get_label_values

Implementation Reference

• src/index.ts:154-176 (handler)

  The MCP tool handler function for 'get_label_values'. It receives the 'label' parameter, calls lokiClient.getLabelValues(label), formats the response as text content, and handles errors.

  async ({ label }, extra) => {
    logger.debug("Label values query tool execution", { label, extra });
  
    try {
      const valuesJson = await lokiClient.getLabelValues(label);
  
      return {
        content: [
          {
            type: "text",
            text: valuesJson,
          },
        ],
      };
    } catch (error) {
      logger.error("Label values query tool execution error", { label, error });
  
      // Create standardized error response
      return createToolErrorResponse(error, "Error getting label values", {
        label,
      });
    }
  }

• src/index.ts:151-153 (schema)

  Zod input schema for the 'get_label_values' tool, defining the required 'label' parameter.

  {
    label: z.string().describe("Label name to get values for"),
  },

• src/index.ts:149-177 (registration)

  Registration of the 'get_label_values' tool on the MCP server using server.tool(), specifying the tool name, input schema, and handler function.

  server.tool(
    "get_label_values",
    {
      label: z.string().describe("Label name to get values for"),
    },
    async ({ label }, extra) => {
      logger.debug("Label values query tool execution", { label, extra });
  
      try {
        const valuesJson = await lokiClient.getLabelValues(label);
  
        return {
          content: [
            {
              type: "text",
              text: valuesJson,
            },
          ],
        };
      } catch (error) {
        logger.error("Label values query tool execution error", { label, error });
  
        // Create standardized error response
        return createToolErrorResponse(error, "Error getting label values", {
          label,
        });
      }
    }
  );

• src/utils/loki-client.ts:423-450 (helper)

  LokiClient.getLabelValues helper method that fetches label values via HTTP and returns them as a JSON string. Called by the tool handler.

  async getLabelValues(labelName: string): Promise<string> {
    this.logger.debug("Retrieving label values list", { labelName });
    try {
      const values = await this.getLabelValuesViaHttp(labelName);
      return JSON.stringify({ values });
    } catch (error: unknown) {
      const errorMsg = error instanceof Error ? error.message : String(error);
      this.logger.error("Getting label values failed", {
        error,
        errorMsg,
        labelName,
      });
      if (error instanceof LokiClientError) {
        throw error;
      }
      throw new LokiClientError(
        "execution_failed",
        `Failed to get label values: ${errorMsg}`,
        {
          cause: error as Error,
          details: {
            command: "label values",
            labelName,
          },
        }
      );
    }
  }

• src/utils/loki-client.ts:457-550 (helper)

  Private LokiClient.getLabelValuesViaHttp method implementing the HTTP API call to retrieve label values from Loki (/loki/api/v1/label/{label}/values).

  private async getLabelValuesViaHttp(labelName: string): Promise<string[]> {
    try {
      const config = this.auth.getConfig();
  
      if (!config.addr) {
        throw new LokiClientError(
          "http_query_error",
          "Loki server address (addr) is not configured",
          { details: { command: "label values", labelName } }
        );
      }
  
      // Build URL for label values endpoint
      const url = `${config.addr}/loki/api/v1/label/${encodeURIComponent(
        labelName
      )}/values`;
  
      // Prepare request headers
      const headers: Record<string, string> = {};
  
      // Add authentication headers
      if (config.username && config.password) {
        const auth = Buffer.from(
          `${config.username}:${config.password}`
        ).toString("base64");
        headers["Authorization"] = `Basic ${auth}`;
      } else if (config.bearer_token) {
        headers["Authorization"] = `Bearer ${config.bearer_token}`;
      }
  
      if (config.tenant_id) {
        headers["X-Scope-OrgID"] = config.tenant_id;
      }
  
      if (config.org_id) {
        headers["X-Org-ID"] = config.org_id;
      }
  
      this.logger.debug("Executing HTTP label values query", {
        url,
        labelName,
        headers: {
          ...headers,
          Authorization: headers.Authorization ? "[REDACTED]" : undefined,
        },
      });
  
      // Make the HTTP request
      const response = await axios.get<{ status: string; data: string[] }>(
        url,
        {
          headers,
          // Handle TLS options
          ...(config.tls_skip_verify
            ? { httpsAgent: { rejectUnauthorized: false } }
            : {}),
        }
      );
  
      if (
        response.data &&
        response.data.data &&
        Array.isArray(response.data.data)
      ) {
        return response.data.data;
      }
  
      return [];
    } catch (error: unknown) {
      let errorMsg = "HTTP label values query failed";
      let errorDetails: Record<string, unknown> = {
        command: "label values",
        labelName,
      };
  
      if (axios.isAxiosError(error)) {
        const axiosError = error as AxiosError;
        errorMsg = `HTTP label values query failed: ${axiosError.message}`;
        errorDetails = {
          ...errorDetails,
          status: axiosError.response?.status,
          statusText: axiosError.response?.statusText,
          responseData: axiosError.response?.data,
        };
      } else if (error instanceof Error) {
        errorMsg = `HTTP label values query failed: ${error.message}`;
      }
  
      throw new LokiClientError("http_query_error", errorMsg, {
        cause: error as Error,
        details: errorDetails,
      });
    }
  }