Cloud Spanner for global distribution in GCP - Step-by-Step Execution

Process Flow - Cloud Spanner for global distribution

Client sends data request

↓

Cloud Spanner receives request

↓

Check data location

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Local region

↓

Read/Write locally

↓

Return response

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Data synchronized across regions

Cloud Spanner receives a request, processes it locally if possible, replicates data globally for consistency, and returns the response.

Execution Sample

GCP

1. Client sends write request to Spanner
2. Spanner writes data in local region
3. Spanner replicates data to other regions
4. Spanner confirms write success
5. Client receives confirmation

This sequence shows how Cloud Spanner handles a write request globally with replication and confirmation.

Process Table

Step	Action	Region	Data State	Response to Client
1	Client sends write request	Client location	No change	No response yet
2	Spanner writes data locally	Local region	Data written locally	No response yet
3	Spanner replicates data	Other regions	Data replicated	No response yet
4	Spanner confirms write success	All regions	Data consistent globally	Write success confirmation
5	Client receives confirmation	Client location	Data consistent globally	Write success confirmation received

💡 Write confirmed after data is replicated and consistent across all regions

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
Data State	No data	Written locally	Replicated globally	Consistent globally	Consistent globally
Client Response	None	None	None	Write success	Write success

Key Moments - 2 Insights

Why does Cloud Spanner replicate data to other regions before confirming the write?

Because Cloud Spanner ensures global consistency by replicating data to all regions before confirming, as shown in steps 3 and 4 of the execution_table.

Does the client get a response immediately after the local write?

No, the client only receives confirmation after data is replicated globally and consistency is ensured, as seen in step 5 of the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the data replicated to other regions?

A Step 3

B Step 2

C Step 4

D Step 5

💡 Hint

Check the 'Action' column in execution_table row for Step 3.

According to variable_tracker, what is the client response after Step 3?

A Write success

B Write failure

C No response yet

D Data inconsistent

💡 Hint

Look at 'Client Response' variable after Step 3 in variable_tracker.

If replication to other regions is delayed, which step's timing is most affected?

A Step 2 - Local write

B Step 3 - Data replication

C Step 4 - Write confirmation

D Step 5 - Client receives confirmation

💡 Hint

Refer to the 'Action' and 'Data State' columns in execution_table for Step 3.

Concept Snapshot

Cloud Spanner handles global data by:
- Receiving client requests
- Writing data locally
- Replicating data across regions
- Ensuring global consistency
- Confirming writes only after replication
This guarantees strong consistency worldwide.

Full Transcript

Cloud Spanner is a database service that manages data globally. When a client sends a write request, Spanner writes the data in the local region first. Then, it replicates the data to other regions to keep everything consistent. Only after the data is replicated and consistent everywhere does Spanner confirm the write success back to the client. This process ensures that data is always synchronized globally, providing strong consistency and high availability.