How to fix BulkItemResponse: failed to execute bulk item (index) in Elasticsearch

// Example bulk request
POST /_bulk?filter_path=items.*.error
{ "index": { "_index": "my-index", "_id": "1" } }
{ "title": "Test document" }
{ "index": { "_index": "my-index", "_id": "2" } }
{ "title": "Another document" }

// Response showing only errors
{
  "items": [
    {
      "index": {
        "error": {
          "type": "document_missing_exception",
          "reason": "[_doc][1]: document missing",
          "index_uuid": "abc123",
          "shard": "0",
          "index": "my-index"
        }
      }
    }
  ]
}

# Check if index exists
curl -X GET "localhost:9200/my-index" -u "username:password"

# Check index settings and mappings
curl -X GET "localhost:9200/my-index/_settings" -u "username:password"
curl -X GET "localhost:9200/my-index/_mapping" -u "username:password"

# Create the index if it doesn't exist (with auto-create enabled)
curl -X PUT "localhost:9200/my-index" -u "username:password" -H 'Content-Type: application/json' -d'
{
  "settings": {
    "number_of_shards": 1,
    "number_of_replicas": 1
  }
}
'

// Bad: String in numeric field
{
  "price": "not-a-number"  // Error if price is mapped as float
}

// Good: Correct type
{
  "price": 29.99
}

// Bad: Missing required field
{
  "name": "Product"
  // Error if "category" is required
}

// Good: Includes required field
{
  "name": "Product",
  "category": "electronics"
}

curl -X GET "localhost:9200/my-index/_validate/query?explain" -u "username:password" -H 'Content-Type: application/json' -d'
{
  "query": {
    "bool": {
      "must": [
        { "match": { "title": "test" } }
      ]
    }
  }
}
'

// Update operation - document must exist
{ "update": { "_index": "my-index", "_id": "1" } }
{ "doc": { "status": "updated" } }

// Delete operation - document must exist
{ "delete": { "_index": "my-index", "_id": "1" } }

// Create operation - document must NOT exist (or use op_type=index)
{ "create": { "_index": "my-index", "_id": "1" } }
{ "title": "New document" }

// Update with upsert
{ "update": { "_index": "my-index", "_id": "1", "retry_on_conflict": 3 } }
{
  "doc": { "status": "updated" },
  "doc_as_upsert": true  // Creates document if it doesn't exist
}

// Example: Process bulk requests with error handling
async function processBulkWithRetry(documents, batchSize = 1000) {
  const batches = [];
  for (let i = 0; i < documents.length; i += batchSize) {
    batches.push(documents.slice(i, i + batchSize));
  }

  const results = [];
  for (const batch of batches) {
    let retryCount = 0;
    let success = false;

    while (!success && retryCount < 3) {
      try {
        const response = await elasticsearchClient.bulk({
          body: batch.flatMap(doc => [
            { index: { _index: 'my-index', _id: doc.id } },
            doc
          ])
        });

        if (response.errors) {
          // Handle individual failed items
          const failedItems = response.items.filter(item => item.index.error);
          console.log('Failed items: ' + failedItems.length);

          // Optionally retry failed items individually
          for (const item of failedItems) {
            // Implement individual retry logic
          }
        }

        results.push(response);
        success = true;
      } catch (error) {
        retryCount++;
        if (retryCount === 3) {
          throw new Error('Failed after 3 retries: ' + error.message);
        }
        await new Promise(resolve => setTimeout(resolve, 1000 * retryCount));
      }
    }
  }

  return results;
}