Resource Graph
6 
7A single ARG query returns the App Insights name, instrumentation key, connection string, and Log Analytics workspace for a given function app:
8 
9```bash
10az graph query -q "
11resources | where type =~ 'microsoft.web/sites' and name == '<func-app-name>'
12| project funcName=name, rg=resourceGroup
13| join kind=inner (resources | where type =~ 'microsoft.insights/components' | project appiName=name, rg=resourceGroup, instrumentationKey=properties.InstrumentationKey, connectionString=properties.ConnectionString, workspaceId=properties.WorkspaceResourceId) on rg
14| project funcName, appiName, instrumentationKey, connectionString, workspaceId
15" -o json
16```
17 
18> 💡 **Tip:** This join matches by resource group. If App Insights is in a different resource group, use the CLI fallback below.
19 
20### Fallback: CLI Commands
21 
22#### Step 1: Get the App Insights connection string from app settings
23 
24```bash
25az functionapp config appsettings list \
26  --name <func-app-name> -g <rg-name> \
27  --query "[?name=='APPLICATIONINSIGHTS_CONNECTION_STRING' || name=='APPINSIGHTS_INSTRUMENTATIONKEY']"
28```
29 
30#### Step 2: Find the App Insights resource by instrumentation key
31 
32```bash
33az monitor app-insights component show \
34  --query "[?instrumentationKey=='<key>'] | [0].{name:name, rg:resourceGroup, workspaceId:workspaceResourceId}"
35```
36 
37#### Step 3: Find the Log Analytics workspace
38 
39```bash
40az monitor app-insights component show --app <appinsights-name> -g <rg-name> \
41  --query "workspaceResourceId" -o tsv
42```
43 
44### Confirm logs are flowing
45 
46Query App Insights `traces` table to verify the function app is sending telemetry:
47 
48```bash
49az monitor app-insights query --apps <appinsights-name> -g <rg-name> \
50  --analytics-query "traces | where operation_Name != '' | take 1 | project timestamp, operation_Name, message"
51```
52 
53For `FunctionAppLogs` (available in Log Analytics only, not App Insights), query the workspace directly:
54 
55```bash
56az monitor log-analytics query -w <workspace-guid> \
57  --analytics-query "FunctionAppLogs | where _ResourceId contains '<func-app-name>' | take 5 | project TimeGenerated, FunctionName, Message, Level"
58```
59 
60> ⚠️ **Classic App Insights:** Some function apps use classic App Insights without a linked Log Analytics workspace (`workspaceId` is null). In this case, `FunctionAppLogs` is **not available** — use the `traces`, `requests`, and `exceptions` tables via `az monitor app-insights query` instead. As a last resort, `az webapp log tail --name <func-app-name> -g <rg-name>` can stream live logs directly.
61 
62If results are returned, logs are flowing. If empty, verify the `APPLICATIONINSIGHTS_CONNECTION_STRING` app setting matches this App Insights instance.
63 
64> ⚠️ **Always prefer querying App Insights or Log Analytics** for function app logs. `az webapp log tail` can stream live logs directly but App Insights provides richer data, historical queries, and correlation across requests.
65 
66> 💡 **Tip:** App Insights logs can be delayed by a few minutes. If you don't see recent data, wait 3-5 minutes and query again.
67 
68---
69 
70## Check Recent Deployments
71 
72Correlate issues with recent deployments by listing deployment history:
73 
74```bash
75az rest --method get \
76  --uri "/subscriptions/<subscription-id>/resourceGroups/<rg-name>/providers/Microsoft.Web/sites/<func-app-name>/deployments?api-version=2023-12-01"
77```
78 
79Compare deployment timestamps against when errors started appearing in App Insights to identify if a deployment caused the issue.
80 
81