Troubleshoot log queries (READ)

This guide helps you troubleshoot errors that occur when querying logs from Loki. When Loki rejects or fails query requests, it’s typically due to query syntax errors, exceeding limits, timeout issues, or storage access problems.

Before you begin, ensure you have the following:

• Access to Grafana Loki logs and metrics
• Understanding of LogQL query language basics
• Permissions to configure limits and settings if needed

Monitoring query errors

Query errors can be observed using these Prometheus metrics:

• loki_request_duration_seconds - Query latency by route and status code
• loki_logql_querystats_bytes_processed_per_seconds - Bytes processed during queries
• loki_frontend_query_range_duration_seconds_bucket - Frontend query latency

You can set up alerts on 4xx and 5xx status codes to detect query problems early. This can be helpful when tuning limits configurations.

LogQL parse errors

Parse errors occur when the LogQL query syntax is invalid. Loki returns HTTP status code 400 Bad Request for all parse errors.

Error: Failed to parse the log query

Error message:

failed to parse the log query

Or with position details:

parse error at line <line>, col <col>: <message>

Cause:

The LogQL query contains syntax errors. This could be due to:

• Missing or mismatched brackets, quotes, or braces
• Invalid characters or operators
• Incorrect function syntax
• Invalid duration format

Common examples:

Resolution:

Start with a simple stream selector: {job="app"}, then add filters and operations incrementally to identify syntax issues.

• Check bracket matching - Ensure all {, }, (, ), [, ] are properly closed.
• Verify string quoting - All label values and filter strings must be quoted.
• Use valid duration units - Use ns, us, ms, s, m, h, d, w, y , for example, 5m not 5minutes.
• Review operator syntax - Ensure label matchers use proper operators (=, !=, =~, !~). Check the LogQL documentation for correct operator usage.
• Use Grafana Assistant - If you are a Cloud Logs user, you can use Grafana Assistant to write or revise your query using natural language, for example, “What errors occurred for application foo in the last hour?”

Properties:

• Enforced by: Query Frontend/Querier
• Retryable: No (query must be fixed)
• HTTP status: 400 Bad Request
• Configurable per tenant: No

Error: At least one equality matcher required

Error message:

parse error : queries require at least one regexp or equality matcher that does not have an empty-compatible value. For instance, app=~".*" does not meet this requirement, but app=~".+" will

Cause:

The query uses only negative matchers (!=, !~) or matchers that match empty strings (=~".*"), which would select all streams. This is prevented to protect against accidentally querying the entire database.

Invalid examples:

logql Copy

{foo!="bar"}
{app=~".*"}
{foo!~"bar|baz"}

Valid examples:

logql Copy

{foo="bar"}
{app=~".+"}
{app="baz", foo!="bar"}

Resolution:

• Add at least one positive matcher that selects specific streams.
• Use .+ instead of .* in regex matchers to require at least one character.
• Add additional label selectors to narrow down the query scope.
• Use Grafana Assistant - If you are a Cloud Logs user, you can use Grafana Assistant to write or revise your query using natural language, for example, “Find logs containing ’foo’ but not ‘bar’ or ‘baz’.”

Properties:

• Enforced by: Query Frontend
• Retryable: No (query must be fixed)
• HTTP status: 400 Bad Request
• Configurable per tenant: No

Error: Only label matchers are supported

Error message:

only label matchers are supported

Cause:

The query was passed to an API that only accepts label matchers (like the series API), but included additional expressions like line filters or parsers.

Resolution:

• Use only stream selectors for APIs that don’t support full LogQL:

  logql Copy

  # Valid for series API
  {app="foo", env="prod"}
  
  # Invalid for series API
  {app="foo"} |= "error"

Properties:

• Enforced by: API handler
• Retryable: No (query must be fixed)
• HTTP status: 400 Bad Request
• Configurable per tenant: No

Error: Log queries not supported as instant query type

Error message:

log queries are not supported as an instant query type, please change your query to a range query type

Cause:

A log query (one that returns log lines rather than metrics) was submitted to the instant query endpoint (/loki/api/v1/query). Log queries must use the range query endpoint.

Resolution:

• Convert to a range query Convert log queries to range queries with a time range. Range queries are the default in Grafana Explore.

• Use the range query endpoint /loki/api/v1/query_range for log queries.

• Convert to a metric query if you need to use instant queries:

  logql Copy

  # This is a log query (returns logs)
  {app="foo"} |= "error"
  
  # This is a metric query (can be instant)
  count_over_time({app="foo"} |= "error"[5m])

• Use Grafana Assistant - If you are a Cloud Logs user, you can use Grafana Assistant to write or revise your query.

Properties:

• Enforced by: Query API
• Retryable: No (use correct endpoint or query type)
• HTTP status: 400 Bad Request
• Configurable per tenant: No

Error: Invalid aggregation without unwrap

Error message:

parse error : invalid aggregation sum_over_time without unwrap

Cause:

Aggregation functions like sum_over_time, avg_over_time, min_over_time, max_over_time require an unwrap expression to extract a numeric value from log lines.

Resolution:

• Add an unwrap expression to extract the numeric label:

  logql Copy

  # Invalid
  sum_over_time({app="foo"} | json [5m])
  
  # Valid - unwrap a numeric label
  sum_over_time({app="foo"} | json | unwrap duration [5m])

Properties:

• Enforced by: Query Parser
• Retryable: No (query must be fixed)
• HTTP status: 400 Bad Request
• Configurable per tenant: No

Error: Invalid aggregation with unwrap

Error message:

parse error : invalid aggregation count_over_time with unwrap

Cause:

The count_over_time function doesn’t use unwrapped values - it just counts log lines. Using it with unwrap is invalid.

Resolution:

• Remove the unwrap expression for count_over_time:

  logql Copy

  # Invalid
  count_over_time({app="foo"} | json | unwrap duration [5m])
  
  # Valid
  count_over_time({app="foo"} | json [5m])

• Use sum_over_time if you want to sum unwrapped values.

Properties:

• Enforced by: Query Parser
• Retryable: No (query must be fixed)
• HTTP status: 400 Bad Request
• Configurable per tenant: No

Query limit errors

These errors occur when queries exceed configured resource limits. They return HTTP status code 400 Bad Request.

Error: Maximum series reached

Error message:

maximum number of series (<limit>) reached for a single query; consider reducing query cardinality by adding more specific stream selectors, reducing the time range, or aggregating results with functions like sum(), count() or topk()

Cause:

The query matches more unique label combinations (series) than the configured limit allows. This protects against queries that would consume excessive memory.

Default configuration:

• max_query_series: 500 (default)

Resolution:

• Add more specific stream selectors to reduce cardinality:

  logql Copy

  # Too broad
  {job="ingress-nginx"}
  
  # More specific
  {job="ingress-nginx", namespace="production", pod=~"ingress-nginx-.*"}

• Reduce the time range of the query.

• Use label filters to narrow down results: {job="app"} |= "error"

• Use aggregation functions to reduce cardinality:

  logql Copy

  sum by (status) (rate({job="nginx"} | json [5m]))

• Increase the limit if resources allow:

  YAML Copy

  limits_config:
    max_query_series: 1000  #default is 500

Properties:

• Enforced by: Query Frontend
• Retryable: No (query must be modified)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Cardinality issues

Error message:

cardinality limit exceeded for {}; 100001 entries, more than limit of 100000

Cause:

The query produces results with too many unique label combinations. This protects against queries that would generate excessive memory usage and slow performance.

Default configuration:

• cardinality_limit: 100000

Resolution:

• Use more specific label selectors to reduce the number of unique streams.

• Apply aggregation functions to reduce cardinality:

  logql Copy

  sum by (status) (rate({job="nginx"}[5m]))

• Use by() or without() clauses to group results and reduce dimensions:

  logql Copy

  sum by (status, method) (rate({job="nginx"} | json [5m]))

  Another alternative is using drop or keep to reduce the number of labels and hence the cardinality:

  logql Copy

  # Drop high-cardinality labels like request_id or trace_id
  {job="nginx"} | json | drop request_id, trace_id, session_id
  
  # Keep only the labels you need
  {job="nginx"} | json | keep status, method, path

• Increase the limit if needed:

  YAML Copy

  limits_config:
    cardinality_limit: 200000  #default is 100000

Properties:

• Enforced by: Query Engine
• Retryable: No (query must be modified)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Max entries limit per query exceeded

Error message:

max entries limit per query exceeded, limit > max_entries_limit_per_query (<requested> > <limit>)

Cause:

The query requests more log entries than the configured maximum. This applies to log queries (not metric queries).

Default configuration:

• max_entries_limit_per_query: 5000

Resolution:

• Reduce the limit parameter in your query request.

• Add more specific filters to return fewer results:

  logql Copy

  {app="foo"} |= "error" 

• Reduce the time range of the query.

• Increase the limit if needed:

  YAML Copy

  limits_config:
    max_entries_limit_per_query: 10000  #default is 5000

Properties:

• Enforced by: Querier/Query Frontend
• Retryable: No (query must be modified)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Query would read too many bytes

Error message:

the query would read too many bytes (query: <size>, limit: <limit>); consider adding more specific stream selectors or reduce the time range of the query

Cause:

The estimated data volume for the query exceeds the configured limit. This is determined before query execution using index statistics.

Default configuration:

• max_query_bytes_read: 0B (disabled by default)

Resolution:

• Add more specific stream selectors to reduce data volume.

• Reduce the time range of the query.

• Increase the limit if resources allow:

  YAML Copy

  limits_config:
    max_query_bytes_read: 10GB

Properties:

• Enforced by: Query Frontend
• Retryable: No (query must be modified)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Too many chunks (count)

Error message:

the query hit the max number of chunks limit (limit: 2000000 chunks)

Cause:

The number of chunks that the query would read exceeds the configured limit. This protects against queries that would scan excessive amounts of data and consume too much memory.

Default configuration:

• max_chunks_per_query: 2000000

Resolution:

• Narrow stream selectors to reduce the number of matching chunks:

  logql Copy

  # Too broad
  {job="app"}
  
  # More specific
  {job="app", environment="production", namespace="api"}

• Reduce the query time range to scan fewer chunks.

• Increase the limit if resources allow:

  YAML Copy

  limits_config:
    max_chunks_per_query: 5000000  #default is 2000000

Properties:

• Enforced by: Query Frontend
• Retryable: No (query must be modified)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Stream matcher limits

Error message:

max streams matchers per query exceeded, matchers-count > limit (1500 > 1000)

Cause:

The query contains too many stream matchers. This limit prevents queries with excessive complexity that could impact query performance.

Default configuration:

• max_streams_matchers_per_query: 1000

Resolution:

• Simplify your query by using fewer label matchers.

• Combine multiple queries instead of using many OR conditions.

• Use regex matchers to consolidate multiple values:

  logql Copy

  # Good: 3 matchers using regex patterns
  {cluster="prod", namespace=~"api|web", pod=~"nginx-.*"}

• Increase the limit if needed:

  YAML Copy

  limits_config:
    max_streams_matchers_per_query: 2000  #default is 1000

Properties:

• Enforced by: Querier
• Retryable: No (query must be modified)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Query too large for single querier

Error message:

query too large to execute on a single querier: (query: <size>, limit: <limit>); consider adding more specific stream selectors, reduce the time range of the query, or adjust parallelization settings

Or for un-shardable queries:

un-shardable query too large to execute on a single querier: (query: <size>, limit: <limit>); consider adding more specific stream selectors or reduce the time range of the query

Cause:

Even after query splitting and sharding, individual query shards exceed the per-querier byte limit.

Default configuration:

• max_querier_bytes_read: 150GB (per querier)

Resolution:

• Add more specific stream selectors.

• Reduce the time range or Break large queries into smaller time ranges.

• Simplify the query if possible - some queries cannot be sharded.

• Increase the limit (requires more querier resources):

  YAML Copy

  limits_config:
    max_querier_bytes_read: 200GB  # default is 150GB

• Scale querier resources

Properties:

• Enforced by: Query Frontend
• Retryable: No (query must be modified)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Interval value exceeds limit

Error message:

[interval] value exceeds limit

Cause:

The range vector interval (in brackets like [5m]) exceeds configured limits.

Resolution:

• Reduce the range interval in your query:

  logql Copy

  # If [1d] is too large, try smaller intervals
  rate({app="foo"}[1h])

• Check your configuration for max_query_length limits. The default is 30d1h.

Properties:

• Enforced by: Query Engine
• Retryable: No (query must be modified)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Time range errors

These errors relate to the time range specified in queries.

Error: Query time range exceeds limit

Error message:

the query time range exceeds the limit (query length: <duration>, limit: <limit>)

Cause:

The difference between the query’s start and end time exceeds the maximum allowed query length.

Default configuration:

• max_query_length: 721h (30 days + 1 hour)

Resolution:

• Reduce the query time range:

  logcli Copy

  # Instead of querying 60 days
  logcli query '{app="foo"}' --from="60d" --to="now"
  
  # Query 30 days or less
  logcli query '{app="foo"}' --from="30d" --to="now"

• Increase the limit if storage retention supports it:

  YAML Copy

  limits_config:
    max_query_length: 2160h  # 90 days

Properties:

• Enforced by: Query Frontend/Querier
• Retryable: No (query must be modified)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Data is no longer available

Error message:

this data is no longer available, it is past now - max_query_lookback (<duration>)

Cause:

The entire query time range falls before the max_query_lookback limit. This happens when trying to query data older than the configured lookback period.

Default configuration:

• max_query_lookback: 0 (The default value of 0 does not set a limit.)

Resolution:

• Query more recent data within the lookback window.

• Adjust the lookback limit if the data should be queryable:

  YAML Copy

  limits_config:
    max_query_lookback: 8760h  # 1 year

  Caution

  The lookback limit should not exceed your retention period.

Properties:

• Enforced by: Query Frontend/Querier
• Retryable: No
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Invalid query time range

Error message:

invalid query, through < from (<end> < <start>)

Cause:

The query end time is before the start time, which is invalid.

Resolution:

• Swap start and end times if they were reversed.
• Check timestamp formats to ensure times are correctly specified.

Properties:

• Enforced by: Query Frontend/Querier
• Retryable: No (query must be fixed)
• HTTP status: 400 Bad Request
• Configurable per tenant: No

Required labels errors

These errors occur when queries don’t meet configured label requirements.

Error: Missing required matchers

Error message:

stream selector is missing required matchers [<required_labels>], labels present in the query were [<present_labels>]

Cause:

The tenant is configured to require certain label matchers in all queries, but the query doesn’t include them.

Default configuration:

• required_labels: [] (none required by default)

Resolution:

• Check with your administrator about which labels are required.

• Add the required labels to your query:

  logql Copy

  # If 'namespace' is required
  {app="foo", namespace="production"}

Properties:

• Enforced by: Query Frontend
• Retryable: No (query must include required labels)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Not enough label matchers

Error message:

stream selector has less label matchers than required: (present: [<labels>], number_present: <count>, required_number_label_matchers: <required>)

Cause:

The tenant is configured to require a minimum number of label matchers, but the query has fewer.

Default configuration:

• minimum_labels_number: 0 (no minimum by default)

Resolution:

• Add more label matchers to meet the minimum requirement:

  logql Copy

  # If minimum is 2, add another selector
  {app="foo", namespace="production"}

Properties:

• Enforced by: Query Frontend
• Retryable: No (query must meet requirements)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Timeout errors

Timeout errors occur when queries take too long to execute.

Error: Request timed out

Error message:

request timed out, decrease the duration of the request or add more label matchers (prefer exact match over regex match) to reduce the amount of data processed

Or:

context deadline exceeded

Cause:

The query exceeded the configured timeout. This can happen due to:

• Large time ranges
• High cardinality queries
• Complex query expressions
• Insufficient cluster resources
• Network issues

Default configuration:

• query_timeout: 1m
• server.http_server_read_timeout: 30s
• server.http_server_write_timeout: 30s

Resolution:

• Reduce the time range of the query.

• Add more specific filters to reduce data processing:

  logql Copy

  # Less specific (slower)
  {namespace=~"prod.*"}
  
  # More specific (faster)
  {namespace="production"}

• Prefer exact matchers over regex when possible.

• Add line filters early in the pipeline:

  logql Copy

  {app="foo"} |= "error" | json | level="error"

• Increase timeout limits (if resources allow):

  YAML Copy

  limits_config:
    query_timeout: 5m
  
  server:
    http_server_read_timeout: 5m
    http_server_write_timeout: 5m

• Use sampling for exploratory queries

  logql Copy

   {job="app"} | line_format "{{__timestamp__}} {{.msg}}" | sample 0.1

• Check for network issues between components.

Properties:

• Enforced by: Query Frontend/Querier
• Retryable: Yes (with modifications)
• HTTP status: 504 Gateway Timeout
• Configurable per tenant: Yes (query_timeout)

Error: Request cancelled by client

Error message:

the request was cancelled by the client

Cause:

The client closed the connection before receiving a response. This is typically caused by:

• Client-side timeout
• User navigating away in Grafana
• Network interruption

Resolution:

• Increase client timeout in Grafana or LogCLI.
• Optimize the query to return faster.
• Check network connectivity between client and Loki.

Properties:

• Enforced by: Client
• Retryable: Yes
• HTTP status: 499 Client Closed Request
• Configurable per tenant: No

Query blocked errors

These errors occur when queries are administratively blocked.

Error: Query blocked by policy

Error message:

query blocked by policy

Cause:

The query matches a configured block rule. Administrators create tenant policies and rate limiting rules to block specific queries or query patterns to protect the cluster from expensive or problematic queries.

Resolution:

• Check with your Loki administrator about blocked queries and to review policy settings.
• Modify the query to avoid the block pattern:
  • Change the stream selectors
  • Adjust the time range
  • Use different aggregations
• Request the block to be removed if the query is legitimate.

Configuration reference:

YAML Copy

limits_config:
  blocked_queries:
    - pattern: ".*"          # Regex pattern to match
      regex: true
      types:                 # Query types to block
        - metric
        - filter
      hash: 0               # Or block specific query hash

Properties:

• Enforced by: Query Engine
• Retryable: No (unless block is removed)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Querying is disabled

Error message:

querying is disabled, please contact your Loki operator

Cause:

Query parallelism is set to 0, effectively disabling queries for the tenant.

Resolution:

• Contact your Loki administrator to enable querying.

• Check configuration for max_query_parallelism:

  YAML Copy

  limits_config:
    max_query_parallelism: 32     #(the default)

Properties:

• Enforced by: Query Frontend
• Retryable: No (until configuration is fixed)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Error: Multi variant queries disabled

Multi variant queries are an experimental feature that enables support for running multiple query variants over the same underlying data. For example, running both a rate() and count_over_time() query over the same range selector.

Error message:

multi variant queries are disabled for this instance

Cause:

The query uses the variants feature, but it’s disabled for the tenant or instance.

Resolution:

• Remove variant expressions from the query.

• Enable the feature if needed:

  YAML Copy

  limits_config:
    enable_multi_variant_queries: true  #default is false

Properties:

• Enforced by: Query Engine
• Retryable: No (until feature is enabled)
• HTTP status: 400 Bad Request
• Configurable per tenant: Yes

Pipeline processing errors

Pipeline errors occur during log line processing but don’t cause query failures. Instead, affected log lines are annotated with error labels.

Understanding pipeline errors

When a pipeline stage fails (for example, parsing JSON that isn’t valid JSON), Loki:

1. Does NOT filter out the log line
2. Adds an __error__ label with the error type
3. Optionally adds __error_details__ with more information
4. Passes the log line to the next pipeline stage

Error types

Viewing pipeline errors

To see logs with errors:

logql Copy

{app="foo"} | json | __error__!=""

To see error details:

logql Copy

{app="foo"} | json | __error__!="" | line_format "Error: {{.__error__}} - {{.__error_details__}}"

Filtering out errors

To exclude logs with parsing errors:

logql Copy

{app="foo"} | json | __error__=""

To exclude specific error types:

logql Copy

{app="foo"} | json | __error__!="JSONParserErr"

Dropping error labels

To remove error labels from results:

logql Copy

{app="foo"} | json | drop __error__, __error_details__

Authentication and connection errors

These errors occur when connecting to Loki, often when using LogCLI.

Error: No org ID

Error message:

text Copy

no org id

Cause:

Multi-tenancy is enabled but no tenant ID was provided in the request.

Resolution:

1. Add the X-Scope-OrgID header in your request.

2. For LogCLI, use the --org-id flag:

   Bash Copy

   logcli query '{app="foo"}' --org-id="my-tenant"

3. In Grafana, configure the tenant ID in the data source settings.

Properties:

• Enforced by: Loki API
• Retryable: Yes (with tenant ID)
• HTTP status: 400 Bad Request
• Configurable per tenant: No

Error: Authentication configuration conflict

Error message:

text Copy

at most one of HTTP basic auth (username/password), bearer-token & bearer-token-file is allowed to be configured

Or:

text Copy

at most one of the options bearer-token & bearer-token-file is allowed to be configured

Cause:

Multiple authentication methods are configured simultaneously in LogCLI.

Resolution:

1. Use only one authentication method:

   Bash Copy

   # Basic auth
   logcli query '{app="foo"}' --username="user" --password="pass"
   
   # OR bearer token
   logcli query '{app="foo"}' --bearer-token="token"
   
   # OR bearer token file
   logcli query '{app="foo"}' --bearer-token-file="/path/to/token"

Properties:

• Enforced by: LogCLI
• Retryable: Yes (with correct configuration)
• HTTP status: N/A (client-side error)
• Configurable per tenant: No

Error: Run out of attempts while querying

Error message:

text Copy

run out of attempts while querying the server

Cause:

LogCLI exhausted all retry attempts when trying to reach Loki. This usually indicates:

• Network connectivity issues
• Server unavailability
• Authentication failures

Resolution:

1. Check Loki server availability.

2. Verify network connectivity.

3. Check authentication credentials.

4. Increase retries if transient issues are expected:

   Bash Copy

   logcli query '{app="foo"}' --retries=5

Properties:

• Enforced by: LogCLI
• Retryable: Yes (automatic retries exhausted)
• HTTP status: Varies
• Configurable per tenant: No

Error: WebSocket connection closed unexpectedly

Error message:

text Copy

websocket: close 1006 (abnormal closure): unexpected EOF

Cause:

When tailing logs, the WebSocket connection was closed unexpectedly. This can happen if:

• The querier handling the tail request stopped
• Network interruption occurred
• Server-side timeout

Resolution:

1. LogCLI will automatically attempt to reconnect, up to 5 times.
2. Check Loki querier health if reconnections fail.
3. Review network stability between client and server.

Properties:

• Enforced by: Network/Server
• Retryable: Yes (automatic reconnection)
• HTTP status: N/A (WebSocket error)
• Configurable per tenant: No

Data availability errors

These errors occur when requested data is not available.

Error: No data found

Error message:

text Copy

no data found

Or an empty result set with no error message.

Cause:

The query time range contains no matching log data. This can happen if:

• No logs match the stream selectors
• The time range is outside the data retention period
• Log ingestion is not working
• Stream labels don’t match any existing streams

Resolution:

1. Verify the time range contains data for your streams.

2. Check if log ingestion is working correctly:

   Bash Copy

   # Check if any data is being ingested
   logcli query '{job=~".+"}'

3. Verify stream selectors match existing log streams:

   Bash Copy

   # List available streams
   curl http://loki:3100/loki/api/v1/series

4. Check data retention settings to ensure logs are still available.

5. Use broader selectors to test if any data exists:

   logql Copy

   {job=~".+"}

Properties:

• Enforced by: Query Engine
• Retryable: Yes (with different parameters)
• HTTP status: 200 OK (with empty result)
• Configurable per tenant: No

Error: Index not ready

Error message:

text Copy

index not ready

Or:

text Copy

index gateway not ready for time range

Cause:

The index for the requested time range is not yet available for querying. This can happen when:

• Index files are still being synced from storage
• The index gateway is still starting up
• Querying data older than the configured ready index period

Default configuration:

• query_ready_index_num_days: 0 (all indexes are considered ready)

Resolution:

1. Wait for the index to become available - this is often a temporary issue during startup.

2. Query more recent data that’s available in ingesters:

   logql Copy

   {app="foo"} # Query last few hours instead of older data

3. Check the configuration for index readiness:

   YAML Copy

   query_range:
     query_ready_index_num_days: 7  #default is 0

4. Verify index synchronization is working correctly by checking ingester and index gateway logs.

Properties:

• Enforced by: Index Gateway/Querier
• Retryable: Yes (wait and retry)
• HTTP status: 503 Service Unavailable
• Configurable per tenant: No

Error: Tenant limits

Error message:

text Copy

max concurrent tail requests limit exceeded, count > limit (10 > 5)

Cause:

The tenant has exceeded the maximum number of concurrent streaming (tail) requests. This limit protects the cluster from excessive resource consumption by real-time log streaming.

Default configuration:

• max_concurrent_tail_requests: 10

Resolution:

1. Reduce the number of concurrent tail/streaming queries.

2. Use batch queries instead of real-time streaming where possible:

   logql Copy

   # Instead of tailing in real-time
   # Use periodic range queries
   {app="foo"} |= "error"

3. Increase the limit if more concurrent tails are needed:

   YAML Copy

   limits_config:
     max_concurrent_tail_requests: 20  #default is 10

Properties:

• Enforced by: Querier
• Retryable: Yes (when connections are available)
• HTTP status: 429 Too Many Requests
• Configurable per tenant: Yes

Storage errors

These errors occur when Loki cannot read data from storage.

Error: Failed to load chunk

Error message:

text Copy

failed to load chunk '<chunk_key>'

Cause:

Loki couldn’t retrieve a chunk from object storage. Possible causes:

• Chunk was deleted or moved
• Storage permissions issue
• Network connectivity to storage
• Storage service unavailable

Resolution:

1. Check storage connectivity from Loki components.
2. Verify storage credentials and permissions.
3. Check for chunk corruption or deletion.
4. Review storage service status.

Properties:

• Enforced by: Storage Client
• Retryable: Yes (automatically)
• HTTP status: 500 Internal Server Error
• Configurable per tenant: No

Error: Object not found in storage

Error message:

text Copy

object not found in storage

Cause:

The requested chunk or object doesn’t exist in storage. This might happen if:

• Data was deleted due to retention
• Compaction removed the chunk
• Chunk was never written successfully

Resolution:

1. Check if data is within retention period.
2. Verify data was ingested successfully.
3. Review compaction jobs for issues.

Properties:

• Enforced by: Storage Client
• Retryable: No (data doesn’t exist)
• HTTP status: 404 or 500 depending on context
• Configurable per tenant: No

Error: Failed to decode chunk

Error message:

text Copy

failed to decode chunk '<chunk_key>' for tenant '<tenant>': <error>

Cause:

A chunk was retrieved from storage but couldn’t be decoded. This indicates chunk corruption.

Resolution:

1. Report to Loki administrators for investigation.
2. Check for storage data integrity issues.
3. Note that the corrupted chunk data may be unrecoverable.

Properties:

• Enforced by: Storage Client
• Retryable: No (chunk is corrupted)
• HTTP status: 500 Internal Server Error
• Configurable per tenant: No

Troubleshooting workflow

Follow this workflow when investigating query issues:

1. Check the error message - Identify which category of error you’re encountering.

2. Review query syntax - Use the LogQL documentation to validate your query.

3. Check query statistics - In Grafana, enable “Query Inspector” to see:

   • Bytes processed
   • Number of chunks scanned
   • Execution time breakdown

4. Simplify the query - Start with a basic selector and add complexity:

   logql Copy

   # Start simple
   {app="foo"}
   
   # Add filters
   {app="foo"} |= "error"
   
   # Add parsing
   {app="foo"} |= "error" | json
   
   # Add label filters
   {app="foo"} |= "error" | json | level="error"

5. Check metrics for query performance:

   promql Copy

   # Query latency
   histogram_quantile(0.99, sum(rate(loki_request_duration_seconds_bucket[5m])) by (le, route))
   
   # Query errors
   sum by (status_code) (rate(loki_request_duration_seconds_count[5m]))

6. Review Loki logs for detailed error information:

   Bash Copy

   kubectl logs -l app=loki-read --tail=100 | grep -i error

7. Test with LogCLI for more detailed output:

   Bash Copy

   logcli query '{app="foo"}' --stats --limit=10

Related resources

• Learn more about LogQL Query Language
• Configure appropriate query limits
• Learn more about Query performance tuning
• Review the LogCLI documentation
• Learn more about LogQL query optimization
• Review query performance best practices
• Use query debugging features to analyze slow queries
• Explore the Grafana Loki GitHub repository for community support