### Install Trillian Development Tools Locally

Source: https://github.com/google/trillian/blob/master/README.md

Installs essential development tools for Trillian locally using 'go install'. Ensure you are in the Trillian directory before running these commands.

```bash
cd $(go list -f '{{ .Dir }}' github.com/google/trillian); \
    go install github.com/golang/mock/mockgen; \
    go install google.golang.org/protobuf/proto; \
    go install google.golang.org/protobuf/cmd/protoc-gen-go; \
    go install google.golang.org/grpc/cmd/protoc-gen-go-grpc; \
    go install github.com/pseudomuto/protoc-gen-doc/cmd/protoc-gen-doc; \
    go install golang.org/x/tools/cmd/stringer
```

--------------------------------

### Storage.Begin()

Source: https://github.com/google/trillian/blob/master/docs/storage/commit_log/commit_log_based_storage_design.md

Starts a Trillian transaction by reading and verifying the current state from the database and Kafka.

```APIDOC
## Storage.Begin()

### Description
Starts a Trillian transaction. This operation reads the current STH, treeRevision, and sthOffset from the database and verifies them against the corresponding entry in Kafka. It returns a LogTX struct containing these values.

### Method
`Begin` (method on `CQComboStorage`)

### Endpoint
N/A (This is a method call within the Trillian system)

### Parameters
None

### Request Body
None

### Request Example
```golang
// Example usage (conceptual)
logTX, err := storage.Begin()
```

### Response
#### Success Response
- **LogTX** (LogTX) - A transaction object containing the initial state.
- **error** (error) - An error if the transaction could not be started.

#### Response Example
```golang
// Conceptual success response
// logTX object would be returned
```

#### Error Handling
- Returns an error if the local DB has data ahead of the STHs topic.
- Returns an error if the local DB committed to an invalid STH from the topic.
- Returns an error if the local DB has different data than the STHs topic.
```

--------------------------------

### Install golangci-lint

Source: https://github.com/google/trillian/blob/master/README.md

Installs the golangci-lint linter from source to version v2.10.1. This tool is used for running code linters as part of the codebase checks.

```bash
go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.10.1
```

--------------------------------

### Start Trillian Servers with Etcd Quotas

Source: https://github.com/google/trillian/blob/master/quota/etcd/README.md

Ensure logserver and logsigner are started with the necessary flags to enable etcd quotas. The `--etcd_servers` flag specifies the etcd connection, and `--quota_system=etcd` activates the etcd quota manager.

```bash
trillian_log_server \
  --etcd_servers=... \
  --rpc_endpoint=localhost:8090 \
  --quota_system=etcd

trillian_log_signer --etcd_servers=... --quota_system=etcd
```

--------------------------------

### Start Trillian Transaction with Storage.Begin()

Source: https://github.com/google/trillian/blob/master/docs/storage/commit_log/commit_log_based_storage_design.md

Initiates a Trillian transaction by reading and verifying the latest STH from the database and Kafka. The HBase implementation buffers writes locally until `Commit` is called.

```golang
func (ls *CQComboStorage) Begin() (LogTX, error) {
  // create db and cq "TX" objects

  tx := &splitTX{...}

  // read `dbSTH` (containing `treeRevision` and `sthOffset`) from local DB
  tx.dbSTH, tx.treeRevision, tx.stdOffset := dbTX.latestSTH()

  // Sanity check that the STH table has what we already know.
  ourSTH := cqTX.GetSTHAt(tx.sthOffset)

  if ourSTH == nil {
    return nil, fmt.Errorf("should not happen - local DB has data ahead of STHs topic")
  }
  if ourSTH.expectedOffset != dbSTH.sthOffset {
    return nil, fmt.Errorf("should not happen - local DB committed to invalid STH from topic")
  }
  if ourSTH.timestamp != dbSTH.timestamp || ourSTH.tree_size != dbSTH.tree_size {
    return nil, fmt.Errorf("should not happen - local DB has different data than STHs topic")
  }

  ...

  return tx, nil
}
```

--------------------------------

### Create a Sequencing-Based Global Write Quota

Source: https://github.com/google/trillian/blob/master/quota/etcd/README.md

Use grpcurl to create a new quota configuration. This example sets up a global write quota with a max_tokens value implying a 4-hour backlog based on an expected 50 QPS sequencing performance. The quota state is set to ENABLED.

```bash
grpcurl -plaintext -d @ localhost:8090 v1beta1/quotas/global/write/config <<EOF
{
  "name": "quotas/global/write/config",
  "config": {
    "state": "ENABLED",
    "max_tokens": 288000,
    "sequencing_based": {
    }
  }
}
EOF
```

--------------------------------

### Clone Trillian Repository

Source: https://github.com/google/trillian/blob/master/examples/deployment/README.md

Clone the Trillian repository to access build and example deployment files. This is the initial step for any deployment method.

```shell
git clone https://github.com/google/trillian.git
cd trillian
```

--------------------------------

### Verify Local Trillian Installation

Source: https://github.com/google/trillian/blob/master/examples/deployment/README.md

Check the metrics endpoint to verify that your local Trillian installation is running correctly. This is a simple way to confirm the server is accessible.

```shell
curl localhost:8091/metrics
```

--------------------------------

### Example Signer Metrics Output

Source: https://github.com/google/trillian/blob/master/docs/howto/freeze_a_ct_log.md

This sample output from the signer metrics endpoint shows key indicators like `is_master`, `sequencer_sequenced`, and `signing_runs` for a given log ID, which are crucial for monitoring integration.

```text
entries_added{logid="987654321"} 54
is_master{logid="987654321"} 1
known_logs{logid="987654321"} 1
master_resignations{logid="987654321"} 7
sequencer_batches{logid="987654321"} 54
sequencer_sequenced{logid="987654321"} 54
sequencer_tree_size{logid="987654321"} 7.095373e+07
signing_runs{logid="987654321"} 54
```

--------------------------------

### Start Kubernetes Proxy

Source: https://github.com/google/trillian/blob/master/examples/deployment/kubernetes/mysql/README.md

Initiate the Kubernetes proxy to access the cluster's dashboard and services via localhost. This is necessary for monitoring and retrieving service details.

```shell
kubectl proxy
```

--------------------------------

### Generate Basic Merkle Tree Visualization

Source: https://github.com/google/trillian/blob/master/docs/merkletree/treetex/README.md

Run the treetex tool to generate LaTeX output for a Merkle tree and pipe it to pdflatex to create a PDF. Ensure LaTeX is installed.

```bash
go run github.com/google/trillian/docs/merkletree/treetex | pdflatex
```

--------------------------------

### Get Entry and Proof API

Source: https://github.com/google/trillian/blob/master/docs/api.md

Retrieves a specific log entry along with its inclusion proof. Supports specifying the tree size and includes charge-to information.

```APIDOC
## POST /trillian.Trillian/GetEntryAndProof

### Description
Retrieves a specific log entry and its inclusion proof. This endpoint is useful for verifying the existence and integrity of a particular leaf within the log.

### Method
POST

### Endpoint
/trillian.Trillian/GetEntryAndProof

### Parameters
#### Request Body
- **log_id** (int64) - Required - The ID of the log.
- **leaf_index** (int64) - Required - The index of the leaf to retrieve.
- **tree_size** (int64) - Required - The target tree size for the proof.
- **charge_to** (ChargeTo) - Optional - Information about who to charge for the operation.

### Response
#### Success Response (200)
- **proof** (Proof) - The inclusion proof for the leaf.
- **leaf** (LogLeaf) - The requested log leaf data.
- **signed_log_root** (SignedLogRoot) - The signed root of the log at the time of the proof.

#### Response Example
```json
{
  "proof": {
    "leaf_index": "123",
    "leaf_hash": "...",
    "audit_path": ["...", "..."]
  },
  "leaf": {
    "leaf_value": "...",
    "leaf_proof": "..."
  },
  "signed_log_root": {
    "log_id": "456",
    "timestamp": "1678886400",
    "root_hash": "...",
    "tree_size": "1000",
    "signature": {
      "sig": "..."
    }
  }
}
```
```

--------------------------------

### Example CTFE Configuration

Source: https://github.com/google/trillian/blob/master/docs/howto/freeze_a_ct_log.md

This configuration snippet shows how to locate the `log_id` within a Trillian CTFE configuration file, which is necessary for freezing the log.

```protobuf
config {
	log_id: 987654321
	prefix: "the_name_of_the_log"
	roots_pem_file: "... roots file name ....".
	public_key: {
		der: ".... bytes of the public key"
	}
	private_key: {
		[type.googleapis.com/keyspb.PrivateKey] {
			der: ".... bytes of the private key ....".
		}
	}
}
```

--------------------------------

### Highlight Compact Range Proofs in Merkle Tree

Source: https://github.com/google/trillian/blob/master/docs/merkletree/treetex/README.md

Visualize compact range proofs using the --ranges flag, specifying a comma-separated list of start:end indices for the ranges to be highlighted.

```bash
go run github.com/google/trillian/docs/merkletree/treetex --tree_size=18 --ranges=1:4,7:14
```

--------------------------------

### Run Trillian with Docker Compose

Source: https://github.com/google/trillian/blob/master/examples/deployment/README.md

Deploy Trillian locally using Docker Compose for a simple setup with a local MySQL database. This command brings up the database, schema initialization container, and the Trillian server.

```shell
# Set a random password
export MYSQL_ROOT_PASSWORD="$(openssl rand -hex 16)"

# Bring up services defined in this compose file.  This includes:
# - local MySQL database
# - container to initialize the database
# - the trillian server
docker-compose -f examples/deployment/docker-compose.yml up
```

--------------------------------

### Get Leaves by Range API

Source: https://github.com/google/trillian/blob/master/docs/api.md

Retrieves a range of leaves from a log, specified by a starting index and a count. Includes charge-to information.

```APIDOC
## POST /trillian.Trillian/GetLeavesByRange

### Description
Retrieves a specified range of leaves from a log. This is useful for fetching multiple contiguous leaves efficiently.

### Method
POST

### Endpoint
/trillian.Trillian/GetLeavesByRange

### Parameters
#### Request Body
- **log_id** (int64) - Required - The ID of the log.
- **start_index** (int64) - Required - The starting index of the range (inclusive).
- **count** (int64) - Required - The number of leaves to retrieve.
- **charge_to** (ChargeTo) - Optional - Information about who to charge for the operation.

### Response
#### Success Response (200)
- **leaves** (LogLeaf) - Repeated - A list of LogLeaf objects within the specified range.
- **fetched_leaf_count** (int64) - The number of leaves actually fetched.
- **proof** (Proof) - An inclusion proof for the range of leaves.
- **signed_log_root** (SignedLogRoot) - The signed root of the log at the time of the request.

#### Response Example
```json
{
  "leaves": [
    {
      "leaf_value": "...",
      "leaf_proof": "..."
    },
    {
      "leaf_value": "...",
      "leaf_proof": "..."
    }
  ],
  "fetched_leaf_count": "2",
  "proof": {
    "leaf_index": "0",
    "leaf_hash": "...",
    "audit_path": ["...", "..."]
  },
  "signed_log_root": {
    "log_id": "456",
    "timestamp": "1678886400",
    "root_hash": "...",
    "tree_size": "1000",
    "signature": {
      "sig": "..."
    }
  }
}
```
```

--------------------------------

### Build Trillian Log Server with All Storage Implementations

Source: https://github.com/google/trillian/blob/master/storage/README.md

Builds the `trillian_log_server` binary including all default storage and quota implementations. This results in a larger binary size.

```bash
> cd cmd/trillian_log_server && go build && ls -sh trillian_log_server
62M trillian_log_server*
```

--------------------------------

### Get Inclusion Proof API

Source: https://github.com/google/trillian/blob/master/docs/api.md

Retrieves an inclusion proof for a specific leaf index within a log. Includes charge-to information.

```APIDOC
## POST /trillian.Trillian/GetInclusionProof

### Description
Retrieves an inclusion proof for a specific leaf index. The `proof` field may be empty if the requested `tree_size` is larger than the server's current tree size, indicating potential server instance skew. In such cases, `signed_log_root` will reflect the server's known tree size.

### Method
POST

### Endpoint
/trillian.Trillian/GetInclusionProof

### Parameters
#### Request Body
- **log_id** (int64) - Required - The ID of the log.
- **leaf_index** (int64) - Required - The index of the leaf for which to retrieve the proof.
- **tree_size** (int64) - Required - The target tree size for the proof.
- **charge_to** (ChargeTo) - Optional - Information about who to charge for the operation.

### Response
#### Success Response (200)
- **proof** (Proof) - The inclusion proof.
- **signed_log_root** (SignedLogRoot) - The signed root of the log at the time of the proof.

#### Response Example
```json
{
  "proof": {
    "leaf_index": "123",
    "leaf_hash": "...",
    "audit_path": ["...", "..."]
  },
  "signed_log_root": {
    "log_id": "456",
    "timestamp": "1678886400",
    "root_hash": "...",
    "tree_size": "1000",
    "signature": {
      "sig": "..."
    }
  }
}
```
```

--------------------------------

### Download Proto Definitions using wget

Source: https://github.com/google/trillian/blob/master/third_party/googleapis/README.md

This script downloads specific proto definitions from the Googleapis repository using wget. Ensure the GA_VERSION environment variable is set to the desired commit hash.

```sh
export GA_VERSION=c81bb701eb53991d6faf74b2656eaf539261a122
mkdir -p google/api
wget https://raw.githubusercontent.com/googleapis/googleapis/$GA_VERSION/google/api/annotations.proto -O google/api/annotations.proto
wget https://raw.githubusercontent.com/googleapis/googleapis/$GA_VERSION/google/api/http.proto -O google/api/http.proto
mkdir -p google/rpc
wget https://raw.githubusercontent.com/googleapis/googleapis/$GA_VERSION/google/rpc/code.proto -O google/rpc/code.proto
wget https://raw.githubusercontent.com/googleapis/googleapis/$GA_VERSION/google/rpc/status.proto -O google/rpc/status.proto
```

--------------------------------

### Initialize and Apply Terraform Infrastructure

Source: https://github.com/google/trillian/blob/master/deployment/README.md

Use this command to initialize Terraform and apply the infrastructure for Trillian deployment. Replace PROJECT_ID with your actual Google Cloud Project ID.

```shell
terraform init && terraform apply -var="gcp_project=PROJECT_ID"
```

--------------------------------

### Build Trillian Log Server with MySQL and PostgreSQL

Source: https://github.com/google/trillian/blob/master/storage/README.md

Builds the `trillian_log_server` binary including both MySQL and PostgreSQL storage and their associated quota implementations. This results in a moderate binary size.

```bash
> cd cmd/trillian_log_server && go build -tags=mysql,postgresql && ls -sh trillian_log_server
40M trillian_log_server*
```

--------------------------------

### Prepare MySQL Database

Source: https://github.com/google/trillian/blob/master/examples/deployment/kubernetes/mysql/README.md

Run the script to prepare the MySQL database for Trillian usage after the cluster has been provisioned. This script initializes the database schema and settings.

```shell
$GOPATH/src/github.com/google/trillian/storage/mysql/kubernetes/resetdb.sh
```

--------------------------------

### List All Configured Quotas

Source: https://github.com/google/trillian/blob/master/quota/etcd/README.md

Retrieve a full list of all currently configured quotas using grpcurl. The `view: "FULL"` option ensures all details of each quota are returned.

```bash
grpcurl -plaintext -d '{"view": "FULL"}' localhost:8090 v1beta1/quotas
```

--------------------------------

### Get Inclusion Proof by Hash API

Source: https://github.com/google/trillian/blob/master/docs/api.md

Retrieves an inclusion proof for a given leaf hash within a specified tree size. Supports ordering by sequence and includes charge-to information.

```APIDOC
## POST /trillian.Trillian/GetInclusionProofByHash

### Description
Retrieves an inclusion proof for a given leaf hash. The `proof` field in the response can be repeated if multiple leaves have the same hash. If a leaf's index is beyond the requested `tree_size`, its corresponding proof entry will be missing.

### Method
POST

### Endpoint
/trillian.Trillian/GetInclusionProofByHash

### Parameters
#### Request Body
- **log_id** (int64) - Required - The ID of the log.
- **leaf_hash** (bytes) - Required - The Merkle tree hash of the leaf entry to be retrieved.
- **tree_size** (int64) - Required - The target tree size for the proof.
- **order_by_sequence** (bool) - Optional - If true, results are ordered by sequence.
- **charge_to** (ChargeTo) - Optional - Information about who to charge for the operation.

### Response
#### Success Response (200)
- **proof** (Proof) - Repeated - The inclusion proof(s).
- **signed_log_root** (SignedLogRoot) - The signed root of the log at the time of the proof.

#### Response Example
```json
{
  "proof": [
    {
      "leaf_index": "123",
      "leaf_hash": "...",
      "audit_path": ["...", "..."]
    }
  ],
  "signed_log_root": {
    "log_id": "456",
    "timestamp": "1678886400",
    "root_hash": "...",
    "tree_size": "1000",
    "signature": {
      "sig": "..."
    }
  }
}
```
```

--------------------------------

### Build and Fetch Trillian Code

Source: https://github.com/google/trillian/blob/master/README.md

Clone the Trillian repository, navigate into the directory, and build all Go packages. This command fetches dependencies and compiles the project.

```bash
git clone https://github.com/google/trillian.git
cd trillian

go build ./...
```

--------------------------------

### Get Latest Signed Log Root API

Source: https://github.com/google/trillian/blob/master/docs/api.md

Retrieves the latest signed root of a log. Optionally, it can return a consistency proof between a specified previous tree size and the latest size.

```APIDOC
## POST /trillian.Trillian/GetLatestSignedLogRoot

### Description
Retrieves the latest signed root of a log. If `first_tree_size` is provided and non-zero, the response will include a consistency proof between `first_tree_size` and the new tree size, provided `first_tree_size` is not greater than the available tree size on the server.

### Method
POST

### Endpoint
/trillian.Trillian/GetLatestSignedLogRoot

### Parameters
#### Request Body
- **log_id** (int64) - Required - The ID of the log.
- **charge_to** (ChargeTo) - Optional - Information about who to charge for the operation.
- **first_tree_size** (int64) - Optional - If non-zero, a consistency proof will be included if this size is valid.

### Response
#### Success Response (200)
- **signed_log_root** (SignedLogRoot) - The latest signed root of the log.
- **proof** (Proof) - A consistency proof, if `first_tree_size` was requested and valid.

#### Response Example
```json
{
  "signed_log_root": {
    "log_id": "456",
    "timestamp": "1678886400",
    "root_hash": "...",
    "tree_size": "1000",
    "signature": {
      "sig": "..."
    }
  },
  "proof": {
    "leaf_index": "0",
    "leaf_hash": "...",
    "audit_path": ["...", "..."]
  }
}
```
```

--------------------------------

### Build Experimental Map with Beam Go

Source: https://github.com/google/trillian/blob/master/experimental/batchmap/README.md

Use this command to run the Beam Go pipeline for map generation. Adjust output directory and runner as needed. Be mindful of file system inodes for large key counts or strata.

```bash
go run ./cmd/build/mapdemo.go --output=/tmp/mapv1 --runner=PrismRunner
```

--------------------------------

### Set Up AWS Deployment Variables

Source: https://github.com/google/trillian/blob/master/examples/deployment/aws/README.md

Before deploying, set environment variables for the database password and network access CIDR. Ensure your AWS keys are accessible to Terraform.

```shell
cd examples/deployment/aws/ 

# Set a random password
export TF_VAR_DB_PASSWORD "$(openssl rand -hex 16)"
# Substitute this variable with a block you'll be accessing from
export TF_VAR_WHITELIST_CIDR="0.0.0.0/0"
```

--------------------------------

### Test Map Hasher Scheme: Empty Subtree Hashing

Source: https://github.com/google/trillian/blob/master/docs/MapHashers.md

Recursively defines the hash of an empty subtree at a given level 'n' in the test MapHasher scheme. It starts with the hash of an empty leaf (E0) and applies HashChildren.

```go
n = 0: E0 := HashLeaf(nil)
n = 1: E1 := HashChildren(E0, E0)
n = 2: E2 := HashChildren(E1, E1)
...
```

--------------------------------

### Run Trillian Deployment Script

Source: https://github.com/google/trillian/blob/master/docs/CloudSpanner.md

Execute the deployment script after configuring environment variables. This script initiates the Trillian deployment on Google Cloud.

```bash
./scripts/deploy_gce.sh
```

--------------------------------

### Update Trillian Dependencies

Source: https://github.com/google/trillian/blob/master/README.md

Commands for managing Trillian's dependencies using Go modules. Use 'go get' to fetch specific versions or the latest commit, and 'go mod tidy' to clean up unused dependencies.

```bash
go get package/path       # Fetch the latest published version
go get package/path@X.Y.Z # Fetch a specific published version
go get package/path@HEAD  # Fetch the latest commit 
go get -u
go mod tidy
```

--------------------------------

### Build Trillian Log Server with CRDB Implementation

Source: https://github.com/google/trillian/blob/master/storage/README.md

Builds the `trillian_log_server` binary with only the CockroachDB (crdb) storage and associated quota implementation. This significantly reduces the binary size.

```bash
> cd cmd/trillian_log_server && go build -tags=crdb && ls -sh trillian_log_server
37M trillian_log_server*
```

--------------------------------

### Render Domain Model to Full Model

Source: https://github.com/google/trillian/blob/master/docs/claimantmodel/experimental/cmd/render/README.md

Use this command to render a domain-level Claimant Model into a full model, outputting snippets to stdout. Iterate on the input YAML based on the output.

```bash
go run ./docs/claimantmodel/experimental/cmd/render --domain_model_file /tmp/cmfun/model.yaml
```

--------------------------------

### Provision a Trillian Tree

Source: https://github.com/google/trillian/blob/master/examples/deployment/kubernetes/README.md

Use this script to provision a new tree into the Trillian log. It utilizes kubectl to forward requests to the Trillian Log's admin API. Ensure you have the example-config.sh file available.

```bash
./provision_tree.sh example-config.sh
```

--------------------------------

### Highlight Inclusion Proof in Merkle Tree

Source: https://github.com/google/trillian/blob/master/docs/merkletree/treetex/README.md

Visualize an inclusion proof by specifying the leaf index with the --inclusion flag. This highlights the path from the specified leaf to the root.

```bash
go run github.com/google/trillian/docs/merkletree/treetex --tree_size=23 --inclusion=13
```

--------------------------------

### InitLog API

Source: https://github.com/google/trillian/blob/master/docs/api.md

Initializes a new log within the Trillian system. This operation requires a Log ID and optionally accepts charge-to information.

```APIDOC
## POST /trillian/InitLog

### Description
Initializes a new log. The server will assign a new Log ID if one is not provided.

### Method
POST

### Endpoint
/trillian/InitLog

### Request Body
- **log_id** (int64) - Optional - The ID to assign to the new log. If not provided, the server will generate one.
- **charge_to** (ChargeTo) - Optional - Information about who is to be charged for the log creation.

### Request Example
```json
{
  "log_id": 12345,
  "charge_to": {
    "name": "example-user"
  }
}
```

### Response
#### Success Response (200)
- **created** (SignedLogRoot) - The signed root of the newly created log.
```

--------------------------------

### Verify Experimental Map

Source: https://github.com/google/trillian/blob/master/experimental/batchmap/README.md

Verify a specific key's inclusion and commitment within the generated map tiles. Ensure map directory, logtostderr flag, and other parameters match those used during map construction.

```bash
go run cmd/verify/verify.go --logtostderr --map_dir=/tmp/mapv1 --key=5
```

--------------------------------

### Create Kubernetes Secret for Spanner Key

Source: https://github.com/google/trillian/blob/master/docs/CloudSpanner.md

Use this command to create a Kubernetes secret from a downloaded service account key file. Ensure the key is properly restricted.

```bash
kubectl create secret generic spanner-key --from-file=key.json=service-key.json
```

--------------------------------

### Abstract Signer Process in Go

Source: https://github.com/google/trillian/blob/master/docs/storage/commit_log/commit_log_based_storage_design.md

This Go code outlines the abstract process for a Trillian signer. It handles reading from local DB, sanity checks against the Kafka STHs topic, and either updating the STHs topic as master or catching up with existing STHs. Ensure idempotency for retries.

```go
func SignerRun() {
  // if any of the below operations fail, just bail and retry

  // read `dbSTH` (containing `treeRevision` and `sthOffset`) from local DB
  dbSTH.treeRevision, dbSTH.sthOffset = tx.LatestSTH()

  // Sanity check that the STH table has what we already know.
  ourSTH := kafka.Read("STHs/<treeID>", dbSTH.sthOffset)
  if ourSTH == nil {
    klog.Errorf("should not happen - local DB has data ahead of STHs topic")
    return
  }
  if ourSTH.expectedOffset != dbSTH.sthOffset {
    klog.Errorf("should not happen - local DB committed to invalid STH from topic")
    return
  }
  if ourSTH.timestamp != dbSTH.timestamp || ourSTH.tree_size != dbSTH.tree_size {
    klog.Errorf("should not happen - local DB has different data than STHs topic")
    return
  }

  // Look to see if anyone else has already stored data just ahead of our STH.
  nextOffset := dbSTH.sthOffset
  nextSTH := nil
  for {
    nextOffset++
    nextSTH = kafka.Read("STHs/<treeID>", nextOffset)
    if nextSTH == nil {
      break
    }
    if nextSTH.expectedOffset != nextOffset {
      // Someone's been writing STHs when they weren't supposed to be, skip
      // this one until we find another which is in-sync.
      klog.Warning("skipping unexpected STH")
      continue
    }
    if nextSTH.timestamp < ourSTH.timestamp || nextSTH.tree_size < ourSTH.tree_size {
      klog.Fatal("should not happen - earlier STH with later offset")
      return
    }
  }

  if nextSTH == nil {
    // We're up-to-date with the STHs topic (as of a moment ago) ...
    if !IsMaster() {
      // ... but we're not allowed to create fresh STHs.
      return
    }
    // ... and we're the master. Move the STHs topic along to encompass any unincorporated leaves.
    offset := dbSTH.tree_size
    batch := kafka.Read("Leaves", offset, batchSize)
    for b := range batch {
      db.Put("/<treeID>/leaves/<b.offset>", b.contents)
    }

    root := UpdateMerkleTreeAndBufferNodes(batch, treeRevision+1)
    newSTH := STH{root, ...}
    newSTH.treeRevision = dbSTH.treeRevision + 1
    newSTH.expectedOffset = nextOffset
    actualOffset := kafka.Append("STHs/<treeID>", newSTH)
    if actualOffset != nextOffset {
      klog.Warning("someone else wrote an STH while we were master")
      tx.Abort()
      return
    }
    newSTH.sthOffset = actualOffset
    tx.BufferNewSTHForDB(newSTH)
    tx.Commit() // flush writes
  } else {
    // There is an STH one ahead of us that we're not caught up with yet.
    // Read the leaves between what we have in our DB, and that STH...
    leafRange := InclusiveExclusive(dbSTH.tree_size, nextSTH.tree_size)
    batch := kafka.Read("Leaves", leafRange)
    // ... and store them in our local DB
    for b := range batch {
      db.Put("<treeID>/leaves/<b.offset>", b.contents)
    }
    newRoot := tx.UpdateMerkleTreeAndBufferNodes(batch, treeRevision+1)
    if newRoot != nextSTH.root {
      klog.Warning("calculated root hash != expected root hash, corrupt DB?")
      tx.Abort()
      return
    }
    tx.BufferNewSTHForDB(nextSTH)
    tx.Commit() // flush writes
    // We may still not be caught up, but that's for the next time around.
  }
}
```

--------------------------------

### Render Full Claimant Model

Source: https://github.com/google/trillian/blob/master/docs/claimantmodel/experimental/cmd/render/README.md

After resolving TODOs in the full model YAML, use this command to generate markdown snippets and a mermaid sequence diagram. This command assumes the full model file has been saved.

```bash
go run ./docs/claimantmodel/experimental/cmd/render --full_model_file /tmp/cmfun/full.yaml
```

--------------------------------

### Monitor Log Integration Metrics

Source: https://github.com/google/trillian/blob/master/docs/howto/freeze_a_ct_log.md

Fetch and filter metrics from the signer to monitor the integration status of queued leaves for a specific log ID. This helps confirm that the log has finished processing all entries before freezing.

```bash
curl ${METRICS_URI} | grep ${LOG_ID} | grep -v delay | grep -v latency | grep -v quota
```