Azure Functions Pocket Book — Uplatz
55+ deep-dive flashcards • Single column • Triggers & Bindings • Durable Functions • Dev/Deploy • Performance & Security • Interview Q&A
Cheat-friendly explanations • Readable CLI/SDK snippets • Production-oriented tips
1) What is Azure Functions?
Event-driven, serverless compute. Write small functions that run on triggers (HTTP, queue, timer, events). You manage code; Azure manages servers & scaling.
# Check Core Tools
func --version
az extension add -n azure-dev2) Hosting Plans
Consumption (pay per execution, true serverless), Premium (pre-warmed, VNET, no cold start), Dedicated/App Service (reserved). Choose by latency/VNET/cost.
3) Languages & Runtimes
C#, JavaScript/TypeScript, Python, Java, PowerShell, Custom Handlers. Function runtime versions align with language workers.
4) Triggers & Bindings
Triggers start your function; input/output bindings connect to services (Storage, Service Bus, Cosmos DB, SignalR). No SDK boilerplate for common I/O.
5) Function App Structure
A Function App hosts one or more functions sharing a runtime & settings. Each function has function.json describing its bindings.
func init myapp --worker-runtime node
cd myapp
func new --name httpHello --template "HTTP trigger"6) When to Use
Lightweight APIs, event processing, schedulers, glue code, ETL steps, webhooks. Not ideal for long CPU-bound tasks—offload to containers/jobs.
7) Pricing Basics
Consumption charges = executions + GB-s + outbound. Premium = instance uptime + executions. Watch networking egress and storage transactions.
8) Cold Starts
Cold start = first request spins up worker. Premium plan pre-warms to avoid. For HTTP on Consumption, use “Always On” with APIM ping or warmers (non-critical).
9) HTTP Trigger
Quick APIs or webhooks. Auth levels: anonymous, function, admin.
// JavaScript (index.js)
module.exports = async function (context, req) {
const name = (req.query.name || (req.body && req.body.name) || "world");
context.res = { body: `Hello, ${name}!` };
};
// function.json (excerpt)
{
"bindings":[
{"authLevel":"function","type":"httpTrigger","direction":"in","name":"req","methods":["get","post"]},
{"type":"http","direction":"out","name":"res"}
]
}10) Timer Trigger
CRON schedules for cleanup or reports.
{
"schedule": "0 0 6 * * *", "type":"timerTrigger","direction":"in","name":"myTimer"
}11) Queue Storage Trigger
Fires on new messages; use poison queue for failed retries.
{
"type":"queueTrigger","name":"msg","queueName":"tasks","connection":"AzureWebJobsStorage","direction":"in"
}12) Service Bus Trigger
For enterprise messaging (queues/topics).
{
"type":"serviceBusTrigger","name":"sbMsg","queueName":"orders","connection":"ServiceBusConn","direction":"in"
}13) Event Grid Trigger
React to resource events (Blob created, custom events) with durable delivery and retries.
14) Event Hubs Trigger
High-throughput streaming ingestion; tune batch size & checkpointing for throughput.
15) Blob Trigger
ETL pipelines on file drops (e.g., convert images, parse CSV).
16) Cosmos DB Trigger
React to inserts/updates on a collection for projections/denormalization.
17) Output Bindings
Write to queues/blobs/tables/SignalR without SDK glue.
{
"bindings":[
{"type":"httpTrigger","name":"req","direction":"in"},
{"type":"queue","name":"outMsg","queueName":"tasks","connection":"AzureWebJobsStorage","direction":"out"}
]
}
18) Core Tools & Emulator
Install Azure Functions Core Tools and Azurite (Storage emulator) for local triggers.
npm i -g azure-functions-core-tools@4
npm i -g azurite
azurite & # start storage emulator
func start # run functions locally19) local.settings.json
Local-only configuration for connection strings and app settings (not deployed).
{
"IsEncrypted": false,
"Values": {
"AzureWebJobsStorage": "UseDevelopmentStorage=true",
"FUNCTIONS_WORKER_RUNTIME": "node"
}
}20) VS Code Extension
Scaffolds functions, debugs breakpoints, deploys with one click. Pair with Azure CLI for auth.
21) function.json & host.json
function.json defines bindings; host.json controls runtime (concurrency, logging, batching).
{
"version":"2.0",
"logging": {"applicationInsights":{"samplingSettings":{"isEnabled":true,"maxTelemetryItemsPerSecond":5}}},
"extensions": {"serviceBus": {"maxConcurrentCalls": 16}}
}22) Python Example
# __init__.py
import logging
def main(req):
name = (req.params.get('name') or 'world')
return f"Hello, {name}!"
23) Zip Deploy + Run From Package
Immutable deployments increase reliability.
func azure functionapp publish my-func-app --typescript --publish-local-settings -i
# or
az functionapp deployment source config-zip -g rg -n my-func-app --src package.zip24) GitHub Actions
# .github/workflows/deploy.yml (Node)
- uses: actions/setup-node@v4
- run: npm ci && npm run build
- uses: Azure/functions-action@v1
with:
app-name: my-func-app
package: '.'25) App Settings & Key Vault
Use Key Vault references (@Microsoft.KeyVault(...)) and managed identity; never hardcode secrets.
26) Slots
Staging slots allow safe swaps; mark connection strings as “slot setting” if they differ.
27) Containerized Functions
Package as a Linux container to control dependencies; supports Premium/Dedicated.
FROM mcr.microsoft.com/azure-functions/node:4-node18
COPY . /home/site/wwwroot28) VNET Integration
Required to reach private endpoints (databases, storage). Premium plan recommended for stable connections.
29) Concurrency & Batching
Tune Service Bus/Event Hub batch sizes; use parallelism for CPU-light handlers; beware long CPU sections—offload.
30) Retries & Poison
Storage queues have poison queues; Service Bus has DLQ. Configure retry policies in host.json or bindings.
31) Timeouts & Memory
Default timeout varies by plan (Consumption has limits). Use Premium for longer processing. Keep memory steady—avoid big in-memory buffers.
32) Idempotency
Make handlers safe to retry. Use dedupe IDs, ETags, or state checks to avoid duplicate side effects.
33) Parallel Fan-out
For many independent tasks, queue messages and process concurrently. For orchestrations, consider Durable Functions.
34) Auth Levels
HTTP trigger authLevel: anonymous, function (requires key), admin (master key). Prefer Azure AD / APIM for production APIs.
35) Azure AD Protection
Enable “Easy Auth” (App Service Authentication) or front with APIM/Front Door and validate JWT scopes/roles.
36) Managed Identity
Access Storage, Key Vault, Cosmos DB without secrets via MSI and RBAC.
az functionapp identity assign -g rg -n my-func-app
az role assignment create --assignee <principalId> --role "Storage Blob Data Reader" --scope <storage-scope>37) Private Endpoints
Lock down function ingress with Private Endpoints + Application Gateway/Front Door for external publishing.
38) Application Insights
Built-in logging, metrics, live metrics, sampling. Correlate traces across services.
# host.json logging sample above; also configure APPINSIGHTS_CONNECTIONSTRING39) Structured Logs
Use ILogger (C#) / context.log (JS) with consistent fields. Don’t log secrets or large payloads.
40) Alerts & Dashboards
Alerts on failure rate, function duration, 5xx, queue backlog. Pin charts in Azure Dashboard for on-call.
41) What is Durable Functions?
State orchestration on top of Functions. Patterns: function chaining, fan-out/fan-in, async HTTP APIs, human interaction, sagas.
42) Orchestrator Constraints
Orchestrators must be deterministic—no random time.now or non-deterministic I/O. Use context.currentUtcDateTime and activity functions.
43) Sample (JS)
// orchestration.js
const df = require("durable-functions");
module.exports = df.orchestrator(function* (context) {
const items = yield context.df.callActivity("GetItems");
const results = yield context.df.callSubOrchestrator("ProcessItems", items);
return results.length;
});44) Durable Entities
Lightweight stateful objects (counters, carts). Access via signals; good for per-key coordination.
45) Human Interaction
External events pause orchestration until approval; combine with timeouts and compensating actions (saga).
46) Pattern — API + Queue
HTTP receives request → enqueue job → immediate 202 response → worker processes async → client polls status endpoint.
47) Pattern — ETL on Blob
Blob trigger parses file → writes cleaned data to Data Lake → Event Grid notifies downstream.
48) Common Pitfall — Large Files
Don’t buffer whole files in memory. Stream to Storage/Bus; use temp files on /home if needed; consider durable patterns.
49) Common Pitfall — Long Work
Hitting timeout? Move to Durable, break into activities, or offload to containerized batch jobs.
50) Interview — Functions vs Logic Apps?
Answer: Functions = code-first, flexible; Logic Apps = designer-first workflows & connectors. Often used together.
51) Interview — Consumption vs Premium?
Answer: Consumption is cheapest but can have cold start & limits; Premium offers pre-warmed instances, VNET, longer timeouts.
52) Interview — Mitigate cold start?
Answer: Premium pre-warmed, smaller bundles, keep warm pings (non-critical), avoid heavy startup, use DI & lazy init.
53) Interview — Ensuring idempotency?
Answer: Use message IDs, de-dup tables, blob ETags, and transactional outbox; handle retries safely.
54) Troubleshoot Failures
Check App Insights traces, “Function execution” logs, DLQs/poison queues, Kudu console, and recent deployments for config drift.
55) Production Checklist
CI/CD with run-from-package, slots & swaps, Key Vault refs, MSI + RBAC, private endpoints/VNET, alerts & dashboards, lifecycle docs & runbooks.